Term
| Which genes regulate apoptosis? |
|
Definition
| bcl-2 and bcl-xL inhibit apoptosis; bwx, bnd and bcl-xS favour apoptosis. Some B cell lymphomas overexpress bcl-2= reduced cell death. |
|
|
Term
| What happens if DNA repair genes are disabled? |
|
Definition
| Predisposes to mutations in oncogenes, tumour suppressor genes and apoptosis regulating genes. Both alleles must be inactivated. |
|
|
Term
| What conditions may arise due to dysfunctional DNA repair genes? |
|
Definition
1) Hereditary non-polyposis colon cancer (HNPCC)
2) Xeroderma pigmentosum
3) Ataxia telangiectasia
4) Fanconi's anaemia. |
|
|
Term
| What is the additional function of p53 (tumour suppressor gene) and c-myc (oncogene)? |
|
Definition
|
|
Term
| What is the latent period? |
|
Definition
| Interval between the application of a known carcinogen and the detection of a tumour. |
|
|
Term
| What happens in initiation? |
|
Definition
| An event inducing a lesion in the cell genome bestowing neoplastic potential (transformation). |
|
|
Term
| What happens in promotion? |
|
Definition
| An event stimulating clonal proliferation of initiated transformed cell. |
|
|
Term
| What is the difference between direct carcinogens and procarcinogens? |
|
Definition
| Procarcinogens require metabolic conversion to ultimate carcinogens. |
|
|
Term
| How do chemical carcinogens act? |
|
Definition
| Interaction with DNA- DNA damage- DNA repair- Error prone repair- Viable mutation- Procarcinogenic lesion. |
|
|
Term
| What enzyme is used to convert polycyclic aromatic hydrocarbons into their active form and where do they produce their effects? |
|
Definition
| Mixed function oxidases (cytochrome P450). Since these enzymes are ubiquitous they have an effect at the site of contact but also at more remote sites if absorbed (cigarette smokers). |
|
|
Term
| How do aromatic amines and azodyes produce a carcinogenic effect? |
|
Definition
| They are hydroxylated and conjugated to glucoronic acid in the liver and deconjugated in the urinary tract: bladder cancer (2-naphthylamine). |
|
|
Term
| How can dietary nitrites/ nitrates lead to GI tract cancers? |
|
Definition
| They are metabolised by gut commensual bacteria to form nitrosamines which are potent carcinogens. |
|
|
Term
| How do viral early genes cause cancer? |
|
Definition
| They encode transforming proteins which bind to growth-regulating proteins. |
|
|
Term
| What Herpes viruses can cause cancers? |
|
Definition
1) Epstein Barr virus: Burkitt's lymphoma, nasopharyngeal carcinoma
2) Human herpes virus 8: Kaposi's sarcoma. |
|
|
Term
| What Papova viruses can cause cancers? |
|
Definition
| Human papilloma virus (HPV): warts and cervical cancer. |
|
|
Term
| What Hepadna viruses can cause cancers? |
|
Definition
| Hep. B: Hepatocellular carcinoma. |
|
|
Term
| What is the difference between fast transforming and slow transforming retroviruses? |
|
Definition
| FT carry v-onc into the cell and integrate it into the genome. ST integrate a DNA copy of the viral genome into the host genome near an oncogene and tumour suppressor gene. |
|
|
Term
| How does HTLV-1 cause leukaemia/ lymphoma? |
|
Definition
| It integrates the Tax gene into CD4+ T cells which turns on genes encoding IL2 which leads to proliferation. |
|
|
Term
| How is HTLV-1 transmitted? |
|
Definition
| Sexual intercourse, blood products or breast feeding. |
|
|
