Amplifications of stemness genes and the capacity of breast tumors for metastasis.

Nikolai Litviakov,Marina Ibragimova,Polina Kazantseva,Eugeny Garbukov,Natalia Tarabanovskaya,Alina Pevzner,Matvey Tsyganov,Artem Doroshenko,Irina Deryusheva,Elena Slonimskaya

doi:10.18632/oncotarget.27608

Abstract

Introduction: The phenomenon of non-CSC (cancer stem cell) to CSC plasticity has been previously described in multiple studies and occurs during the ectopic expression of stemness genes such as OCT3, SOX2, KLF4, MYC, NOTCH1, and NANOG. In our opinion, acquiring the ability to ectopically express stemness genes, selected by bioinformatics analysis and, accordingly, non-CSC to CSC plasticity, is due to amplification of genes at the following locations: 3q, 5p, 6p, 7q, 8q, 13q, 9p, 9q, 10p, 10q21.1, 16p, 18chr, 19p. This paper demonstrates the significance of stemness gene amplifications leading to metastasis and stem-like cancer cell activity.Materials and Methods: In our studies, stemness gene amplifications were determined using the CytoScan HD Array. We studied the association of changes in stemness gene amplifications in tumors with metastasis treated with neoadjuvant chemotherapy (NAC) in 50 patients with breast cancer. We used qPCR to evaluate the expression of 13 stemness genes in tumors before and after NAC in 98 patients with breast cancer. Using primary cultures from the breast tumor of patient St23784/17 with stemness gene amplifications (SOX2, MYC, KLF4, NOTCH1, NODAL) and patient Ti41749/17 without stemness gene amplifications in the tumor, we studied the expression of stemness genes, proliferative tumor stem-cell activity, mammosphere formation, and expression of the CD44 tumor stem cell marker.Results: The occurrence of amplifications at regions of stemness gene localization during NAC (22% cases) in residual tumors was associated with a very high metastasis rate (91% cases). Eliminating tumor clones with stemness gene amplifications using NAC (42% cases) led to 100% metastasis-free survival.In patients who developed hematogenic metastases after treatment, the expression of 7/13 stemness genes in the residual tumor after NAC was statistically higher than in patients without metastases. Primary cultures of EpCam+ tumor cells from patients with stemness gene amplifications revealed high proliferative activity. After the 3rd passage, the number of tumor cells increased 30-fold. Due to IL-6, this cell population showed a 2.5-fold increase in the EpCam+CD44hiCD24–/low and 2-fold decrease in the EpCam+CD44lowCD24– subpopulations of tumor stem cells; the formation of mammospheres was also observed. Primary cultures of EpCam+ tumor cells from the patient with no stemness gene amplifications had relatively low proliferative activity. IL-6 caused a 2.3-fold increase in the EpCam+CD44lowCD24– and 2-fold decrease in the EpCam+CD44hiCD24–/low subpopulations of tumor stem cells with no induction of mammospheres.Conclusions: The results of this study show that stemness gene amplifications in tumor cells are associated with metastasis and determine their potential stem property activation and non-CSC to CSC plasticity with the formation of EpCam+CD44hiCD24–/low cells, active proliferation, mammosphere formation, and metastasis.

Highlights

The phenomenon of non-cancer stem cells (CSCs) to CSC plasticity has been previously described in multiple studies and occurs during the ectopic expression of stemness genes such as OCT3, SOX2, KLF4, MYC, NOTCH1, and NANOG
The results of this study show that stemness gene amplifications in tumor cells are associated with metastasis and determine their potential stem property activation and non-CSC to CSC plasticity with the formation of EpCam+CD44hiCD24–/low cells, active proliferation, mammosphere formation, and metastasis
In each of the 50 patients, we compared the CNA (CNA–copy number aberration)-genetic landscape of breast tumors before and after neoadjuvant chemotherapy (NAC), and we evaluated changes in stemness gene amplification during the NAC

Summary

Introduction

The phenomenon of non-CSC (cancer stem cell) to CSC plasticity has been previously described in multiple studies and occurs during the ectopic expression of stemness genes such as OCT3, SOX2, KLF4, MYC, NOTCH1, and NANOG. In our opinion, acquiring the ability to ectopically express stemness genes, selected by bioinformatics analysis and, non-CSC to CSC plasticity, is due to amplification of genes at the following locations: 3q, 5p, 6p, 7q, 8q, 13q, 9p, 9q, 10p, 10q21.1, 16p, 18chr, 19p. This paper demonstrates the significance of stemness gene amplifications leading to metastasis and stem-like cancer cell activity. In 2013, Cristine Chaffer et al expressed the opinion that different tumors differ significantly in their non-CSC plasticity, which will determine their malignant potential and ability to progress [4]. Like Cristine Chaffer, we suspect that non-CSC plasticity, stemness induction, and stem-like cell activity determine tumor malignancy and, most importantly, the ability to metastasize. Lack of non-CSC plasticity and induction of a complete stem phenotype, as well as low stem-like cancer cell ability, explain the inability of a tumor to metastasize

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