Serglycin in tumor microenvironment promotes non-small cell lung cancer aggressiveness in a CD44-dependent manner.

Tumor microenvironment (TME) plays an active role in promoting tumor progression. To further understand the communication between TME and tumor cells, this study aimed at investigating the involvement of CD44, a type I cell surface receptor, in the crosstalk between tumor cells and TME. We have previously shown that chondroitin sulfate proteoglycan serglycin (SRGN), a CD44-interacting factor, was preferentially secreted by cancer-associated fibroblasts (CAFs) for promoting tumor growth in breast cancer patients. In this study, we show that SRGN is overexpressed in primary non-small cell lung cancers (NSCLCs), by both carcinoma and stromal cells. Using gain-of-function and loss-of-function approaches, we show that SRGN promotes NSCLC cell migration and invasion as well as colonization in the lung and liver in a CD44-dependent manner. SRGN induces lung cancer cell stemness, as demonstrated by its ability to enhance NSCLC cell sphere formation via Nanog induction, accompanied with increased chemoresistance and anoikis-resistance. SRGN promotes epithelial-mesenchymal transition by enhancing vimentin expression via CD44/NF-κB/claudin-1 (CLDN1) axis. In support, CLDN1 and SRGN expression are tightly linked together in primary NSCLC. Most importantly, increased expression of SRGN and/or CLDN1 predicts poor prognosis in primary lung adenocarcinomas. In summary, we demonstrate that SRGN secreted by tumor cells and stromal components in the TME promotes malignant phenotypes through interacting with tumor cell receptor CD44, suggesting that a combined therapy targeting both CD44 and its ligands in the TME may be an attractive approach for cancer therapy.

Involvement of the XpsN protein in formation of the XpsL-xpsM complex in Xanthomonas campestris pv. campestris type II secretion apparatus.

The xps gene cluster is required for the second step of type II protein secretion in Xanthomonas campestris pv. campestris. Deletion of the entire gene cluster caused accumulation of secreted proteins in the periplasm. By analyzing protein abundance in the chromosomal mutant strains, we observed mutual dependence for normal steady-state levels between the XpsL and the XpsM proteins. The XpsL protein was undetectable in total lysate prepared from the xpsM mutant strain, and vice versa. Introduction of the wild-type xpsM gene carried on a plasmid into the xpsM mutant strain was sufficient for reappearance of the XpsL protein, and vice versa. Moreover, both XpsL and XpsM proteins were undetectable in the xpsN mutant strain. They were recovered either by reintroducing the wild-type xpsN gene or by introducing extra copies of wild-type xpsL or xpsM individually. Overproduction of wild-type XpsL and -M proteins simultaneously, but not separately, in the wild-type strain of X. campestris pv. campestris caused inhibition of secretion. Complementation of an xpsL or xpsM mutant strain with a plasmid-borne wild-type gene was inhibited by coexpression of XpsL and XpsM. The presence of the xpsN gene on the plasmid along with the xpsL and the xpsM genes caused more severe inhibition in both cases. Furthermore, complementation of the xpsN mutant strain was also inhibited. In both the wild-type strain and a strain with the xps gene cluster deleted (XC17433), carrying pCPP-LMN, which encodes all three proteins, each protein coprecipitated with the other two upon immunoprecipitation. Expression of pairwise combinations of the three proteins in XC17433 revealed that the XpsL-XpsM and XpsM-XpsN pairs still coprecipitated, whereas the XpsL-XpsN pair no longer coprecipitated.

Induction of pulmonary fibrosis in organ-cultured rat lung by cadmium chloride and transforming growth factor-beta1.

Cadmium chloride (CdCl2) exposure has been reported to induce pulmonary fibrosis in rats. Accumulating evidence has shown that cytokines play a pivotal role in the excessive production of connective tissue components in pulmonary fibrosis. In this report, rat lung slice cultures were used to study the synergistic involvement of transforming growth factor-beta1 (TGF-beta1) in CdCl2-induced alveolar fibrosis. Rat lung slices were maintained at the interphase of air and medium on a polyester mesh stretched on a plastic scaffold. Treatment of lung slices with 2.5, 5 or 10 microM CdCl2 for 7 days resulted in 85, 40 and 6% respectively for relative survival. Under these culture conditions, CdCl2 alone did not induce alveolar fibrosis in rat lung slices. However, in the presence of 0.5 ng/ml TGF-beta1, CdCl2 at a dose ranging from 1 to 5 microM increased the thickness of alveolar septa. Furthermore, the thickness of alveolar septa in lung slices treated with CdCl2 was dose-dependently increased by the presence of TGF-beta1. The thickened alveolar septa were apparently due to the deposition of excessive extracellular matrix, as revealed by trichrome stain and ultrastructural examination. Our results also show that fibrogenic activity induced by the combined treatment with CdCl2 and TGF-beta1 can be reduced by co-treatment with 200 microg/ml lambda-carrageenan, a TGF-beta1 inhibitor. Therefore, the present results indicate that TGF-beta1 can synergistically stimulate the fibrogenic activity in lung tissue subsequent to CdCl2 injury.