Colorectal carcinomas molecular pathophysiology powerpoint presentation

1. Moderated by - Dr. K.K. Prasad
Ph. D. Seminar
Presented by –
Jaspreet
Molecular pathophysiology of Colorectal
cancer: an emerging Field

2. Colorectal Cancer (CRC)
Introduction
 Colorectal cancer (CRC) is one of the most common
form of gastrointestinal cancer in world today
 In Asia Pacific Area , it is the fastest emerging
gastrointestinal cancer
(Chauvenet M, 2009)
 It is one of the leading causes of cancer related deaths in
both men and women

3. Prevalence
 It is 4th most common cancer (after lung, prostate, & breast
cancers)
 2nd most common cause of cancer death (after lung cancer)
 2008: 130,000 new cases of CRC
56,500 deaths caused by CRC

4. Colorectal Cancer
Incidence Rates* by Race/Ethnicity and Sex, U.S.,
1999–2008

6. Comparatively , incidence rates of large and small bowel cancer
are low in India
(Sinha R, 2007)
Incidence rates vary from
(i) 3.7-7 /1,00,000 for men
(ii) 3-0.4/1,00,000 for women

7.  In cancer 2008, 6889 cases were reported among Indians &
Pakistani immigrants
 These cases includes 51% men and 49% women
 Among men, 30% cases were prostrate cancer , 10% cases
were lung cancer & 9% cases were colorectal cancer
 Among women , 38% cases were breast cancer, 15% cases
were genital cancer & 7% cases were colorectal cancer

8.  CRC is particularly a disease affecting above 40 years
 90% of cases occur in person above the age of 50 years
(Pal, 2006)
 In younger patients, CRC is uncommon but had
advanced stage at time of clinical presentation with
poor outcome
(Sing LJ ,2006)
There is solitary mass
attached via long stalk to
colonic mucosa. It is discreet
& does not involve wall of
colon. surface is dark red
(hemorrhagic). stool guaiac
was positive.

9. Typical sites of incidence and symptoms of colon cancer

10. Formation of carcinoma
Colon cancers result from a series of pathologic changes that transform normal colonic
epithelium into invasive carcinoma. Specific genetic events, shown by vertical arrows,
accompany this multistep process. The various chemopreventive agents exert their
effects at different steps in this pathway, and this is depicted on the basis of the
available epidemiologic evidence, the results of studies in animals, and the known
mechanisms of action of the agents

11. Staging
 It is a process of determining how far the cancer has spread
 Stage is the most powerful predictor of prognosis
 Based on TNM classification:
T= Tumor penetration into colon wall
N= Nodal involvement
M= Distant metastases

12.  Stage I- Invades into muscle layer, but not into subserosa
 Stage II- Invades into subserosa, other organs, or
associated with perforation, no nodal involvement
 Stage III- Lymph Node involvement
 Stage IV- Distant spread to other organs (liver, lungs)

13. Five-year relative survival by stage
 Stage I >90%
 Stage IIA 70-85%
 Stage IIB 55-65%
 Stage IIIA 45-55%
 Stage IIIB 35-45%
 Stage IIIC 25-35%
 Stage IV 8%

14.  A Mucosa 80%
 B Into or through M. propria 50%
 C1 Into M. propria, + LN ! 40%
 C2 Through M. propria, + LN! 12%
 D distant metastatic spread <5%
Dukes staging system

15. Multiple adenomatous polyps of the cecum are seen here in a case of familial polyposis

16. This is familial polyposis in which the mucosal surface of the colon is essentially a carpet of
small adenomatous polyps. Of course, even though they are small now, there is a 100%
risk over time for development of adenocarcinoma, so a total colectomy is done, generally
before age 20

17. An encircling adenocarcinoma of the rectosigmoid region is seen here. There is a
heaped up margin of tumor at each side with a central area of ulceration. This
produces the bleeding that allows detection through a stool guaiac test. Normal
mucosa appears at the right. The tumor encircles the colon and infiltrates into the
wall. Staging is based upon the degree of invasion into and through the wall

18. At high magnification, the normal colonic epithelium at the left contrasts with the atypical
epithelium of the adenomatous polyp at the right. Nuclei are darker and more irregularly
sized and closer together in the adenomatous polyp than in the normal mucosa.
However, the overall difference between them is not great, so this benign neoplasm
mimics the normal tissue quite well and this, therefore, well-differentiated

19.  Histologically identical tumours may have drastically
different prognosis
 Response to treatment prompted theory that, rather than
single malignancy, CRC is a heterogenous, multifactorial
disease
(Deschoolmeester 2010)
 It is theorized, perhaps, that individual tumours are
initiated & progress in unique manner
Not necessarily identical amongst all tumours

