POU5F1 and neoplasm: High expression levels of OCT4A and OCT4Bv, suggesting that OCT4-positive cells are relatively common among cancer cell lines and tumours, were closely related to SPP1 expression, and ablation of OCT4-positive cells significantly decreased SPP1C-expression levels, suggesting that OCT4A might directly or indirectly up-regulate SPP1C expression in a subpopulation of cancer cells.