PTEN and familial pancreatic carcinoma: The conclusion is that miR‐21 regulates 5‐FU drug resistance in pancreatic cancer by reducing the expression of its targets, PTEN and PDCD4. And PTEN and PDCD4, as tumor suppressors, not only can inhibit tumor growth and invasion, but also can downregulate the 5‐FU resistance induced by miR‐21 in pancreatic cancer cells.