Studies have shown that miRNAs are abnormally expressed in PF and exert promotion or suppression functions in PF, such as miR‐9, miR‐21 and miR‐29.41, 42 miR‐7 is down‐regulated in serum samples of DM patients than that of normal individuals.24 In lung cancer, TLR9 suppressed miR‐7 expression level to enhance the growth and metastasis of tumour.25 These researches indicated that miR‐7 might involve in the progression of PF. Here, TLR9 is linked to lung cancer.