Cancer is an abnormal growth of cells which tend to proliferate in an uncontrolled way and, in some cases, to metastasize(spread).

1. Strategies To Combat Drug
Resistance In Anticancer
Therapy
• Presented By:
• Gandham Malasree
• M Pharmacy
• Regd no: 620209502002
• Dept of Pharmaceutical Chemistry
AU COLLEGE OF PHARMACEUTICAL SCIENCES, VISAKHAPATNAM

2. CONTENT
• Introduction
• Type of tumors
• Treatment for cancer
• Goal of treatment
• Problems associated with chemotherapy
• Need for studying anticancer drug resistance
• Anticancer agent resistance
• Test to determine resistance
• Conclusion

3. INTRODUCTION
•DEFINITION: Cancer is an abnormal growth of cells which tend to proliferate in
an uncontrolled way and, in some cases, to metastasize(spread).
•The medical term for tumor(or) cancer is Neoplasm, which means a relatively
autonomous growth (or) uncoordinated cell proliferation of body tissue.

4. TYPES OF TUMORS
• Not all tumors are cancerous; tumors are of 2 types
• –benign
• - malignant
• Benign tumors: are non cancerous growth in the body. Unlike
cancerous cells they do not spread (metastasize) to other parts of the
body.
• Malignant tumors: are cancer cells, cells in this tumors can damage
nearby cells of tissue and spread to other parts of the body. The
spread of cancer from one part of the body to another is called
metastasis.

5. TREATMENT OF CANCER
• CHEMOTHERAPY – rapidly dividing cell metastasised cancers(promising
therapy)
• RADIOTHERAPY – in combination with other therapies iodine-131
( thyroid cancer)
• SURGERY
• IMMUNOTHERAPY- immune system made stronge to fight with cancer
• HORMONE THERAPY- altering hormone level and killing cancer cells
• GENE THERAPY – replacing defective genes

6. The purposes of these therapies include
• The kinases inhibition that involved in the cell proliferation,
• Improving the rapid immune responses in cancer,
• Specializing the medications,
• Drug delivery into cancer cells and
• Reducing the side effects of anticancer drugs, etc.

7. A true cure requires the eradication of every
neoplastic cell.
Control of the disease, to extend survival
and maintain the best quality of life.
Individual maintains a “near - normal”
existence of life
GOAL OF TREATMENT

8. Problems associated with chemotherapy
Cancer drugs are:
•Anticancer agents are nothing but toxins which are used to kill the cancer
cells and therefore, not surprising that all cells including cancer cells have an in
build defence mechanism how’s ultimate goal is to protect them self from
toxins.
•This lead to produce resistance for anticancer agents which are used to treat
the cancer disease.

9. Needs of studing mechanisms of resistance for anticancer
agents:
Cancer is the 2nd leading cause of death in world, so it’s important to study the cause,
factors, treatment and also its treatment resistance.
So that we can overcome all the drawbacks and get an effective solution to cure the
same.
So, to study the resistance mechanisms of anticancer agent is important , this will help us
to proceed with rational treatment for cancer with excluding the maximum chances of
treatment failure of the same.

10. NEED
Rationale therapy
Development of new
drug
Overcome from
drawback

11. RESISTANCE
• Resistance is the reduction in effectiveness of medication due to different
means of mechanisms
• The development of drug resistance is minimized by short-term,
intensive, intermittent therapy with combinations of drugs.
• Drug combinations are also effective against a broader range of resistant
cells in the tumor population.

12. Mechanism of drug resistance

13. ANTI-CANCER DRUG RESISTANCE
• Anticancer drugs resistance is a complex process that arises from altering in the
drug targets.
• Advances in the DNA microarray, proteomics technology and the development
of targeted therapies provide the new strategies to overcome the drug resistance.
• Although a design of the new chemotherapy agents is growing quickly, effective
chemotherapy agent has not been discovered against the advanced stage of
cancer (such as invasion and metastasis).
• The cancer cell resistance against the anticancer agents can be due to many
factors such as the individual’s genetic differences, especially in tumoral somatic
cells.

14. • Also, the cancer drug resistance is acquired, the drug resistance can be occurred by
different mechanisms, including multi-drug resistance, cell death inhibiting (apoptosis
suppression), altering in the drug metabolism, epigenetic and drug targets, enhancing
DNA repair and gene amplification.
• Drug resistance is a well-known phenomenon that results when diseases become
tolerant to pharmaceutical treatments. This concept was first considered when
bacteria became resistant to certain antibiotics, but since then similar mechanisms
have been found to occur in other diseases, including cancer.
• Some methods of drug resistance are disease specific, while others, such as drug
efflux, which is observed in microbes and human drug resistant cancers, are
evolutionarily conserved.

