Tyrosine kinase inhibitor therapy prescribed for non-urologic diseases can modify PSA titers in urology patients.

Background: The tyrosine kinase inhibitors (TKI), imatinib and nilotinib, are used to treat chronic myelogenous leukemia (CML). In three CML patients being monitored for urologic diseases, we observed that switching of TKI therapy affected prostate-specific antigen (PSA) titers. Urologists and other medical professionals need to be aware of the potential side-effects of drugs that patients may be receiving for other indications to modify this important prostate diseases indicator. TKIs may affect PSA titers independent of prostate growth or volume.

Materials And Methods: We followed PSA levels in urology patients who were also undergoing TKI treatment for CML. We determined the effects of nilotinib and imatinib on proliferation, AR and PSA expression in the LNCaP and 22Rv1 prostate cancer (PCa) cell lines using real-time PCR and Western blotting.

Results: Clinically, nilotinib and dasatinib reversibly reduced PSA titers compared to imatinib. At high doses nilotinib and imatinib both demonstrated antiproliferative effects in the PCa cells. At low doses expression of AR and PSA was decreased by both drugs, at mRNA and protein levels. Nilotinib exerted greater effects at lower doses than imatinib.

Conclusions: Nilotinib down-regulates serum PSA in patients being treated for non-urological indications, potentially masking a clinical useful marker, we cannot exclude a similar but smaller effect of imatinib. Nilotinib and imatinib both decreased AR and PSA expression in PCa cell lines with the nilotinib effect evident at lower doses. Urologists must appreciate the effects of drugs provided for other diseases on PSA titers and be aware that sudden changes may not reflect underlying prostatic disease.