medical pharmacology course anti-neoplastic chemotherapy issam makhoul m.d. hematology/oncology...

Medical Pharmacology CourseAnti-Neoplastic Chemotherapy

Issam Makhoul M.D.

Hematology/Oncology Division

Internal Medicine Department

University of Arkansas for Medical Sciences

October 3, 2007

I-Biology of cancer

When “Strength is Weakness”

• Integrity and diversity of tissues can be traced to the autonomy and versatility of cells

• The same autonomy and versatility can lead to cancer by – Allowing access to information that is usually denied to the

cells– Corruption of the genetic information– This would divert the cells to acquire novel highly unusual

phenotypes that may be incompatible with the normally assigned roles of these cells in organismic structure and physiology

• Cancers are tissue growths that arise in the “wrong space and time”

Risk of cancer is low at the cellular level

• At steady state, an adult human body has more than 1013 cells

• The number of cells in average human lifetime is 1016

• The risk of having cancer is around 10% • Knowing that cancer is a clonal process, the

risk of developing cancer at the cellular level is 1/1017

Cancer is an Inefficient Process

1. Adapted from Hanahan D, et al. Cell. 2000;100:57-70.

Evadingapoptosis

Self-sufficiency in growth

signals

Tissue invasionand metastasis

Limitless replicative potential

Sustainedangiogenesis

Insensitivity to antigrowth

signals

Cancercells

Hallmarks of Cancer

Benign vs. Malignant Tumors

• Benign tumors grow locally without invading neighboring tissues or spreading metastases– Most tumors are benign– Harmless– Occasionally, might be symptomatic due to their hormonal

secretions spatial

• Malignant tumors invade locally and spawn metastases– Invasion of the basement membrane– Spreading metastases through the lymphatic and vascular

systems

Hallmarks of Cancer

• Self sufficiency in growth signals • Insensitivity to antigrowth signals • Limitless replicative potential • Evasion of programmed cell death (apoptosis) • Sustained angiogenesis • Tissue invasion and metastasis• Evasion of elimination by the immune system• Acquisition of genomic instability

Potential Consequences ofEGFR Dysregulation

Signaling cascades

EGFR

PI3K MAPK

NucleusGene activation

Cell cycle progression

M G1

SG2

MycFos

Jun

PP

MAPK = mitogen-activated protein kinase.Roskoski. Biochem Biophys Res Commun. 2004;319:1.Rowinsky. Annu Rev Med. 2004;55:433.

Survival

Proliferation

AngiogenesisInvasion

Apoptosis

Metastasis

Hallmarks of Cancer

• Self sufficiency in growth signals • Insensitivity to antigrowth signals • Limitless replicative potential • Evasion of programmed cell death (apoptosis) • Sustained angiogenesis • Tissue invasion and metastasis • Evasion of elimination by the immune system• Acquisition of genomic instability

Insensitivity to Antigrowth Signals

• Two types:– Soluble growth inhibitors (TGF-/TGF-R)– Immobilized inhibitors on extra-cellular matrix and/or

surface of nearby cells• Antigrowth signals function by one of tow

mechanisms:– By forcing the cells out of the active proliferative cycle

into G0– By inducing differentiation

• Role of c-myc– Myc-Mad differentiation– Myc-Max proliferation

Hallmarks of Cancer

• Self sufficiency in growth signals • Insensitivity to antigrowth signals • Limitless replicative potential • Evasion of programmed cell death (apoptosis) • Sustained angiogenesis • Tissue invasion and metastasis • Evasion of elimination by the immune system• Acquisition of genomic instability

Figure 10.13b The Biology of Cancer (© Garland Science 2007)

Telomeres and DNA Senescence Crisis

Consequences Of Telomere Shortening

Figure 10.14a The Biology of Cancer (© Garland Science 2007)

Telomerases are Upregulated in Cancers

• Telomerases are enzymes that counteract incomplete replication at the end of chromosomes, by lengthening telomeres

• Persistent or expression of telomerase activity immortalizes cells

Hallmarks of Cancer

• Self sufficiency in growth signals • Insensitivity to antigrowth signals • Limitless replicative potential • Evasion of programmed cell death (apoptosis) • Sustained angiogenesis • Tissue invasion and metastasis • Evasion of elimination by the immune system• Acquisition of genomic instability

