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Penetration of the mammary gland basement membrane by cancer cells is a crucial first step in tumor invasion. Using a mouse model of ductal carcinoma in situ, we previously found that inhibition of peptidylarginine deiminase 2 (PAD2, aka PADI2) activity appears to maintain basement membrane integrity in xenograft tumors. The goal of this investigation was to gain insight into the mechanisms by which PAD2 mediates this process. For our study, we modulated PAD2 activity in mammary ductal carcinoma cells by lentiviral shRNA-mediated depletion, lentiviral-mediated PAD2 overexpression, or PAD inhibition and explored the effects of these treatments on changes in cell migration and cell morphology. We also used these PAD2-modulated cells to test whether PAD2 may be required for EGF-induced cell migration. To determine how PAD2 might promote tumor cell migration in vivo, we tested the effects of PAD2 inhibition on the expression of several cell migration mediators in MCF10DCIS.com xenograft tumors. In addition, we tested the effect of PAD2 inhibition on EGF-induced ductal invasion and elongation in primary mouse mammary organoids. Lastly, using a transgenic mouse model, we investigated the effects of PAD2 overexpression on mammary gland development. Our results indicate that PAD2 depletion or inhibition suppresses cell migration and alters the morphology of MCF10DCIS.com cells. In addition, we found that PAD2 depletion suppresses the expression of the cytoskeletal regulatory proteins RhoA, Rac1, and Cdc42 and also promotes a mesenchymal to epithelial-like transition in tumor cells with an associated increase in the cell adhesion marker, E-cadherin. Our mammary gland organoid study found that inhibition of PAD2 activity suppresses EGF-induced ductal invasion. In vivo, we found that PAD2 overexpression causes hyperbranching in the developing mammary gland. Together, these results suggest that PAD2 plays a critical role in breast cancer cell migration. Our findings that EGF treatment increases protein citrullination and that PAD2 inhibition blocks EGF-induced cell migration suggest that PAD2 likely functions within the EGF signaling pathway to mediate cell migration.

While organ‐confined prostate cancer (PCa) is mostly therapeutically manageable, metastatic progression of PCa remains an unmet clinical challenge. Resistance to anoikis, a form of cell death initiated by cell detachment from the surrounding extracellular matrix, is one of the cellular processes critical for PCa progression towards aggressive disease. Therefore, further understanding of anoikis regulation in PCa might provide therapeutic opportunities. Here, we discover that PCa tumours with concomitant inhibition of two tumour suppressor phosphatases, PP2A and PTEN, are particularly aggressive, having < 50% 5‐year secondary‐therapy‐free patient survival. Functionally, overexpression of PME‐1, a methylesterase for the catalytic PP2A‐C subunit, inhibits anoikis in PTEN‐deficient PCa cells. In vivo, PME‐1 inhibition increased apoptosis in in ovo PCa tumour xenografts, and attenuated PCa cell survival in zebrafish circulation. Molecularly, PME‐1‐deficient PC3 cells display increased trimethylation at lysines 9 and 27 of histone H3 (H3K9me3 and H3K27me3), a phenotype known to correlate with increased apoptosis sensitivity. In summary, our results demonstrate that PME‐1 supports anoikis resistance in PTEN‐deficient PCa cells. Clinically, these results identify PME‐1 as a candidate biomarker for a subset of particularly aggressive PTEN‐deficient PCa. A subset of prostate cancer (PCa) tumours present simultaneous inactivation of two tumour suppressor phosphatases; phosphatase and tensin homolog (PTEN) and protein phosphatase 2A (PP2A). PP2A is inhibited via overexpression of PME‐1. Such cancers are particularly aggressive and often relapse from standard therapy, indicating PME‐1 as a potential clinically applicable biomarker for PCa. Mechanistically, PME‐1 expression protects cancer cells from anoikis, promoting their survival outside the primary tumour.

