Cloning, expression, purification, and immunoblotting analysis of recombinant type III fibronectin domains of human oncostatin M receptor.

BACKGROUND: The human oncostatin M receptor subunit , commonly known as the oncostatin M receptor (OSMR), is a cell surface protein and belongs to the family of type I cytokine receptors. It is highly expressed in several cancers and is a potential therapeutic target. Structurally, OSMR consists of three major domains: the extracellular, transmembrane, and cytoplasmic domains. The extracellular domain further comprises four Type III fibronectin subdomains. The functional relevance of these type III fibronectin domains is not known yet, and it is of great interest to us to understand their role in OSMR-mediated interactions with other oncogenic proteins. METHODS & RESULTS: The four type III fibronectin domains of hOSMR were amplified by PCR using the pUNO1-hOSMR construct as a template. The molecular size of the amplified products was confirmed by agarose gel electrophoresis. The amplicons were then cloned into a pGEX4T3 vector containing GST as an N-terminal tag. Positive clones with domain inserts were identified by restriction digestion and overexpressed in E. coli Rosetta (DE3) cells. The optimum conditions for overexpression were found to be 1 mM IPTG and an incubation temperature of 37 °C. The overexpression of the fibronectin domains was confirmed by SDS-PAGE, and they are affinity purified by using glutathione agarose beads in three repetitive steps. The purity of the isolated domains analyzed by SDS-PAGE and western blotting showed that they were exactly at their corresponding molecular weights as a single distinct band. CONCLUSION: In this study, we have successfully cloned, expressed, and purified four Type III fibronectin subdomains of hOSMR.

Cancer Stem Cells and Circulatory Tumor Cells Promote Breast Cancer Metastasis.

Breast cancer (BC) is a highly metastatic, pathological cancer that significantly affects women worldwide. The mortality rate of BC is related to its heterogeneity, aggressive phenotype, and metastasis. Recent studies have highlighted that the tumor microenvironment (TME) is critical for the interplay between metastasis mediators in BC. BC stem cells, tumor-derived exosomes, circulatory tumor cells (CTCs), and signaling pathways dynamically remodel the TME and promote metastasis. This review examines the cellular and molecular mechanisms governing the epithelial to mesenchymal transition (EMT) that facilitate metastasis. This review also discusses the role of cancer stem cells (CSCs), tumor-derived exosomes, and CTs in promoting BC metastasis. Furthermore, the review emphasizes major signaling pathways that mediate metastasis in BC. Finally, the interplay among CSCs, exosomes, and CTCs in mediating metastasis have been highlighted. Therefore, understanding the molecular cues that mediate the association of CSCs, exosomes, and CTCs in TME helps to optimize systemic therapy to target metastatic BC.

Regulatory T cells: Their role in triple-negative breast cancer progression and metastasis.

Triple-negative breast cancer (TNBC) is an aggressive and immunogenic subtype of breast cancer. This tumorigenicity is independent of hormonal or HER2 pathways because of a lack of respective receptor expression. TNBC is extremely prone to drug resistance and early recurrence because of T-regulatory cell (Treg) infiltration into the tumor microenvironment (TME) in addition to other mechanisms like genomic instability. Tumor-infiltrating Tregs interact with both tumor and stromal cells as well as extracellular matrix components in the TME and induce an immune-suppressive phenotype. Hence, treatment of TNBC with conventional therapies remains challenging. Understanding the protective mechanism of Tregs in shielding TNBC from antitumor immune responses in the TME will pave the way for developing novel, immune-based therapeutics. The current review focuses on the role of tumor-infiltrating Tregs in tumor progression and metabolic reprogramming of the TME. The authors have extended their focus to oncotargeting Treg-mediated immune suppression in breast cancer. Because of its potential role in the TME, modulating Treg activity may provide a novel strategic intervention to combat TNBC. Both under laboratory conditions and in clinical trials, currently available anticancer drugs and natural therapeutics as potential agents for targeting Tregs are explored.

Autophagy-Induced Drug Resistance in Liver Cancer.

Autophagy is a self-destructive process that occurs in the cells during abnormal conditions like protein aggregation due to misfolding, nutrient deprivation, damage to vital cell organelles, pathogenic infections, and during cancer. Typically, autophagy plays a key role in the renovation of new cells by balancing the equilibrium between cell death and cell renewal. Dysregulation of autophagy has a profound effect on protein turnover, mitochondrial homeostasis, clearance of damaged organelles, and cellular metabolism, which lead to neurodegenerative, metabolic, and proliferative diseases. Despite its antitumorigenic role, autophagy can promote cell proliferation by enhancing chemotherapeutic resistance in liver cancer. In the present review, we provide a comprehensive overview and discussion on the role of autophagy in the drug-resistant mechanisms of liver cancer.

Tumor microenvironment: Challenges and opportunities in targeting metastasis of triple negative breast cancer.

Triple negative breast cancer (TNBC) is most aggressive subtype of breast cancers with high probability of metastasis as well as lack of specific targets and targeted therapeutics. TNBC is characterized with unique tumor microenvironment (TME), which differs from other subtypes. TME is associated with induction of proliferation, angiogenesis, inhibition of apoptosis and immune system suppression, and drug resistance. Exosomes are promising nanovesicles, which orchestrate the TME by communicating with different cells within TME. The components of TME including transformed ECM, soluble factors, immune suppressive cells, epigenetic modifications and re-programmed fibroblasts together hamper antitumor response and helps progression and metastasis of TNBCs. Therefore, TME could be a therapeutic target of TNBC. The current review presents latest updates on the role of exosomes in modulation of TME, approaches for targeting TME and combination of immune checkpoint inhibitors and target chemotherapeutics. Finally, we also discussed various phytochemicals that alter genetic, transcriptomic and proteomic profiles of TME along with current challenges and future implications. Thus, as TME is associated with the hallmarks of TNBC, the understanding of the impact of different components can improve the clinical benefits of TNBC patients.

