Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) is a major advance in treating NSCLC with EGFR-activating mutations. However, acquired resistance, due partially to secondary mutations limits their use. Here we report that NSCLC cells with acquired resistance to gefitinib or osimertinib (AZD9291) exhibit EMT features, with a decrease in E-cadherin, and increases in vimentin and stemness, without possessing any EGFR secondary mutations. Knockdown of E-cadherin in parental cells increased gefitinib resistance and stemness, while knockdown of vimentin in resistant cells resulted in opposite effects. Src activation and Hakai upregulation were found in gefitinib-resistant cells. Knockdown of Hakai elevated E-cadherin expression, attenuated stemness, and resensitized the cells to gefitinib. Clinical cancer specimens with acquired gefitinib resistance also showed a decrease in E-cadherin and an increase in Hakai expression. The dual HDAC and HMGR inhibitor JMF3086 inhibited the Src/Hakai and Hakai/E-cadherin interaction to reverse E-cadherin expression, and attenuated vimentin and stemness to restore gefitinib sensitivity. The EMT features of AZD9291-resistant H1975 cells were related to the upregulation of Zeb1. Both gefitinib and AZD9291 sensitivity was restored by JMF3086 through reversing EMT. Our study not only revealed a common mechanism of EMT in both gefitinib and AZD9291 resistance beyond EGFR mutations per se, but also provides a new strategy to overcome it.

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.

Ultraviolet C (UVC) is a DNA damage inducer, and 20 J/m2 of UVC irradiation caused cell growth inhibition and induced cell death after exposure for 24–36 h. The growth of NIH 3T3 cells was significantly suppressed at 24 h after UVC irradiation whereas the proliferation of A431 cells was inhibited until 36 h after UVC irradiation. UVC irradiation increased COX-2 expression and such up-regulation reached a maximum during 3–6 h in NIH 3T3 cells. In contrast, UVC-induced COX-2 reached a maximum after 24–36 h in A431 cells. Measuring prostaglandin E2 (PGE2) level showed a biphasic profile that PGE2 release was rapidly elevated in 1–12 h after UVC irradiation and increased again at 24 h in both cell lines. Treatment with the selective COX-2 inhibitor, SC-791, during maximum expression of COX-2 induction, attenuated the UVC induced-growth inhibition in NIH 3T3 cells. In contrast, SC-791 treatment after UVC irradiation enhanced death of A431 cells. These data showed that the patterns of UVC-induced PGE2 secretion from NIH 3T3 cells and A431 cells were similar despite the differential profile in UVC-induced COX-2 up-regulation. Besides, COX-2 might play different roles in cellular response to UVC irradiation in various cell lines.

Melanoma is notoriously resistant to current cancer therapy. However, the chemoresistance mechanism of melanoma remains unclear. The present study unveiled that chemotherapy drug cisplatin induced the formation of giant cells, which exhibited enlargement in cell diameter and nucleus in mice and human melanoma cells. Giant cells were positive with melanoma maker S100 and cancer stem cell markers including ABCB5 and CD133 in vitro and in vivo. Moreover, giant cells retained the mitotic ability with expression of proliferation marker Ki-67 and exhibited multiple drug resistance to doxorubicin and actinomycin D. The mitochondria genesis/activities and cellular ATP level were significantly elevated in giant cells, implicating the demand for energy supply. Application of metabolic blockers such as sodium azide or 2-deoxy glucose abolished the cisplatin-induced giant cells formation and expression of cancer stemness markers. The present study unveils a novel chemoresistance mechanism of melanoma cells via size alteration and the anti-neoplastic strategy by targeting giant cells.

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