Iotzova-Weiss Guergana, Freiberger Sandra N, Johansen Pål, Kamarachev Jivko, Guenova Emmanuella, Dziunycz Piotr J, Roux Guillaume A, Neu Johannes, Hofbauer Günther F L
Department of Dermatology, University Hospital Zurich, Zurich, Switzerland.
PLoS One. 2017 Oct 5;12(10):e0185668. doi: 10.1371/journal.pone.0185668. eCollection 2017.
TLR4 is an innate immune receptor with expression in human skin, keratinocytes as well as squamous cell carcinoma (SCC) of the skin. In the present study we investigate the role of TLR4 as a negative regulator of keratinocyte proliferation. We present here that the expression of TLR4 increased with the differentiation of cultured keratinocytes in a passage-dependent manner or under calcium-rich conditions. Moreover, the down-regulation of TLR4 by specific knockdown increased the proliferation of HaCaT keratinocytes in vitro. In addition, subcutaneously injected HaCaT keratinocytes with shTLR4 formed growing tumors in nude mice. In contrast, we observed lower proliferation and increased migration in vitro of the SCC13 cell line stably overexpressing TLR4 in comparison to SCC13 TLR4 negative cells. In vivo, SCC13 TLR4-overexpressing tumors showed delayed growth in comparison to TLR4 negative tumors. The overexpression of TLR4 in SCC13 tumor cells was followed by phosphorylation of ERK1/2 and JNK and increased expression of ATF3. In gene expression arrays, the overexpression of TLR4 in tumor cells correlated with gene expression of ATF-3, IL-6, CDH13, CXCL-1 and TFPI. In summary, TLR4 negatively regulates the proliferation of keratinocytes and its overexpression reduces tumor growth of SCC cells.
Toll样受体4（TLR4）是一种天然免疫受体，在人类皮肤、角质形成细胞以及皮肤鳞状细胞癌（SCC）中均有表达。在本研究中，我们探究了TLR4作为角质形成细胞增殖负调节因子的作用。我们在此展示，TLR4的表达随着培养的角质形成细胞在传代依赖性方式下或在富含钙的条件下分化而增加。此外，通过特异性敲低TLR4可增加体外HaCaT角质形成细胞的增殖。另外，皮下注射携带shTLR4的HaCaT角质形成细胞可在裸鼠体内形成生长的肿瘤。相反，与SCC13 TLR4阴性细胞相比，我们观察到稳定过表达TLR4的SCC13细胞系在体外增殖较低且迁移增加。在体内，与TLR4阴性肿瘤相比，过表达TLR4的SCC13肿瘤生长延迟。SCC13肿瘤细胞中TLR4的过表达伴随着细胞外信号调节激酶1/2（ERK1/2）和应激活化蛋白激酶（JNK）的磷酸化以及活化转录因子3（ATF3）表达的增加。在基因表达阵列中，肿瘤细胞中TLR4的过表达与ATF - 3、白细胞介素 - 6（IL - 6）、钙黏蛋白13（CDH13）、CXC趋化因子配体1（CXCL - 1）和组织因子途径抑制物（TFPI）的基因表达相关。总之，TLR4负调节角质形成细胞的增殖，其过表达可降低SCC细胞的肿瘤生长。