Talin: A Potential Drug Target for Cancer Therapy.

Talin is an intracellular cytoskeletal protein and one of the major components of the focal adhesion complex. It mainly acts as an interlink between transmembrane integrin receptors and cytosolic F-actin. Apart from integrins and actin, it also interacts with various other proteins in the adhesion complex to regulate their functional dynamics. Talin undergoes a variety of post-translational modifications and they are implicated in the control of cell motility. There are two talin isoforms (talin1 and talin2) in mammals and they are encoded by TLN1 and TLN2 genes, respectively. Recent studies showed that both the isoforms have some mechanistic dissimilarities in terms of their interaction with membrane-bound integrins. Among the two isoforms, talin1 was well studied, and most of the information available till now comes from talin1. The present review is aimed to provide an updated overview on the cellular significance of talin in normal and cancerous cells.

Prognostic Role of Hedgehog-GLI1 Signaling Pathway in Aggressive and Metastatic Breast Cancers.

Glioma-associated oncogene homolog 1 (GLI1) is reported as an amplified gene in human glioblastoma cells. It is a krupple like transcription factor, belonging to the zinc finger family. The basic function of GLI1 is normal neural development at various stages of human. The GLI1 gene was first mapped on the chromosome sub-bands 12q13.3-14.1. Further, single nucleotide polymorphism is mostly observed in translating a region of 5' and 3'- UTR of GLI1 gene in addition to two post-transcriptional splice variants, GLIΔN and tGLI. Additionally, it also regulates a plethora of gene which mediates crucial cellular processes like proliferation, differentiation, oncogenesis, EMT, and metastasis. It also regulates tumor tolerance, chemoresistance, and radioresistance. Aberrant expression of GLI1 predicts the poor survival of breast cancer patients. GLI1 is an essential mediator of the SHH signaling pathway regulating self-renewal of stem cells, angiogenesis, and expression of FOXS1, CYR61. GLI1 mediated HH pathway can induce apoptosis. Hence, GLI1 can be a future diagnostic, prognostic marker, and as well as a potent target of therapeutics in breast cancer.

DNA damage in the presence of chemical genotoxic agents induce acetylation of H3K56 and H4K16 but not H3K9 in mammalian cells.

Histone covalent modifications play a significant role in the regulation of chromatin structure and function during DNA damage. Hyperacetylation of histones is a DNA damage dependent post translational modification in yeast and mammals. Although acetylation of histones during DNA damage is well established, specific lysine residues that are acetylated is being understood very recently in mammals. Here, in the present study, acetylation of three different lysine residues Histone3Lysine 9 (H3K9), Histone3Lysine 56 (H3K56) and Histone4Lysine 16 (H4K16) were probed with specific antibodies in mammalian cell lines treated with genotoxic agents that induce replication stress or S-phase dependent double strand breaks. Immunoblotting results have shown that DNA damage associated with replication arrest induce acetylation of H3K56 and H4K16 but not H3K9 in mammals. Immunofluorescence experiments further confirmed that acetylated H3K56 and H4K16 form nuclear foci at the site of DNA double strand breaks. Colocalization of H3K56ac with γ H2AX and replication factor PCNA proved the existence of this modification at the site of DNA damage and its probable role in DNA damage repair. Put together, the present data suggests that acetylation of H3K56 and H4K16 are potent DNA damage dependent histone modifications but not H3K9 in mammals.

p300-mediated acetylation of histone H3 lysine 56 functions in DNA damage response in mammals.

The packaging of newly replicated and repaired DNA into chromatin is crucial for the maintenance of genomic integrity. Acetylation of histone H3 core domain lysine 56 (H3K56ac) has been shown to play a crucial role in compaction of DNA into chromatin following replication and repair in Saccharomyces cerevisiae. However, the occurrence and function of such acetylation has not been reported in mammals. Here we show that H3K56 is acetylated and that this modification is regulated in a cell cycle-dependent manner in mammalian cells. We also demonstrate that the histone acetyltransferase p300 acetylates H3K56 in vitro and in vivo, whereas hSIRT2 and hSIRT3 deacetylate H3K56ac in vivo. Further we show that following DNA damage H3K56 acetylation levels increased, and acetylated H3K56, which is localized at the sites of DNA repair. It also colocalized with other proteins involved in DNA damage signaling pathways such as phospho-ATM, CHK2, and p53. Interestingly, analysis of occurrence of H3K56 acetylation using ChIP-on-chip revealed its genome-wide spread, affecting genes involved in several pathways that are implicated in tumorigenesis such as cell cycle, DNA damage response, DNA repair, and apoptosis.

DNA mediated disassembly of hRad51 and hRad52 proteins and recruitment of hRad51 to ssDNA by hRad52.

Purified human Rad51 and Rad52 proteins exhibit multiple oligomeric states, in vitro. Single-stranded DNA (ssDNA) renders high molecular weight aggregates of both proteins into smaller and soluble forms that include even the monomers. Consequently, these proteins that have a propensity to interact with each other's higher order forms by themselves, start interacting with monomeric forms in the presence of ssDNA, presumably reflecting the steps of protein assembly on DNA. In the same conditions, DNA binding assays reveal hRad52-mediated recruitment of hRad51 on ssDNA. Put together, these studies hint at DNA-induced disassembly of higher-order forms of Rad51 and Rad52 proteins as steps that precede protein assembly during hRad51 presynapsis on DNA, in vitro.