Targeting vascular endothelial growth factor (VEGF)-receptor-signaling in renal cell carcinoma

Molecular mechanism of inhibition of the abnormal proliferation of human umbilical vein endothelial cells by hydroxysafflor-yellow A

Context It has been found that hydroxysafflor-yellow A (HSYA) inhibits angiogenesis and the proliferation of abnormal human umbilical vein endothelial cells (HUVECs) in our previous study; however, the mechanism is still unclear. Objective This study investigates the mechanisms of HSYA inhibiting abnormal proliferation of HUVECs through detecting the expression of vascular endothelial growth factor (VEGF) and its receptor (KDR), and the protein expression in the Ras-Raf-MEK-ERK-signalling pathway. Materials and methods HepG2 cell cultural supernatant was used to culture HUVECs to make promote abnormal proliferation, and HSYA was added into the medium. The expression of VEGF, KDR, c-myc, N-ras and NF-κB1 in abnormal HUVEC was detected by RT-qPCR and ELISA at the mRNA and protein levels. Protein expression of ERK signal pathway was measured by Western blot. Results Compared with the abnormal proliferation of HUVECs without any treatment, HSYA inhibited the expression of VEGF and KDR in vitro. Similarly, the protein expression of Ras, p-raf, p-ERK and p-p38MARK in the abnormal HUVECs was reduced when they were treated by HSYA, especially in p-ERK, yet the total raf, ERK, p38MAPK and Akt were not changed whether HSYA existed or not. HSYA could also inhibit the expression of c-myc, N-ras, and NF-κB1. Conclusion When the abnormal HUVECs were treated with HSYA, the low expression of VEGF and KDR reduced the expression of oncogene and transcription factor through the Ras-Raf-MEK-ERK1/2 pathway of the MAPK family. This resulted in inhibiting the abnormal proliferation of HUVECs and angiogenesis.

MicroRNA-195 targets VEGFR2 and has a tumor suppressive role in ACHN cells via PI3K/Akt and Raf/MEK/ERK signaling pathways

Increasing evidence indicates that dysregulation of miR-195 may contribute to the occurrence and development of multiple types of human malignancies. However, the function and the mechanism of miR-195 in clear cell renal cell carcinoma (ccRCC) are still not fully understood. In the present study, we used qRT-PCR to detect the expression of miR-195 in ccRCC tissues and normal kidney tissues. MTT assay was performed to detect the cell viability of miR-195. Migration and invasion were evaluated by Transwell migration and Matrigel invasion assays, respectively. Additionally, apoptosis levels were evaluated using TUNEL assays, and signaling pathway changes were determined by western blot analysis. We observed that miR-195 was downregulated in clear cell renal cell carcinoma samples compared with normal renal samples. We identified that overexpression of miR-195 inhibited ACHN cell viability, migration, invasion, and it also induced cell apoptosis by targeting VEGFR2 via PI3K/Akt and Raf/MEK/ERK signaling pathways. These findings indicate that miR-195 has a tumor suppressive role in ACHN cells and miR-195 may be a promising candidate target for prevention and treatment of renal cell carcinoma.

Dysregulation of the vascular endothelial growth factor and semaphorin ligand-receptor families in prostate cancer metastasis

Background

The vascular endothelial growth factor (VEGF) family is central to cancer angiogenesis. However, targeting VEGF as an anti-cancer therapeutic approach has shown success for some tumor types but not others. Here we examine the expression of the expanded VEGF family in prostate cancer, including the Semaphorin (Sema) family members that compete with VEGFs for Neuropilin binding and can themselves have pro- or anti-angiogenic activity.

Results

First, we used multivariate statistical methods, including partial least squares and clustering, to examine VEGF/Sema gene expression variability in previously published prostate cancer microarray datasets. We show that unlike some cancers, such as kidney cancer, primary prostate cancer is characterized by both a down-regulation of the pro-angiogenic members of the VEGF family and a down-regulation of anti-angiogenic members of the Sema family. We found pro-lymphangiogenic signatures, including the genes encoding VEGFC and VEGFD, associated with primary tumors that ultimately became aggressive. In contrast to primary prostate tumors, prostate cancer metastases showed increased expression of key pro-angiogenic VEGF family members and further repression of anti-angiogenic class III Sema family members. Given the lack of success of VEGF-targeting molecules so far in prostate cancer, this suggests that the reduction in anti-angiogenic Sema signaling may potentiate VEGF signaling and even promote resistance to VEGF-targeting therapies. Inhibition of the VEGF ‘accelerator’ may need to be accompanied by promotion of the Sema ‘brake’ to block cancer angiogenesis. To leverage our mechanistic understanding, and to link multigene expression changes to outcomes, we performed individualized computational simulations of competitive VEGF and Sema receptor binding across many tumor samples. The simulations suggest that loss of Sema expression promotes angiogenesis by lowering plexin signaling, not by potentiating VEGF signaling via relaxation of competition.

Conclusions

The combined analysis of bioinformatic data with computational modeling of ligand-receptor interactions demonstrated that enhancement of angiogenesis in prostate cancer metastases may occur through two different routes: elevation of VEGFA and reduction of class 3 Semaphorins. Therapeutic inhibition of angiogenesis in metastatic prostate cancer should account for both of these routes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-015-0201-z) contains supplementary material, which is available to authorized users.

