Characterization of SOX2, OCT4 and NANOG in Ovarian Cancer Tumor-Initiating Cells

Abstract

The identification of tumor-initiating cells (TICs) has traditionally relied on surface markers including CD133, CD44, CD117, and the aldehyde dehydrogenase (ALDH) enzyme, which have diverse expression across samples. A more reliable indication of TICs may include the expression of embryonic transcription factors that support long-term self-renewal, multipotency, and quiescence. We hypothesize that SOX2, OCT4, and NANOG will be enriched in ovarian TICs and may indicate TICs with high relapse potential. We evaluated a panel of eight ovarian cancer cell lines grown in standard 2-D culture or in spheroid-enriching 3-D culture, and correlated expression with growth characteristics, TIC marker expression, and chemotherapy resistance. RNA-sequencing showed that cell cycle regulation pathways involving SOX2 were elevated in 3-D conditions. HGSOC lines had longer doubling-times, greater chemoresistance, and significantly increased expression of SOX2, OCT4, and NANOG in 3-D conditions. CD117+ or ALDH+/CD133+ cells had increased SOX2, OCT4, and NANOG expression. Limiting dilution in in vivo experiments implicated SOX2, but not OCT4 or NANOG, with early tumor-initiation. An analysis of patient data suggested a stronger role for SOX2, relative to OCT4 or NANOG, for tumor relapse potential. Overall, our findings suggest that SOX2 may be a more consistent indicator of ovarian TICs that contribute to tumor repopulation following chemotherapy. Future studies evaluating SOX2 in TIC biology will increase our understanding of the mechanisms that drive ovarian cancer relapse.

Disulfiram Transcends ALDH Inhibitory Activity When Targeting Ovarian Cancer Tumor-Initiating Cells

“…Previously, we and others found that ALDH1A1 and ALDH1A2 mRNAs were upregulated in TIC growth conditions ( 5 ) and that ALDH activity is increased in TIC-enriching spheroid growth conditions under the influence of RelB transcriptional activity ( 17 ). We selected EOC cell lines with high ALDH activity to test the ALDH1A1 specific inhibitors, NCT-505 and NCT-506.…”

“…The TIC population is characterized by enhanced chemoresistance, resistance to cell death, oxidative stress mitigation, and the ability to reestablish cancer after the bulk population is reduced by first line, broad-targeting treatments ( 1 – 4 ). TIC populations in EOC can be identified by the expression of molecular markers, namely, CD133, NANOG , and SOX2 expression ( 5 ). Despite extensive characterization of identifying markers of TICs, these markers provide little opportunity for therapeutic targeting.…”

LncRNA RP11-499E18.1 Inhibits Proliferation, Migration, and Epithelial–Mesenchymal Transition Process of Ovarian Cancer Cells by Dissociating PAK2–SOX2 Interaction

“…Former investigations pointed out that SOX2 was an interacting protein of PAK2 ( Huttlin et al, 2015 , 2017 ). Besides, SOX2 was reported to be associated with early tumor initiation ( Robinson et al, 2021 ), and its level in high-grade serous carcinoma (HGSC) effusions was demonstrated to be markers of clinically aggressive disease ( Sherman-Samis et al, 2019 ). Additionally, SOX2 expression was found to be positively correlated with the proliferation and migration capacities of tumor cells ( Chen B. et al, 2019 ; Meng et al, 2020 ), and its high expression is a poor prognostic marker for OC.…”

Changes in Stem Cell Regulation and Epithelial Organisation during Carcinogenesis and Disease Progression in Gynaecological Malignancies

“…Following sequential carboplatin treatment of 2D cultured ovarian cancer cell lines, only SOX2 expression remained elevated after the third treatment, suggesting a role for SOX2 in platinum resistance [56]. Knockdown of SOX2 reduced spheroid formation and improved platinum sensitivity [56]. Additionally, while the presence of traditional CSC markers (CD117, CD133, ALDH1) was variable across cell lines, SOX2 was consistently increased in 3D conditions, and elevated in recurrent cases of ovarian cancer, suggesting it may be a more reliable functional marker of CSC and disease recurrence.…”

“…A recent study by Robinson et al aimed to characterize the roles of SOX2, OCT4, and NANOG in ovarian CSCs [56]. Following sequential carboplatin treatment of 2D cultured ovarian cancer cell lines, only SOX2 expression remained elevated after the third treatment, suggesting a role for SOX2 in platinum resistance [56]. Knockdown of SOX2 reduced spheroid formation and improved platinum sensitivity [56].…”