STAT4 and lung cancer: The major findings of the present study can be summarized as follows: (1) CFH and STAT4 expression levels were correlated in lung cell lines and human lung cancer tissues; (2) STAT4 regulated CFH expression by directly binding the CFH promoter as a transcription factor; (3) the SOCS family negatively regulated CFH expression by suppressing the STAT4 pathway; and (4) epigenetic gene regulation, such as methylation, did not influence the expression of the SOCS family but did regulate STAT4 expression in lung cancer.