SPP1 and neoplasm: There were no correlations between tumour cell OPN-C and SPP1 (Spearmans r = 0.003, p = 0.98) or tumour cell OPN-N and SPP1 (Spearmans r = −0.047, p = 0.65) and regression analysis show no relationships of the variables of gene- and protein expression (R2 > 0.01).