Thus, we postulated that advanced stage disease does not prohibit for associating specific biomarkers with functional phenotypes. Accordingly, our approach to biological discovery emphasizes designing appropriate functional bioassays to characterize both the cell phenotypes and molecular biology underlying tumor initiation, as well as tumor progression. Lung cancer is the leading cause of cancer mortality in both men and women; with non small cell lung cancer accounting for 80�C85% of cases. For comprehending the biology underlying this high mortality, we have selected an advanced stage disease model. Lung cancer SAR131675 VEGFR/PDGFR inhibitor patients presenting with MPE have significantly higher mortality than those Niraparib structure without MPE, or those who have cytologically negative effusions. Thus, the MPE-tumor burden is imbued with biological properties that diminish survival of cancer patients. Importantly, the MPE bulk tumor population is comprised of heterogeneous subpopulations. In part, this heterogeneity can be characterized by biomarkers typically associated with features of CSC. An objective of the present study was to determine if we could identify a tumor cell subset that displayed an increased competence for tumor propagation and maintenance, and to begin to characterize the molecular bases for these properties. We first studied CD44 as a selection marker for cells predicted to have high tumorigenic potential because it has previously identified CSC in various epithelial cancers, including breast, head and neck,, pancreatic, and prostate malignancies. CD44 is highly expressed in different lung cancer subtypes,, and its expression is related to poor prognosis in patients. Recent studies in NSCLC cell lines also characterize CD44hi cells as CSC. MPE-primary cultures contain a subpopulation of cells that highly expresses CD44. When these cells are sorted from the MPE-primary cultures, they exhibit high tumorigenic potential, including engraftment of tumors in NOD/SCID IL2cRnull mice in limiting dilutions of cell transplants. These properties are characteristic of CSC. Fractions of CD44hi cells are associated with an elevated expression of another CSC-marker associated with xenobiotic metabolism, ALDH. The CD44hi/ALDHhi phenotype is evident in both squamous cell and adenocarcinoma of the lung, suggesting that similar marker profiles may label behaviorally aggressive cell fractions across the various ����lineages���� of lung cancers. MPE tumors commonly display hyperploidy and chromosomal abnormalities. FISH analysis detected a common specific abnormality in 1p36 region, suggesting that this region may play an important role in contributing to aggressive behavioral properties. Our previous study detected intratumoral heterogeneity in advance stage of lung cancer by surface marker analysis, immunohistochemistry and FACS. This study extends the earlier observations, and also verifies that subsets of MPE tumor cells express variable levels of embryonal and polycomb complex-associated molecular markers. These stem cell markers have previously been implicated in mediating ����CSC properties����, including high tumorigenic potentials. These markers include PTEN, OCT-4, BMI-1, hTERT, SUZ12, EZH2. In early analyses, we are unable to associate specific embryonal or polycomb markers with higher tumorigenic potentials. In the three current MPE primary samples tested, only one of the CD44hi subsets expressed the predicted pattern of candidate CSC-marker expression than the isogenic CD44lo cells. The other two samples were quite variable in the expression of markers on this panel. On the basis of a primary samples that displays a highly variable expression of markers, we can speculate that it is unlikely that individual molecular markers will reliably predict the highly tumorigenic CSC-phenotype in lung cancers.