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

Department of Dermatology and Skin Diseases Research Center, University of Alabama at Birmingham, USA.
Molecular Carcinogenesis (Impact Factor: 4.81). 07/2011; 50(7):516-27. DOI: 10.1002/mc.20744
Source: PubMed


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 CsA-treated 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 E-cadherin. CsA-treated xenograft tumors manifested increased TGFβ1 expression and TGFβ-dependent signaling characterized by increased nuclear p-Smad 2/3. 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.

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Available from: Laura Timares, Aug 22, 2014
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    ABSTRACT: Cyclosporine A (CsA) is an immunosuppressive drug commonly used for maintaining chronic immune suppression in organ transplant recipients. It is known that patients receiving CsA manifest increased growth of aggressive non-melanoma skin cancers. However, the underlying mechanism by which CsA augments tumor growth is not fully understood. Here, we show that CsA augments the growth of A431 epidermoid carcinoma xenograft tumors by activating tumor growth factor β-activated kinase1 (TAK1). The activation of TAK1 by CsA occurs at multiple levels by kinases ZMP, AMPK and IRAK. TAK1 forms heterodimeric complexes with TAK binding protein 1 and 2 (TAB1/TAB2) which in term activate nuclear factor κB (NFκB) and p38 MAP kinase. Transcriptional activation of NFκB is evidenced by IKKβ-mediated phosphorylation-dependent degradation of IκB and consequent nuclear translocation of p65. This also leads to enhancement in the expression of its transcriptional target genes cyclin D1, Bcl2 and COX-2. Similarly, activation of p38 leads to enhanced inflammation-related signaling shown by increased phosphorylation of MAPKAPK2 and which in turn phosphorylates its substrate HSP27. Activation of both NFκB and p38 MAP kinase provide mitogenic stimuli to augment the growth of SCCs.
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