21.  As a result, focus of CRC research is shifting from clinical
perspective towards developing an understanding of
molecular basis of this malignancy
 individual susceptibility
 development, progression, response,
 resistance to antitumour treatment & metastatic spread
(Markowitz 2009)
 Cancer develops through multiple & sequential genetic
alterations
 Some patients may have synchronous alterations in two or
three different pathways

22.  Through clonal selections, cancer cell “chooses” genetic
alterations most conducive to growth through proliferation
of cells that possess desired qualities with apoptosis of
those that do not

23.  First model of colorectal tumorigenesis put forward by
Fearon and Vogelstein outlined a four-step sequential
pathway for development of cancer, in which
 Step 1: APC inactivation causes adenoma development
 Step 2: KRAS mutations promote adenomatous growth
 Step 3: genetic alterations of chromosome 18q allowed
progression with biallelic loss
 Step 4: p53 inactivation triggers the final transition to
carcinoma

24.  Only 5% of adenomas will progress to cancer development
indicating that carcinogenesis requires additional molecular
modifications, with greater emphasis on ↑ proliferation
• It is suggested CRC is initiated by “cancer-initiating stem
cells” with ability to self-renew, perpetuate, & generate
variety of differentiated cells
 These cells are proposed to harbour initial mutation of APC
in one of the 107 crypts of the gastrointestinal tract
which then colonize the crypt with mutated cells
(Perea 2011)

25.  Carcinogenesis is now viewed as imbalance b/w mutation
development & cell-cycle control mechanisms
 When cell-cycle is no longer capable of controlling mutation
rate, it is referred to as “genomic instability”
 Three separate pathways have been identified that
contribute to this imbalance:
(1) chromosomal instability (CIN)
(2) microsatellite instability (MSI)
(3) CpG island methylator phenotype (CIMP)

26.  Chromosomal Instability:
 The chromosomal instability (CIN) pathway, also known as
suppressor pathway, is the most common type of genomic
instability [8], encompassing 50–85% of CRCs
(Goel, 2007)
 Various mechanisms that contribute to CIN have been
identified & categorized to include
(a) sequence changes
(b) chromosome number alterations
(c) chromosome rearrangements
(d) gene amplification
(Grady and Carethers, 2008)

27.  Common finding in chromosomally instable neoplasms is
loss of 18q, a finding identified in up to 70% of primary
CRCs
 Genes on this chromosome include deleted in colorectal
carcinoma (DCC), SMAD2, and SMAD4
 CIN can be detected early in dysplastic crypt foci & is more
commonly found in distal colon; however, whether or not it
precedes APC inactivation remains unclear
(Worthley and Leggett,2010)
There remains no clear evidence to discern
whether CIN is cause or consequence of
malignancy

28. Microsatellite Instability:
 A microsatellite is stretch of DNA containing pattern of 1–5
nucleotides in length with tandem repeats
 Minimum of 500,000 microsatellites are estimated within
genome
 Microsatellite instability (MSI) is detected in 15% of CRCs &
arises when microsatellites become abnormally long or short
due to gain/loss of repeated units
 This pathway of genomic instability was first reported in 1993
at the detection of thousands of somatic alterations in length
of DNA from a CRC

29.  Elongation or shortening of microsatellite is primarily due
to inactivation of DNA mismatch repair (MMR) genes
which are responsible for correcting base-base DNA
replication errors
 TGFβRII, EGFR, & BAX, which contain simple repeats, are
often mutated in these tumours

30. Additional genes affected by MSI include
• Regulators of proliferation (GRB1, TCF-4, WISP3, activin
receptor-2 insulin-like GF-2 receptor, axin-2, CDX)
• Cell cycle or apoptosis (caspase-5, RIZ, BCL-10, PTEN, hG4-
1, FAS) and DNA repair (MBD-4, BLM, CHK1, MLH3, RAD50,
MSH3, MSH6)
(Boland and A. Goel, 2010)
• Use of MSI as a prognostic factor remains uncertain
although it is suggested that it may be useful in selection of
individual therapeutic regimes

31.  Hereditary nonpolypsis colorectal cancer, now referred to
as Lynch syndrome because of its extraintestinal
manifestations
is due to a mutant germline MMR gene causing loss of MMR
function with somatic inactivation of the wild-type allele
These patients usually develop multiple tumours b/w 20–30
years in colon and may have extracolonic manifestations in
rectum, endometrium, renal pelvis, ureter, stomach, ovary,
skin, brain, and/or small intestine