16. 1. DRUG INACTIVATION
• Drug activation is in-vivo process where the agent interact with different kind of
proteins, this interaction lead to modification, degradation or complex formation with
protein or different molecule which lead to activation of this agents.
• This anticancer agent may go metabolic activation which result to acquire clinical
efficiency. But cancer cells produce resistance to this mechanisms which lead to decrease
in activation of this agent.
• Example of this is acute myelogenous leukemia with cytarabine (AraC), this drug is
activated after multiple phosphorylation which result to AraC-triphosphate, down
regulation or mutation lead to decrease in the activation of AraC in this pathway, which
lead to produce AraC resistance.
• The another example which can be include is cytochrome P450 (CYP450), glutathione-
Stransferase(GST) superfamily. The cytochrome system is been classified into two class.

17. • Class 1 include CYP1A1, CYP1A2 , CYP2E1, and CYP3A4, which are well conserved,
functional polymorphisms is not important, and are active in the metabolism of drugs
and procarcinogens.
• Class II is composed of CYP2B6, CYP2C9, CYP2C19, and CYP2D6, which are highly
polymorphic and active in drug metabolism.
• Class II drugs are more viable then class I drugs because of that the CYP are more
suitable in drug metabolism because of that it is more affective towards anticancer drug
resistance.
• In liver , the CYP1A1 and CYP1A2 from class I do metabolism of procarcinogens to
carcinogens which is responsible for many anticancer drug metabolisms, CYP
polymorphism is not associated with carcinogens then to might be it’s mutation can
affect the drug metabolisms like increasing the degradation and excretion of the drug by
kidney, which lead to that, that the drug is not able to maintain the proper level in the
body and therefore the cancer is been considered to resistance to it.

18. • In liver , the CYP1A1 and CYP1A2 from class I do metabolism of procarcinogens to
carcinogens which is responsible for many anticancer drug metabolisms, CYP
polymorphism is not associated with carcinogens then to might be it’s mutation can
affect the drug metabolisms like increasing the degradation and excretion of the drug by
kidney, which lead to that, that the drug is not able to maintain the proper level in the
body and therefore the cancer is been considered to resistance to it.

20. 2. ALTERATION OF DRUG TARGET
• The molecular target is most important factor for determining the efficiency of the
drugs , while the alteration of this targets by modification or mutation leads to failure of
the treatment by anticancer agents. In cancer this type of alteration can be cause of drug
resistance.
• Example : anticancer drugs that target enzyme known as topoisomerase II, this enzyme
is responsible in prevention of cancer cell DNA super coiling or under coiling, but the
anticancer agents stabilize it lead to inhibition or damage of DNA or stopping of
mitotic process of the cells.
• The cancer cells can produce drug resistance because of this circumstances: Mutation
of topoisomerase II lead to resistance of anticancer agents and inhibition of the same
due to mutation of the topoisomerase II. • For example, the treatment of breast cancer
tumours with Herceptin.

21. • For example, the treatment of breast cancer tumours with Herceptin.

22. 3. EFFLUX PUMP
• Drug efflux pump is one of the most important and well studied mechanism of drug
resistance where the cancer cells do not let the drug to accumulate in the cell at desire
concentration to its effect which lead to failure of the therapy.
• The ATP- binding casscette protein transporter (ABC) is responsible for the efflux of
the drugs and is well known studied regulated in human plasma membrane of healthy
cells.
• ABC transporters are transmembrane protein which is present in healthy cells as well in
large extend of cancer cells who’s mechanism is to transport different type of substance
to cross cellular regions.
• This transporters structure varies from protein to protein and can exit in different
count in different species ( eg : human has 49 transporters of ABC family), this
transporters are of 2 type based on distinct domain –
1. Highly conserved nucleotide binding domain and
2. Transmembrane domain

23. • This transporters are mainly substrate specific and able to efflux many drugs including
vinca alkaloids, epipodophyllotoxins, anthracyclines, taxanes, and kinase inhibitors out
of the cells.
• And thus protect cancer cells and inhibit many first line therapy and produce
anticancer resistance the MDR1 which produce Pgp is the very first efflux pump
transporter which produce anticancer agent resistance was been determined.
• This is been largly extended in colon , kidney and liver when this tissue become
cancerous then MDR1 level increase which try to make failure of the treatment.
• Tissues which are not associated with it that is lung, breast and prostate have
produced drug resistance due to MRP 1 and BCRP. BCRP protect normal cells from
the toxine like xenobiotics and also maintain level of heme and folate which is
expressed in stem cells.

24. • One of the example is estradiol used in the treatment of breast cancer.
• It is the most effective drug that can be used in breast cancer but have been resist due to
efflux pump mechanism of cancer cells.

