The role of the UTS2 gene polymorphisms and plasma Urotensin-II levels in breast cancer.

Breast cancer is the most common malignancy predominantly affecting women. To date, numerous numbers of studies were reported novel genetic contributors with diagnostic, prognostic, and therapeutic potential for the breast carcinogenesis. However, the role of urotensin-II in breast carcinogenesis has not been elucidated yet. Urotensin-II is a somatostatin-like cyclic tiny peptide identified by its potent vasoconstrictor activity. Soon after its discovery, its involvement in many disease states as well as its expression in various tissues including the tumors have been demonstrated. Moreover, there is strong evidence that suggest urotensin-II as the significant contributor of angiogenesis as well as cell proliferation and tumor biology. In this study, enzyme-linked immunosorbent assay (ELISA) and restriction fragment length polymorphism analysis were used to evaluate plasma levels of urotensin-II and Thr21Met and Ser89Asn polymorphisms of UTS2 gene in breast cancer patients. In the present case-control study, we noticed a significant decrease in the levels of urotensin-II protein in the plasma of the breast cancer patients (p < 0.05). Also, Thr21Met polymorphism in the UTS2 gene was associated with the risk of developing breast cancer (p < 0.0001), whereas the genotype frequency of Ser89Asn was found to be similar in patients and controls (p > 0.05). In addition, we demonstrated the gradual decreasing of urotensin-II protein levels from TT and TM to MM genotypes. In conclusion, these results strongly suggest that urotensin-II could contribute to breast carcinogenesis and Thr21Met polymorphism can be an important risk factor in developing breast tumors.

Off-target function of the Sonic hedgehog inhibitor cyclopamine in mediating apoptosis via nitric oxide-dependent neutral sphingomyelinase 2/ceramide induction.

Sonic hedgehog (SHh) signaling is important in the pathogenesis of various human cancers, such as medulloblastomas, and it has been identified as a valid target for anticancer therapeutics. The SHh inhibitor cyclopamine induces apoptosis. The bioactive sphingolipid ceramide mediates cell death in response to various chemotherapeutic agents; however, ceramide's roles/mechanisms in cyclopamine-induced apoptosis are unknown. Here, we report that cyclopamine mediates ceramide generation selectively via induction of neutral sphingomyelin phosphodiesterase 3, SMPD3 (nSMase2) in Daoy human medulloblastoma cells. Importantly, short interfering RNA-mediated knockdown of nSMase2 prevented cyclopamine-induced ceramide generation and protected Daoy cells from drug-induced apoptosis. Accordingly, ectopic wild-type N-SMase2 caused cell death, compared with controls, which express the catalytically inactive N-SMase2 mutant. Interestingly, knockdown of smoothened (Smo), a target protein for cyclopamine, or Gli1, a downstream signaling transcription factor of Smo, did not affect nSMase2. Mechanistically, our data showed that cyclopamine induced nSMase2 and cell death selectively via increased nitric oxide (NO) generation by neuronal-nitric oxide synthase (n-NOS) induction, in Daoy medulloblastoma, and multiple other human cancer cell lines. Knockdown of n-NOS prevented nSMase2 induction and cell death in response to cyclopamine. Accordingly, N-SMase2 activity-deficient skin fibroblasts isolated from homozygous fro/fro (fragilitas ossium) mice exhibited resistance to NO-induced cell death. Thus, our data suggest a novel off-target function of cyclopamine in inducing apoptosis, at least in part, by n-NOS/NO-dependent induction of N-SMase2/ceramide axis, independent of Smo/Gli inhibition.