32.  Majority of cases are due to autosomal-dominant inheritance
of mutation in either MLH1 or MSH2
 Approximately 1/3 of these patients will have no pathogenic
mutation in their mismatch repair genes
(Venkatachalam 2010)
 In these cases, Lynch syndrome arises from germline
epimutations inactivating genes through promoter
methylation
 That is usually identified in families that show no MMR gene
sequence mutation

33.  This most commonly occurs through hypermethylation at
EPCAM that inactivates downstream gene MSH2
 To confirm diagnosis, testing for BRAF is indicated, as it is
virtually never mutated in Lynch syndrome though it is
mutated in 40–50% of sporadic MSI tumours

34. CpG Island Methylation Phenotype
Newest of three genomic instability pathways, CpG island
methylator phenotype (CIMP) was originally grouped
together with MSI
 Epigenetic modification of methylation is well recognized
as crucial event in altering gene expression associated
with carcinogenesisis more frequent in cancer than
genetic changes
• Methylation of promoter CpG islands occurs in all tissue
types in carcinogenesis
• Methylationleads to transcriptional silencing of genes
involved in tumour suppression, cell cycle control, DNA
repair, apoptosis, & invasion

35.  Clinically, CIMP+ tumours share some characteristics with
MSI-H tumours including proximal location & poor degree
of differentiation
 Unlike MSI, tumours may have particularly poor prognosis
 These tumours often have KRAS and/or BRAF mutations
 CIMP & CIN positivity are mutually exclusive

36.  Similar to MSI, prognostic significance of CIMP remains ill
defined, with some studies finding an adverse effect on
prognosis and others no effect
 As such CIMP+ tumours confer worse prognosis than MSI
tumours, though concurrent MSI with CIMP positivity may
improve prognosis compared with an MSI−/CIMP+ tumour
 It has been suggested adverse effect associated with CIMP
positivity may not be innate, but rather due to KRAS or
BRAF mutations
(Deschoolmeester 2010)

37. Alternative Serrated Neoplastic Pathway:
 Serrated polyps are lesions composed of epithelial
infoldings creating serrated appearance
 Approximately 20% of CRCs originate from serrated
pathway of neoplasia

38.  In this context, two separate molecular pathways have
been proposed
(a) BRAF-mut with CIMP-H is seen in majority of syndromic,
nonsyndromic cancers, and MSI cancers.
(b) KRAS-mut are CIMP-low, no hMLH-1 activation,
 and are MSS withmany of them harbouring p53mutations
 like conventional CRCs
12–15% of MSI cancers occur by epigenetic
silencing of promoter methylation of DNA
mismatch repair gene hMLH-1 as key step
leading to MSI with rapid progression from
low to high grade dysplasia to invasive
cancer

39.  The clinical outcome for MSI-negative tumours worsens
when correlated with methylation
 In tumours positive for MSI, those also positive for CIMP
conferred a worse prognosis
 Chromosomal instability and microsatellite instability
are mutually exclusive
• Recognition of genomic instability & subtype is important to
guide systemic therapy & affects outcome
(Kim and G. Deng 2007)

40. Genomic Modifications
a) Mutational Inactivation of Tumour-Suppressor Genes :
 In carcinogenic transformation, tumour growth is often
facilitated by inactivation of these genes through deletions,
mutations, promoter methylation, or mutation of one allele
with loss of the other
 Several key players in carcinogenetic process have been
identified and are well elucidated in the literature
Genes include APC, TP53, & TGF-β.

41. Changes resulting in colon cancer

42. Mutations in the APC pathway cause increased proliferation

43.  Alternatively, β-catenin gain-of-function mutations with
fully intact APC gene have been detected in up to 50% of
colonic tumours with same result of increased proto-
oncogene expression
 Mutation to either APC gene or β-catenin that activates
signalling pathway has been detected in majority of CRCs &
is suspected to be an initiating event of carcinogenesis
 Distribution of β-catenin within cell once APC gene has
been mutated appears to be heterogeneous

44.  It is postulated tumour microenvironment may be an
important factor in CRC growth & dissemination
 Growth factors, chemokines, inflammatory factors, &
extracellular matrix are suspected to interact with Wnt-
signalling pathway resulting in heterogenous intracellular
β-catenin distribution
(Huang and X. Du, 2008)
 APC gene has been implicated in development of FAP), an
inherited condition characterized by numerous of
adenomas lining large intestine by 20-30 years with high
propensity for malignant transformation

