Squamous cell lung cancer

Lung cancer remains the leading cause of cancer death in the world for both men and women. Prevention studies have largely been ineffective. A chemoprevention trial using the prostacyclin analogue iloprost demonstrated improvement in endobronchial histology in former smokers. An ongoing trial is investigating lung cancer chemoprevention with pioglitazone, which decreases lung cancer risk in diabetics. The effects of iloprost and pioglitazone are mediated by PPARγ and its downstream targets. We hypothesize that response to iloprost and pioglitazone depends on expression of PPARγ and that measures of prostacyclin and PPARγ activity will correlate with histology. We will measure a PPARγ expression in biopsy tissues to determine if expression can predict response to iloprost. We will assess methylation and acetylation in tissues with loss of PPARγ expression, which could identify a potential role for demethylation or deacetylation agents in creating a response to chemoprevention. We will measure activity of iloprost and pioglitazone through QPCR of downstream targets. Previously generated tissues from mouse models of lung cancer chemoprevention will be used to correlate markers with human samples. miRNA have the potential to be important markers but there is little information on miRNA associated with lung cancer chemoprevention. We identify potential miRNA markers of iloprost and pioglitazone activity in dysplastic cell lines treated with iloprost or pioglitazone and in tissues from mouse models of chemoprevention. Data from this project will inform future clinical trials using iloprost and pioglitazone, improve targeted lung cancer chemoprevention, and identify relevant miRNA markers for future chemoprevention studies.

Whole genome pooled retroviral shRNA screens were performed in NSCLC cell lines A549 and NCI-H460. Out of nearly 18,000 genes, the top hit whose knockdown most reproducibly showed cytoxicity was PSMA1, a core subunit of the 20S proteasome. The combination of radiotherapy and PSMA1 knockdown significantly enhanced tumor control in a mouse xenograft model. We observed that proteasome inhibition results in increases in nuclear 1κBa, which in turn decreases NF-κB binding to the promoters of Fanconi Anemia/Homologous Recombination (HR) genes including FANCD2 and BRCA1. This reduces the expression and subsequent availability of these DNA repair proteins for recruitment to double strand breaks (DSBs) induced by radiation. These mechanistic studies provided the basis for the proposed hypothesis-driven translational research.

The central hypothesis is that high levels of HR-mediated repair of radiation-induced DNA DSBs are associated with poor tumor control, which may be improved with proteasome inhibitors. First, CT-guided fractionated radiotherapy ± bortezomib will be tested in diverse genetically engineered mouse models of NSCLC to identify mutations and other biomarkers associated with responses to radiation and/or proteasome inhibitors. Immunofluorescence and immunohistochemistry against proteins, identified in prior mechanistic studies, as well as gene expression profiling (GEP), will be performed. Then, the biomarkers will be examined in archived specimens from patients treated with radiotherapy, to assess associations with outcomes. DASL will be used to perform GEP studies using formalin-fixed, paraffin-embedded specimens. The goal will be to identify pathway-based expression signatures that predict poor outcomes with radiotherapy and improved outcomes with addition of proteasome inhibitors.