Curcumin potentiates the ability of sunitinib to eliminate the VHL-lacking renal cancer cells 786-O: rapid inhibition of Rb phosphorylation as a preamble to cyclin D1 inhibition
Curcumin, an important component of the culinary spice turmeric, has been shown to harbor anticancer properties against a wide range of cancer cells with minimal toxicity toward normal cells. Two general tyrosine kinase inhibitors (TKIs) sunitinib and sorafenib are currently used in treating renal cancer. Though the use of these TKIs has significantly improved survival, both elicit distressing side effects, limiting their long-term use. We tested the activity of sunitinib and sorafenib to eliminate 786-O renal cancer cells and the efficacy of curcumin to enhance this process. A four-fold decrease in the IC50 of sunitinib, from 4.5 muM to 1.2 muM, was observed in the presence of 20-muM curcumin. However, curcumin did not potentiate the activity of sorafenib. The sunitinib-curcumin (SunC) combination sharply inhibited hyperphosphorylation of the tumor suppressor protein Rb within 8 hours of SunC treatment. Although the levels of cyclin D1 did not change in 8 hours, its expression was dramatically inhibited after 24 hours of SunC exposure. Since curcumin is known to inhibit the cyclin D1-dependent G1/S-phase kinase CDK4 and the cyclin B-dependent G2/M-phase kinase CDK1 that catalyze phosphorylation-mediated inactivation of Rb, our results indicate that SunC containing a lower dose of sunitinib would be effective in restoring the tumor suppressor activity of Rb, thereby truncating cell cycle and triggering cell death. Our results submit the possibility of using SunC as an effective antitumor formulation to reduce the dose and risk of adverse effects of sunitinib.
Male human papillomavirus infection post-kidney transplant: an overlooked disease [Editorial]
While immunosuppressive regimens improve the overall survival of renal transplant recipients, they also contribute to the long-term complications of post-transplant malignancies. Chronic immune suppression in renal transplant recipients (RTR) increases the risk of viral-associated cancers. In male RTR, human papillomavirus (HPV) is implicated in the development of penile, anal, oropharyngeal, and non-melanoma skin carcinomas. Despite the significance of this virus in RTR, there is an overall deficiency in the understanding of the natural history of HPV infection in male RTR. In the next 20 years, it is believed that cancers will be the leading cause of death in kidney transplant recipients. HPV-associated carcinomas are of particular interest since they are sexually transmitted and in theory may be preventable diseases. This commentary highlights some of the progress made in understanding how HPV is transmitted amongst couples in the general population. It also summarizes the current knowledge of HPV infection in male RTR and describes the deficiencies in published medical literature.