Chromosomal instability is a hallmark of cancer that results from ongoing errors in chromosome segregation during mitosis. Although chromosomal instability is a major driver of tumour evolution, its role in metastasis has not been established. Here we show that chromosomal instability promotes metastasis by sustaining a tumour cell-autonomous response to cytosolic DNA. Errors in chromosome segregation create a preponderance of micronuclei whose rupture spills genomic DNA into the cytosol. This leads to the activation of the cGAS-STING (cyclic GMP-AMP synthase-stimulator of interferon genes) cytosolic DNA-sensing pathway and downstream noncanonical NF-κB signalling. Genetic suppression of chromosomal instability markedly delays metastasis even in highly aneuploid tumour models, whereas continuous chromosome segregation errors promote cellular invasion and metastasis in a STING-dependent manner. By subverting lethal epithelial responses to cytosolic DNA, chromosomally unstable tumour cells co-opt chronic activation of innate immune pathways to spread to distant organs.

Aberrations in nuclear size and shape are commonly used to identify cancerous tissue. However, it remains unclear whether the disturbed nuclear structure directly contributes to the cancer pathology or is merely a consequence of other events occurring during tumorigenesis. Here, we show that highly invasive and proliferative breast cancer cells frequently exhibit Akt-driven lower expression of the nuclear envelope proteins lamin A/C, leading to increased nuclear deformability that permits enhanced cell migration through confined environments that mimic interstitial spaces encountered during metastasis. Importantly, increasing lamin A/C expression in highly invasive breast cancer cells reflected gene expression changes characteristic of human breast tumors with higher LMNA expression, and specifically affected pathways related to cell-ECM interactions, cell metabolism, and PI3K/Akt signaling. Further supporting an important role of lamins in breast cancer metastasis, analysis of lamin levels in human breast tumors revealed a significant association between lower lamin A levels, Akt signaling, and decreased disease-free survival. These findings suggest that downregulation of lamin A/C in breast cancer cells may influence both cellular physical properties and biochemical signaling to promote metastatic progression.

Cancer metastasis is the process by which cells from the primary tumor invade into the surrounding extracellular matrix and neighboring tissue and spread to distant organs in the body through the blood or lymphatic system. This process is responsible for majority of cancer related deaths. During metastasis, cancer cells encounter very tiny interstitial spaces, smaller than the size of the cell’s nucleus. Migration through such confined spaces, puts considerable pressure on the nucleus, which is the largest and stiffest organelle in the cell. The nucleus experiences severe deformations and in some cases, nuclear envelope rupture as well as DNA damage during this migration. Here, we investigated the cause of DNA damage and the impact of DNA damage repair kinases during confined migration. We also examined the role of nuclear envelope protein lamin A/C in promoting confined cancer cell migration in breast cancers. Using cell-lines, live-cell imaging and microfluidic devices that mimic the interstitial spaces found in vivo, we show that DNA damage is caused by two distinct but overlapping events–nuclear deformation and nuclear envelope rupture. The main cause of DNA damage, varies for each cell line. Moreover, nuclear deformation during confined migration or due to nuclear compression leads to increased replication stress, possibly due to replication fork stalling. Our findings suggest that nuclear deformation during confined migration, causes DNA damage by increasing replication stress. We also evaluated the role of DNA damage repair kinase ATM in promoting confined migration. Using chemical inhibitors, stable and conditional depletion of ATM, we show that ATM regulates levels of nuclear lamin A protein. Furthermore, lack of ATM makes nuclei more deformable and increases migration speed through confined spaces, similar to those encountered during metastasis. Additionally, we examined the role of A-type lamins in modulating nuclear deformability and promoting breast cancer progression. Our results indicate that more aggressive breast cancers have low lamin A/C expression which correlates to increased nuclear deformability in those cells. Moreover, increasing lamin A levels reduces nuclear deformability and impedes migration through confined spaces in aggressive breast cancer cells. Lamin A levels also modulate cell shape and proliferation rates and are associated with poor disease-free survival in breast cancer patients. Thus we have identified a new role for ATM in modulating nuclear mechanics by regulating lamin levels and established A-type lamins as a potential clinical marker to predict breast cancer patient outcomes. This thesis, thus, provides mechanistic insights into the cause of DNA damage as well as the role of nuclear envelope proteins (like lamins) and DNA damage repair proteins (like ATM) during confined migration.

