Biomechanical interactions of cancer cells with the microvasculature during metastasis

Metastasis is a major, life-threatening complication of cancer. The bloodstream is the most important disseminative route for cancer cells liberated from their parent tumors. Single circulating cancer cells are arrested in the microvasculature, where the vast majority are killed by rapid or slow processes, and the relatively few survivors grow into micrometastases. We review the underlying causes of one type of rapid cancer cell death in the microcirculation, namely, that caused by biomechanical interactions of cancer cells with microvessel walls, which may result in cell surface membrane expansion and lethal rupture. These lethal interactions appear to be important rate-regulators in hematogenous metastasis, and to dictate some aspects of metastatic patterns. Although these are not the only interactions involving cancer cells, in contrast to others involving cellular and humoral defense mechanisms, they have received comparatively little attention.     

Cancer type‐dependent genetic interactions between cancer driver alterations indicate plasticity of epistasis across cell types

Cancers, like many diseases, are normally caused by combinations of genetic alterations rather than by changes affecting single genes. It is well established that the genetic alterations that drive cancer often interact epistatically, having greater or weaker consequences in combination than expected from their individual effects. In a stringent statistical analysis of data from > 3,000 tumors, we find that the co‐occurrence and mutual exclusivity relationships between cancer driver alterations change quite extensively in different types of cancer. This cannot be accounted for by variation in tumor heterogeneity or unrecognized cancer subtypes. Rather, it suggests that how genomic alterations interact cooperatively or partially redundantly to driver cancer changes in different types of cancers. This re‐wiring of epistasis across cell types is likely to be a basic feature of genetic architecture, with important implications for understanding the evolution of multicellularity and human genetic diseases. In addition, if this plasticity of epistasis across cell types is also true for synthetic lethal interactions, a synthetic lethal strategy to kill cancer cells may frequently work in one type of cancer but prove ineffective in another.     

Synthetic lethal interactions for the development of cancer therapeutics: biological and methodological advancements

Synthetic lethal interaction is defined as a combination of two mutations that is lethal when present in the same cell; each individual mutation is non-lethal. Synthetic lethal interactions attract attention in cancer research fields since the discovery of synthetic lethal genes with either oncogenes or tumor suppressor genes (TSGs) provides novel cancer therapeutic targets. Due to the selective lethal effect on cancer cells harboring specific genetic alterations, it is expected that targeting synthetic lethal genes would provide wider therapeutic windows compared with cytotoxic chemotherapeutics. Here, we review the current status of the application of synthetic lethal screening in cancer research fields from biological and methodological viewpoints. Very recent studies seeking to identify synthetic lethal genes with K-RAS and p53, which are known to be the most frequently occurring oncogenes and TSGs, respectively, are introduced. Among the accumulating amount of research on synthetic lethal interactions, the synthetic lethality between BRCA1/2 and PARP1 inhibition has been clinically proven. Thus, both preclinical and clinical data showing a preferential anti-tumor effect on BRCA1/2 deficient tumors by a PARP1 inhibitor are the best examples of the synthetic lethal approach of cancer therapeutics. Finally, methodological progress regarding synthetic lethal screening, including barcode shRNA screening and in vivo synthetic lethal screening, is described. Given the fact that an increasing number of synthetic lethal genes for major cancerous genes have been validated in preclinical studies, this intriguing approach awaits clinical verification of preferential benefits for cancer patients with specific genetic alterations as a clear predictive factor for tumor response.     

Mechanisms for the biomechanical destruction of L1210 leukemia cells: a rate regulator for metastasis.

Mechanical trauma appears to be one significant cause of the rapid intravascular death of cancer cells and, as such, could act as an important rate regulator for the metastatic process. Intravascular mechanical trauma to cancer cells is thought to be a consequence of shape transitions, occurring when they are deformed from spherical shape by entry into, and passage along, capillaries having smaller diameters than themselves. These transitions from spherical shape require increases in surface area; first, an apparent increase in surface area is accomplished by a reversible, nonlethal surface membrane unfolding. If this is insufficient to meet geometric demands, it is followed by a true increase in surface area, resulting in increased tension in the cancer cell surface membrane, leading to its lethal rupture.     

Mechanisms for the biomechanical destruction of L1210 leukemia cells: A rate regulator for metastasis

Mechanical trauma appears to be one significant cause of the rapid intravascular death of cancer cells and, as such, could act as an important rate regulator for the metastatic process. Intravascular mechanical trauma to cancer cells is thought to be a consequence of shape transitions, occurring when they are deformed from spherical shape by entry into, and passage along, capillaries having smaller diameters than themselves. These transitions from spherical shape require increases in surface area; first, an apparent increase in surface area is accomplished by a reversible, nonlethal surface membrane unfolding. If this is insufficient to meet geometric demands, it is followed by a true increase in surface area, resulting in increased tension in the cancer cell surface membrane, leading to its lethal rupture.     