25. 4. DNA DAMAGE REPAIR
• The DNA damage repair mechanism has the vital role in anticancer resistance. As the
cell nature or mechanism of the damage DNA repair lead to produce drug resistance
effect on chemotherapy , and the damage DNA repair mechanism of the cell can reverse
the damage produce by the drug to the cancer cells in chemotherapy and lead to produce
its resistance.
• Example : platinum containing chemotherapeutic agents like cisplatin, cause harmful
DNA cross linked which lead to apoptosis. And resistance of this can arise due to
nucleotide homologous recombination , this lead to repair the primary damage of DNA
and lead to failure of the treatment of the anticancer drugs which lead to produce drug
resistance and inhibit the response of the anticancer agents.
• Increase DNA repair activity lead to increase resistance , this provide the opportunities
to chemotherapy:

26. • 1. Targeting the overactive damage DNA repair pathway with chemotherapeutic drugs.
• 2. Another is the knowledge of the dysfunctional damage DNA repair could allow
proper prescription of a DNA-damage causing drug, which induces damage only
repaired by the defective pathway.
• In both the cases, it is essential to identify the over-active and under-active DDR
mechanisms.

28. 5. CELL DEATH INHIBITION
• The cell death is mainly done by two mechanism i.e. apoptosis and autophagy
regulatory events. While they both are acting antagonistic to each other but they both
act in cell death mechanisms.
• The apoptosis is consists of 2 distinct pathway:
1. An intrinsic pathway which is associated with the mitochondria Beta cell lymphoma
2 (BCL2) , cascade 9.
2. The extrinsic pathway where the death receptors are involved on the surface of the
cell
• Both the intrinsic and extrinsic pathways get activated when there is the increase in the
level of the cascade 3 which ultimately lead to apoptosis of the cell and do cell death.

29. • In several types of cancers, BCL-2 family proteins, Akt, and other antiapototic proteins
are highly expressed and decrease transcription modulators and are highly active, making
these good targets for drug development.
• Example: flurouracil in combination with chlorouracil has greater effect for cell death
mechanism which is been inhibited by this cell death inhibition mechanism.

31. 6. EPITHELIAL-MESENCHYMAL TRANSITION AND
METASTASIS
• The epithelial to mesenchymal transition (EMT) is a mechanism by which solid
tumors become metastatic. Metastasis itself is a complex phenomenon that includes
changes in a cancer cell and the stromal cells that make up its environment.
• During EMT, cells within a tumor reduce the expression of cell adhesion receptors,
including integrins and cadherins, which help in cell-cell attachment, and increase the
expression of cell adhesion receptors that induce cell motility.
• Cell motility is also dependent on cytokines and chemokines, which may be released
by cells in the microenvironment of tumors or by the tumors themselves.
Additionally, higher expression of metalloproteases on the surface of tumors helps to
clear the road for the cells to move outward, promoting metastasis.
• The role of EMT in cancer drug resistance is an emerging area of research.

32. • Death of these cancer progenitor cells via epigenetic drug treatment may be one way
to prevent remote site metastasis.
• Several factors during EMT play significant roles in the development of drug
resistance, but these are dependent on the metastatic grade of the tumor, which is
defined as the level of differentiation and degree of EMT.
• For example, in ERBB2 (HER2) positive breast cancer, tumors that express high levels
of β1 integrins develop more resistance to antibody inhibitors such as transtuzumab.
• Drug resistance in cancer cells may also develop during the signaling processes of
differentiation, which are essential for EMT.
• For example, the increased expression of integrin αvβ1 in colon cancer positively
regulates transforming growth factor β (TGFβ) expression, which is required for EMT,
and it further serves as a survival signal for cancer cells against drugs.
• Integrin αvβ1 interacts with stromal cell adhesion molecules to convey such signals .

33. • The role of stromal cells in causing drug resistance has also been investigated. B-Raf is
an intermediate kinase in the down-stream signaling pathway initiated by receptor
tyrosine kinases.
• Resistance against B-Raf inhibitor drugs was observed in melanoma cells when they
were co-cultured with fibroblast cells , indicating that stromal cells may influence the
development of drug resistance.
• This is one reason why so many drugs fail clinical trials in in vivo animal models despite
high efficacy against cancer in cell cultures.
• EMT and cancer metastasis involve numerous variables.
• Metastatic cancer cells are often a heterogeneous population, in which cell
differentiation is not uniform.
• This difference is one of the reasons why some patients are more responsive to
treatments than the other.

34. • It appears that EMT, while favoring the formation of more metastatic cancer cells,
also provide signals for increasing survival which may cause drug resistance in some
if not all the cells present in a tumor.
• Since this is a very complex and dynamic mechanism, thorough investigation is
necessary to fully understand each step in the regulation of drug action and thus,
drug resistance.

