Chapter 26-Cancer Cells

What is cancer?

Cancer is a disease that arises from abnormalities of cell function.

What role do gene mutations play in cancer?

Gene mutations and changes in gene expression play a central role in cancer.

Which type of cancer accounts for about 90% of all cases?

Carcinomas arise from epithelial cells covering external and internal body surfaces.

What are sarcomas?

Sarcomas develop from supporting tissues, such as bone, cartilage, fat, and muscle.

How do lymphomas and leukemias differ?

Lymphomas are solid masses, while leukemias proliferate mainly in the bloodstream.

What is a tumor?

A tumor (or neoplasm) is a mass of tissue resulting from uncontrolled cell division.

What is cell differentiation?

Cell differentiation is the process by which cells acquire specialized properties.

How do skin cells replace aging cells?

New cells are generated by divisions in the basal layer of the skin.

What happens during the disruption of balance in cell function?

In tumors, cell division is uncoupled from cell differentiation and death.

What characterizes benign tumors?

Benign tumors grow in a confined local area and are rarely dangerous.

What is the main difference between malignant tumors and benign tumors?

Malignant tumors are capable of invading surrounding tissues and spreading.

What is anchorage-independent growth in cancer cells?

Cancer cells grow well not only when anchored but also when suspended in liquid or semisolid medium.

How do normal cells respond to density-dependent inhibition of growth?

Normal cells stop dividing when they form a monolayer in culture.

What characteristic do cancer cells exhibit with respect to density-dependent inhibition?

Cancer cells continue to divide and pile up upon one another.

What is telomere length, and why is it important for cancer cells?

Cancer cells maintain telomere length to continue dividing indefinitely.

What happens to telomeres during normal cell division?

Telomere DNA sequences are lost from the ends of chromosomes with each division.

What enzyme do most cancer cells produce to maintain telomere length?

Telomerase is the enzyme that adds telomere sequences to the ends of DNA molecules.

What triggers a halt to the normal cell cycle?

Normal cells stop dividing at the restriction point under suboptimal conditions.

What is apoptosis?

Apoptosis is the programmed cell death that cancer cells often evade.

How do cancer cells change during the initiation stage of development?

Normal cells are converted into a precancerous state during the initiation stage.

What role do promoting agents play in cancer?

Promoting agents stimulate cell proliferation in already initiated cells.

What hypothesis explains the enhanced ability of certain tumor cells to spread?

The 'seed and soil' hypothesis suggests that cancer cells thrive in specific microenvironments.

What role does angiogenesis play in tumor growth?

Angiogenesis is necessary for tumors to grow larger than a few millimeters.

What are the main angiogenesis-activating molecules?

Vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF).

What happens when angiogenesis inhibitors are reduced?

There is an increase in angiogenesis, allowing tumors to grow more effectively.

What are the two types of metastasis described?

Invasion is direct penetration into nearby tissues, while metastasis involves spreading through the bloodstream.

How do cancer cells promote their own metastasis?

By producing proteases that degrade barriers to their movement.

What happens to most cancer cells that enter the bloodstream?

Few survive the hostile environment of the bloodstream to form secondary tumors.

What is the impact of local microenvironments on metastasis?

Certain microenvironments foster better growth for cancer cells, affecting their metastatic potential.

What is the main cause of increased cancer rates in transplant patients?

Transplant patients on immunosuppressive drugs have a higher incidence of cancers.

How do some cancers evade the immune system?

By expressing different antigens or producing molecules that inhibit T lymphocytes.

What role do extracellular matrix components play in cancer?

They create barriers that cancer cells must overcome to invade and metastasize.

How does the immune system generally protect against cancer?

Through immune surveillance that detects and destroys cancer cells.

What factor may contribute to cancer cells forming in the lungs more than other organs?

The first capillary bed cancer cells encounter is often in the lungs.

Why do certain cancer cells grow better at specific sites?

Interactions with local cells may provide growth factors that support tumor growth.

What is the relationship between normal cell response and cancer cell behavior at the restriction point?

Normal cells stop dividing at the restriction point, while cancer cells do not respond appropriately.

What defines the restriction point in the cell cycle?

It's the control point that determines progression from G1 phase into S phase.

How can the tumor microenvironment influence cancer progression?

It can facilitate or inhibit tumor cell behavior, affecting growth and metastasis.

What is the significance of restoring E-cadherin in cancer cells?

Restoring E-cadherin can inhibit the formation of invasive tumors.

What is intratumor heterogeneity?

The mixture of genetically distinct cell populations within a single tumor.

In the process of tumor progression, what happens under selection pressure?

Cells that exhibit enhanced growth or invasive properties are favored.

How does the immune system's response change as a tumor grows?

Selection for tumor cells that elicit weaker immune responses can occur.

What is the significance of the 1971 study by Judah Folkman?

He suggested that tumors release signaling molecules that trigger angiogenesis.

How does tumor angiogenesis occur?

Tumor cells release activating molecules like VEGF, promoting new blood vessel formation.

What is the impact of increased angiogenesis activators on cancer?

It facilitates tumor growth by providing necessary nutrients and oxygen.

Why are mechanisms of apoptosis critical in cancer therapy?

Cancer cells often evade programmed cell death, leading to uncontrolled growth.

What do mutant mice with no immune response indicate about cancer susceptibility?

They have increased cancer rates, suggesting immune surveillance is crucial.

What type of cancers do AIDS patients show increased rates of?

They show increased rates of specific virus-induced cancers.

What is demonstrated by injecting melanoma cells into healthy mice?

It shows that certain cancer cells can metastasize more effectively.

How do immune molecules challenge cancer progression?

Some cancers produce molecules that can kill or inhibit immune cells like T lymphocytes.

What two processes are crucial in cancer cell invasion?

Increased motility and the degradation of barriers through protease production.

Why is understanding the stages of cancer development vital for treatment?

It helps identify potential intervention points in the multistep process of cancer development.

What characterizes the process of tumor initiation?

Transition of normal cells to a precancerous state through DNA damage.

What experimental evidence supports the stages of initiation and promotion in cancer development?

Mice treated with DMBA and then irritated with croton oil developed tumors, indicating a two-step process.