Graduation Year

2018

Document Type

Thesis

Degree

M.S.P.H.

Degree Name

MS in Public Health (M.S.P.H.)

Degree Granting Department

Epidemiology and Biostatistics

Major Professor

Janice Zgibor, Ph.D.

Committee Member

Jong Park, Ph.D.

Committee Member

Skai Schwartz, Ph.D.

Keywords

biochemical recurrence of prostate cancer, gene expression, obesity, health disparity

Abstract

In the US, the incidence and mortality rates of prostate cancer (PCa) are higher among African American men compared to European American men. Obesity is an important risk factor of PCa. Obesity is known to alter the gene expression profiles in prostate tumors. This study evaluates the impact of obesity and the expression of obesity-related genes on the progression of PCa in African American men.

The primary outcome of interest is biochemical recurrence (BCR) of PCa. There were 48 African American prostate cancer patients in the study. The tissue samples included 42 normal tissues, 40 Prostate Intraepithelial Neoplasia (PIN) and 45 tumor tissues (127 tissue samples in total). We assembled 99 obesity-related genes and determined the levels of their expression in the three types of tissue samples using Nanostring Technologies. An ANOVA test was used to compare the means for gene expression among normal, PIN and tumor tissue samples. Unconditional logistic regression models were used to calculate odds ratios (ORs) and their respective 95% confidence intervals (95% CIs) to determine the association between obesity and BCR as well as gene expression and BCR. Results were regarded as statistically significant if p-values were less than 0.05. A Kaplan Meier Curve was constructed to depict the survival time and time to event (BCR) among obese and non-obese African American prostate cancer patients. Patients were followed up from the date of first surgery to the date of biochemical recurrence or date of last follow-up. Statistical analysis was done with SAS 9.4 software.

Forty-three obesity-related genes were statistically significantly associated with biochemical recurrence. There was no association between obesity and biochemical recurrence (BCR) in obese African American men compared to non-obese African American men (OR= 2.03, 95% CI = 0.22 - 18.77, p-value= 0.53). Twenty genes showed an upward trend in gene expression among normal, PIN and tumor tissue samples including ADIPOR1, AKRIC4, ALOX12, ALOX15, CRYBB2, EIF5A, ERG, GNPDA2, HNF1B, HSD3B1, KLK4, LEP, MC4R, MTCH2, PCSK1, PIK3CB, SLC2A2, STAT1, SULT1A1, YY1. The probability of survival (not having BCR) is lower in obese African American men compared to non-obese African American men as indicted in the Kaplan Meier curve. In other words, the probability of developing BCR is higher in obese African American men compared to non-obese African American men.

We did not find a significant association between obesity and biochemical recurrence. However, we elucidated some obesity-related genes that could explain PCa carcinogenesis. Further studies are needed to determine functional significance of these selected obesity-related genes and the role they play in encouraging PCa progression in African American men.

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