Arsenic trioxide inhibits the growth of cancer stem cells derived from small cell lung cancer by downregulating stem cell- maintenance factors and inducing apoptosis via the Hedgehog signaling blockade

Abstract

Background: Small cell lung cancer (SCLC) is the most deadly and aggressive type of primary lung cancer, with the 5-year survival rate lower than 5%. The FDA has approved arsenic trioxide (As 2 O 3 ) for acute promyelocytic leukemia (APL) treatment. However, its role in SCLC-derived cancer stem cells (CSCs) remains largely unknown.Methods: CSCs were enriched from SCLC cell lines by culturing them as spheres in conditioned serumfree medium. Then, qPCR, western blot, serial passage, limiting dilution, Transwell, and tumorigenesis assay were performed to verify the cells' stem phenotypic characteristics. Anticancer efficiency of As 2 O 3 was assessed in these cells using CCK8, colony formation, sphere formation, flow cytometry, qPCR, western blot analysis in vitro, and tumor growth curve, immunofluorescence, and TUNEL staining analyses in vivo.Results: The fifth-passage SCLC spheres showed a potent self-renewal capacity, higher clonal formation efficiency (CFE), SOX2, c-Myc, NANOG, and OCT4 levels, and invasion ability, and stronger tumorigenesis capacity than the parental SCLC cells, indicating that the SCLC sphere cells displayed CSC features. As 2 O 3 inhibited the proliferation, clonality and sphere forming ability of SCLC-derived CSCs and suppressed the tumor growth of CSCs-derived xenograft tumors. As 2 O 3 induced apoptosis and downregulation of SOX2 and c-Myc in vitro and in xenografts. Besides, SOX2 knockdown suppressed SCLC-derived CSCs to selfrenew and induced apoptosis. Mechanistically, expression of GLI1 (a key transcription factor of Hedgehog pathway) and its downstream genes increased in SCLC-derived CSCs, compared to the parental cells. As 2 O 3 dramatically downregulated GLI1 and its downstream genes in vitro and in vivo. The GLI inhibitor (GANT-61) recapitulated and enhanced the effects of As 2 O 3 on SCLC-derived CSCs, including growth suppression, apoptosis induction, and GLI1, SOX2 and c-Myc downregulation. Conclusions: Altogether, As 2 O 3 effectively suppressed SCLC-derived CSCs growth by downregulating stem cell-maintenance factors and inducing apoptosis. These effects are mediated at least partly via the Hedgehog signaling blockade.

Kinase Suppressor of Ras 2 promotes self-renewal and clonogenicity of small-cell lung carcinoma

“…2C). Robust colony formation, a measure of self-renewing capability of an individual cell 33–35 , was observed in KP3 control TPCs. Viability was reduced by 91%, 58%, and 45% with KSR2 RNAi by sh5, 6, and 7, respectively, which is proportional to their effectiveness at targeting KSR2 (Fig.…”

Small cell lung cancer transformation and tumor heterogeneity after sequential targeted therapy and immunotherapy in EGFR-mutant non-small cell lung cancer: A case report

“…Although the mechanism for this is unclear, some theories support this hypothesis. The existence of cancer stem cells, being related to the differentiation and proliferation of cancer cells, were supposed to have ability to differentiate into either SCLC or NSCLC (16)(17)(18)(19)(20). Lung adenocarcinoma and SCLC were found to have the potential shared cell of origin.…”

Identification and characterization of a subpopulation of CD133+ cancer stem‐like cells derived from SK-UT-1 cells

“…Numerous attempts have been made to identify cells with stemness properties in cancer cell lines. Recently, as a functional approach, sphere formation is particularly significant to enrich potential CSC subpopulations when specific CSC-surface markers have not been defined [ 22 , 23 ]. To date, no marker for putative ULMS CSCs has been proposed, and therefore, further study is required to explore the isolation method for ULMS CSCs.…”