WK1: Types of cancer, mutations and viral carcinogenesis

What is the definition of cancer?

an Abnormal, uncontrolled cell growth which can invade surrounding tissues and spread (metastasize) to other parts of the body.

What is metastasis?

The spread of cancer cells from the primary tumor to distant organs through the bloodstream or lymphatic system

What is the difference between benign and malignant tumors?

Benign tumors grow locally, are usually non-invasive, and are non-cancerous . Malignant tumors are invasive, poorly differentiated, and can metastasize (cancerous)

What are the four main types of cancer based on cell origin?

1. Carcinomas

2. Sarcomas

3. Lymphomas

4. Leukaemias

What are carcinomas and where do they originate?

Carcinomas occur from epithelial cells (skin, linings of organs). They make up 85% of cancers (e.g., lung, breast, colon cancer)

What are sarcomas and where do they originate?

Sarcomas arise from mesenchymal tissues (bone, cartilage, fat, muscle). They are rare (~12% of cancers) and often highly malignant

What are lymphomas and where do they originate?

Lymphomas arise from lymph nodes or immune cells (B, T, NK cells). They can spread to other lymphoid tissues, brain, or bone.

What are leukaemias and where do they originate?

Leukaemias arise from immature white blood cells in the bone marrow and flood the bloodstream

What is cancer staging and what does TNM stand for?

Staging describes the extent of cancer spread. TNM = Tumor size, Node involvement, Metastasis

What is cancer grading?

Grading describes how abnormal cancer cells look under a microscope (Grade I = well-differentiated, Grade IV = poorly differentiated).

What does Stage IV mean?

The cancer has metastasized to distant organs.

What are the three main causes of DNA mutations?

1) Mistakes in DNA replication,

2) Spontaneous chemical changes,

3) Mutagenic agents (chemical, physical, endogenous ROS).

What are ROS and how do they cause mutations?

Reactive Oxygen Species (ROS) are generated during normal metabolism and can damage DNA by causing oxidative lesions

Give examples of physical and chemical mutagens.

Physical: UV rays, X-rays. Chemical: vinyl chloride, nitrosamines (found in tobacco smoke

What is a familial cancer syndrome?

An inherited genetic defect in DNA repair or tumor suppressor genes that increases cancer risk.

Name three inherited cancer syndromes and the genes involved.

1. BRCA1/BRCA2 → breast/ovarian cancer

2. TP53 (Li-Fraumeni) → multiple cancers

3. XP (Xeroderma pigmentosum) → skin cancer from UV damage

What type of DNA repair is defective in Xeroderma pigmentosum?

Nucleotide-excision repair (NER), which fixes UV-induced DNA damage.

What are the two main types of cancer-causing viruses?

DNA viruses (e.g., HPV, EBV, HBV) and RNA viruses (e.g., HCV, HTLV-1)

How do DNA viruses cause cancer?

They integrate into the host genome and express viral oncoproteins that disrupt cell cycle control (e.g., inhibit p53 or Rb)

How do RNA viruses cause cancer?

They reverse transcribe RNA to DNA, integrate into the host genome, and may carry oncogenes or activate host growth genes

What is a direct mechanism of viral carcinogenesis?

the virus acts from within the tumor cell, driving proliferation (e.g., HPV E6/E7 proteins in cervical cancer).

What is an indirect mechanism?

the virus causes chronic inflammation or immunosuppression, promoting cancer development (e.g., HCV-induced liver cirrhosis → hepatocellular carcinoma).

Which virus causes cervical cancer?

Human Papillomavirus (HPV).

Which virus is associated with Burkitt’s lymphoma and nasopharyngeal carcinoma?

Epstein-Barr Virus (EBV).

Which virus causes adult T-cell leukemia/lymphoma?

Human T-lymphotropic virus 1 (HTLV-1).

How many mutations are typically required to cause cancer?

Between 3–20+ “driver mutations,” depending on the cancer type.

What is the sequence of changes from normal tissue to cancer?

Normal → Hyperplasia → Dysplasia → Neoplasia (benign) → Malignancy (cancer) → Metastasis.

What is the difference between hyperplasia and neoplasia?

Hyperplasia is an increase in cell number but with normal control. Neoplasia is uncontrolled, abnormal cell growth forming a tumor

What are the three main phases of carcinogenesis at the cellular level?

Initiation (DNA damage), Promotion (cell proliferation), Progression (malignancy and metastasis)

What happens during initiation?

A permanent DNA mutation occurs in a stem cell or progenitor cell, often due to a mutagen

What happens during promotion?

The initiated cell is stimulated to divide repeatedly (e.g., by hormones, inflammation), forming a benign tumor.

What happens during progression?

Accumulation of additional mutations leads to invasive and metastatic properties

What are oncogenes?

Mutated versions of normal genes (proto-oncogenes) that promote cell growth and division (e.g., RAS, MYC).

What are tumor suppressor genes?

Genes that normally inhibit cell division or promote apoptosis (e.g., p53, Rb). Loss of function leads to cancer.

What is apoptosis and why is it important in cancer?

Programmed cell death. Cancer cells often evade apoptosis, allowing them to survive and proliferate.