The RNA-binding protein KSRP aggravates malignant progression of clear cell renal cell carcinoma through transcriptional inhibition and post-transcriptional destabilization of the NEDD4L ubiquitin ligase.

BACKGROUND: KH-type splicing regulatory protein (KHSRP, also called KSRP), a versatile RNA-binding protein, plays a critical role in various physiological and pathological conditions through modulating gene expressions at multiple levels. However, the role of KSRP in clear cell renal cell carcinoma (ccRCC) remains poorly understood. METHODS: KSRP expression was detected by a ccRCC tissue microarray and evaluated by an in silico analysis. Cell loss-of-function and gain-of-function, colony-formation, anoikis, and transwell assays, and an orthotopic bioluminescent xenograft model were conducted to determine the functional role of KRSP in ccRCC progression. Micro (mi)RNA and complementary (c)DNA microarrays were used to identify downstream targets of KSRP. Western blotting, quantitative real-time polymerase chain reaction, and promoter- and 3-untranslated region (3'UTR)-luciferase reporter assays were employed to validate the underlying mechanisms of KSRP which aggravate progression of ccRCC. RESULTS: Our results showed that dysregulated high levels of KSRP were correlated with advanced clinical stages, larger tumor sizes, recurrence, and poor prognoses of ccRCC. Neural precursor cell-expressed developmentally downregulated 4 like (NEDD4L) was identified as a novel target of KSRP, which can reverse the protumorigenic and prometastatic characteristics as well as epithelial-mesenchymal transition (EMT) promotion by KSRP in vitro and in vivo. Molecular studies revealed that KSRP can decrease NEDD4L messenger (m)RNA stability via inducing mir-629-5p upregulation and directly targeting the AU-rich elements (AREs) of the 3'UTR. Moreover, KSRP was shown to transcriptionally suppress NEDD4L via inducing the transcriptional repressor, Wilm's tumor 1 (WT1). In the clinic, ccRCC samples revealed a positive correlation between KSRP and mesenchymal-related genes, and patients expressing high KSRP and low NEDD4L had the worst prognoses. CONCLUSION: The current findings unveil novel mechanisms of KSRP which promote malignant progression of ccRCC through transcriptional inhibition and post-transcriptional destabilization of NEDD4L transcripts. Targeting KSRP and its pathways may be a novel pharmaceutical intervention for ccRCC.

Stabilization of ADAM9 by N-α-acetyltransferase 10 protein contributes to promoting progression of androgen-independent prostate cancer.

N-α-Acetyltransferase 10 protein (Naa10p) was reported to be an oncoprotein in androgen-dependent prostate cancer (PCa; ADPC) through binding and increasing transcriptional activity of the androgen receptor (AR). PCa usually progresses from an androgen-dependent to an androgen-independent stage, leading to an increase in the metastatic potential and an incurable malignancy. At present, the role of Naa10p in androgen-independent prostate cancer (AIPC) remains unclear. In this study, in silico and immunohistochemistry analyses showed that Naa10 transcripts or the Naa10p protein were more highly expressed in primary and metastatic PCa cancer tissues compared to adjacent normal tissues and non-metastatic cancer tissues, respectively. Knockdown and overexpression of Naa10p in AIPC cells (DU145 and PC-3M), respectively, led to decreased and increased cell clonogenic and invasive abilities in vitro as well as tumor growth and metastasis in AIPC xenografts. From the protease array screening, we identified a disintegrin and metalloprotease 9 (ADAM9) as a potential target of Naa10p, which was responsible for the Naa10p-induced invasion of AIPC cells. Naa10p can form a complex with ADAM9 to maintain ADAM9 protein stability and promote AIPC's invasive ability which were independent of its acetyltransferase activity. In contrast to the Naa10p-ADAM9 axis, ADAM9 exerted positive feedback regulation on Naa10p to modulate progression of AIPC in vitro and in vivo. Taken together, for the first time, our results reveal a novel cross-talk between Naa10p and ADAM9 in regulating the progression of AIPC. Disruption of Naa10p-ADAM9 interactions may be a potential intervention for AIPC therapy.

Melatonin-triggered post-transcriptional and post-translational modifications of ADAMTS1 coordinately retard tumorigenesis and metastasis of renal cell carcinoma.