45. TP53
• The tumour suppressor protein p53 & its gene TP53 is well-
studied element of carcinogenic pathway with alterations to its
function found in most human cancers
• TP53 gene is found on short arm of chromosome 17 & is
induced by oncogenic proteins such as c-myc, RAS, &
adenovirus E1A
• Normally, p53 protein is negatively regulated by MDM2, E3-
ubiquitin ligase, & MDM4 that targets p53 for ubiquination
• In presence of cellular stress, MDM2 & MDM4 have disrupted
interactions with activation & transcription of p53
(Pino 2010)

46. p53:
• It is often designated as guardian of genome, has key role
in maintaining genomic stability
 Inactivation of TP53 is a key step in development of CRC
 Mutations & LOH of p53 are important with transition from
adenoma to carcinoma
 Usually both alleles are inactivated by missense mutation
inactivating transcription & 17p chromosomal deletion of
2nd TP53 allele
 This loss of function is found in 4–26% of adenomas, 50%
of adenomas with invasive foci, and 50–75% of CRCs

47. TGF-β:
• SMAD is pathway through which transforming growth factor
beta (TGF-β) protein signals activity
• Pathway is initiated by TGF-β dimer binding to TGF-β Receptor
II that recruits & phosphorylates type I receptor
• This receptor then phosphorylates receptor regulated SMAD
(R-SMAD)
• Family of R-SMADs includes SMAD1, SMAD2, SMAD3, SMAD5,
and SMAD8.
 R-SMAD will then bind to SMAD4 to form complex that enters
nucleus & affects transcription. There, it causes apoptosis &
cell cycle regulation

48. TGF-beta RII mutations, prevent cell cycle inhibitor (p15) and
protease inhibitor (PAI-1) expression

49.  One third of CRCs demonstrate somatic mutations
inactivating TGFBR2 gene
 Inactivating mutations of TGF-β pathway is involved in
adenoma transition to high-grade dysplasia or invasive
carcinoma
 SMAD2 & SMAD4 encode proteins SMAD2 & SMAD4 & are
mutated in 5% and 10–15% of CRCs respectively
 SMAD4 germline mutations are implicated in juvenile
polyposis syndrome, an autosomal dominant condition in
which multiple hamartomas develop throughout GIT
(van den Brink,2004)

50. Activation of Oncogene Pathways:
 Oncogenes are genes with potential to cause cancer
 They encode growth factors, growth factor receptors,
signalling molecules, regulators of cell cycle, & additional
factors implicated in cellular proliferation & survival
 When these genes are mutated, results may include
Overactive gene products, amplifications
altering copy number, alterations that affect
promoter function or modified interactions that
cause transcription/epigenetic modifications

51. RAS and BRAF:
• RAS-RAF-MAPK pathway begins with mitogen (such as
EGF) binding to membrane receptor (such as EGFR), which
allows GTPase Ras to exchange its GDP for GTP, activating
MAP3K (Raf) which activates MAP2K which activates MAPK
• MAPK then activates transcription factors that express
proteins with role in cellular proliferation, differentiation,
and survival
 KRAS mutations have been reported in 40% of CRCs &
contribute to development of colorectal adenomas &
hyperplastic polyps

52.  Attempts have been made at targeting KRAS for cancer
treatment including inhibition of protein expression through
antisense oligonucleotides
 And with blockage of posttranslational modifications to inhibit
downstream effectors
 KRAS mutations have recently gained interest as negative
predictive factor for anti-EGFR therapy response
 Blocking EGFR will have no effect if KRAS is mutated as it
functions downstream of EGF receptors
 Thus, KRAS mutation allows continual activation of
downstream pathway, thus negating effects of drug

53.  Anti-EGFR drugs are not recommended in KRAS-mutated
tumours
 In this context, it has been suggested that all patients with
CRC under consideration for anti-EGFRs should be tested
for KRAS mutation status prior to treatment initiation

54.  BRAF mutations confer worse clinical outcome & thus need
for adajuvant therapy
 Mutations are associated with shorter progression free &
survival
 Though controversial, some studies have found that these
adverse clinical effects of BRAF are negated in CIMP+
tumours
suggesting poor prognosis is not
attributable to BRAF mutation itself, but
is probably attributable to genetic
pathway in which it occurs

55. Phosphatidylinositol 3-Kinase (PI3K):
 PI3Ks are family of enzymes divided into three classes.
 Class 1A PI3Ks, which are composed of one catalytic
subunit & one regulatory subunit
 Catalytic subunit p110α, which is encoded by protein
PIK3CA, has been of particular attention as it is believed to
play significant role in cancer progression
 Its mutation has been detected in approx. 1/3 of CRCs

