Isolation and Characterization of Lung Cancer Stem Cells from p53 Gain-of-Function Mutant Mouse Models

Recent advances in understanding lung biology have shown evidence for the existence of resident lung stem cells. Independent studies in identifying and characterizing these somatic lung stem cells have shown the potential role of these cells in lung repair and regeneration. While identifying a homogenous stem cell pool with unique cell surface markers is still a challenge, the currently available data support the existence of different lung cells with stem cell characteristics of self-renewal and differentiation. Understanding the functional characteristics of these tissue resident stem/progenitor cells has gained much importance with increasing evidence of cancer stem cells, cells in a tumor tissue with stem cell characteristics. Lung cancer is most commonly characterized by loss of p53 function which results in uncontrolled cell divisions. Incidence of p53 point mutations is highest in lung cancer, with a high percentage of missense mutations as a result of tobacco smoking. Certain point mutations in p53 gene results in its oncogenic gain of functions (GOF), with enhanced tumorigenic characteristics. However, there are no available data on characterization of lung stem cells carrying GOF mutations and correlating them with those of normal stem cells. In this study, for the first time we characterized lung stem/ progenitor cells from cancer sensitized mice carrying p53 GOF mutations. Our results show that there is distinct morphological and cell proliferation difference between the Sca-1 expressing cells established from mice lungs carrying different p53 genotypes. Additionally, our results suggest that Sca-1 expressing subpopulation of cells are significantly higher in p53 mutant carrying mice lungs than those in p53^+/+ wild type. We also noted that Sca-1 expressing p53 mutants show tumorigenic properties of p53 accumulation, migration, and colony formation in non-adherent culture conditions. When the cells across the different genetic backgrounds were subjected to mesenchymal lineage differentiation, we noted that Sca-1^High p53^+/+ wild type readily differentiated into adipogenic and osteogenic lineages. However, the mesenchymal differentiation ability of the cells isolated from p53 mutants is not evident compared to their wild type counterparts. Results from our studies demonstrate the stem cell and tumorigenic nature of Sca-1 cells carrying p53 GOF mutations. This study lays the foundation and rationale for elaborate cellular and molecular level investigation of resident stem/progenitor cells expressing p53 GOF mutations. The insights on these resident stem/progenitor cells will ultimately shed light on cancer progression and development of new models and therapeutics for lung cancer.