Increased expression of dermal LL37 may trigger migration of CCR7+ regulatory T cells in extramammary Paget's disease

LL-37 Might Promote Local Invasion of Melanoma by Activating Melanoma Cells and Tumor-Associated Macrophages

LL-37 can stimulate various skin-resident cells to contribute to tumor development. Since tumor (T) stage is determined by the vertical invasion of tumor cells in melanoma, we hypothesized that the LL-37 expression level is correlated with the T stage in melanoma patients. Immunohistochemical staining of LL-37 was performed in each stage of melanoma (Tis-T4), suggesting the ratio of LL-37-expressing cells correlate positively to T stage severity. Next, to examine pro-angiogenetic factors induced by LL-37 stimulation, the B16F10 melanoma model was used. Intra-tumorally administered CRAMP, the mouse ortologe of LL-37, significantly increased the mRNA expression of CXCL5, IL23A, MMP1a, and MMP9 in B16F10 melanoma. To confirm the induction of pro-angiogenic factors, A375 human melanoma cells were stimulated by LL-37 in vitro. The mRNA expression of CXCL5, IL23A, and MMP9, but not MMP1, were significantly increased by LL-37 stimulation. Moreover, LL-37-stimulated A375 culture supernatant promoted tube networks, suggesting that these tumor-derived factors promote the pro-angiogenic effect on tumor development. In contrast to melanoma cell lines, M2 macrophages stimulated by LL-37 in vitro significantly increased their expression and secretion of MMP-1, but not MMP-9 expression. Collectively, these results suggest that LL-37 stimulates both tumor cells and macrophages to promote melanoma invasion by the induction of pro-angiogenic factors.

Stromal Factors as a Target for Immunotherapy in Melanoma and Non-Melanoma Skin Cancers

Immune checkpoint inhibitors (ICIs), such as anti-programmed cell death 1 (PD1) antibodies (Abs) and anti-cytotoxic T-lymphocyte associated protein 4 (CTLA4) Abs, have been widely administered for not only advanced melanoma, but also various non-melanoma skin cancers. Since profiles of tumor-infiltrating leukocytes (TILs) play important roles in immunotherapy using ICIs, it is important to evaluate cancer stromal cells such as tumor-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs), as well as stromal extracellular matrix protein, to predict the efficacy of ICIs. This review article focuses particularly on TAMs and related factors. Among TILs, TAMs and their related factors could be the optimal biomarkers for immunotherapy such as anti-PD1 Ab therapy. According to the studies presented, TAM-targeting therapies for advanced melanoma and non-melanoma skin cancer will develop in the future.

Possible roles of CXCL13/CXCR5 axis in the development of bullous pemphigoid

CXCL13 recruits CXCR5⁺ follicular helper T (Tfh) cells in inflammatory lesions to develop secondary lymphoid organs. Tfh cells activate B cells to produce antibodies during humoral immune responses. Indeed, as previous reports suggested, CXCR5⁺ cell numbers were increased in the peripheral blood of bullous pemphigoid (BP) patients when compared with healthy donors, and the ratio of CXCR5⁺ cells was positively correlated with the anti-BP180-NC16A titers. From the above findings, in this report, we hypothesized that a chemokine related to CXCR5⁺ cells, namely CXCL13, may play a role in the development of BP. We performed immunohistochemical staining of CXCR5, CXCL13, LL37, CXCL10 and CCL20 for 10 cases of BP and 10 cases of pemphigus vulgaris (PV), and quantitatively analyzed the staining by digital microscopy. Moreover, we investigated the CXCL10 and CXCL13 production in BP and PV patients by enzyme-linked immunosorbent assay. The immunomodulatory effects of LL37 on the production of T-helper 17-related chemokines were evaluated using monocyte-derived M2 macrophages. Immunohistochemical staining and digital microscopic analysis showed that the ratios of CXCR5⁺ , CXCL13⁺ and LL37⁺ cells in the dermis were significantly higher in BP patients than in PV patients. Notably, the ratio of CXCL13⁺ cells was positively correlated with the anti-BP180-NC16A titers. Moreover, the serum levels of CXCL13 were positively correlated with the anti-BP180-NC16A titers. Furthermore, CD163⁺ M2 macrophages stimulated by LL37 in vitro produced CXCL10 and CCL20. In the lesional skin of BP, CD163⁺ macrophages CXCL10 and CCL20 were produced. The serum levels of CXCL10 were negatively correlated with the anti-BP180-NC16A titers. The present study results indicate that the mechanism of the development of BP may involve the CXCL13/CXCR5-mediated migration of Tfh cells.