Cancer Research Projects
Neuroblastoma, a cancer derived from incompletely differentiated neural crest cells, is the most lethal human childhood cancer, and therapeutic approaches do little to change patient outcomes. Neural crest cells normally migrate throughout the developing embryo and differentiate into multiple cell types during development. When cells that are supposed to become part of the nervous system fail to differentiate, they may cause neuroblastoma. Cells that fail to differentiate at earlier stages of development are more likely to cause an aggressive neuroblastoma that is highly metastatic and untreatable.
We are studying signal transduction pathways activated by receptors in the receptor tyrosine kinase family that instruct cells to differentiate or remain undifferentiated and in a stem cell-like state. Receptor tyrosine kinases all appear to activate the same four intracellular signaling pathways, yet some receptors cause proliferation, and others, differentiation. A critical gap in knowledge exists about the molecular mechanisms that distinguish responses to different receptors, and how these mechanisms go awry in neuroblastoma.
We attack this problem using two different approaches. One approach is to take neuroblastoma cells apart and examine the dynamic changes in signaling proteins in response to receptors that cause differentiation or de-differentiation. Another is to examine signaling pathways globally by collecting large scale data on protein phosphorylation to determine which signal transduction pathways are activated in neuroblastoma cells. We analyzed the data using a combination of graph theory and pattern recognition techniques that resolve data structure into networks that incorporate statistical relationships and protein-protein interaction data. These approaches give rise to the hypothesis that two proteins, FYN and LYN, act as central hubs in the signaling network, and change activity and intracellular localization differently depending on whether the cell receives signals to differentiate or remain in a stem cell-like proliferating state. Understanding the fundamental mechanism by which different receptors elicit distinct cell responses that control the decision to differentiate will open points of attack for new strategies to manipulate cancer cells to cease proliferation, differentiate, or commit cell suicide.
Lung cancer is still the third largest cause of cancer mortality despite a decline in cigarette smoking. We collaborated with the LINCS Consortium and Cell Signaling Technology to examine protein modifications in lung cancer cell lines. Proteins covalently modify one another to govern signal transduction, which affects many cellular processes, including cytoskeletal rearrangements, chromatin accessibility, RNA processing, translation, and transcription. Signaling pathways involving post-translational protein modifications can go awry to cause cancer. Many signaling pathways are known, yet there are many that remain to be characterized. The study of protein modifications provides both characteristic signatures for known pathways, and clues to new pathways that may drive or mark oncogenesis. Acquisition of large scale data for different post-translational modifications, including phosphorylation, methylation and acetylation, has been achieved through generation of modification-specific antibodies and mass spectrometry. To understand molecular signaling pathways that are active in lung tumor-derived cell lines, we examined patterns in protein phosphorylation and other post-translational modifications on a large scale. We combined pattern recognition and clustering techniques with network analysis to elucidate signaling pathways likely to be active in lung cancer cells. The analysis has elucidated several signaling pathways that are active in different lung cancers, which will motivate new experiments to uncover points of attach for new drug therapies. This study was published as the cover article in Science Signaling 22 May 2018.