Effect of tyrosine kinase inhibitor treatment of renal cell carcinoma on the accumulation of carbonic anhydrase IX-specific chimeric monoclonal antibody cG250

OBJECTIVE

To investigate the effect of three different tyrosine kinase inhibitors (TKIs) on the biodistribution of chimeric monoclonal antibody (mAb) cG250, which identifies carbonic anhydrase IX (CAIX), in nude mice bearing human renal cell carcinoma (RCC) xenografts. TKIs represent the best, but still suboptimal treatment for metastatic RCC (mRCC) and combined therapy or sequential therapy might be beneficial. CAIX is abundantly over expressed in RCC and clinical trials have shown abundant and specific tumour accumulation of cG250. Combining a TKI with mAb cG250, involved in a different effector mechanism, might lead to improved tumour responses and survival in patients with mRCC.

MATERIALS AND METHODS

Nude mice bearing human RCC xenografts were treated orally with 0.75 mg/day sunitinib, 1 mg/day vandetanib, 1 mg/day sorafenib or vehicle control for 7 or 14 days. At 7 days, mice were injected i.v. with 185 kBq/5 µg (125) I-cG250. Mice were killed at predetermined days and cG250 biodistribution was determined. Tumours were analysed by immunohistochemistry for the presence of endothelial cells, laminin, smooth muscle actin, CAIX expression and uptake of mAb cG250.

RESULTS

While on TKI treatment, tumour uptake of cG250 decreased dramatically, tumour growth was slightly inhibited and vascular density decreased considerably as judged by various markers. When treatment was stopped at 7 days, there was robust neovascularization, mainly at the tumour periphery. Consequently, cG250 uptake also recovered, albeit cG250 uptake appeared to be restricted to the tumour periphery where vigorous neovascularization was visible.

CONCLUSIONS

Simultaneous administration of a TKI and mAb cG250 severely compromised mAb accumulation. However, shortly after discontinuation of TKI treatment mAb accumulation was restored. Combined treatment strategies with TKI and mAb should be carefully designed.

Endothelial function of von Hippel-Lindau tumor suppressor gene: control of fibroblast growth factor receptor signaling

von Hippel-Lindau (VHL) disease results from germline and somatic mutations in the VHL tumor suppressor gene and is characterized by highly vascularized tumors. VHL mutations lead to stabilization of hypoxia-inducible factor (HIF), which up-regulates proangiogenic factors such as vascular endothelial growth factor (VEGF). This pathway is therefore believed to underlie the hypervascular phenotypes of the VHL tumors. However, recent studies have identified novel VHL functions that are independent of the HIF-VEGF pathway. In addition, a potential role of VHL in the tumor microenvironment, which carries heterozygous VHL mutations in VHL patients, has been overlooked. Here, we report a novel HIF-independent VHL function in the endothelium. VHL knockdown in primary human microvascular endothelial cells caused defective turnover of surface fibroblast growth factor (FGF) receptor, increased extracellular signal-regulated kinase signaling, and ETS1 activation, leading to increased cell motility in response to FGF and three-dimensional cord formation in vitro. HIF-alpha knockdown in VHL loss-of-function endothelial cells does not impede their elevated in vitro angiogenic activity. Importantly, the elevated angiogenic response to FGF is recapitulated in Vhl-heterozygous mice. Thus, partial loss of function of VHL in endothelium may be a contributing factor in tumor angiogenesis through a HIF-VEGF-independent mechanism.

Cyr61/CCN1 and CTGF/CCN2 mediate the proangiogenic activity of VHL-mutant renal carcinoma cells

The von Hippel-Lindau (VHL) protein serves as a negative regulator of hypoxia-inducible factor (HIF)-alpha subunits. Since HIF regulates critical angiogenic factors such as vascular endothelial growth factor (VEGF) and lesions in VHL gene are present in a majority of the highly vascularized renal cell carcinoma (RCC), it is believed that deregulation of the VHL-HIF pathway is crucial for the proangiogenic activity of RCC. Although VEGF has been confirmed as a critical angiogenic factor upregulated in VHL-mutant cells, the efficacy of antiangiogenic therapy specifically targeting VEGF signaling remains modest. In this study, we developed a three-dimensional in vitro assay to evaluate the ability of RCC cells to promote cord formation by the primary human dermal microvascular endothelial cells (HDMECs). Compared with VHL wild-type cells, VHL-mutant RCC cells demonstrated a significantly increased proangiogenic activity, which correlated with increased secretion of cysteine-rich 61 (Cyr61)/cysteine-rich 61-connective tissue growth factor-nephroblastoma overexpressed (CCN) 1, connective tissue growth factor (CTGF)/CCN2 and VEGF in conditioned culture medium. Both CCN proteins are required for HDMEC cord formation as shown by RNA interference knockdown experiments. Importantly, the proangiogenic activities conferred by the CCN proteins and VEGF are additive, suggesting non-overlapping functions. Expression of the CCN proteins is at least partly dependent on the HIF-2alpha function, the dominant HIF-alpha isoform expressed in RCC. Finally, immunohistochemical staining of Cyr61/CCN1 and CTGF/CCN2 in RCC tissue samples showed that increased expression of these proteins correlates with the loss of VHL protein expression. These findings strengthened the notion that the hypervascularized phenotype of RCC is afforded by multiple proangiogenic factors that function in parallel pathways.