Cell and Molecular Biology

Cancer biology

Dynamics of cell junction proteins during tumor progression

Cell junction complexes play a major role in cell adhesion and migration which are highly regulated during crucial processes like embryogenesis, wound healing and also in perturbed conditions as in tumorigenesis. It is well-established that alterations in cell adhesion processes are the hallmark of aggressive malignant tumors. Much of the research in cancer, over the last decade, has been focused on understanding the metastatic potential of cancer cells. Metastasis is a complex multi-step process involving cell invasion, migration, intra/extravasation, and changes in cell adhesion properties. Once the tumors are formed at the primary site, they shed some of the cells to the circulatory system through a process termed as Epithelial to Mesenchymal transition (EMT).These circulating tumor cells (CTC) disseminate into distant sites and colonize them through a reverse process to EMT called Mesenchymal to Epithelial transition (MET). Both EMT and MET help cells to re-establish at target site, thus completing the metastatic loop as shown in figure.

Schematic representation of the metastasis formation by circulating tumor cells (CTCs) undergoing epithelial to mesenchymal transition (EMT) and mesenchymal to epithelial transition (MET) changes in their cellular characteristics

The circulating tumour cells (CTC) are different from the cells at primary tumour in that they have metastatic potential. Some of the specific clonal population of CTC, called cancer stem cells (CSC), are responsible for driving tumour recurrence and metastasis. CSC have the capacity of self-renewal, have long term proliferative potential and are known to be highly resistant to chemo and radiotherapy. Since metastasis is the main reason for the tumour associated deaths, understanding the molecular mechanism of CTCs biology and the EMT process are the key focus of current research. During EMT, cancer cells change their adhesive property to more of migratory and invasive characteristics which involve dramatic reorganization of cytoskeleton and cell junction complexes. The molecular processes that determine such cellular changes are poorly understood and many dynamic cell junction proteins require better functional and molecular characterization. In order to better understand the molecular mechanism of regulation of cell junction proteins, it is relevant to identify the potential binding partners of these cell junction proteins. To identify the potential binding partners, a global approach of screening the cDNA library of humans was undertaken using yeast two hybrid system. A schematic representation of identifying protein-protein interaction using human cDNA library is shown in the Figure 2 (A and B).The representative positive clones of the library screening is shown in the Figure c.

(A) Schematic representation to determine protein-protein interaction through yeast two-hybrid system. The protein of interest “X” is expressed as a fusion of GAL4-DNA binding domain and forms a bait plasmid and the protein “Y” is expressed as a fusion of GAL4 activation domain and this represents the prey plasmid. If both the proteins interact with each other, their interaction drives the expression of reporter genes
(B) Schematics of the Yeast two hybrid library screening of one of the cell junction protein along with the human cDNA library
(C) Representative of the diploids growing on selective nutrient media. The blue colonies represent the interaction between two proteins

Cancer Genomics

Evidences from recent studies have supported the theory that cancer is a disease of genomes and that cancer cells exhibit high genomic heterogeneity within the tumor. Whole genome sequencing of single cancer cellswithin the tumor using next generation sequences (NGS) technologies at the lab have enabled the researchers to understand the clonal evolution of mutations and how these mutations have contributed to tumor progression and therapeutic resistance. To better understand the mutational status in cancers, researchers at the lab, with collaborators in the computational engineering laboratory, are developing databases to identify multiple cancer biomarkers from whole genome sequencing data. The developed databases can be utilized for diagnosis, clinical and translational research and for academic purposes.