PTGIR and neoplasm: Other pairs of co-expressed genes encoding prostanoid receptors were as follows: PTGIR-PTGER2, r = 0.72 − 0.75, TGCT tumor; PTGER4-PTGER2, 0.68–0.78, SKCM tumor; PTGDR-PTGER2, r = 0.66 − 0.74, SKCM tumor; PTGDR-PTGER3, 0.59–0.67, PAAD tumor.