Upregulation of CD26 expression in epithelial cells and stromal cells during wound-induced skin tumour formation

Abstract

We have previously described InvEE transgenic mice in which non-dividing, differentiating epidermal cells express oncogenically activated MAPK kinase 1 (MEK1). Skin wounding triggers tumour formation in InvEE mice via a mechanism that involves epidermal release of IL-1a and attraction of a pro-tumorigenic inflammatory infiltrate. To look for potential effects on the underlying connective tissue, we screened InvEE and wild-type epidermis for differential expression of cytokines and immune modulators. We identified a single protein, CD26 (dipeptidyl peptidase-4). CD26 serum levels were not increased in InvEE mice. In contrast, CD26 was upregulated in keratinocytes expressing mutant MEK1 and in the epithelial compartment of InvEE tumours, where it accumulated at cell-cell borders. CD26 expression was increased in dermal fibroblasts following skin wounding but was downregulated in tumour stroma. CD26 activity was stimulated by calcium-induced intercellular adhesion in keratinocytes, suggesting that the upregulation of CD26 in InvEE epidermis is due to expansion of the differentiated cell layers. IL-1a treatment of dermal fibroblasts stimulated CD26 activity, and therefore epidermal IL-1a release may contribute to the upregulation of CD26 expression in wounded dermis. Pharmacological blockade of CD26, via Sitagliptin, reduced growth of InvEE tumours, while combined inhibition of IL-1a and CD26 delayed tumour onset and reduced tumour incidence. Our results demonstrate that inappropriate activation of MEK1 in the epidermis leads to changes in dermal fibroblasts that, like the skin inflammatory infiltrate, contribute to tumour formation.

Dipeptidylpeptidase 4 inhibition enhances lymphocyte trafficking, improving both naturally occurring tumor immunity and immunotherapy

“…Prior experimental studies have evaluated dipeptidylpeptidases as targets for tumor therapy; however, these studies have been limited by their use of chemical inhibitors that block the activity of both DPP4 and FAP 36,37 . As a notable exception, one report showed that DPP4 is upregulated in a model of MEK1induced skin tumors and that treatment with sitagliptin delays malignant transformation 38 . Although that study suggests that DPP4 inhibition might be synergistic with interleukin 1 (IL1) receptor antagonist therapy, the authors do not consider a role for the regulation of lymphocyte trafficking.…”

Macrophage Infiltration and Alternative Activation during Wound Healing Promote MEK1-Induced Skin Carcinogenesis

“…The overall picture that emerges from our studies of wound-induced tumor formation is of tumorigenesis via collaboration between multiple cell types and signaling molecules, including upregulation of IL-1α in differentiating keratinocytes driving increased expression of the dipeptidyl peptidase CD26 in fibroblasts (6, 8), recruitment of macrophages and other immune cells and a pivotal role of macrophages in both creating an immunosuppressive environment and stimulating keratinocytes to proliferate.…”

“…At least 2 regions per wound and animal were analyzed and a minimum of 3 mice used per data point. For quantifications using flow cytometry a 1.5 x 2 cm piece of back skin was harvested; dermal and epidermal cells were isolated as described previously (8) and labelled with the following antibodies: CD45-APC Cy7, CD3-PerCP (both BD), CD11b-PacBlue (Invitrogen), CD11b-AF594, MHC class II-brilliant violet 421 (all Biolegend), F4/80-PE, F4/80-alexa 647, Gr1-alexa 660 (RB6-8C5) and Ly6C-eF780 (all eBioscience). Labeled cells were sorted on a BD FACSARIA II cell sorter.…”

“…In this model MEK1 expressing, non-dividing cells stimulate keratinocytes in the basal layer to divide and form the proliferative compartment of the tumor (6). MEK1 expressing suprabasal cells recruit an inflammatory infiltrate via secretion of pro-inflammatory cytokines including IL-1α (7), which in turn induces expression of CD26 on stromal fibroblasts (8). …”

Suppression of lung metastases by the CD26/DPP4 inhibitor Vildagliptin in mice

“…A role of CD26/DPP4 in tumor biology has been suggested according to its functional and enzymatic properties in T cell lymphoma, mesothelioma, melanoma, renal carcinoma, colorectal cancer, and lung cancer [9][10][11][12][13][14][15]. Recently, a CD26/DPP4 antibody was employed as a therapeutic measure in mesothelioma and T-cell lymphoma showing down-regulation of RPB1 followed by inhibitory DNA binding of CD26/DPP4 [16][17][18].…”