Research Thesis Assignment

Biol 491 Senior Seminar

Carmen Major

September 17, 2020

Prostate Cancer in African American Men Is Associated with Downregulation of Zinc Transporters

In the United States, African American men have a 35% higher incidence rate and a 223% higher mortality rate due to prostate cancer when compared to other racial groups. This is due to downregulation of zinc transporters and the loss of the ability to retain normal intracellular levels of zinc. Africa is a mineral-rich continent and the levels of zinc are very high. It was hypothesized that Africans may have genetically decreased the quantity of zinc absorption capacity so they would not absorb abnormal amounts of zinc. Zinc is an essential nutrient to all organisms because it is a required catalytic cofactor of zinc dependent enzymes. Absorbing abnormal amounts of zinc could lead to death in certain parts of the brain and other disorders.

As a result, the lower the levels of zinc, the higher the rate of prostate cancer. To test this hypothesis, 58 prostate cancer tissues were evaluated from two major racial groups (30 from Caucasians and 28 from African Americans) to see if they were able to express two major human zinc transporters, hZIP1 and hZIP2, that are responsible for accumulation of zinc in the prostate glands. Reverse transcriptase in situ polymerase chain reaction was used as well as semiquantitative reverse- transcriptase polymerase chain reaction (SQ-RT-PCR). SQ-RT-PCR was used to show the standard curves of in vitro transcribed mRNAs of hZIP2. By using semiquantitative reverse- transcriptase polymerase chain reactions, it showed that zinc ions are produced and discharged from the epithelial cells into the acinic lumen and the intercellular canaliculi.

Prostate secretory epithelial cells are able to accumulate high intracellular levels of zinc, which can induce mitochondrial apoptogenesis. The prostate contains high amounts of free zinc ions that are excreted into seminal fluid. The expression of zinc transporters also appears to be regulated by prolactin, a peptide hormone produced by the pituitary gland that causes breast to grow and develop milk, and testosterone, a hormone produced by the human body that stimulates spermatozoan production in men.

The specimens from the Caucasian men showed a significantly higher degree of expression of the two zinc transporters than the African American men. All 30 of the specimens from the Caucasian men biopsies displayed a modest degree of expression. From the African American men 26 out of the 28 men displayed a very low expression of both of the zinc transporters. In one of the other two, there was a high expression of hZIP1 and a low expression of hZIP2 and vice versa. The hypothesis stands that there are differences in the zinc transport in different racial groups.