Taken together our results indicate that bcl-2 plays an important role in melanoma angiogenesis, and that VEGF mRNA stabilization and HIF-1-mediated transcriptional activity are two important control points in bcl-2/hypoxia-induced VEGF expression.
Hypoxia-inducible factors 1alpha and 2alpha are related to vascular endothelial growth factor expression and a poorer prognosis in nodular malignant melanomas of the skin.
Collectively, these results identify a new mechanism whereby ET-1/ET-3/ET(B)R axis can promote and interact with the HIF-1alpha-dependent machinery to amplify the COX-mediated invasive behavior of melanoma.
Our microarray profiling data in 35 melanoma and melanocyte cell lines showed that HIF-1alpha gene expression was significantly increased in melanomas harboring BRAF(V600E) mutation.
Our results indicate that HIF-1alpha overexpression is present in most primary melanomas, but is not associated with clinicopathological variables, patient prognosis or survival.
The underlying concept of transfecting a HIF-1alpha shRNA expression vector complexed with Tf-PEI to block HIF-1alpha holds promise as a clinical approach to gene therapy for MM.
We have examined the normoxic expression of HIF-1alpha RNA and protein in normal human melanocytes and a series of human melanoma cell lines isolated from radial growth phase (RGP), vertical growth phase (VGP) and metastatic (MET) melanomas.
This effect was associated with increased melanoma cell expression of tumor suppressor protein 53 and matrix protein TSP1, as well as decreased hypoxia-driven expression of hypoxia inducible factor-1α and inhibition of VEGF production.
We have observed that MITF expression is potently reduced under hypoxic conditions in primary melanocytes and melanoma and clear cell sarcoma cells through hypoxia inducible factor 1 (HIF1)-mediated induction of the transcriptional repressor differentially expressed in chondrocytes protein 1 (DEC1) (BHLHE40), which subsequently binds and suppresses the promoter of M-MITF (melanocyte-restricted MITF isoform).
The microphthalmia-associated transcription factor (MITF) has been proposed to act as a melanoma oncogene; it also stimulates the transcription of hypoxia inducible factor (HIF1A), the pathway of which is targeted by kidney cancer susceptibility genes.
In this context, we have previously demonstrated that under hypoxia bcl-2 promotes hypoxia-inducible factor-1 (HIF-1)-mediated vascular endothelial growth factor (VEGF) expression in melanoma and breast carcinoma.
Using complementary approaches in validated cell lines and freshly obtained human specimens, we report here that mitochondrial respiration and oxidative phosphorylation are slowed in metastatic melanomas, even under normoxic conditions due to the persistence of a high nuclear expression of hypoxia-inducible factor-1α (HIF-1α).
In conclusion, our findings provide evidence that GAB2 is a novel regulator of tumor angiogenesis in NRAS-driven melanoma through regulation of HIF-1α and VEGF expressions mediated by RAS-RAF-MEK-ERK signaling.
Knowledge of the HIF2α interactome is thus a useful resource for investigating the general mechanisms of HIF function and regulation, and here we reveal unexpected, distinct roles for the HIF1 and HIF2 isoforms in melanoma progression.
At the molecular level, we show that melanoma Rh123(low) cells overexpress HIF1α, pluripotency factor OCT4, and the ABCB5 marker of melanoma stem cells and downregulate the expression of Cyclin D1 and CDK4.
We investigated ETV1 in 68 human melanoma brain metastases using FISH for ETV1 gene (located at chromosome 7p21) and centromere chromosome 7 and immunohistochemistry for ETV1, BRAF (V600E) , and ETV1/BRAF associated proteins pMSK1, pRSK1, pp38, pMEK1/2, MAPKAP kinase 2, CIC, HIF-1alpha and Ki-67.
To investigate the role of CD147 in hypoxiainduced MMP2 activation, we performed immunohistochemistry (IHC) staining in 206 normal and melanoma tissue samples, and analyzed the correlation between HIF1α and CD147.
Immunohistochemical studies using a large panel of pigmented lesions revealed that higher levels of HIF-1α and GLUT-1 were detected in advanced melanomas in comparison to melanocytic nevi or thin melanomas localized to the skin.