TGFB1 and Familial prostate cancer: However, the study identified a correlation between a TGFB1 variant (TT for C-509T) and the highest mean value for CD8+ T lymphocyte apoptosis for late genitourinary and gastrointestinal radiotoxicity (close to reaching significance), and a significant correlation between a TGFB1 variant (ProPro for Leu10Pro) and the highest mean value for CD8+ T lymphocyte apoptosis for gastrointestinal radiotoxicity in prostate cancer patients [52].