Silencing of STRN4 suppresses the malignant characteristics of cancer cells.
Bottom Line: We previously reported that STRN4 directly associated with protein kinases, such as MINK1, TNIK and MAP4K4, which are associated with tumor suppression or tumor progression.However, it remains unclear whether STRN4 is associated with tumor progression.Our results demonstrate a possible role of STRN4 in tumor progression.
Affiliation: Department of Gastroenterology and Hepatology, Nagoya University Graduate School of Medicine, Nagoya, Japan.Show MeSH
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Mentions: We next assessed the anchorage-independent growth of the STRN4-depleted cells. Among the cancer cell lines we tested, KP4, PK9, HCT116, TE1 and SKOV3 formed colonies when cultured in the soft agar; therefore, we used these cell lines for the colony formation assay. siRNA-transfected cells were cultured in soft agar, and colony formation was evaluated 2 weeks later. The STRN4 siRNA-transfected cells formed significantly fewer colonies than the control siRNA-transfected cells (Fig. 3a). To confirm that the suppression of colony formation was mediated by STRN4 depletion, we performed a rescue experiment. STRN4-expressing KP4 cells were transfected with siSTRN4-3 and subjected to colony formation. The exogenous expression of STRN4 clearly inhibited the suppression of colony formation by siSTRN4-3 transfection (Fig. 3b). Anoikis is a form of cell apoptosis induced by the detachment of cells from the extracellular matrix. We hypothesized that the suppression of colony formation by STRN4 knockdown was associated with the promotion of anoikis. Cells transfected with siRNA were cultured in suspension for 48 h, and apoptotic cells were then detected via TUNEL assay. As shown in Figure 3(c), STRN4 depletion clearly increased the ratio of apoptotic cells after 48 h of suspension culture. A rescue experiment confirmed that the induction of anoikis was mediated by STRN4 depletion (Fig. 3d).
Affiliation: Department of Gastroenterology and Hepatology, Nagoya University Graduate School of Medicine, Nagoya, Japan.