High expression of transcription factor POU2F1 confers improved survival on smokers with lung adenocarcinoma: a retrospective study of two cohorts.

ABSTRACT

Background: Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related mortality worldwide and its most important risk factor is tobacco smoking. While smoking is associated with inferior outcome in NSCLC patients, smoking also correlates with a higher tumor mutational burden. In contrast to adenocarcinomas (ADC) of non-smokers, that frequently harbor targetable gain-of-function mutations, NSCLC smokers largely present with non-targetable loss-of-function mutations of genes associated with DNA-damage repair. The transcription factor Pit-1, Oct1/2, Unc-86 (POU) domain class 2 transcription factor 1 (POU2F1) is a widely expressed bipotential stabilizer of repressed and inducible transcriptional states and frequently deregulated in cancer. Methods: Via immunohistochemistry, we evaluated POU2F1 protein expression on a tissue micro array of 217 operable stage I-III NSCLC patients. Findings were reproduced in a gene expression database of 1144 NSCLC patients, filtered for POU2F1 mRNA expression. After retroviral overexpression of POU2F1 in A549 cells, we evaluated for clonogenic growth and proliferation. Additionally, CRISPR-Cas9 mediated POU2F1 knockdown in A549 cells was likewise analyzed. Results: High protein expression of POU2F1 in 217 NSCLC patients resulted in improved outcome of smokers with ADC [hazard ratio (HR) 0.30 (0.09-0.99), P=0.035]. Moreover, gene expression analysis confirmed favorable outcome of high POU2F1 mRNA expression in smokers with ADC [HR 0.41 (0.24-0.69), P<0.001]. Other than that, retrovirally induced overexpression of POU2F1 in A549 cells significantly reduced both, clonogenic growth as well as proliferation of NSCLC cells, whereas CRISPR-Cas9 mediated knockdown of the protein did not have any impact. Conclusions: Our data suggest that high expression of POU2F1 mediates a less aggressive cancer phenotype in smokers with ADC NSCLC. Pharmacological induction of genes and signaling pathways controlled by POU2F1 may provide novel avenues for future targeted NSCLC therapies in smokers.