P2RY4 and lung cancer: Next, we determined the expression levels of P2X sub-families P2RX1–7 and P2Y receptors P2RY1, P2RY2, P2RY4, P2RY5 (LPAR6), P2RY6, P2RY7 (LTB4R), P2RY8, P2RY9 (LPAR4), P2RY10–14 in normal lung tissues and lung cancer tissues.