Induction of cancer stem cells from mouse fibroblasts

Natural biological agents that can transform normal somatic cells into cancer stem cells, have not been identified. We earlier reported that cell free chromatin particles (cfChPs) that circulate in blood of cancer patients can horizontally transfer themselves to healthy cells to induce dsDNA breaks and inflammation. Here we show that a single cell clone D5 developed from NIH3T3 mouse fibroblast cells treated with cfChPs isolated from sera of cancer patients exhibited upregulation of stemness related transcription factors OCT4, SOX2 and KLF4 and surface markers CD34, CD44 and CD133, and the ability to form spheroids in appropriate culture medium. Transcriptome analysis revealed upregulation of the stemness-associated gene Kruppel-like factor 4 (Klf4), a key Yamanaka factor for the induction of pluripotent stem cells. Additionally, several cancer-related pathways involved in invasion, metastasis, and stemness were found to be upregulated. These pathways included those related to ERBB signaling, P53, cellular senescence, ATM, CTCF and apoptosis. Subcutaneous inoculation into SCID mice resulted in development of malignant tumours which expressed the endoderm marker alpha fetoprotein confirming their stem cell property. Our results suggest the cfChPs that circulate in blood of cancer patients can transform susceptible somatic cells into cancer stem cells with the potential to promote metastasis.