Ataxia-telangiectasia mutated (ATM) is one of the three main apical kinases at the crux of DNA damage response and repair in mammalian cells. ATM activates a cascade of downstream effector proteins to regulate DNA repair and cell cycle checkpoints in response to DNA double-strand breaks. While ATM is predominantly known for its role in DNA damage response and repair, new roles of ATM have recently begun to emerge, such as in regulating oxidative stress or metabolic pathways. Here, we report the surprising discovery that ATM inhibition and deletion lead to reduced expression of the nuclear envelope protein lamin A. Lamins are nuclear intermediate filaments that modulate nuclear shape, structure, and stiffness. Accordingly, inhibition or deletion of ATM resulted in increased nuclear deformability and enhanced cell migration through confined spaces, which requires substantial nuclear deformation. These findings point to a novel connection between ATM and lamin A and may have broad implications for cells with ATM mutations—as found in patients suffering from Ataxia Telangiectasia and many human cancers—which could lead to enhanced cell migration and increased metastatic potential. Competing Interest Statement SD has received compensation for consultant/advisory services from Lytix Biopharma, Mersana Therapeutics, EMD Serono, Ono Pharmaceutical, and Genentech, and research support from Lytix Biopharma and Boehringer-Ingelheim for unrelated projects. Jan Lammerding has provided paid consulting services for BridgeBio.

Summary Cancer metastasis, i.e., the spreading of tumor cells from the primary tumor to distant organs, is responsible for the vast majority of cancer deaths. In the process, cancer cells migrate through narrow interstitial spaces substantially smaller in cross-section than the cell. During such confined migration, cancer cells experience extensive nuclear deformation, nuclear envelope rupture, and DNA damage. The molecular mechanisms responsible for the confined migration-induced DNA damage remain incompletely understood. While in some cell lines, DNA damage is closely associated with nuclear envelope rupture, we show that in others, mechanical deformation of the nucleus is sufficient to cause DNA damage, even in the absence of nuclear envelope rupture. This deformation-induced DNA damage, unlike nuclear envelope rupture-induced DNA damage, occurs primarily in S/G2 phase of the cell cycle and is associated with replication forks. Nuclear deformation, resulting from either confined migration or external cell compression, increases replication stress, possibly by increasing replication fork stalling, providing a molecular mechanism for the deformation-induced DNA damage. Thus, we have uncovered a new mechanism for mechanically induced DNA damage, linking mechanical deformation of the nucleus to DNA replication stress. This mechanically induced DNA damage could not only increase genomic instability in metastasizing cancer cells, but could also cause DNA damage in non-migrating cells and tissues that experience mechanical compression during development, thereby contributing to tumorigenesis and DNA damage response activation. Competing Interest Statement The authors have declared no competing interest. Footnotes * ↵7 Lead contact * Updated version with new results and slight modifications to the text.

Infrastructure plays a very important role in shaping the economy of a country. The government is responsible for providing social and physical infrastructure which leads to human welfare, reduction of poverty and employment opportunities. But, the government alone cannot fund the infrastructure projects on its own. Therefore, the governments are partnering with the private sector for investing in infrastructure. The paper outlines the need for private sector participation in infrastructure and looks at the risks peculiar to infrastructure financing. The paper also studies the various models of public private participation and attempts to look at a viable model. [PUBLICATION ABSTRACT]

While organ-confined PCa is mostly therapeutically manageable, metastatic progression of PCa remains an unmet clinical challenge. Resistance to anoikis, a form of cell death initiated by cell detachment from the surrounding extracellular matrix, is one of the cellular processes critical for PCa progression towards aggressive disease. Therefore, further understanding of anoikis regulation in PCa might provide therapeutic opportunities. Here, we discover that PCa tumors with concomitantly compromised function of two tumor suppressor phosphatases, PP2A and PTEN, are particularly aggressive, having less than 50% 5-year secondary-therapy free patient survival. Functionally, overexpression of PME-1, a PP2A inhibitor protein, inhibits anoikis in PTEN-deficient PCa cells. In vivo, PME-1 inhibition increased apoptosis in in ovo PCa tumor xenografts, and attenuated PCa cell survival in zebrafish circulation. Molecularly, PME-1 deficient PCa cells display increased trimethylation at lysines 9 and 27 of histone H3 (H3K9me3 and H3K27me3), a phenotype corresponding to increased apoptosis sensitivity. In summary, we discover that PME-1 overexpression supports anoikis resistance in PTEN-deficient PCa cells. Clinically, the results identify PME-1 as a candidate biomarker for a subset of particularly aggressive PTEN-deficient PCa. Competing Interest Statement The authors have declared no competing interest.