Pathophysiology - Biology of Cancer

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Week 1 - Biology of Cancer

What is cancer caused by?

The malfunction or mutation of genes involved in cell division and cell proliferation.

2 Mutational Routes

Stimulation and Inhibition

Stimulation

Leads to tumor formation - oncogene.

Inhibition

Causes inactivity.

Oncogene

A gene with the potential to cause cancer.

2 Properties that define Cancer Cells

Autonomy and Anaplasia

Autonomy

Cancer cells act independently from normal cell functions.

Anaplasia

Loss of differentiation. Cancer cells lose its ability to function normally, control growth, and control division.

Transformation

Process by which a normal cell becomes a cancerous cell.

Tumor Grading

Estimates differentiation of cancer cells. 4 Grades.

Grade I

Well differentiated. Tumor closely resembles the tissue of origin and retains some specialized function.

Grade II

Moderately differentiated. Tumor has less resemblance to tissue of origin. More variation in size and shape of tumor cells; increased mitoses.

Grade III

Poorly to very poorly differentiated. Tumor does not closely resemble tissue of origin. Much variation in size and shape of tumor cells; greatly increased mitoses.

Grade IV

Very poorly differentiated. Tumor has no resemblance to the tissue of origin. Great variation in size and shape of tumor cells.

Cell Differentiation

Proliferation cells are transformed into different and more specialized cell types, which determines the microscopic characteristics of the cell, function, and lifespan. Adult cell has all its specific sets of characteristics and can no longer divide.

Benign Neoplasms

Benign tumor that has lost its ability to suppress the genetic program for cell replication but retain normal cellular differentiation.

Benign Neoplasms grow by:

Expansion, not infiltration.

Benign Neoplasm Properties

Capsule is mark of demarcation. Usually do not cause death. Known to secrete abnormal hormones.

Malignant Neoplasms

Destructive tumors that grow rapidly, spread widely, and tend to cause death. Robs normal tissue from blood, nutrients, space, and release enzymes and toxins that destroy themselves and other tissues.

Destructive nature of Malignant Neoplasms due to:

Lack of cell differentiation, cell characteristics, rate of growth, and ability to spread and metastasize.

Tumors are classified on the basis of:

Tissue of origin, malignancy, degree of differentiation, and anatomic site.

Carcinomas

Cancers of epithelial tissues.

Sarcomas

Cancers of connective tissues.

Lymphomas

Cancers of lymphatic tissues.

Leukemias

Cancer of the blood-forming organs (primarily bone marrow).

Causes of Cancer

Gene-environment interaction, Inherited genes, Oncogenic viruses.

Causes of Cancer: Gene-environment Interaction

Environmental agents cause cancer by increasing frequency of mutations such as cigarette smoke, carcinogens, x-rays, and UV light.

Causes of Cancer: Inherited Genes

Certain oncogenes can be inherited such as Retinoblastoma (childhood cancer of the eye), Wilms tumor (childhood cancer of the kidney), and breast cancer.

Causes of Cancer: Oncogenic Viruses

Cancer causing viruses that cause a specific type of malignant or benign tumor in susceptible individuals. Divided into 2 groups by nucleic acid: RNA and DNA viruses.

Cancer Development Stages (3)

1. Initiation - Causes irreversible changes to DNA after exposure to a carcinogen.
2. Promotion - Initiated cells become cancerous.
3. Progression - Cells become more biologically defective.

Proliferation

Process of cell division. Adaptive mechanism for replacing body cells.

Differentiation

Process of specialization where by new cells acquire the structure and function of the ones they replace.

Doubling Time

The amount of time it takes a mass to double its cell population.

Cells That Do Not Proliferate or Divide

Well-differentiated neurons, skeletal cells, and cardiac muscle cells.

Parent Cells

Continue to divide and reproduce. (blood, skin, liver cells)

Undifferentiated Stem Cells

Cells that can enter the cell cycle and produce large numbers of parent cells when the need arises.

Metastasis

Spread of cancer cells from primary site of origin to distant site. The challenge of reducing cancer mortality is to control this.

3 Mechanisms of Metastasis

Direct or Continuous Extension
Lymphatic Spread
Bloodstream Dissemination

Continuous Extension

Metastasis in which tumors extend into several areas without breaking from the parent tumor which include tissue spaces, lymph and blood vessels, body cavities, and cerebrospinal spaces.

Lymphatic Spread

Metastasis by lymphatics involving the invasion and penetration of tumor cells into lymphatics. Tumor cells carried to the lymph nodes. Often, a mass in the region lymph node is evidence of this metastasis.

Bloodstream Dissemination

Metastasis that is complex and requires tumor cells to detach from blood vessels and spread to distant organs. Involves getting past host defenses, surviving the mechanical trauma of the bloodstream, and lodge in the vascular bed of the target organ.

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