Evasion of Programmed Cell Death (Apoptosis)

• Resistance to apoptosis is a common trait to cancers– Mutation of p53– PI3 kinase-AKT/PKB hyperactivation – Upregulation of decoy receptor for FAS-L– Overexpression of BCL2

Hallmarks of Cancer

• Self sufficiency in growth signals • Insensitivity to antigrowth signals • Limitless replicative potential • Evasion of programmed cell death (apoptosis) • Sustained angiogenesis • Tissue invasion and metastasis • Evasion of elimination by the immune system• Acquisition of genomic instability

The Angiogenic Switch

1-2 mm

Angiogenic

Switch

Small tumor• Nonvascular• “Dormant”

Larger tumor• Vascular• Metastatic potential

Hallmarks of Cancer

• Self sufficiency in growth signals • Insensitivity to antigrowth signals • Limitless replicative potential • Evasion of programmed cell death (apoptosis) • Sustained angiogenesis • Tissue invasion and metastasis • Evasion of elimination by the immune system• Acquisition of genomic instability

Table 14.2 The Biology of Cancer (© Garland Science 2007)

Activation of Epithelial-Mesenchymal Transition (EMT)

Table 14.3 The Biology of Cancer (© Garland Science 2007)

Transcription Factors Orchestrating the EMT

Cancers Arise From Stem Cells

• Stem cells possess:– Self-renewal capacity (immortality)– Differentiation capacity (organ repair and

replacement of lost cells)

• Cancer is a defect of stem cell control– Defect of patterning (Defect of organ

formation)– It involves both the stem cells and their stroma

II-The Cell Cycle

The Cell Cycle

• It is the ability of a cell to produce exact replicas of itself

• Cell cycle phases are:– Resting stage (G0)

– Interphase • G1=active gene expression

• S=DNA synthesis, DNA doubles 1N2N

• G2=post synthetic phase

– Mitosis phase or M-phase

III-Chemotherapy for cancer

• Genetic make up of cancers differs from their normal counterparts only by less than 0.5%

• The difference in gene expression is often quantitative rather than qualitative

• Chemotherapy cannot discriminate between normal and cancer cells (risk of toxicity)

• Cancer cells need longer time than normal cells to recover from injury induced by chemotherapy

Choice of chemotherapy

• The choice of chemotherapy depends on factors related to – A. the tumor– B. the host – C. the drugs

A. Tumor

• Organ of origin and type of cell

• Cancers are clonal processes

• Clonal evolution

• Growth fraction

• Growth rate

Tumors Keep Features of the Differentiated Tissue From Which

They Arose• Epithelia: carcinomas

– Squamous cell carcinomas– Adenocarcinomas

• Mesenchymal cells– Sarcomas

• Hematopoietic cells– Leukemias and lymphomas

• Central and peripheral NS– Neuroectodermal tumors

• Non classified– SCLC

Figure 2.17 The Biology of Cancer (© Garland Science 2007)

Exponential cell kinetic (Skipper model)

• L1210 murine leukemia• Growth rate is constant and growth fraction > 90%• Doubling time forms a straight line on a semilog

plot• The cytotoxic effects of cancer drugs in this tumor

model follow log cell-kill kinetics• The closest human tumors to this model are

trophoblastic neoplasms, germ cell tumors and Burkitt’s lymphoma

• The concept of log-cell kill is the rationale for giving multiple cycles of chemotherapy to eliminate the tumor and achieve cure.

The Gompertzian Model

• The growth fraction of the tumor is not constant • Growth rate peaks when the tumor is

approximately 37% of its maximum size • Response to chemotherapy in drug-sensitive

tumors depends on where the tumor is on its particular growth curve

• Sensitive Gompertzian-growing tumors respond to cytotoxic drugs in a Gompertzian fashion

Explanation of the Gompertzian model

• Skipper model applies only to proliferating cells • Expanding solid tumors outgrow their blood supply

leading to anoxia and slowing of the cell cycle • Certain cells exit the cell cycle into G0 or resting

phase • Resting cells become temporarily resistant to

chemotherapy (kinetic resistance to chemotherapy)

How can we increase cell cycling in a given tumor?