Focus: A Multifaceted Battle Against Cancer: Approaches to Identifying Synthetic Lethal Interactions in Cancer

Targeting synthetic lethal interactions is a promising new therapeutic approach to exploit specific changes that occur within cancer cells. Multiple approaches to investigate these interactions have been developed and successfully implemented, including chemical, siRNA, shRNA, and CRISPR library screens. Genome-wide computational approaches, such as DAISY, also have been successful in predicting synthetic lethal interactions from both cancer cell lines and patient samples. Each approach has its advantages and disadvantages that need to be considered depending on the cancer type and its molecular alterations. This review discusses these approaches and examines case studies that highlight their use.     

Modulation of prostate cancer growth in bone microenvironments

Bone remains one of the major sites, and most lethal host organs, for prostate cancer metastasis. Prostate cell spread and establishment in bone depends on multiple reciprocal modifications of bone stromal and epithelial cancer cell behaviors. This review focuses on recent advances in the characterization of cell-cell and cell-matrix interplay, effects on cell growth, adhesion and invasion, and several therapeutic possibilities for co-targeting prostate cancer cells and bone stroma. We address the topic from three main perspectives: (1) the normal and aging bone stromal environment, (2) the "reactive" bone stromal environment, and (3) the cancerous prostate epithelial cells themselves. First, normal, and especially aging, bones provide uniquely rich and "fertile soil" for roaming cancer cells. The interactions between prostate cancer cells and insoluble extracellular matrices, soluble growth factors, and/or sex steroid hormones trigger bone remodeling, through increased osteoclastogenesis and furthur matrix metalloproteinase activity. Second, after cancer cell arrival and establishment in the bone, host stromal cells respond, becoming "reactive" in a process again involving extracellular matrix remodeling, together with growth factor and steroid receptor signaling this process ultimately enhances cancer cell migration, stromal transdifferentiation, and invasion of the cancer tissues by stromal, inflammatory, and immune-responsive cells. Third, prostate cancer cells also respond to supportive bone microenvironments, where soluble and matrix-associated molecules affect cancer cell growth and gene expression, especially altering cancer cell surface receptor and integrin-mediated cell signaling. We discuss both integrin cell-matrix and gap junctional cell-cell communication between cancer cells and their microenvironments during prostate cancer progression.     

突变型p53与其合成致死基因的研究进展

恶性肿瘤的靶向治疗已经成为现阶段肿瘤治疗的热点。随着人们对癌基因认知的加深,借助合成致死的方法靶向治疗肿瘤已成为针对肿瘤特异性治疗的新策略。p53基因突变在肿瘤的形成和发展过程中具有重要作用。因此,了解肿瘤中与突变型p53基因有合成致死关系的靶基因的作用方式,有助于指导由突变型p53基因诱发肿瘤的个性化治疗。与突变型p53基因具有合成致死关系的靶基因可分为细胞周期调控基因和细胞非周期调控基因,文章综述了这两类靶基因与突变型p53基因如何构成合成致死作用以及此作用的现实意义。     

Radiosensitizing and cytocidal effects of misonidazole: evidence for separate modes of action

Hypoxic BP-8 murine sarcoma cells were exposed to misonidazole and/or radiation and the kinetics and extent of cell death were evaluated with the [125I]iododeoxyuridine-prelabeling assay. Cell death after treatment with lethal doses of misonidazole was rapid and essentially complete within 2 or 3 days after drug exposure. In contrast, radiation death became apparent only after a delay period of 4 days and was complete by Day 10 after irradiation. Radiosensitization by short exposures to sublethal doses of misonidazole affected only the delayed component of cell death, that is, the radiation component of death. In experiments involving sequential radiation and drug treatment, prior irradiation of cells did not enhance the direct cytocidal effects of misonidazole, as evidenced by the fact that the early component of cell death was equal in control and preirradiated cells. However, postirradiation treatment with misonidazole did enhance the delayed radiation component of cell death. These results suggest that radiosensitization and direct killing by misonidazole are two distinct phenomena mediated by different cellular mechanisms, and radiosensitization by misonidazole represents a two-component effect composed of true dose modification and dose additive damage interactions, but these additive effects must occur at a site different from the cellular structure responsible for direct drug-induced cell death.     

Atomic Force Microscopy Reveals a Role for Endothelial Cell ICAM-1 Expression in Bladder Cancer Cell Adherence

Cancer metastasis is a complex process involving cell-cell interactions mediated by cell adhesive molecules. In this study we determine the adhesion strength between an endothelial cell monolayer and tumor cells of different metastatic potentials using Atomic Force Microscopy. We show that the rupture forces of receptor-ligand bonds increase with retraction speed and range between 20 and 70 pN. It is shown that the most invasive cell lines (T24, J82) form the strongest bonds with endothelial cells. Using ICAM-1 coated substrates and a monoclonal antibody specific for ICAM-1, we demonstrate that ICAM-1 serves as a key receptor on endothelial cells and that its interactions with ligands expressed by tumor cells are correlated with the rupture forces obtained with the most invasive cancer cells (T24, J82). For the less invasive cancer cells (RT112), endothelial ICAM-1 does not seem to play any role in the adhesion process. Moreover, a detailed analysis of the distribution of rupture forces suggests that ICAM-1 interacts preferentially with one ligand on T24 cancer cells and with two ligands on J82 cancer cells. Possible counter receptors for these interactions are CD43 and MUC1, two known ligands for ICAM-1 which are expressed by these cancer cells.     

