Updated version of molecular basis, with implied clinical aspect of the molecular basis. (contents are taken from standard textbook and i dont own the copyright for the content details.)

1. Moderator- Dr. Deviprasad D Date-29-08-20
Presenter- Dr. Sreenivas Kamath K

2.  Introduction
 Normal cell cycle
 Cancer hallmarks
 Carcinogens
 Genetic aberrations in cancer cells, progression, syndromes.
 Cancer hallmarks molecular level
 Implication of molecular biology in our clinical practice

3. What is Normal ?
What is cancer ?
How ?
Who ?
Why ?
What will we benefit from this ?

4.  Cancer is a genetic disease – Philadelphia chromosome
 Molecular biology is defined as “the branch of science concerned
with the formation, organisation, and activity of macromolecules
essential to life”
 Born following discovery of restriction endonuclease
 Predict the growth, progression, and response
 Formed the basis of treatment and prognosis of H & N Ca

5. G1
SG2
M
G0
Rb E
Mi
CycD
CDC4 or CDK6
P
E
DHFR
TK, TS , DNA pol
CDC2
CycE
E2F-1
RbRb
Rb
P
P
P
P
P
P
P
P P
ANTI PROLIFERATIVE
SIGNALS
CDKN2A
P16
CDKN1A
P21
CDKN1B
P27
P53
CycE
CDK2
CycA
CDK2
CycA
CDC2
CycE
CDC2
PHOSPHATASE

6.  Proto-oncogene: Normal cellular genes whose products are involved
in normal cell growth and repair process.
 Oncogene: Mutated or overexpressed version of protooncogene.
 Oncoproteins: Products of oncogenes that cause uncontrolled
proliferation of cells by several mechanisms.
Category of Oncogene Protooncogene Examples
Growth factors
HGF HGF Thyroid malignancy
Growth factor Receptors
EGF Receptor family EGFR HNSCC
Receptor for Neurotrophic
factors
RET Medullary carcinoma Thyroid,
MEN 2A
Signal Transduction protein
GTP binding protein N RAS Melanoma
RAS signal transduction protein BRAF Melanoma

7.  Tumor suppressor is a protein or gene, is associated with
suppression of any of the various hallmarks of cancer.
 Tumor suppressor genes apply brakes and prevent uncontrolled cell
proliferation
 RB, p53, BRCA 1 and BRCA 2, WT1, APC/β-catenin, SMAD 2 and
SMAD 4, NF1 and NF2, TGF-β receptor, E-cadherin.

8.  In 2000 Douglas Hanahan and Robert Weinberg- published in Cell
journal –”Hall mark of Cancer”.
 6 primary tumor phenotypes
1. Self sufficiency to anti-growth signals
2. Insensitivity to antigrowth signals
3. Evading apoptosis
4. Limitless replicative potential
5. Sustained angiogenesis
6. Tissue invasion and metastasis
 In 2011, “Hallmarks of cancer- New generation” in cell journal.
7. Enabling characteristics- Genome instability and mutation, tumor promoting
inflammation
8. Emerging hallmark- Avoiding immune destruction, deregulating cellular energetics
1. The hallmarks of cancer- https://doi.org/10.1016/S0092-8674(00)81683-9
2. The hallmarks of cancer; New generation- https://doi.org/10.1016/j.cell.2011.02.013

10.  3 major mechanisms which cause DNA damage
 Mutations
 Viral oncogenesis
 Epigenetic modification

11.  Tobacco
 Alcohol
 Betal nut
 Viral oncogens
 Inorganic carcinogens
 Organic carcinogens

12.  Tobacco smoke: more than 4000 chemicals, at least 60 of which have
been shown to be carcinogenic
 Tobacco carcinogens are broadly grouped into
 Polycyclic aromatic hydrocarbons (i.e. benzo[a]pyrenes)
 Aromatic amines
 Heterocyclic aromatic amines
 Aldehydes
 Asz-arenes (dibenz[a,h]acridine and 7H-dibenzo[c,g]carbazole)
 N-nitrosamines (N-nitrosodiethylamine)

13. • Once absorbed, carcinogens require activation by cellular enzymes
(i.e. cytochrome P450 group) to promote tumorigenesis
• Effects can be offset by detoxifying enzymes (i.e. GSTM1)
• Dysfunction of these enzymatic pathways has been associated with
increased risk for HNSCC

14.  Not chemically complex like tobacco
 Interaction of alcohol with body is complex
 LIVER, oral cavity and esophagus
 Carcinogenic conc is achieved even with mouth
gargle.
 Increases the uptake of the certain carcinogen
when used along with smoking

15.  Areca nut is the seed of the fruit of the oriental palm, Areca catechu,
and is the basic ingredient of a variety of widely used chewed
products
 May be mixed with tobacco products or wrapped in the leaf of the
piper betel plant
 Arecoline has been isolated from the betal nut.

