Oncopathophysiology

1. Oncopathophysiology Tornóci László Semmelweis University Institute of Pathophysiology

2. A few risk factors of malignant tumors • smoking • diet • viruses • hormones • irradiation • environmental pollution

3. Malignant tumorsare monoclonal Virtually all malignant tumors are of monoclonal origin. All descendants of a single cell are called a clone in cellular biology. Members of a clone are genetically identical in theory. First proof: CML G6PD, Fialkow

4. Consequences of clonality#1 Exponential cell growth

5. Consequences of clonality#2 Exponential cell growth

6. Heterogeneity The mutation rate of malignant tumors is higher than that of the healthy tissues.The original clone will give rise tosubclonesbecause of this (heterogeneity). • Why do some cancers appear to ‘accelerate’? • Why are the therapeutical results better: • with cases that have been diagnosed early? • after the first use of a chemotherapeutical drug,than aftersubsequent uses?

7. The malignant transformation The malignant transformationis not a single step, but it is believed to bea result of 5-10 subsequent somatic mutations (accumulating in the same cell).This is the so called multi-step theory. • This is why: • tumors are seen more frequently with age • there are inherited malignant tumor syndromes • (e.g. Li-Fraumeni sy: p53 mutation)

8. Development of colon cc. CGAP: Cancer Genome Anatomy Project

9. Genes affected by the malignant transformation proto-oncogenes tumor suppressor genes genes correcting DNA genes controlling apoptosis

10. Mechanisms of the genetical changes • pointmutation (eg. ras proto-oncogene) • gene amplification (eg. ERBB2 in breast cancer, resistance to drugs) • chromosomal aberrations (eg. reciprocal translocation, Ph chromosome) • epigenetic mechanisms

11. The Philadelphia chromosome

12. The Philadelphia chromosome Genes affected by the reciprocal translocation: ABL (9q34.1) Abelson leukemia proto-oncogene BCR (22q11) breakpoint cluster region The result is a new, abnormal, fusion gene on chromosome 9,which is translated into a protein that has tyrosine kinaseenzyme activity. This is specificallyinhibited by the drug called Gleevec.Very good results have been achieved in CML and some other malignancies using this novel drug.

13. Epigenetic mechanisms A gene control mechanism which is not coded in the DNA sequence. Such is eg. parental imprinting (gene expression depending on the parent’s sex). The mechanism of imprinting is selective methylation of genes. (Methylated genes are not expressed.) Most malignant tumors seem to have less methylated genes, than healthy cells.

14. A few important tumor suppressor genes • p53, p21, Rb • HNPCC • BRCA1, BRCA2

15. Function of p53 gene

16. Function of p53 WAF1: wild type p53-activated fragment 1 Cip1: cdk-interacting protein 1 sdi1: senescent cell derived inhibitor 1 cdk: cyclin dependent kinase cyc: cyclin

17. Function of the Rb gene Cell cycle continues in the presence of phosphorylated (inactive) pRb; however, if pRb is not phosphorylated, then the cell cycle stops because of binding the transcription factors

18. HNPCC HNPCC: Hereditary nonpolyposis colon cancer • Incidence cca. 1:200 • It is present in 15% of colon cancers • Risk of developing colon, ovarian, uterine and kidney • tumors • It is analogous with MutS/MutL gene of yeast

19. BRCA1 • Incidencecca. 1:200 • In a family with breast cancer cases a BRCA1 positive woman has an 85% lifetime chance to develop breast or ovarian cancer • Prophylactic bilateral mastectomyis advised

20. Problems with genetic tests • What to do if the test is positive? • A negativeresult cannot ensure that the person tested will not get cancer. • The most important privacy issue of the future: how our tissues will be handled? (Our geneticcode is our own secret: the employer, the insurance company must not learn it!)

21. surgery chemotherapy irradiation gene therapy inhibition of angiogenesis immunotherapy Therapeutical approaches Classicmethods Newmethods

22. Examples of using gene therapy to treat malignant tumors • reintroduce the normal copy of an inactivated tumor suppressor gene (would need 100% efficacy) • introduce genes coding for antigenes, cytokinesto enhance the immune response • Introduce a gene causing toxicity (thymidine kinase gene + gancyclovir treatment) • artificial viruses (cytopathogenic adenovirus, that can infect only cells deficient of p53)

23. Angiogenesis #1 • Tumors can grow to a maximum size of 1 mm without their own blood supply (in situ carcinoma) • Tumorsspend a significant amount of time in the „in situ” stage, before they become angiogenetic, this is when they start growing • Metastasis is angiogenesis dependent (it is both needed for leaving the primary tumor and for the growth of the metastasis)

24. VEGF (vascular endothelial growth factor) FGFs(fibroblast growth factors) angiopoietins thrombospondin-1 (induced by p53) angiostatin endostatin Angiogenesis #2 Several tumorsproduce materials stimulating or inhibiting angiogenesis. The primary tumor can inhibit the growth of metastases or the growth of other tumors. Endogenous promoters Endogenous inhibitors

25. Inhibition of angiogenesis • Methods/drugs: • endogenous inhibitors • gene therapy • drugs (eg. thalidomid=Contergan) Even leukemiaswere proved to be angiogenesis dependent! (Increased microvascularizationis seen in the bone marrow.) Vascular endothelial cells are said genetically stable,soresistance is not likely to develop against the inhibitors of angiogenesis.

26. Targeted inhibition of angiogenesis using nanoparticles nanoparticles tumor endothelium ag-inhibiting gene target-recognizing molecules integrins