• Debulking surgery

Resistance to chemotherapy

• Two types: kinetic resistance and genetic resistance• Kinetic resistance, by entering G0:

– Temporary – Reversible when the cell reenters the cell cycle

• Genetic resistance, by mutation: – Malignant cells are genetically unstable– Malignant cells have higher rate of mutation than normal cells

(10-5 vs. 10-6) – Resistance to chemotherapy occurs in mutant clones: The # of

drug-resistant clones // the length of time the tumor has been present or the # of cell divisions

The Goldie-Coldman hypothesis

• Resistance to two drugs should be less likely than 1/1010

• Multi-drug chemotherapy should be more effective than single-drug therapy

Combination chemotherapy

• Drugs used in combination therapy should – Be active as single agents– Have different mechanisms of action– Have different dose-limiting toxicity – Have different patterns of resistance – Be used at their optimal doses and schedule, with

toxicity being the dose limiting factor

Mechanisms of resistance to chemotherapy

• Decreased drug transport into cells (methotrexate…) • Increased drug transport out of cells by increased

expression of MDR gene (vinca alkaloids, etoposide and anthracyclines)

• Reduced activation of drug (cytarabine, 6-MP, 6-TG, methotrexate…)

• Increased inactivation of drug or active metabolite (cytarabine…)

• Increased DNA repair (all alkylating agents, antitumor antibiotics, topo.II inhibitors)

Mechanisms of resistance to chemotherapy

• Use of alternate pathways as source of metablolites (methotrexate, 5-FU, 6-MP, 6-TG…)

• Gene amplification of enzyme target of drug action (methotrexate, 5-FU, 2-deoxycoformycin)

• Loss of apoptosis (loss of p53 or bcl2 expression in a tumor cancer cell can lead to resistance to all chemotherapeutic agents).

• Alteration of target to reduce drug binding (vinvristine, methotraxate, 5-FU, hydeoxyurea, doxo)

B. The host

• Non-selectivity of cancer drugs results in toxicity to normal tissues especially rapidly dividing cells (bone marrow, skin, GI tract and hair follicles)

• Supportive care– Recombinant growth factors (G-CSF, GM-CSF, erythropoietin)– Blood product transfusion (RBC, platelet) – The use of modern antibiotics

• Normal tissues never develop resistance• The effect of chemotherapy on normal tissue is cumulative • Most chemotherapy agents are metabolized in the liver and

excreted by the kidney

C. Drugs

• Chemotherapy agents differ in their– mechanism of action – Spectrum– dose and route of administration

• Pharmacokinetics is – the study of the drug absorption, distribution, metabolism, and

excretion

• The area under the curve (AUC) in a plot of in vivo concentration versus time IS

– The most important parameter in dose level

C. Drugs

• Pharmacodynamics – the study of dose-effect relationships or the action of the drug on

the body and includes both toxic and therapeutic effects• Chemotherapy agents show a steep dose-response curve

and modest dose reduction may lead to substantial reductions in tumor cell kill

• Chemotherapy agents have narrow therapeutic window• Increase of dose intensity by:

– Regional administration of a drug– Bone marrow rescue

IV- Antineoplastic agents

Mechanism of action• Agents that damage the DNA template by:

– Alkylation• Nitrogen mustards• Nitrosoureas • Others

– Platinum crosslinking– DNA double-strand cleavage via topoisomerase II:

• Antibiotics• Podophyllotoxins: etoposide, teniposide

– DNA single-strand cleavage via topoisomerase I: • topotecan, irinotecan

– Intercalation, blocking DNA synthesis: • dactinomycin, mithramycin

Mechanism of action

• Spindle poisons:– Vinca alkaloids: vincristine, vinblastine,

vendesine, vinorelbine – Taxanes: taxol, taxotere

Mechanism of action

• Antimetabolites (enzyme inhibitors)– Thymidylate synthase: 5-fluorouracil

– Dihydrofolate reductase: methotrexate

– DNA polymerase: cytosine arabinoside (cytarabine), fludarabine

– Ribonucleotide reductase: hydoxyurea

– Phosphoribosylpyrophosphate amidotransferase: 6-MP, 6-TG

– Adenosine deaminase: deoxycoformycin

Mechanism of action

• Hormonal and antihormonal agents:– Agonists: estrogens, androgens, progestins,

corticosteroids– Antagonists: tamoxifen, amioglutethimide,

leuprolide, flutamide– Aromatase inhibitors: anastrozole, letrozol,

examestene

Mechanism of action

• Biologic response modifiers:– Interferons, interleukins, BCG

• Differentiation agents – All trans-retinoic acid (ATRA)