56.  Due to its inhibitory effect on Akt, phosphatase & tensin
homolog (PTEN) acts as tumour suppressor gene in this
pathway
 In CRC, PTEN gene may be inactivated by somatic
mutations, allelic loss or hypermethylation of enhancer
region
 Mutation of PTEN is later event in carcinogenesis that is
correlated with advanced & metastatic tumours
 Though it is clear that PTEN mutations in stage II CRC is a
poor prognostic marker, its role in other stages of CRC
remains uncertain

57. MicroRNA:
 Micro RNA (miRNA) is short RNA 8–25 nucleotides in length
that binds to mRNA to control translation of complementary
genes
• Over 1,000 miRNA sequences have been identified, each
controlling hundreds of genes for total of over 5,300 genes
30% of the human genome
• These short RNAs play a regulatory role in development,
cellular differentiation, proliferation, and apoptosis

58.  miRNA dysregulation is suggested to play role in
carcinogenesis when their mRNA targets are tumour
suppressor genes or oncogenes through silencing &
overexpression respectively
 Half miRNAs are located at breakpoints of chromosomes
therefore, at higher risk of dysregulation
 Overexpression of miR-31, -183, -17-5, -18a, -20a, & -92 &
underexpression of miR-143 and -145 are common in CRC
 It remains unclear, however, which miRNA changes are
causative & which are result of carcinogenesis

59.  (i) APC: miR-135a, miR-135b cause decreased translation
 (ii) PI3K: miR-126 stabilizes PI3K signal, is lost in CRC
 (iii) PTEN: miR-21 is repressed
 (iv) KRAS: miR-143 causes decreases expression
 (v) p53: miR-34a induces apoptosis, ↓ in 36% of primary
CRCs, miR-192, miR-194-2, & miR-215 are ivolved in cell
cycle arrest & are also down regulated in CRC

60.  miRNA has same potential for identification as
mRNA/proteins for screening, diagnosis, & prognostic
prediction of CRC
 It has been further proposed that miRNA pattern could be
indicative of prognosis and act as a molecular target for
treatment
(Yang 2009)

61. Epigenetic Changes
 Epigenetic changes are those that alter genetic expression
without modifying actual DNA
• These changes are detected in approximately 40% of CRC
• These factors are conveyed during cellular division
• Epigenetic changes, can be subclassified into two broad
categories:
(1) histone modification (2) DNA methylation

62. Histone Modification :
 Histones are proteins that package cellular DNA into
nucleosomes & play role in gene regulation
 Mutually exclusive modifications that have been identified
in CRC include deacetylation & methylation of lysine 9 in
histone H3
 If acetylation occurs at this position, gene is expressed
whereas if it is methylated, gene is silenced
 It is suggested that universal marker for malignant
transformation is loss of monoacetylation from Lys 16 &
trimethylation at Lys 20 on histone H4
( Wong 2007)

63. DNA Methylation
 Over 40% of human DNA contains
 short interspersed transposable elements (SINEs)
 long interspersed transposable elements (LINEs)
That are normally methylated but become hypomethylated
in CRC development
 These changes are believed to occur early in carcinogenesis,
as hypomethylation is detected in benign polyps but is not
changed once they become malignant

64. Metastatic Colorectal Cancer
 Final stage of CRC involves detachment from primary
cancer, migration, access to blood/lymph,& development of
secondary tumour
 Each step in metastatic spread requires definitive genetic
and epigenetic changes
 However, exact mechanisms underlying these changes
remain largely unknown
 Approximately 50% of patients with CRC will die due to
complications of metastases

65.  Growth factors such as prostaglandin E2, EGF, & VEGF as
well as molecular mediators of epithelial-mesenchymal
transition have been identified as potentiators of metastatic
spread
 Biological agents specifically targeting these markers have
increased median survival time of mCRC to 23.5 months
Therefore, early recognition of these molecular
changes involved in this process with
development of therapeutic strategies to
combat these events is a high priority in CRC
treatment

66. Growth Factor Pathways:
 Prostaglandin and Cyclooxygenase-2:
 Prostaglandin E2 is mainly produced & secreted by
fibroblasts in stroma & epithelial cells
 Its signal is transduced through interactions of
endoprostanoid receptors
 Activation of endoprostanoids initiates cascade that
activates EGFR and PI3K/Akt signalling pathways resulting
in β-catenin translocation to the nucleus
 Signalling of prostanoid thus plays an important role in
development of adenoma & is strongly associated with CRC
through the regulation of proliferation, survival, migration,
and invasion
(Zlobec 2010)

