Overview of Cancer: Videos & Practice Problems

Cancer is a disease characterized by unregulated cell division, leading to tumor formation. Tumors can be benign, remaining localized, or malignant, which invade surrounding tissues and metastasize. Major cancer types include carcinomas (epithelial cells), leukemias/lymphomas (blood and immune system), and sarcomas (connective tissue). Carcinogens, such as tobacco, contribute to cancer through DNA mutations, often involving oncogenes and tumor suppressor genes. Tumor cells exhibit genetic instability, loss of contact inhibition, and undergo angiogenesis, requiring blood supply for growth, while evading apoptosis.

Overview of Cancer

Cancer is a complex disease characterized by unregulated cell division, leading to the formation of tumors. Tumors can be classified into two main types: benign and malignant. Benign tumors remain localized and do not invade surrounding tissues, while malignant tumors can spread to distant organs through a process known as metastasis.

There are three primary categories of cancer: carcinomas, leukemias/lymphomas, and sarcomas. Carcinomas, which arise from epithelial cells, account for the majority of cancer cases. Leukemias and lymphomas are cancers of the blood and immune system, respectively, while sarcomas, which originate in connective tissues, are much rarer.

The development of cancer is influenced by various factors, including carcinogens—substances that can cause cancer, such as tobacco, which is responsible for approximately 30% of all cancer cases. Epidemiology plays a crucial role in identifying these carcinogens by studying disease patterns within populations.

Cancer typically arises from DNA mutations, which accumulate over time. This process begins with tumor initiation, where genetic alterations lead to abnormal cell proliferation. As mutations accumulate, tumor progression occurs, allowing cells to divide uncontrollably and form tumors. The mutations often affect two types of genes: oncogenes and tumor suppressor genes. Oncogenes, when mutated, promote cell growth, while tumor suppressor genes normally inhibit cell growth. When these genes are altered, it can lead to cancer development.

Cancer cells exhibit several distinct characteristics. They are genetically unstable, accumulating mutations at a rapid rate. Unlike normal cells, which stop dividing when they come into contact with other cells (a phenomenon known as contact inhibition), cancer cells continue to proliferate, leading to tumor formation. Additionally, cancer cells can induce angiogenesis, the formation of new blood vessels, to supply nutrients and oxygen to the growing tumor. They also often have defects in apoptosis, the programmed cell death process, allowing them to survive and accumulate instead of dying off.

Understanding these fundamental concepts of cancer is essential for further exploration into its causes, types, and treatment options.

Which of the following is not a characteristic of tumor cells?

• A. Undergo angiogenesis
• B. Are genetically unstable
• C. Perfectly control apoptosis
• D. Loose contact inhibition

Answer: (C)

Which of the following genes normally suppress tumor growth, but when mutated allow for tumor growth?

• A. Carcinogens
• B. Oncogene
• C. Tumor suppressors
• D. Proto-oncogenes

Answer: (C)

Here’s what students ask on this topic:

What is the difference between benign and malignant tumors?

Benign tumors are non-cancerous growths that remain confined to their original location and do not invade surrounding tissues. They are usually encapsulated, making them easier to remove surgically. Malignant tumors, on the other hand, are cancerous and can invade nearby tissues and organs. They have the ability to spread to distant parts of the body through a process called metastasis. Malignant tumors are more dangerous and challenging to treat due to their aggressive nature and potential to cause widespread damage.

What are the main types of cancer?

The main types of cancer are carcinomas, leukemias/lymphomas, and sarcomas. Carcinomas originate in epithelial cells and are the most common type, accounting for the majority of cancer cases. Leukemias are cancers of the blood, while lymphomas affect the immune system. Together, they make up about 7% of cancers. Sarcomas are rare and develop in connective tissues such as bone, muscle, and fat, comprising around 3% of all cancers. Each type has various subtypes with different characteristics and treatment approaches.

How do carcinogens cause cancer?

Carcinogens are substances that can cause cancer by inducing DNA mutations. These mutations can occur in genes that regulate cell growth and division, such as oncogenes and tumor suppressor genes. Oncogenes, when mutated, promote uncontrolled cell growth, while mutations in tumor suppressor genes impair the cell's ability to regulate division and repair DNA. Common carcinogens include tobacco, which is linked to 30% of all cancers, and other environmental factors. The study of how carcinogens affect populations is known as epidemiology.

What is the role of oncogenes and tumor suppressor genes in cancer development?

Oncogenes and tumor suppressor genes play crucial roles in cancer development. Oncogenes are mutated forms of proto-oncogenes, which normally promote cell growth and division. When mutated, oncogenes cause uncontrolled cell proliferation. Tumor suppressor genes, on the other hand, normally inhibit cell growth and promote DNA repair. When these genes are mutated, their regulatory functions are lost, leading to unchecked cell division and tumor formation. Both types of gene mutations are essential for the initiation and progression of cancer.

What are the characteristics of tumor cells?

Tumor cells exhibit several distinct characteristics: genetic instability, loss of contact inhibition, angiogenesis, and defects in apoptosis. Genetic instability leads to rapid accumulation of mutations. Loss of contact inhibition allows cells to continue dividing even when surrounded by other cells, forming tumors. Angiogenesis is the formation of new blood vessels to supply nutrients to the growing tumor. Defects in apoptosis prevent the programmed cell death that normally eliminates damaged cells, allowing cancer cells to survive and proliferate.