(P 374) ARHGEF4 EXPRESSION IN SOFT TISSUE SARCOMA CORRELATES WITH LOCAL GROWTH PATTERN AND LOCAL RECURRENCE: COMPREHENSIVE GENOMIC ANALYSIS IN SEARCH OF BIOMARKER OF LOCAL GROWTH PATTERN

Objective: Soft tissue sarcoma(STS) is known to respect barriers to tumor spread while its infiltrative and expanding growth patterns are not investigated in molecular level. We hypothesized presence of genes up regulated or down regulated during local growth of STS. We have explored to discover candidate genes involved in the growth pattern of soft tissue sarcoma and sought its correlation with clinical outcomes including local recurrence and metastasis.

Methods: We have collected tumor cells from central and peripheral areas separately and performed Whole transcriptome sequencing(WTS) in 3 Undifferentiated Pleomorphic Sarcoma (UPS) and one pleomorphic liposarcoma (P-LPS) tissues. We have selected 58 candidate genes and performed real time PCR to choose the genes that showed higher expression in peripheral areas than central areas of STS. ARHGEF4, which is mainly located at cytoplasm and involved in regulation of actin cytoskeleton, showed increased expression in periphery than central tumor. To investigate the role of ARHGEF4 in cell invasion, migration, and cell viability, Boyden chamber assay, wound healing assay, and MTT assay were performed with patient-derived STS cell lines after knock down of ARHGEF4 by short interfering RNA(siRNA). We have performed immunohistochemistry for ARHGEF4 expression in biopsy specimens of 66 patients with UPS and myxofibrosarcoma(MFS).

Results: Knockdown of ARHGEF4 by siRNA resulted in decreased cell invasion, migration, and cell viability in patient-derived STS cell lines. Expression of ARHGEF4 showed correlation with infiltrative and expanding histologic growth pattern (p=0.023). The elevated expression of ARHGEF4 was associated with a trend towards decreased local recurrence-free survival (p=0.148).

Conclusion: These results suggest ARHGEF4 could serve as a biomarker and a therapeutic target of local growth pattern in STS.