67.  These high levels may be induced by inflammation or
mitogen associated upregulation of COX-2
 The mediator of prostaglandin E2, or due to loss of 15-
prostaglandin dehydrogenase (PDGH), rate-limiting enzyme
catalyzing prostaglandin E2 breakdown
 Loss of PDGH is high & is reported in up to 80% of
colorectal adenomas & carcinomas
 COX-2 upregulation can be induced by growth factors,
cytokines, inflammatory mediators, tumour promoters, & is
overexpressed in ∼43% of adenomas & 86% carcinomas

68. Epidermal Growth Factor (EGF):
 Epidermal growth factor receptor (EGFR), member of
family of receptor tyrosine kinases, is cell-surface receptor
that binds epidermal growth factor, transforming growth
factor α (TGF-α), amphiregulin, betacellulin, and epiregulin
 EGFR activation promotes invasiveness & spread by
activating serine protease, which aids in degradation of
extracellular matrix

69.  Finally, it is an initiating event in RAS-RAF-MAPK pathway
& PI3K-Akt pathway as described above with prominent
roles in carcinogenesis
 Overexpression of EGFR occurs in 65–70% of CRCs, it is
more commonly seen in advanced stage tumours
 In this context, EGFR has been identified as an important
therapeutic target in metastatic CRC (mCRC)

70.  Pharmacological inhibitors of EGFR have significantly
benefited CRC patient population through
I. Both monoclonal antibodies to interfere with receptor
signalling
II. Tyrosine kinase inhibitors to interfere with catalytic
activity of cytoplasmic domain
 Two monoclonal antibody (cetuximab and panitumumab)
and two tyrosine-kinase inhibitor (Geftinib and Erlotinic)
drugs have been created
 The higher patient’s EGFR overexpression, the better the
response to anti-EGFR treatment

71. Vascular Endothelial Growth Factor:
Angiogenesis, development of new blood vessels from
preexisting ,is normally vital process during development
and wound healing
• However, in carcinogenesis, angiogenesis is necessary to
transport oxygen and nutrients into a growing neoplasm
 These two processes differ in balance between pro- and
antiangiogenic signals
 In carcinogenesis, balance b/w these factors is lost, with
proangiogenic factors predominating
 In CRC, neovascularization is driven by hypoxia stimulating
production of angiogenic factors such as VEGF

72.  Serum levels of VEGF are associated with poor prognosis
and VEGFR1 gene expression may be predictive of tumour
recurrence
 Based on important role that angiogenesis & VEGF play in
advanced CRCs, a monoclonal antibody therapy was created
to inhibit this process
 Bevacizumab: combined with chemotherapy increases
survival of patients with mCRC when compared with
chemotherapy or bevacizumab alone
 Three VEGF tyrosine kinase inhibitors have additionally
 been created: Vatalanib, Afibercept, and Sunitinib

73.  Detection of Molecular Events
 Though colonoscopy remains the gold standard for CRC
screening, fewer than 60% of those eligible over age of 50
have undergone this test
 Reasons for this may include procedural factors such as test
discomfort, invasiveness, embarrassment, and lack of
availability of trained personnel/facilities/equipment
 Further, despite uncertainty, malignant potential serrated
lesions is beyond doubt as they represent precursors to an
important proportion of overall CRC burden

74.  Blood and feces are the two media in which targets for
earlier molecular detection of CRC have been developed
 Fecal occult blood testing (FOBT) is a non invasive method
of testing for blood in stool that is commonly conducted as
first-line screening for CRC
 This screening tool has reduced CRC mortality by 15–33%
 There has been recent interest in detection of molecular
markers in fecal specimens as screening tool for CRC
 This detection is based on the natural process of
coprocytobiology (colonocytes shedding from colonic
mucosa & being excreted in stool at rate of 1010 cells/day)

75. Blood:
• Tumour cells circulating in peripheral blood may be
reflective of tumour genetic characteristics & therefore,
useful in predicting metastatic & recurrence potential
 One of the oldest & well-researched markers is
carcinoembryonic antigen (CEA) that is positive once CRC
is established; however, it does not readily detect early
disease

76. Conclusion
 Therefore, despite many strides in understanding
development & progression of CRC, a lot remains largely
unknown due to multifactorial process
 Despite abundance of molecular pathways & markers
continually being reported, CRC mortality rates remain high
 Indicating poor translation from laboratory to clinical
setting
 Goal for future lies in development of research tools that
can target early detection of many of ongoing well-
recognized subcellular molecular events to improve burden
of mortality and morbidity related to colorectal carcinoma

