Aberrant alterations of the expressions and S-nitrosylation of calmodulin and the downstream factors in the brains of the rodents during scrapie infection.

The aberrant alterations of calmodulin (CaM) and its downstream substrates have been reported in some neurodegenerative diseases, but rarely described in prion disease. In this study, the potential changes of Ca2+/CaM and its associated agents in the brains of scrapie agent 263K-infected hamsters and the prion infected cell line SMB-S15 were evaluated by various methodologies. We found that the level of CaM in the brains of 263K-infected hamsters started to increase at early stage and maintained at high level till terminal stage. The increased CaM mainly accumulated in the regions of cortex, thalamus and cerebellum of 263K-infected hamsters and well localization of CaM with NeuN positive cells. However, the related kinases such as total and phosphorylated forms of CaMKII and CaMKIV, as well as the downstream proteins such as CREB and BDNF in the brain of 263K-infected hamsters were decreased. Further analysis showed a remarkable increase of S-nitrosylated (SNO) form of CaM in the brains of 263K-infected hamsters. Dynamic analysis of S-nitrosylated CaM showed the SNO form of CaM abnormally increases in a time-dependent manner during prion infection. Compared with that of the normal partner cell line SMB-PS, the CaM level in SMB-S15 cells was increased, meanwhile, the downstream proteins, such as CaMKII, p-CaMKII, CREB, as well as BDNF, were also increased, especially in the nucleic fraction. No SNO-CaM was detected in the cell lines SMB-S15 and SMB-PS. Our data indicate an aberrant increase of CaM during prion infection in vivo and in vitro.

ADAM17 targets MMP-2 and MMP-9 via EGFR-MEK-ERK pathway activation to promote prostate cancer cell invasion.

ADAM17, also known as tumor necrosis factor-α converting enzyme (TACE), is involved in proteolytic ectodomain shedding of cell surface molecules and cytokines. Although aberrant expression of ADAM17 has been shown in various malignancies, the function of ADAM17 in prostate cancer has not been clarified. In the present study, we sought to elucidate whether ADAM17 contributes to prostate cancer cell invasion, as well as the mechanism involved in the process. The expression pattern of ADAM17 was investigated in human prostate cancer cells. The results showed that ADAM17 expression levels are correlated with the invasive ability of androgen-independent prostate cancer cell lines. Further, ADAM17 was overexpressed in cells showing high invasion characteristics, activation of the EGFR-MEK-ERK pathway, up-regulation of MMP-2, MMP-9, and an increased TGF-α release into the supernatant. However, AG1478, PD98059 and antibody against TGF-α deactivating the EGFR-MEK-ERK signaling pathway, abolished up-regulation of MMP-2, MMP-9 and prevented cell invasion. In addition, cells with knockdown of ADAM17 by siRNA exhibited low invasive ability, deactivated EGFR-MEK-ERK signaling pathway, reduced TGF-α released and down-regulation of MMP-2, MMP-9. However, these effects could be reversed by simultaneous addition of TGF-α. These data demonstrated that ADAM17 contributes to androgen-independent prostate cancer cell invasion by shedding of EGFR ligand TGF-α, which subsequently activates the EGFR-MEK-ERK signaling pathway, leading finally to overexpression of MMP-2 and MMP-9. This study suggests that the ADAM17 expression level may be a new predictive biomarker of invasion and metastasis of prostate cancer, and ADAM17 could provide a target for treating metastatic PCa.

Hypoxia increases CX3CR1 expression via HIF-1 and NF­κB in androgen-independent prostate cancer cells.

The unique CX3C chemokine CX3CL1 and its cognate receptor CX3CR1 have been implicated in organ-specific metastasis of various types of tumors. Hypoxia, a common phenomenon in solid tumors, is associated with a malignant cancer phenotype. Previous studies have proved that hypoxia facilitates cancer cell metastasis through upregulation of specific chemokine receptors. We hypothesized that hypoxia could upregulate CX3CR1 expression and lead to an increased chemotactic response to CX3CL1 in prostate cancer cells. In the present study, we found that CX3CR1 expression was significantly increased in androgen-independent prostate cancer cells, including DU145, PC-3 and PC-3M, following exposure to hypoxia. This upregulation of CX3CR1 corresponded to a significant increase in migration and invasion of prostate cancer cells under hypoxic conditions, which was attenuated after knocking down CX3CR1 expression. In addition, we examined the possible role of HIF-1 and NF-κB in the process of hypoxia-induced CX3CR1 expression and hypoxia-mediated metastasis. Attenuation of HIF-1 and NF-κB transcriptional activity by siRNAs or pharmacological inhibitors, abrogated hypoxia-induced upregulation of CX3CR1, and also prevented the migration and invasion of DU145 cells under a hypoxic environment. In summary, our study demonstrated that HIF-1 and NF-κB are essential for hypoxia-regulated CX3CR1 expression, which is associated with increased migratory and invasive potential of prostate cancer cells. CX3CR1 signaling is a potential therapeutic target in the adjuvant treatment of prostate cancer.