36. 7.ROLE OF EPIGENETICS IN CANCER DRUG RESISTANCE
• Important set of mechanisms that cause resistance to cancer and which can also do
influence carcinogenesis.
• Certain circumstances in life can cause genes to be silenced or expressed over time. In
other words, they can be turned off (becoming dormant) or turned on (becoming
active).
• The two main types of epigenetic changes are
1. DNA methylation
2. Histone modification via acetylation or methylation
 DNA methylation consists of methyl groups binding to cytosines at CG-
dinucleotides within regions known as CpG islands, primarily found in upstream gene
promoter regions.

37. • However, methylation can occur at other locations also throughout the genome.
• Conversely, histone modifications alter chromatin conformation. For example, histone
acetylation opens the chromatin, while deacetylation closes it.
• These mechanisms ultimately regulate the expression of genes throughout the
chromosome, and in cancer, this normal regulation is broken.
• For example, tumor suppressor genes are often silenced via hypermethylation, and
oncogenes are over-expressed from hypomethylation. However, epigenetic mechanisms
are usually reversible, and researchers may be able to take advantage of this opportunity
to develop treatments that can counteract drug resistant cancers.
• Methylation at the cell promoter controls MDR1 transcription, increases drug
resistance, and decreases drug accumulation, making it an excellent target for epigenetic
treatment. Specifically, anti-methylation drugs might be useful in sensitizing multidrug
resistant cancer cells to other types of drugs.
• Example :treated with nontoxic doses of the demethylating agent 2-deoxy-5-azacytidine
(DAC).

38. CANCER CELL HETEROGENEITY
• We have seen several mechanisms by which the cancer cells produce resistance to the
anticancer cells. But here , in this mechanism the cancer cells do increase in growth of
already resistant cancer cells towards anticancer agents.
• Recent studies has finding that the heterogeneous cancer cells has the stem cell
properties with which it started producing cells which are having born anticancer
resistance property.
• The anticancer agents are build to treat or fight with cancer cells which are sensitive to
them, but this heterogeneity in cancer cells lead to produce cells which are not sensitive
to anticacner treatment, this lead to expand of cancer in the patient, with the failure of
the treatment.
• Many of this cells are present in the circulation system of patient which may also lead
to develop cancer in other distinct organs.

39. • Example: study on acute myeloid leukemia determined two co-existing dominant
clones. One was the drug sensitive and the other drug resistant. It is possible that re-
occurrence of this disease in patients after successful therapy may be the result of cancer
cell growth from the drug resistant clone .
• Example : Taxanes and platinum compound used in cancer treatment.

41. MULTIDRUG RESISTANCE
• This resistance is due to adenosine triphosphate– dependent pumping of drugs out of
the cell in the presence of Pglycoprotein.
• For example, cells that are resistant to the cytotoxic effects of the Vinca alkaloids are
also resistant to dactinomycin and to the anthracycline antibiotics, as well as to colchicine,
and vice versa.
• These drugs are all naturally occurring substances, each of which has a hydrophobic
aromatic ring and a positive charge at neutral pH.
• Certain drugs at high concentrations (for example, verapamil) can inhibit the pump and,
thus, interfere with the efflux of the anticancer agent. However, these drugs are
undesirable because of adverse pharmacologic actions of their own.

42. DRUG RESISTANCE TESTING
• Not all patients are necessarily resistant to CTX. Some tumors may be highly resistant to
most cytotoxic drugs, while others may be quite sensitive. Therefore, it would be useful to
have some tests, which could predict resistance and subsequent clinical failure.
• This would spare patients from the trauma of ineffective CTX.
• A company called IMPATH (Los Angeles, Calif., USA) has developed a cell culture drug
resistance assay, which they claim can help in the selection of chemotherapeutic agents
that have the greatest likelihood of being clinically effective.
• Their method essentially measures 3H-thymidine uptake into cultured tumour cells,
taken from fresh biopsy specimens, in the presence of various drugs; an algorithm applied
to the data is used to determine the probability that a patient will respond to the various
therapies tested in the assay.
• Kern and Weisenthal reported that this assay used in clinical trials was highly accurate in
demonstrating that cells extremely resistant in vitro were also resistant in vivo. The
usefulness of such in vitro testing however remains a controversial matter.

43.  Therefore, such treatment regimens should be considered and developed to counteract
the increasing prevalence of drug resistance in cancers.
 Cancer progenitor cells are often drug resistant as well.
 These progenitor cells can persist in patients seemingly in remission, and they are able
to remain stationary or migrate to other sites during metastasis.
 Thus, cancer progenitor cells can cause cancer relapse at the original tumor site or in
distant organs.
 The next step in anticancer therapy development should target the elimination of such
cancer progenitor cells.
 Additionally, the existence of a small population of drug resistant cancer cells poses
another complexity that is difficult to address
CONCLUSIONS