• Miscellanous:– Mitotane, asparaginase, prednimustine,

estramastine

Cell Cycle Specificity

Alkylating agents:

• The most important classes of alkylating agents are – Nitrogen mustards (mechlorethamine,

cyclophosphamide, ifosfamide, melphalan, chlorambucil)

– Alkyl sulfonates (busulfan) – Nitosoureas (BCNU, CCNU, MeCCNU)

Properties

• Add functional groups (alkyl groups) to nitrogen (an SN2 reaction)

• The 7 nitrogen atom of guanine is most susceptible DNA is the most common molecule alkylated

• These agents will also alkylate proteins• Exert the most effect on proliferating cells• Alkylating agents are not cell cycle phase specific

Properties

• Chemical characteristics of alkylating agents – Mechlorethamine: the least stable, rapidly metabolized– Cyclophosphamide: inactive in its parent compound

and needs to be activated by hepatic cytochrome P 450 – Melphalan: stable – Chlorambucil: stable

Consequences of alkylation

• Alkylation of guanine causes – Mispairing: instead of G+C, G will pair with T

and point mutation will be introduced during DNA replication (G+C T+A)

– Cross-linking bifunctional alkylating agents can • Cross-link DNA and interfere with replication.

• Cause covalent linkage between proteins and DNA and thus interfere with transcription

Clinical characteristics of alkylating agents

• Clinical uses: – Hodgkin’s disease, lymphomas, multiple myeloma, carcinoma

of the breast, ovary, melanoma, peripheral stem cell mobilization

• Toxicities: – myelosuppression – hemorrhagic cystitis (cyclophophamide, probably acrolein), – sterility – secondary leukemia (5-7 years latency, mutations of 5, 7 or 8

chromosomes)

Antibiotics

• Anthracyclines (Isolated from Streptomyces peuceitus) – Daunorubicin

– Doxorubicin

– Idarubicin

– Mitoxantrone

• Bleomycin (Isolated from Streptomyces veicillus)• Dactinomycin (Isolated from Streptomyces species) • Mitomycin C (Isolated from Streptomyces caespitosus)

Mechanism of action of antibiotics

• Anthracyclines (daunorubicin, doxorubicin, idarubicin, mitoxantrone)– intercalate into DNA and prevent replication – can react with cytochrome P450 to generate free radicals,

which requires the presence of iron element

• Mitoxantrone (synthetic anthracenedione) generates fewer free radicals lower toxicity to normal tissues, especially cardiac cells.

• These molecules are cytotoxic by inducing DNA strand breaks (topoisomerase II inhibitors)

Mechanism of action of antibiotics

• Bleomycin:– It binds to iron (Fe++) and react with molecular oxygen to

cause free radical formation which induces DNA strand breaks

• Dactinomycin:– It intercalates between guanosine-cytosine pairs in DNA,

blocking transcription by DNA-dependent RNA polymerase

• Mitomycin C:– It alkylates the DNA by cross-linking DNA at the N6 position

of adenine and the N7 position of guanine

Clinical characteristics of antibiotics:

• Anthracyclines:– Clinical use: acute leukemia, lymphomas, breast

cancer, sarcomas – Toxicities: cardiotoxicity (cardiomyopathy)

myelosuppression, vesicants

• Bleomycin: – Clinical use: testicular cancer, lymphomas,

Hodgkin’s disease – Toxicities: pulmonary fibrosis

Clinical characteristics of antibiotics:

• Dactinomycine: – Clinical use: Wilm’s tumors, rhabdomyosarcoma,

Kaposi’s sarcoma, gestational choriocarcinoma, Hodgkin’s disease

– Toxicity: myelosuppression

• Mitomycin C – Clinical use: GI, head and neck, anal cancer – Toxicities: late myelosuppression

Antimetabolites

• Folic acid analogs

• Pyrimidine analogs

• Purine analogs

Mechanism of action

• These compounds substitute an enzyme substrates or cofactors and inhibit purine or pyrimidine biosynthesis.