16.  Oncogenic viruses
 Ebstein barr virus
 Human papilloma virus

17.  May be responsible for development of HNSCC
 Is a retrovirus that primarily infects transitional epithelial tissues
 The family contains over 70 different genotypes
 Classified into three risk categories for the onset of malignant
phenotypes:
 High (types 16, 18) - associated with cervical and anogenital cancers
 Medium (types 31, 33)
 Low (types 6, 11) - cause non-cancer pathologies (e.g. papillomas and
condylomas)

18.  Early viral proteins, E6 and E7,
 26 per cent prevalence of HPV; vast majority HPV-16
 Oropharynx
 Predilection for non-smokers (up to 50 per cent of cases)
 Associated with sexual history, implicating direct exposure as a
cause for infection
 Immunosuppression increase the risk for infection HNSCC

19. E7
E6

20.  Member of the herpes family
 Implicated in the pathogenesis of following:
The African form of Burkitt lymphoma
 B-cell lymphomas in immunosuppressed individuals
 A subset of Hodgkin lymphoma
 Nasopharyngeal cancer
 Some gastric carcinomas and
 Rare forms of T cell lymphomas and natural killer (NK) cell lymphomas

22. Nickel- Mining and welding
Arsenic- naturally present
Asbestos- sheets, glass
Tar products – pavement and roof
Chromium- stainless steel and metal finishing
Cadmium – used to produce other metals
Vinyl chloride- vinyl products
Berrylium – aerospace compound, nuclear reactor

23.  Industrial- aromatic amines, Polyvinylchlorides,
 Atmospheric pollution-polycyclic aromatic hydrocarbons – fossil fuel
 Contaminant in drinking water- halogenated organic compound
from chlorination of water
 Food contaminant- cured tobacco, cooked/ sated meat, aflatoxin

24.  Genetic aberrations
 Genetic progression
 Genetic inheritance

25.  Susceptibility to the carcinogenic effects varies and is depends on
hereditary factor
 Certain inherited genetic polymorphisms can increase HNSCC risk
by affecting the function of:
 Carcinogen activating enzymes (i.e. cytochrome P450 group or ADH)
 Detoxifying enzymes (GSTM1 or ALDH)
 Prominent cell cycle regulators (such as cyclin D1 (CCND1), p53 and P21
(Waf1/CIP1))

29.  Many types of epigenetic modification
 Most common is the methylation of cytosine residues at so-called
CpG islands in the promoter regions of TSGs
 Results in the reduced transcription and silencing of the gene
 CDKN2A (p16INK4A) hypermethylation has been observed to be
associated with reduced overall survival

31.  90–100% of both HPV+ and HPV- HNSCC
 TP53, RB1, CDKN2A, CCND1, E2F1, MYC, HPV E6, and HPV E7

32.  Mutated in 50-60% cases ( maximum in HPV + cases)
 Blocked in cases of HPV+ by E6 protein
 Loss of function due to missense mutation
 Acts as a sequence specific DNA binding protein that controls the
transcription of many proteins (up to 1000)
 Normal circumstances under control of other genes
 MDM2, MDM4

33.  RB gene was first TSG discovered – Alfred Knudsen
 Retinoblastoma, and the two-hit hypothesis
 Regulate the G1-S phase of cell cycle
 Binding to and inhibiting the activity of a family of transcription
factors called E2Fs.
 CDKN2A- encode p14 and p16 which are having tumour suppressor
activity

34. Cyclin D1 is the protein encoded by the CCND1 gene
Amplified in H & N Ca
Loss of normal cell cycle regulation at the G1-S checkpoint
Let-7c is a microRNA (miRNA)
Regulates a number of target genes
Was associated with increased CDK6 expression,

