Single cell phospho‐specific flow cytometry can detect dynamic changes of phospho‐Stat1 level in lung cancer cells

Abstract

Single cell phospho-specific flow cytometry (SCPFC) enables the investigation of signaling network interactions and the categorization of disease outcome. While this method has been successfully used to study hematologic disorders, its application on solid tumors has not been examined. This study aimed to demonstrate the ability of SCPFC to detect dynamic changes of Tyrosine phospho-Stat1 (pStat1) in solid tumor models and in human tumor samples. In the human lung cancer cell line PC14PE6/ AS2, the fluorescence intensity changes of pStat1 after IFN-c stimulation were compatible to results obtained by Western blot analysis. In metastatic animal models, cancer cells from subcutaneous tumors, malignant ascites, and peritoneal tumors responded to IFN-c. The pStat1 was activated in these cells after IFN-c stimulation, with a 1.5-to 2.5-fold increase in fluorescence intensity compared to the unstimulated control. To examine the potential clinical application of SCPFC, cancer cells were collected from malignant pleural effusions (MPEs) of lung cancer patients to observe the activation of pStat1 after IFN-c stimulation. Cell apoptosis after cisplatin treatment was evaluated by Annexin V staining, which showed that MPE cancer cells with higher pStat1 changes after IFN-c stimulation were more resistant to cisplatin. In conclusion, there is a preliminary application of SCPFC to solid tumors and links to drug sensitivity are promising. ' 2010 International Society for Advancement of Cytometry Key terms flow cytometry; phospho-Stat1; lung cancer; malignant pleural effusion MOST human neoplasms have aberrant signal transduction elements. Understanding the structure and regulation of these elements will provide more insights into cancer treatment. Among these signaling networks, phospho-protein members of signaling cascades govern the initiation and regulation of proliferative signals within cells. It is proposed that the phosphorylation of key signaling molecules in response to particular stimuli correlates with certain mutations and the body's response to cancer treatment.Using multi-parameter flow cytometry, single cell phospho-specific flow cytometry (SCPFC) has revealed that potentiated phospho-proteins in leukemia cells like Stats, p38, and Erk respond to several key stimuli, including IL-3, IFN-c, GCSF, GM-CSF, and FL (flt3 ligand) (1). By recording the basal patterns and changes in activity of phospho-proteins, expression profiles have been correlated with a mutant form of Flt3 (fms-like tyrosine kinase 3) and with disease outcome. Unfortunately, although SCPFC is well demonstrated in hematologic oncology (2-4), its application in solid tumors has not been fully examined.The signal transducer and activator of transcription (Stat) proteins are a family of transcription factors that mediate normal cell differentiation, tumor cell proliferation, and apoptosis. Previous studies have identified a suppression effect of Stat1 on

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