Cyclosporine a mediates pathogenesis of aggressive cutaneous squamous cell carcinoma by augmenting epithelial‐mesenchymal transition: Role of TGFβ signaling pathway

Abstract

Organ transplant recipients (OTRs) develop multiple aggressive and metastatic non-melanoma skin cancers (NMSCs). Yet, the underlying mechanism remains elusive. Employing a variety of immune-compromised murine models, immunoblotting, immunohistochemical and immunofluorescence techniques, we show that human squamous xenograft tumors in nude mice grow faster and become significantly larger in size following treatment with the immunosuppressive drug, cyclosporine A (CsA). Re-injected tumor cells isolated from CsAtreated xenografts continued to form larger tumors in nude mice than those from vehicle-controls and retained the CsA-signatures of calcineurin signaling inhibition. Similar results were obtained when these tumors were grown in SCID-beige mice or in immuno-competent mice inoculated with syngeinic tumor cells. Consistently, tumors in the CsA group manifested enhanced cellular proliferation and decreased apoptosis. Tumors in CsA-treated animals also showed an augmented epithelial-mesenchymal transition (EMT) characterized by an increased expression of fibronectin, α-SMA, vimentin, N-cadherin, MMP-9/-2, snail and twist with a concomitant decrease in Ecadherin. CsA-treated xenograft tumors manifested increased TGFβ1 expression and TGFβ-dependent signaling characterized by increased nuclear p-Smad2/3. Our data demonstrate that CsA alters the phenotype of skin SCCs to an invasive and aggressive tumor-type by enhancing expression of proteins regulating EMT acting through the TGFβ1 signaling pathway providing at least one unique mechanism by which multiple aggressive and metastatic NMSCs develop in OTRs.

Combined inhibition of p38 and Akt signaling pathways abrogates cyclosporine A-mediated pathogenesis of aggressive skin SCCs

“…As observed earlier [16], we found that CsA treatment led to the development of larger tumors as compared to the vehicle-treated controls (Figure 1A). These tumors continued to grow beginning from day 6 to day 14.…”

“…CsA treatment significantly increased the levels of proliferation markers cyclin D1 and proliferating cell nuclear antigen (PCNA) as compared to vehicle-treated control group (Figure 2A and B) confirming our earlier observation [16, 19]. However, administration of inhibitors of p38 or Akt alone or in combination to CsA-treated animals significantly decreased the expression of these proteins (Figure 2A and B and Suppl.…”

“…CNI-based immunosuppressive regimens such as CsA and tacrolimus have been associated with greater incidence of skin cancer [15]. We earlier demonstrated a role of TGF-β signaling pathway in the formation of larger and aggressive tumors in CsA-treated A431 human epidermoid xenograft murine model involving an enhancement of epithelial–mesenchymal transition (EMT) [16]. CsA enhanced the tumor growth of subcutaneously injected colon adenocarcinoma cells in immunodeficient mice bearing a heart allograft [17].…”

Roles of the immune system in skin cancer

“…CNIs inhibit Langerhans cells, 53,54 dermal dendritic cells (DC) 55,56 , and T-cell signaling and proliferation, and cyclosporine directly promotes tumour development 57–59 . Inhibition of calcineurin enhances carcinoma development in mouse models, and correlative evidence in human SCC implicates induction of ATF3 and bypass of senescence 59,60 . Tacrolimus is increasingly used for OTRs due to a favourable side effect profile as compared to cyclosporine in some settings.…”

Negative regulation of the FOXO3a transcription factor by mTORC2 induces a pro-survival response following exposure to ultraviolet-B irradiation

“…Unlike other cancers where the incidence has stabilized or decreased, the rate of NMSC continues to rise, both within the general population and especially within high-risk groups, such as immunocompromised organ transplant recipients. The incidence of cutaneous squamous cell carcinoma (SCC) is 60–100-fold greater in organ transplant recipients than the general population, and frequently patients are diagnosed with multiple, aggressive SCCs [3, 4]. Thus, the identification of new therapeutic targets in NMSC has significant clinical implications.…”