H2BC21 and cancer: To further investigate whether DNA fusion occurred during the formation of PGCCs, control cancer cells with stable co-expression of H2B-GFP and H2B-mCherry were co-cultured (the same amount of LoVo-H2B-GFP and LoVo-H2B-mCherry cells as well as Hct116-H2B-GFP and Hct116-H2B-mCherry cells were co-cultured).