• They are S phase specific

Methotrexate

• Structurally related to folic acid• Enters cells by using the reduced folate carrier and the folate

receptor protein• Requires polyglutamation by the enzyme folylpolyglutamate

synthase (FPGS) for its cytotoxic activity• It inhibits DHFR and thus inhibits DNA synthesis

– Inhibition of de novo thymidylate synthesis – Inhibition of de novo purine synthesis

• Incorporation of dUTP into DNA resulting in inhibition of DNA synthesis and function

Pyrimidine analogs

Mechanism of action

• They inhibit the conversion of orotic acid to uidine (UMP) resulting in impaired nucleic acid synthesis

• Can be incorporated in DNA or RNA and cause point mutations thus disrupting flow of genetic information resulting in cell death

• 5FU can also act as a substrate for thymidilate synthase (TS) and cause inhibition of thymidine synthesis

Mechanism of action

• Ara C when incorporated into DNA can interfere with DNA replication

• Gemcitabine, once phosphorylated, directly inhibits ribonucleotide reductase and inhibits do novo nucleotide production

• Gemcitabine may also be incorporated into DNA and interfere with DNA replication

Purine analogues

Purine analogues

• 6 thioguanine (6TG)

• 6-mercaptopurine (6MP)

• Fludarabine

• 2’deoxycoformycin (pentostatin)

• 2’ chlorodeoxyadenosine (2-CdA)

Mechanism of action

• 6-thioguanine (6TG) and 6-mecaptopurine (6MP) – These agents are substrates for the enzyme hypxanthine

guanine phosphoribosyl transferase and are converted to thioinosine. Thioinosine inhibits synthesis of adenine and guanine, thus interfering with DNA synthesis

– thioinosine inhibits also the initial conversion of phophoribosyl pyrophosphate + glutamine to ribosylamine-5-phosphate (rate limiting initial step in purine biosynthesis)

Mechanism of action• Fludarabine

– Fludarabine metabolites inhibit DNA polymerase, DNA primase and ribonulceotide reductase

– Is incorporated into DNA and RNA

• 2’deoxycoformycin– It inhibits adenosine deaminase leading to accumulation of intracellular

adenosine and deoxyadenosine nucleotides, which blocks DNA synthesis by inhibiting ribonucleotide reductase

• 2’ chlorodeoxyadenosine– An adenosine deaminase resistant purine analog that induces DNA

strand breaks – It also induces NAD and ATP depletion and apoptosis

Clinical characteristics of antimetabolites

• Methotrexate: – acute lymphoblastic leukemia, osteosarcoma, lymphoma,

carcinoma of the breast, ovary, bladder, head and neck, psoriasis, and rheumatoid arthritis

• 5 fluorouracil (5FU) – breast and colon cancer, esophageal cancer, squamous cell

carcinoma of the head and neck

• Cytosine arabinoside (ara C): – acute myeloid leukemia and lymphoma

• Gemcitabine: – pancreatic cancer, non-small cell lung cancer

Clinical characteristics of antimetabolites

• 6-thioguanine (6TG)/6-mecaptopurine (6MP):– acute lymphoblastic leukemia

• Fludarabine: – chronic lymphocytic leukemia, low grade lymphoma

• 2’deoxycoformycin: – hairy cell leukemia, T- and B-cell lymphomas

• 2’ chlorodeoxyadenosine: – hairy cell leukemia, chronic lymphocytic leukemia, low grade

lymphoma

Toxicities of antimetabolites

• Methotrexate- – myelosuppression, hemorrhagic cystitis

• 5 fluorouracil (5FU) – mucositis, diarrhea

• Cytosine arabinoside (ara C),– myelosuppression, cerebellar dysfunction

• Gemcitabine, – myelosuppression, flu-like syndrome

Toxicities of antimetabolites

• 6-thioguanine (6TG)/6-mecaptopurine (6MP) – Myelosuppression

• Fludarabine– myelosuppression, CD4 T cell depletion, peripheral

neuropathy

• 2’deoxycoformycin– myelosuppression

• 2’ chlorodeoxyadenosine– myelosuppression, especially thrombocytopenia