Hsin-Yi Lan

Cell-cell interactions maintain tissue homeostasis and contribute to dynamic alteration of the tumor microenvironment (TME). Communication between cancer and host cells not only promotes advanced disease aggression but also determines therapeutic response in cancer patients. Despite accumulating evidence supporting the role of tumor-infiltrating immunocytes in modulating tumor immunity, the interplay between heterogeneous tumor subpopulations and immunocytes is elusive. We expanded colorectal cancer stem cells (CRCSCs) as cancer spheroids from the murine colorectal cancer (CRC) cell line CT26 to interrogate tumor-host interactions using a syngeneic tumor model. RNA-sequencing analysis of host cells and tumor exosomes was performed to identify molecular determinants that mediate the crosstalk between CRCSCs and immunocytes. The Cancer Genome Atlas (TCGA) database was used to validate the clinical significance in CRC patients. The expanded CT26 cancer spheroids showed increased stemness gene expression, enhanced spheroid and clonogenicity potential, and an elevated tumor-initiating ability, characteristic of CRCSCs. By examining immune cell composition in syngeneic tumor-bearing mice, a systemic increase in CD11b+/Ly6GHigh/Ly6CLow neutrophils was observed in mice bearing CRCSC-derived tumors. An increased secretion of CRCSC exosomes was observed in vitro, and through in vivo tracking, CRCSC exosomes were found to be transported to the bone marrow. Moreover, CRCSC exosomes prolonged the survival of bone marrow-derived neutrophils and engendered a protumoral phenotype in neutrophils. Mechanistically, tumor exosomal tri-phosphate RNAs induced the expression of interleukin-1β (IL-1β) through a pattern recognition-NF-κB signaling axis to sustain neutrophil survival. CRCSC-secreted CXCL1 and CXCL2 then attracted CRCSC-primed neutrophils to promote tumorigenesis of CRC cells via IL-1β. Moreover, neutrophil depletion using a Ly6G-specific antibody (clone 1A8) attenuated the tumorigenicity of CRCSCs. In human specimens, CRC patients exhibiting an active CRCSC signal (Snail+IL8+) showed elevated tumor infiltration of MPO+ neutrophils, and high (in the top 10%) MPO expression predicted poor survival of CRC patients. This study elucidates a multistep CRCSC-neutrophil interaction during advanced cancer progression. Strategies targeting aberrant neutrophil activation may be developed for combating CSC-related malignancy.

PURPOSE: We investigated the mechanism and clinical significance of the epithelial-mesenchymal transition (EMT)-induced chemoresistance in head and neck squamous cell carcinoma (HNSCC). EXPERIMENTAL DESIGN: The correlation between the expression of different EMT regulators and chemoresistance genes, such as excision repair cross complementation group 1 (ERCC1), was evaluated in cancer cell lines from the NCI-60 database and four human HNSCC cell lines. Ectopic expression of Snail or short-interference RNA-mediated repression of Snail or ERCC1 was done in HNSCC cell lines. Cell viability was examined for cells after cisplatin treatment. A luciferase reporter assay and chromatin immunoprecipitation were used to identify the transcriptional regulation of ERCC1 by Snail. Immunohistochemical analysis of Snail, Twist1, ERCC1, hypoxia inducible factor-1 α (HIF-1α), and NBS1 were done in samples from 72 HNSCC patients receiving cisplatin-based chemotherapy. RESULTS: The correlation between the expression of Snail and ERCC1 was confirmed in different cell lines, including HNSCC cells. In HNSCC cell lines, overexpression of Snail in the low endogenous Snail/ERCC1 cell lines FaDu or CAL-27 increased ERCC1 expression, and hypoxia or overexpression of NBS1 also upregulated ERCC1. Knockdown of Snail in the high endogenous Snail/ERCC1 cell line OECM-1 downregulated ERCC1 expression and attenuated cisplatin resistance. Furthermore, suppression of ERCC1 in Snail- or NBS1-overexpressing HNSCC cells enhanced sensitivity to cisplatin. Snail directly regulated ERCC1 transcription. In patients with HNSCC, coexpression of Snail and ERCC1 correlated with cisplatin resistance and a poor prognosis. CONCLUSIONS: Activation of ERCC1 by Snail is critical in the generation of cisplatin resistance of HNSCC cells.