77. Thank You

78.  Result of interplay between environmental and
genetic factors
 Central environmental factors:
 Diet and lifestyle
 35% of all cancers are attributable to diet
 50%-75% of CRC in the US may be preventable
through dietary modifications
Development of CRC

79. Molecular mechanism involved in
colorectal cancer
CRCs arise from a series of histopathological and
molecular changes that transform normal epithelial cells
Intermediate step is the formation of adenomatous polyp
Adenoma-Carcinoma-Sequence (Vogelstein & Kinzler)
Polyps occur universally in FAP, but FAP accounts for
only 1% of CRCs
Adenomatous Polyps in general population:
33% at age 50
70% at age 70

80.  Glutathione (GSH) and its enzymes
(i) glutathione peroxidase (GSHPx)
(ii) glutathione S-transferase (GST)
(iii) glutathione reductase (GSHR)
Play crucial role in cell defence against tumor disease
.

81.  Changes in GSH level and related enzymes activities
suggest oxidative stress in tumor patients (Subior D,2008)
 Protein phosphoglycerate Kinase 1(PGK1)
induced by free radicals like H2O2 . Therefore, it is
a potential biomarker of intracellular oxidative stress.

82. Immunological Mechanism of Colorectal
cancer
 CD4+ CD25+ T Cells are engaged in maintenance of
immunological tolerance against cancer
 Adaptive T Cells express COX-2 and suppress
responder T Cells in a PGE2- cAMP dependent
manner (Yaqubs, 2008 )
 Patients with colorectal cancer are treated with COX
inhibitor or cAMP antagonist to enhance antitumor
response

83.  Tumor cells can lose major Histocompatibility complex
(MHC) class I molecule
 As a result , they can escape T Cell immune response
 Expression of HLA receptors and HLA class I Antigen is
also studied to evaluate immunological condition of patient
(Facoetti A, 2001)

84.  Interferon-gamma (IFN- gamma) and interleukin –
2(IL-2) are two important cytokines.
 They enhance therapeutic activity of doxorubin
chemotherapy
 IFN- gamma or IL-2 exhibited significant increase in
number of CD25+ infiltrating cells(Lumsden AJ,
2006)
 As a result, antitumor response increases many times

85.  All Metastatic tumors expressed FasL mRNA and protein
(Shiraki K, 1997)
 Fas (APO-1, CD-95) and Fas ligand (FasL) are important
in
(i) auto-immunity
(ii) graft rejection
(iii) anti tumor response.
 Therefore , FasR –FasL (Main apoptotic pathway) may
represent new exciting type of immunotherapy in
treatment of primary childhood tumors (Bodey B, 1999)

86. PREVENTION OF COLORECTAL CANCER
 Environmental factors have a great influence on process that lead to
cancer and nutritional intervention play important role in its
prevention
 Vegetables and certain bioactive plant components possess
protective effects on the development of CRC like
(i) Garlic (Kotezev I , 2008 )
(ii) Curd and Probiotics (Kanauchi O, 2008)
(iii) Turmeric
(iv) Ginger Extract (Manju V, 2005)
(v) Fruits and Vegetables
(vi) Antioxidants like Selenium , Zinc (Thiruvurasundari CJ 2009 )

87. GARLIC
 Oil soluble diallyl sulphide induce apoptosis in Colo 320 DM
colon cancer cells ((Sriram N , 2008)
 Diallyl sulphide (DAS) promote cell cycle arrest at G2/M
phase in Colon 320 DM cells
 The production of reactive oxygen species (ROS) ,
 with time after treatment with DAS

88. Yoghurt and Probiotics
 Lactic acid bacteria (LAB) present in yoghurt and
probiotics favour increase in immune cell activity
 Probiotics may suppress the growth of bacteria that
convert procarcinogens carcinogen (de
Moreno de Le BlancA , 2007)

89. TURMERIC
 Curcumin , a yellow pigment in Turmeric , suppress
gene expression of epidermal growth factor
receptor (EGFR) and cyclin D 1. (Chen A, 2008)
 Reduce transactivation activity of transcription factor
early growth response-1(Egr-1) by suppressing egr-1
Gene expression .

