Hepatoma-derived growth factor (HDGF) participates in tumourigenesis but its role in breast cancer is unclear. We set out to elucidate the expression profile and function of HDGF during breast carcinogenesis. Immunoblot and immunohistochemical studies revealed elevated HDGF expression in human breast cancer cell lines and tissues. Nuclear HDGF labelling index was positively correlated with tumour grade, stage and proliferation index, but negatively correlated with survival rate in breast cancer patients. HDGF over-expression was associated with lymph node metastasis and represented an independent prognostic factor for tumour recurrence. Gene transfer studies were performed to elucidate the influence of cellular HDGF level on the malignant behaviour and epithelial-mesenchymal transition (EMT) of breast cancer cells. Adenovirus-mediated HDGF over-expression stimulated the invasiveness and colony formation of MCF-7 cells. Moreover, HDGF over-expression promoted breast cancer cell EMT by E-cadherin down-regulation and vimentin up-regulation. Conversely, HDGF knockdown by RNA interference in MDA-MB-231 cells attenuated the malignant behaviour and elicited EMT reversal by enhancing E-cadherin expression while depleting vimentin expression. Because HDGF is a secreted protein, we evaluated the cellular function of recombinant HDGF and found that exogenously supplied HDGF enhanced the invasiveness of breast cancer cells by down-regulating E-cadherin and up-regulating vimentin at transcriptional and translational levels. In contrast, blockade of HDGF secretion with an HDGF antibody inhibited the malignant behaviours and EMT. Finally, exogenous HDGF partially reversed benzyl isothiocyanate (BITC)-induced EMT suppression. HDGF over-expression may exert a prognostic role for tumour metastasis and recurrence in breast cancer by modulating EMT. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Malignant melanoma is one of the leading causes of cancer mortality worldwide, underlining the need for effective novel therapies. In this study, the therapeutic efficacy and mechanism of systemic pro-opiomelanocortin (POMC) therapy were evaluated in mice bearing established melanoma. Injection of adenovirus encoding POMC (Ad-POMC) led to hepatic POMC overexpression and elevated adrenocorticotropin (ACTH) levels in the circulation. Systemic POMC therapy significantly attenuated the growth of established melanoma and prolonged the survival of tumor-bearing mice. Histological analysis revealed that systemic POMC therapy induced melanogenic differentiation while reducing melanoma growth. In addition, POMC therapy also elicited a significant reduction in the neovascular network of melanoma. Last, we demonstrated that POMC-derived peptides, including ACTH, α-melanocyte-stimulating hormone (α-MSH), and β-MSH, are involved in POMC-mediated melanogenic differentiation and angiogenesis inhibition. In summary, systemic POMC therapy suppresses melanoma growth via induction of melanogenic differentiation and angiogenesis blockade, thereby demonstrating its potential as a novel treatment modality for melanoma.

These results support the existence of an MC-1R-independent pathway for POMC gene therapy, which further expands the therapeutic spectrum of POMC therapy for multiple types of cancer.

Hypoxia in the tumor microenvironment triggers differential signaling pathways for tumor survival. In this study, we characterize the involvement of hypoxia and reactive oxygen species (ROS) generation in the antineoplastic mechanism of proopiomelanocortin (POMC) gene delivery in a mouse B16-F10 melanoma model in vivo and in vitro. Histological analysis revealed increased TUNEL-positive cells and enhanced hypoxic activities in melanoma treated with adenovirus encoding POMC (Ad-POMC) but not control vector. Because the apoptotic cells were detected mainly in regions distant from blood vessels, it was hypothesized that POMC therapy might render melanoma cells vulnerable to hypoxic insult. Using a hypoxic chamber or cobalt chloride (CoCl2), we showed that POMC gene delivery elicited apoptosis and caspase-3 activation in cultured B16-F10 cells only under hypoxic conditions. The apoptosis induced by POMC gene delivery was associated with elevated ROS generation in vitro and in vivo. Blocking ROS generation using the antioxidant N-acetyl-l-cysteine abolished the apoptosis and caspase-3 activities induced by POMC gene delivery and hypoxia. We further showed that POMC-derived melanocortins, including α-MSH, β-MSH, and ACTH, but not γ-MSH, contributed to POMC-induced apoptosis and ROS generation during hypoxia. To elucidate the source of ROS generation, application of the NADPH oxidase inhibitor diphenyleneiodonium attenuated α-MSH-induced apoptosis and ROS generation, implicating the proapoptotic role of NADPH oxidase in POMC action. Of the NADPH oxidase isoforms, only Nox4 was expressed in B16-F10 cells, and Nox4 was also elevated in Ad-POMC-treated melanoma tissues. Silencing Nox4 gene expression with Nox4 siRNA suppressed the stimulatory effect of α-MSH-induced ROS generation and cell apoptosis during hypoxia. In summary, we demonstrate that POMC gene delivery suppressed melanoma growth by inducing apoptosis, which was at least partly dependent on Nox4 upregulation.

The prognosis of malignant melanoma is poor due to high incidence of metastasis, underscoring the demand for development of novel therapeutic strategies. Stress hormone pro-opiomelanocortin (POMC) is the precursor for several anti-inflammatory peptides that hold promise for management of cancer-related diseases. The present study evaluated the antimetastatic potential and mechanism of POMC therapy for metastatic melanoma. Adenovirus-mediated POMC gene delivery potently inhibited the invasiveness of human and mouse melanoma cells. Moreover, after induction of lung metastasis, systemic POMC expression significantly reduced the foci formation and neovascularization in lungs. Mechanistic studies revealed that POMC therapy inhibited the epithelial-mesenchymal transition (EMT) of melanoma cells by upregulation of E-cadherin and downregulation of vimentin and a-smooth muscle actin (a-SMA). In addition, microarray analysis unveiled POMC gene transfer reduced the mRNA level of multiple prometastatic factors, including hepatoma-derived growth factor (HDGF). Cell culture and immunohistochemical studies further confirmed that POMC gene delivery significantly decreased the expression of HDGF in melanoma cells and tissues. Despite stimulating the invasion and EMT, exogenous HDGF supply only partially attenuated the POMC-mediated invasion inhibition and EMT change in melanoma cells. Finally, we delineated the contribution of melanocortins to POMC-induced inhibition of invasion, HDGF downregulation, and E-cadherin upregulation. Together, these results indicate that HDGF downregulation participates in POMC-induced suppression of metastasis and EMT in melanoma. Mol Cancer Ther; 12(6); 1016-25. Ó2013 AACR.