Targeting the temporal dynamics of hypoxia-induced tumor-secreted factors halts tumor migration
Targeting microenvironmental factors that foster migratory cell phenotypes is a promising strategy for halting tumor migration. However, lack of mechanistic understanding of the emergence of migratory phenotypes impedes pharmaceutical drug development. Using our 3D microtumor model with tight control over tumor size, we recapitulated the tumor size-induced hypoxic microenvironment and emergence of migratory phenotypes in microtumors from epithelial breast cells and patient-derived primary metastatic breast cancer cells, mesothelioma cells, and lung cancer xenograft cells (PDX). The microtumor models from various patient-derived tumor cells and PDX cells revealed upregulation of tumor-secreted factors including matrix metalloproteinase-9 (MMP9), fibronectin (FN), and soluble E-cadherin (sE-CAD), consistent with clinically reported elevated levels of FN and MMP9 in patient breast tumors compared to healthy mammary glands. Secreted factors in the conditioned media of large microtumors induced a migratory phenotype in non-hypoxic, non-migratory small microtumors. Subsequent mathematical analyses identified a two-stage microtumor progression and migration mechanism whereby hypoxia induces a migratory phenotype in the initialization stage which then becomes self-sustained through a positive feedback loop established among the tumor-secreted factors. Computational and experimental studies showed that inhibition of tumor-secreted factors effectively halts microtumor migration despite tumor-to-tumor variation in migration kinetics, while inhibition of hypoxia is effective only within a time window and is compromised by tumor-to-tumor variation, supporting our notion that hypoxia initiates migratory phenotypes but does not sustain it. In summary, we show that targeting temporal dynamics of evolving microenvironments, especially tumor-secreted factors during tumor progression, can halt tumor migration.
Singh M, Tian XJ, Donnenberg VS, Watson AM, Zhang JY, Stabile LP, Watkins SC, Xing J, Sant S. (2019) Targeting the temporal dynamics of hypoxia-induced tumor-secreted factors halts tumor migration. Cancer Res. DOI: 10.1158/0008-5472.CAN-18-3151
|Shilpa Sant, PhD
||Jianhua Xing, PhD
Mr. Nuri Has (left), Dr. Ivet Bahar (middle), and Dr. Sondan Durukanoglu Feyiz (right)
The 15th Annual Kadir Has Awards were held on Friday, March 22nd in Istanbul, Turkey. Member of the Science Academy, Dr. Ivet Bahar, received the Kadir Has “Outstanding Achievement Award” for her contributions to the development of theoretical and computational models for explaining the functional dynamics of biomolecular systems as well as mentoring and teaching a new wave of scientists. She was presented with the award by the Chairman of the Board of Trustees of Kadir Has University, Mr. Nuri Has, the Kadir Has Foundation President, Mr. Can Has, and the President of Kadir Has University, Dr. Sondan Durukanoglu Feyiz.
The Kadir Has Awards seek to recognize the outstanding accomplishments that Turkish scientists have made at the national and international level and to promote people and institutions that have contributed to the development of society.
For more information, please visit http://kadirhasvakfi.org/en/.
Spatial clustering and common regulatory elements correlate with coordinated gene expression
Cellular responses to environmental stimulation are often accompanied by changes in gene expression patterns. Genes are linearly arranged along chromosomal DNA, which folds into a three-dimensional structure. The chromosome structure affects gene expression activities and is regulated by multiple events such as histone modifications and DNA binding of transcription factors. A basic question is how these mechanisms work together to regulate gene expression. In this study, we analyzed temporal gene expression patterns in the context of chromosome structure both in a human cell line under TGF-β treatment and during mouse nervous system development. In both cases, we observed that genes regulated by common transcription factors have an enhanced tendency to be spatially close. Our analysis suggests that spatial co-localization of genes may facilitate the concerted gene expression.
Zhang J, Chen H, Li R, Taft DA, Yao G, Bai F, Xing J. (2019) Spatial clustering and common regulatory elements correlate with coordinated gene expression. PLoS Computational Biology 15(3):e1006786
Title: Role of a Novel Mitotic 4E-BP1 Protein Isoform in Cellular Transformation
PI: Yuan Chang
Co-I: Robin Lee and Patrick Moore
4E-BP1 is the primary gatekeeper for cancer cell cap dependent protein translation. It is directly targeted by mTOR kinase during interphase. We have found that CDK1/CYCB1 substitutes for mTOR during mitosis to phosphorylate 4E-BP1 generating a novel phosphorylation mark at serine (S) 83 that is not present when mTOR phosphorylates 4E-BP1. Unlike other 4E-BP1 phospho-isoforms, phospho-4E-BP1-S83 preferentially localizes to mitotic centrosomes as well as being diffusely distributed in a speckled pattern in the nucleo/cyto-plasm. A mutant form of 4E-BP1 that is unable to be phosphorylated at S83 partially reverses cell transformation caused by the Merkel cell polyomavirus (MCV) small T oncoprotein. This is particularly interesting since discovery of a novel pathway targeted by a tumor virus has always led to discovery of the same pathway being altered in non-infectious cancers. We developed a new phosphospecific antibody to p4E-BP1S83 that allows us to uniquely identify mitosis-related 4E-BP1 phosphorylation and determine its function in cancer cells. With this antibody, we will first survey phosphor-4E-BP-S83 expression in TCGA cancer tissues and anticipate that this approach will be a sensitive measure for activated CDK1 circuits and will provide unique data on cancer-type specific severity. We will next examine the biology of p4E-BP1S83 by identifying S83 phosphospecific effects on mitogenesis and by examining 4E-BP1’s potential role in regulating translation of specific transcripts during mitosis using ribosomal profiling and novel quantitative single cell imaging techniques. Finally, we will generate knock-in mutant mouse models of inactivated and phosphomimetic mitotic 4E-BP1 to determine its role in tumor susceptibility. Our specific aims will advance our fundamental understanding of how a mitosis-specific, hyperphosphorylated form of 4E-BP1 functions in normally cycling cells and how its dysregulation in cancer cells may contribute to human malignancies.