90. Omega -3 polyunsaturated fatty acids.
 Low does of celecoxib in Omega - 3 PUFA diets are
effective against colon carcinogenesis .
 Lowers level and expression of cyclo oxygenase-2
(COX-2). Therefore , chemopreventive (Reddy BS ,
2005)

91. Ginger Extracts
 Increased lipid peroxidation and decrease enzymic and
non- enzymic antioxidants concentration.
 Zerumbone (ZER) , a sesquiterpene compound occurring
in tropical ginger induce phase II. detoxification enzymes
like glutathione peroxidase

92. Fruits and Vegetables
 Contains potential anticarcinogenic compounds and are
protective colorectal adenoma . Some of them are :-
(i) Fiber
(ii) Carotenoids
(iii) Vitmain C
(iv) Folate
(v) Allium compounds

93. Antioxidants
 Selenium supplementation decreased the risk of
lung , colon and prostate cancer. (Reid M E 2008)
 Trans – Resveratrol has high concentration in
lumen, it
(i) activates Caspase 3
(ii) inhibits cell proliferation without cytotoxicity
(iii) induce apoptosis in HT-29 (Juan ME, 2008)

94.  Other Known antioxidants which have anticarcinogenic
activities are :-
(i) Beta – carotene ( Rosignoli P , 2008)
(ii) Alpha – tocopheral
(iii) Na – butyrate
(iv) Caffeine and white tea (Wang R, 2008)
(v) Zinc (Dani V, 2007)
(vi) Isoflavonoids

95. Apart from surgery and Chemotherapy , other methods of
choice in diagnosis and treatment of cancer are :-
(i) Fibreoptic Endoscopy
(ii) Magnetic resonance imaging (MRI)
(iii) Positron emission tomography (PET)
(iv) Radio immunoscintigraphy

96. Some of the medicines used in chemotherapy are :-
 5-fluorouracil (5-FU)
 Leucovorin
 Xeloda
 Irinotecan
 Oxaliplatin
 Targeted Therapies- Avastin, Erbitux

97.  Patients with rectal tumors invading into the muscularis
propria will benefit from preoperative radio-
chemotherapy like adjuvant 5–fluorouracil (5–FU) based
chemotherapy trials (VandenEynde M, 2009)
 5-flurouracil + leucovorin for six months is generally
considered benchmark for adjuvant treatment in stage 3
colon cancer
 Oral chemotherapy drug, xeloda, is equivalent to 5-FU.
Newly approved drug, oxaliplatin given with 5-FU adds
additional benefit

98. Avastin (Bevacizumab)
 Indicated for 1st line treatment of patients with Stage
IV colorectal cancer in combination with 5-FU regimen
infusion every 2 weeks
 Patients treated with Avastin live longer that those
treated with chemotherapy alone

99. Side effects of Avastin are
 High blood pressure (common)
 Protein in urine (common)
 Gastrointestinal Bleeding (rare)
 Stroke and Heart Attack (rare)

100. Erbitux
 Erbitux® is a monoclonal antibody
 Binds to epidermal growth factor receptor
[EGFR] on both normal and tumor cells,
and blocks binding of growth factor
 Results in inhibition of cell growth, cell
death, and other anti-tumor effects
 Over-expression of EGFR is found in many
human cancers including those of the colon
and rectum

103. IN VIVO BIOMARKERS
 Targeted detection and therapy using recent advances
in our knowledge of in vivo cancer biomarkers promise
to significantly improve methods for early detection,
risk stratification, and therapeutic intervention
 Several biomarkers have shown only limited utility:
e.g., CD44, telomerase, transforming growth factor-
(TGF-) , transforming growth factor-ß (TGF-ß),
epidermal growth factor receptor erbB-2 (erbB-2),
epidermal growth factor receptor erbB-3 (erbB-3),
mucin 1 (MUC1), mucin 2 (MUC2) and cytokeratin 20
(CK20)

104.  Prostate specific antigen (PSA) and cancer
antibody or tumor marker 125 (CA 125) have
wider utility .
 However, reduction of mortality using these in
the screening setting has not been shown .
 Fecal occult blood test (FOBT) is the only protein
biomarker shown to decrease cause-specific
mortality in cancer screens .
 This underscores the need to develop new and
novel protein-based markers that can be
reproducibly detected in serum or directly
detected in exfoliated cells at early
stages.(Morikawa T, 2008)

105.  Colorectal cancer (CRC) is a main cause of
morbidity
and mortality in industrial countries
Age,sedentary lifestyles,diet,family history are
some of the risk factors involved. In colorectal
cancer,many changes take place in
a) molecular physiology of cells
b) oxidative changes
c) immunological changes
summary

106.  Although, colorectal cancer can be treated with
surgery and chemotherapy but they have many
side effects
 Therefore, prevention is better than cure.we
should change our lifestyle and imbibe good
dietary habits to reduce the risk of colorectal
cancer.