Concomitant inhibition of AKT and autophagy is required for efficient cisplatin‐induced apoptosis of metastatic skin carcinoma

Abstract

Cutaneous squamous cell carcinoma (cSCC) is one of the most common cancers in the Caucasian population. Although early stages of skin cancer have a high curability and excellent prognosis, advanced cSCC shows resistance to chemotherapy, including cisplatin. The PI3-K/AKT pathway is known to have a role in both skin cancer development and resistance to therapeutic drugs. In this study, we used isogenic cell lines representing different stages of malignant transformation of the keratinocytes that were derived from dysplastic forehead skin (PM1), primary cutaneous SCC (MET1) and its lymph node metastasis (MET4) of an immunosuppressed patient. We show that skin tumor progression parallels enhanced AKT activation and increased resistance to cisplatin-induced apoptosis. Pharmacological AKT inhibition, or specific AKT1 knock down, sensitizes the apoptosis-resistant MET1 and, to a lesser extent, MET4 cells to cisplatin-mediated cell death. Concomitantly autophagy induction was observed in MET4, as demonstrated by accumulation of the autophagic protein marker LC3-II, by analysis of full autophagosome maturation process using tandem mRFP-GFP fluorescence microscopy and by electron microscopy. Counteracting the autophagic process by 3-methyladenine or specific ATG5 knock down enhanced cytotoxicity of cisplatin combined with AKT inhibitor, thus revealing a key role for autophagy in chemoresistance. Taken together, these results indicate that concomitant inhibition of autophagy is required to increase the therapeutic benefit of AKT inhibition for combination therapy with the standard chemotherapeutic agent cisplatin in advanced skin carcinoma.Cutaneous squamous cell carcinoma (cSCC) is one of the most common cancers in the Caucasian population and its incidence is still increasing worldwide, 1,2 and is predicted to increase even further.3 Early SCC of the skin has a high curability and relatively low overall metastatic rate of 3-5%. 4 However, certain tumor and patient characteristics predispose to the development of nodal disease and distant metastases, 5 which portends a poor prognosis, with 5-year survival ranging from 14 to 39%, regardless of the treatment used. Current standard initial treatments for advanced SCC are surgical

Constitutively Active ErbB2 Regulates Cisplatin-Induced Cell Death in Breast Cancer Cells via Pro- and Antiapoptotic Mechanisms

“…We show here that compared with vector control cells, DNErbB2-expressing cells exhibit increased basal autophagy and a greater reduction of autophagic flux upon cisplatin treatment, demonstrating that DNErbB2 signaling regulates the autophagic machinery. In metastatic skin cancer, it has been proposed that autophagy is involved in cisplatin resistance (42). However, neither inhibition nor induction of autophagy affected net cell death induced by cisplatin treatment in MCF-7 cells.…”

Autophagy as a mediator of chemotherapy-induced cell death in cancer

“…The reasons why, in some cases, autophagy participates to cell death while in others, it prevents it, are not understood, especially since both effects can be observed within the same anticancer molecule. Examples for a key role of autophagy in chemoresistance are numerous when DNA damaging agents are used: camptothecin in breast cancer cells [61]; cisplatin in esophageal squamous cell carcinoma cells [62], in metastatic skin carcinomas [63] and in lung adenocarcinoma cells [64]; and 5-fluorouracil in colon cancer cells [65] and in esophageal cancer cells [66]. Similar observations were obtained with the new generation drugs: proteasome inhibitors [67,68], Src kinase inhibitor [69] and anti-HER2 monoclonal antibody [70] are such examples.…”

Sestrin2 Protein Positively Regulates AKT Enzyme Signaling and Survival in Human Squamous Cell Carcinoma and Melanoma Cells

“…The major risk factor for skin cancer is ultraviolet radiation in sunlight and artificial tanning beds, including both UVB (280 -315 nm) and UVA (315-400 nm) radiation (2). Despite many advances in targeted therapies and surgical removal of early stage skin cancers, advanced stage metastatic skin squamous cell carcinoma and melanoma are difficult to treat due to therapeutic resistance (3,4). Sestrins (Sesns) are a family of evolutionarily conserved stress-inducible proteins.…”