Summary of Prostate cancer
Transcript for Prostate cancer
Content Reviewers:Rishi Desai, MD, MPH, Yifan Xiao, MD, Tanner Marshall, MS, Evan Debevec-McKenney, Charles Davis, MD
Prostate cancer, usually refers to prostate adenocarcinoma, where adeno- means gland and carcinoma refers to uncontrolled growth of cells - so prostate cancer is a tumor or growth that originates in the prostate gland.
Only males are born with a prostate, so this condition only affects males and not females.
Typically, when there’s a prostate cancer it’s considered malignant, meaning that the tumor cells can metastasize, or invade and destroy surrounding tissues as well as tissues throughout the body.
The prostate is a small gland, about the size and shape of a walnut, that sits under the bladder and in front of the rectum.
The urethra which is the tube through which urine leaves the bladder, goes through the prostate before reaching the penis.
And that part of the urethra is called the prostatic urethra.
The prostate is covered by a capsule of tough connective tissue and smooth muscle.
Beneath this layer, the prostate can be divided into a few zones.
The peripheral zone, which is the outermost posterior section, is the largest of the zone and contain about 70% of the prostate’s glandular tissue.
Moving inward, the next section is the central zone which contains about 25% of the glandular tissue as well as the ejaculatory ducts that join with the prostatic urethra.
Last, is the transitional zone, which contains around 5% of the glandular tissue as well as a portion of the prostatic urethra.
The transitional zone gets its name because it contains transitional cells which are also found in the bladder.
The transitional zone undergoes hyperplasia, or an increase in the number of cells, in a large percentage of older men, and that often leads to compression of the urethra.
This is called benign prostatic hyperplasia and is often considered a normal part of aging.
At the microscopic level, each of the tiny glands that make up the prostate is surrounded by a basement membrane made largely of collagen.
Sitting within that basement membrane, is a ring of cube-shaped basal cells as well as a few neuroendocrine cells interspersed throughout.
Finally, there’s an inner ring of luminal columnar cells, which are within the lumen or center of the gland.
Luminal cells secrete substances into the prostatic fluid, that make it slightly alkaline that give it nutrients which nourish the sperm and help it survive in the acidic environment of the vagina.
During an ejaculation, sperm leave the testes, travel through the vas deferens, into the ejaculatory ducts, and travel through the prostatic urethra.
Smooth muscles in the prostate contract and push the prostatic fluid into the urethra where it joins the sperm as well as the semen which is the fluid that comes from the seminal vesicles.
The luminal cells also produce prostate specific antigen, or PSA, which helps to liquefy the gel-like semen after ejaculation, thereby freeing the sperm to swim.
The basal cells and luminal cells of the prostate rely on stimulation from androgens, or male sex hormones, for survival.
The androgens include testosterone, which is produced by the testicles, androstenedione and dehydroepiandrosterone which are produced by the adrenal glands, and dihydrotestosterone, which is made from testosterone by the prostate itself.
Without these androgens, the normal prostate cells, particularly the luminal cells, cannot survive, and undergo apoptosis or programmed cell death.
For example, if the testicles are castrated, or removed for some reason, the prostate significantly shrinks in size, largely due to death of the luminal cells.
Prostate adenocarcinoma most often results from a genetic mutation in a luminal cell, but can also be a basal cell, and it results in that cell dividing uncontrollably.
Some risk factors for a genetic mutation include old age, obesity, and a high fat-low fiber diet.
Mutations in two genes that have been linked specifically to prostate cancer are breast cancer gene 1 and breast cancer gene 2, also known as BRCA1 and BRCA2 - both of which also cause breast cancer.