STIP1 and renal cell carcinoma: Furthermore, we examined the immunoreactivity of the STIP1 protein in 10 pairs of matched primary RCC and bone metastasis paraffin-embedded tissues (Figure 2C, 2D), and found a strong correlation of the high STIP1 expression in primary tumors with bone metastatic tumors (the Pearson's correlation coefficient is 0.69).