Altered VEGF mRNA Stability following Treatments with Immunosuppressive Agents

Abstract

The high incidence of cancer and its aggressive progression is a common and major problem in patients receiving immunosuppressive therapy. The calcineurin inhibitors (CNIs) may have protumorigenic effects and can promote the overexpression of several molecules inducing tumor growth. We have recently demonstrated that CNIs can mediate the transcriptional activation of the angiogenic cytokine vascular endothelial growth factor (VEGF) and promote a rapid progression of human renal cancer. Here, we investigated whether the CNI cyclosporine (CsA) and the mTOR inhibitor rapamycin (RAPA) could alter the mRNA stability of VEGF in 786-0 and Caki-1 renal cancer cells. Following actinomycin D treatment, we observed that CsA increased, whereas RAPA decreased the VEGF mRNA stability as observed by real time PCR. It is established that the mRNA-binding protein HuR may play a critical role in VEGF mRNA stability. By using HuR-siRNA, we found that the knockdown of HuR significantly decreased the CNIinduced VEGF mRNA stability. By Western blot analysis, it has been observed that CNI treatment induced the translocation of HuR from the nucleus to the cytoplasm; CNIs also induced the association between HuR and PKC-␦ and promoted the phosphorylation of HuR. Finally, we found that the inhibition of PKC-␦ using a dominant negative plasmid significantly decreased the CsA-induced cytoplasmic translocation of HuR and VEGF mRNA stability. Together, targeting the pathways that promote CNI-induced transcription as well as the mRNA stability of VEGF might serve as novel therapeutics for the prevention and treatment of cancer in immunosuppressed patients.The development of cancer is a critical problem in patients treated with immunosuppressive agents (1-3). The reasons for the high incidence of cancer in these individuals, including patients with organ transplant, are unknown, but have been postulated to include impaired immune surveillance, viral infections, or the direct effects of immunosuppressive agents (2, 4, 5). Nevertheless, some clues to the mechanisms underlying the development of posttransplantation cancer have recently emerged from clinical findings, including the observation that transplant patients receiving the mTOR 2 inhibitor rapamycin (RAPA) do not develop cancer at the same rate as those receiving other immunosuppressive agents such as calcineurin inhibitors (CNIs) (5-9).Vascular endothelial growth factor (VEGF) is a 34 -45-kDa cytokine expressed by tumor cells, endothelial cells, leukocytes, and different other cell types (10 -12). It plays a major role in regulating the process of angiogenesis for the growth and progression of tumors (10). We have recently reported that CNIs may promote the overexpression of VEGF in human renal cancer, one of the major cancers in transplant patients (13). We have observed that CNI-induced VEGF overexpression is mediated through the transcriptional activation mechanism and can lead to a rapid progression of renal tumors (13).The regulation of VEGF expression in tumor cells is complex, inv...

C/EBPβ and Nuclear Factor of Activated T Cells Differentially Regulate Adamts-1 Induction by Stimuli Associated with Vascular Remodeling

“…In addition to inhibiting CN, CsA can exert additional effects on the cell, such as activation of the transforming growth factor ␤1 pathway (26) or stabilization of the RNA encoding VEGF (27). To confirm that the CsA-mediated reduction of Adamts-1 expression by VEGF was not the result of off-target effects of CsA, we transduced ECs and VSMCs with lentiviral vectors encoding LXVP, a peptide that inhibits CN phosphatase activity and blocks its docking site for NFAT (28).…”

Critical role of mTOR in calcineurin inhibitor-induced renal cancer progression

“…It is known that renal tumors are highly angiogenic, and they express VEGF. 5 Our data indicate that CNI treatment promotes the overexpression of VEGF, 5,6 which can turn on the angiogenic switch in renal cancer cells. Thus, CNI-induced and VEGF-mediated angiogenesis may facilitate a rapid progression of dormant tumors in transplant patients.…”

“…3 However, apart from inhibiting NFAT, CNIs may also regulate other signaling molecules playing important roles in tumor growth. Previously, we defined a novel mechanism by which CNIs can activate the proto-oncogene ras and specific isoforms (ζ and δ) of protein kinase C (PKC); [4][5][6] and CNIs can promote a rapid progression of human renal cancer through transcriptional activation of VEGF and VEGF-induced angiogenesis. 5 In contrast to CNIs, RAPA treatment may have an anti-angiogenic effect.…”

Calcineurin inhibitor-induced endothelial cell injury – A role for complement

“…(Schiff et al, 2007) Various published in vitro experimental studies on the effect of cyclosporine on various endothelial cell lines used a wide range of drug concentration ranging from 0.1 µg/ml to 4000 µg/ml over varying durations of exposure (up to 72 hours). (Basu et al, 2010;Bouvier et al, 2009;Farivar et al, 2005;Gooch et al, 2017;Grupper et al, 2013;Ikezoe et al, 2012;Illsinger et al, 2011;Renner et al, 2013;Rodrigues-Diez et al, 2016) Although the levels of cyclosporine maintained clinically is lower than those used in experimental in vitro studies, they are not directly comparable. It is one of the limitations of in vitro models of disease.…”