The role of myofibroblasts in upregulation of S100A8 and S100A9 and the differentiation of myeloid cells in the colorectal cancer microenvironment.
OBJECTIVE
S100A8/A9 and myeloid cells in the tumor microenvironment play an important role in cancer invasion and progression, and the effect of tumor-infiltrated myofibroblasts on myeloid cells in the tumor microenvironment is relatively unknown. Accordingly, we investigated the role of myofibroblasts in the upregulation of S100A8/A9 as well as in the differentiation of myeloid cells in the colorectal cancer (CRC) microenvironment.


METHODS
To investigate the interactions among cancer cells, myofibroblasts, and inflammatory cells in the microenvironment of CRC, we used 10 CRC cell lines, 18CO cells and THP-1 cells, which were co-cultured with each other or cultured in conditioned media (CM) of other cells. Expression of S100A8/A9 was evaluated via Western blot, immunohistochemical staining and immunofluorescence. The secreted factors from the cell lines were analyzed using cytokine antibody array. Flow cytometry analysis was performed to analyze the differentiation markers of myeloid cells.


RESULTS
18CO CM induced increased expression of S100A8/A9 in THP-1 cells. Increased expression of S100A8/A9 was noted in inflammatory cells of the peri- and intra-tumoral areas, along with myofibroblasts in colon cancer tissue. S100A8/A9-expressing inflammatory cells also exhibited CD68 expression in colon cancer tissue, and 18CO CM induced differentiation of THP-1 cells into myeloid-derived suppressor cells (MDSCs) or M2 macrophages expressing S100A8/A9. Significant amounts of IL-6 and IL-8 were detected in 18CO CM, compared to those in both controls and THP-1 CM, and tumor-infiltrated myofibroblasts expressed IL-8 in colon cancer tissue. Finally, neutralizing antibodies to IL-6 and IL-8 attenuated 18CO CM-induced increased expression of S100A8/A9.


CONCLUSIONS
The upregulation of S100A8/A9 in tumor-infiltrated myeloid cells could be triggered by IL-6 and IL-8 released from myofibroblasts, and myofibroblasts might induce the differentiation of myeloid cells into S100A8/9-expressing MDSCs or M2 macrophages in the CRC microenvironment.
Graduate School, Yonsei University College of Medicine, Seoul, Republic of Korea.
Jae Hak
JH
Kim
Sun-Hee
SH
Oh
Eo-Jin
EJ
Kim
Soo Jung
SJ
Park
Sung Pil
SP
Hong
Jae Hee
JH
Cheon
Tae Il
TI
Kim
Won Ho
WH
Kim
D040501:Calgranulin A / Q000096:biosynthesis*; D040502:Calgranulin B / Q000096:biosynthesis*; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002465:Cell Movement; D018920:Coculture Techniques; D015179:Colorectal Neoplasms / Q000473:pathology*; D017077:Culture Media, Conditioned / Q000494:pharmacology; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D022423:Myeloid Cells / Q000473:pathology*; D058628:Myofibroblasts / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D059016:Tumor Microenvironment; D015854:Up-Regulation
D040501:Calgranulin A; D040502:Calgranulin B; D017077:Culture Media, Conditioned; D015850:Interleukin-6; D016209:Interleukin-8