35.  Distinguish normal from viral oncogene when discovered
 Currently believed to have role in
 Cell cycle regulation
 Cell proliferation
 Cell survival/apoptosis,
 Cancer cell metabolism
 Has effects on a huge number of genes including CCND1, TP53 and TERT
 Transcription of gene & also post transcriptional modifications

37.  Altered in approximately 60%
 PIK3CA, EGFR and PTEN (CCND1 and MYC)

38. • Epidermal growth factor receptor EGFR, a
transmembrane receptor protein that has
intracellular tyrosine kinase activity
• PIK3CA encodes the enzyme
phosphatidylinositol- 4,5-bisphosphate 3-
kinase catalytic subunit
• PTEN gene, which encodes an enzyme: the
phosphatase and tensin homolog

39.  40% and 60%
 De-differentiation and the suppression of normal differentiation are
prerequisites for immortalization.
 TP63, NOTCH and FAT1 (MYC)

40. Proliferatio
n
Differentiatio
n
WNT
Catenin

41.  30–40% of head and neck cancers
 FADD, TRAF3 and CASP8 also - TP53, MYC and PIK3CA
 FADD (fas-associated protein with death domain)- FAS and TNFR1
 CASP8 encodes the critical effector caspase 8 for the so-called
extrinsic apoptotic signalling pathway
 TRAF3 is a member of the TNF receptor associated factor (TRAF)
protein family

42.  Tumor progresses hypoxia due to poor vascularistion
 Hypoxia radio-resistance & poor prognosis.
 Regulated by the oxygen-sensitive hypoxia inducible factor 1α gene;
HIF1α
 p53 regulate expression of angiogenesis suppressor
thrombospondin 1 (THBS1) & promotes degradation of HIF1α,
 VEGF, acidic FGF and Basic FGF.

46.  1920s Otto Warburg studied the cellular metabolism of the tumor
cells
 Experiments revealed that tumour cells generate much of their
energy from fermentation (i.e. glycolysis) whereas normal cells
typically use mostly respiration
 Warburg effect- used in PET scan imaging

47.  Diagnosis
 Prognosis
 Monitoring
 Treatment

48.  Tumor specific genetic defect
 Alteration in expression of chemokine receptors-CXCR2, CXCR4
 Immunohistochemistry
 Biomarkers
 PET scan

49.  Certain genetic mutations are associated with poor prognosis
 Such as
 Sporadic P53 mutation have worse prognosis than wild type

50.  The levels of biomarkers are used in the monitoring of relapse/
response of the treatment.
 Biomarkers presence or Tumor associated protein level are used in
the monitoring
 TPA- tissue polypeptide antigen, SCCA- squamous cell carcinoma
antigen, CEA- carcinoembroyonic antigen etc
 P16, PDL1
PET scan

51.  Targeted therapy
 Gene therapy
 Vaccinations – HPV (Gerdasil and Cervarix)

52.  Monoclonal antibody
 Cetuximab- Anti EGFR monoclonal antibody
 Bevacizumab- Anti VEGF monoclonal antibody
 Rituximab- Anti CD20 monoclonal antibody


53. Drug Mechanism of action Remark
CETUXIMAB Anti EGFR chimeric monoclonal antibody
blocks the growth signal pathway
Combined therapy shown to have good
response rate 400mg/m2
1week prior to completion.
BEVACIZUMAB Anti VEGF receptor humanized IgG
monoclonal antibody that inhibits
neoangiogenesis
5-15mg/kg iv every 2 weeks
NIVOLUMAB Nivolumab is a human IgG4 monoclonal
antibody that blocks PD-1 (which blocks t
cell activation)
240 mg Iv once in 2 weeks
IPLIMUMAB Anti CTLA4 humanized monoclonal
antibody (CTLA4 inhibits T cell activation)
3 mg/kg IV q3Week for a maximum of 4
doses

54.  4 major methods of Gene therapy used for head and neck
malignancy
 Chemosensitization
 Immune modulation
 Restorative gene therapy
 Selective oncolysis

55.  Scott Brown 8th edition
 Stellan Maran
 Devita
 Ramdas Nayak – Preparatory manual for pathology

56.  Past few years have brought significant advancements in our understanding of
the biology of HNSCC
 It is expected that prognostic markers and biological therapies that are derived
from increased knowledge will lead to a significant and expanding role in the
treatment of HNSCC in the future.