A disintegrin and metalloprotease with thrombospondin motifs (ADAMTS) family are widely implicated in tissue remodeling events manifested in cancer development. ADAMTS1, the most fully characterized ADAMTS, plays conflicting roles in different cancer types; however, the role of ADAMTS1 in renal cell carcinoma (RCC) remains unclear. Herein, we found that ADAMTS1 is highly expressed in RCC tissues compared to normal renal tissues, and its expression was correlated with an advanced stage and a poor prognosis of RCC patients. In vitro, we observed higher expression of ADAMTS1 in metastatic (m)RCC cells compared to primary cells, and manipulation of ADAMTS1 expression affected cell invasion and clonogenicity. Results from protease array showed that ADAMTS1 is modulated by melatonin through mechanisms independent of the MT1 receptor in mRCC cells, and overexpression of ADAMTS1 relieved the invasion/clonogenicity and growth/metastasis inhibition imposed by melatonin treatment in vitro and in an orthotopic xenograft model. The human microRNA (miR) OneArray showed that miR-181d and miR-let-7f were induced by melatonin and, respectively, targeted the 3'-UTR and non-3'-UTR of ADAMTS1 to suppress its expression and mRCC invasive ability. Clinically, RCC patients with high levels of miR-181d or miR-let-7f and a low level of ADAMTS1 had the most favorable prognoses. In addition, ubiquitin/proteasome-mediated degradation of ADAMTS1 can also be triggered by melatonin. Together, our study indicates that ADAMTS1 may be a useful biomarker for predicting RCC progression. The novel convergence between melatonin and ADAMTS1 post-transcriptional and post-translational regulation provides new insights into the role of melatonin-induced molecular regulation in suppressing RCC progression.

Melatonin inhibits MMP-9 transactivation and renal cell carcinoma metastasis by suppressing Akt-MAPKs pathway and NF-κB DNA-binding activity.

Renal cell carcinoma (RCC) is the most lethal of all urological malignancies because of its potent metastasis potential. Melatonin exerts multiple tumor-suppressing activities through antiproliferative, proapoptotic, and anti-angiogenic actions and has been tested in clinical trials. However, the antimetastastic effect of melatonin and its underlying mechanism in RCC are unclear. In this study, we demonstrated that melatonin at the pharmacologic concentration (0.5-2 mm) considerably reduced the migration and invasion of RCC cells (Caki-1 and Achn). Furthermore, we found that melatonin suppressed metastasis of Caki-1 cells in spontaneous and experimental metastasis animal models. Mechanistic investigations revealed that melatonin transcriptionally inhibited MMP-9 by reducing p65- and p52-DNA-binding activities. Moreover, the Akt-mediated JNK1/2 and ERK1/2 signaling pathways were involved in melatonin-regulated MMP-9 transactivation and cell motility. Clinical samples revealed an inverse correlation between melatonin receptor 1A (MTNR1A) and MMP-9 expression in normal kidney and RCC tissues. In addition, a higher survival rate was found in MTNR1A(high) /MMP-9(low) patients than in MTNR1A(low) /MMP-9(high) patients. Overall, our results provide new insights into the role of melatonin-induced molecular regulation in suppressing RCC metastasis and suggest that melatonin has potential therapeutic applications for metastastic RCC.

Nigericin inhibits insulin-stimulated glucose transport in 3T3-L1 adipocytes.

We used nigericin, a K+/H+ exchanger, to test whether glucose transport in 3T3-L1 adipocytes was modulated by changes in intracellular pH. Our results showed that nigericin increased basal but decreased insulin-stimulated glucose uptake in a time- and dose-dependent manner. Whereas the basal translocation of GLUT1 was enhanced, insulin-stimulated GLUT4 translocation was inhibited by nigericin. On the other hand, the total amount of neither transporter protein was altered. The finding that insulin-stimulated phosphoinositide 3-kinase (PI 3-kinase) activity was not affected by nigericin implies that nigericin exerted its inhibition at a step downstream of PI 3-kinase activation. At maximal dose, nigericin rapidly lowered cytosolic pH to 6.7; however, this effect was transient and cytosolic pH was back to normal in 20 min. Removal of nigericin from the incubation medium after 20 min abolished its enhancing effect on basal but had little influence on its inhibition of insulin-stimulated glucose transport. Moreover, lowering cytosolic pH to 6.7 with an exogenously added HCl solution had no effect on glucose transport. Taken together, it appears that nigericin may inhibit insulin-stimulated glucose transport mainly by interfering with GLUT4 translocation, probably by a mechanism not related to changes in cytosolic pH.