Activating Ly-49 receptors regulate LFA-1-mediated adhesion by NK cells

NK cells are important for innate resistance to tumors and viruses. Engagement of activating Ly-49 receptors expressed by NK cells leads to rapid NK cell activation resulting in target cell lysis and cytokine production. The ITAM-containing DAP12 adapter protein stably associates with activating Ly-49 receptors, and couples receptor recognition with generation of NK responses. Activating Ly-49s are potent stimulators of murine NK cell functions, yet how they mediate such activities is not well understood. We demonstrate that these receptors trigger LFA-1-dependent tight conjugation between NK cells and target cells. Furthermore, we show that activating Ly-49 receptor engagement leads to rapid DAP12-dependent up-regulation of NK cell LFA-1 adhesiveness to ICAM-1 that is also dependent on tyrosine kinases of the Syk and Src families. These results indicate for the first time that activating Ly-49s control adhesive properties of LFA-1, and by DAP12-dependent inside-out signaling. Ly-49-driven mobilization of LFA-1 adhesive function may represent a fundamental proximal event during NK cell interactions with target cells involving activating Ly-49 receptors, leading to target cell death.     

Acidic extracellular pH shifts colorectal cancer cell death from apoptosis to necrosis upon exposure to propionate and acetate,major end-products of the human probiotic propionibacteria

The human probiotic Propionibacterium freudenreichii kills colorectal adenocarcinoma cells through apoptosis in vitro via its metabolites, the short chain fatty acids (SCFA), acetate and propionate. However, the precise mechanisms, the kinetics of cellular events and the impact of environmental factors such as pH remained to be specified. For the first time, this study demonstrates a major impact of a shift in extracellular pH on the mode of propionibacterial SCFA-induced cell death of HT-29 cells, in the pH range 5.5 to 7.5 prevailing within the colon. Propionibacterial SCFA triggered apoptosis in the pH range 6.0 to 7.5, a lethal process lasting more than 96 h. Indeed at pH 7.5, SCFA induced cell cycle arrest in the G2/M phase, followed by a sequence of cellular events characteristic of apoptosis. By contrast, at pH 5.5, the same SCFA triggered a more rapid and drastic lethal process in less than 24 h. This was characterised by sudden mitochondrial depolarisation, inner membrane permeabilisation, drastic depletion in ATP levels and ROS accumulation, suggesting death by necrosis. Thus, in digestive cancer prophylaxis, the observed pH-mediated switch between apoptosis and necrosis has to be taken into account in strategies involving SCFA production by propionibacteria to kill colon cancer cells. This work has been supported by a grant from CRITT santé Bretagne.     

Peroxynitrite promotes mitochondrial permeability transition-dependent rapid U937 cell necrosis: Survivors proliferate with kinetics superimposable on those of untreated cells

A short term exposure to peroxynitrite promotes a time- and concentration-dependent lethal response in U937 cells. The mode of cell death was necrosis and rapid (within minutes) cell lysis was found to occur via a mechanism involving mitochondrial permeability transition. Apoptosis was not detected in cells exposed to low levels of peroxynitrite, or in cells which survived a treatment with toxic amounts of peroxynitrite, neither after the 60 min exposure nor following increasing time intervals of growth in fresh culture medium. Rather, cells treated with peroxynitrite concentrations which were not immediately lethal, as well as the survivors of treatments with toxic levels of peroxynitrite, proliferated with kinetics superimposable on those observed in untreated cells.     

Peroxynitrite promotes mitochondrial permeability transition-dependent rapid U937 cell necrosis: survivors proliferate with kinetics superimposable on those of untreated cells

A short term exposure to peroxynitrite promotes a time- and concentration-dependent lethal response in U937 cells. The mode of cell death was necrosis and rapid (within minutes) cell lysis was found to occur via a mechanism involving mitochondrial permeability transition. Apoptosis was not detected in cells exposed to low levels of peroxynitrite, or in cells which survived a treatment with toxic amounts of peroxynitrite, neither after the 60 min exposure nor following increasing time intervals of growth in fresh culture medium. Rather, cells treated with peroxynitrite concentrations which were not immediately lethal, as well as the survivors of treatments with toxic levels of peroxynitrite, proliferated with kinetics superimposable on those observed in untreated cells.     

Synthetic lethal hubs associated with vincristine resistant neuroblastoma

Chemotherapy of cancer experiences a number of shortcomings including development of drug resistance. This fact also holds true for neuroblastoma utilizing chemotherapeutics as vincristine. We performed a comparative analysis of molecular and cellular mechanisms associated with vincristine resistance utilizing cell line as well as human tissue data. Differential gene expression analysis revealed molecular features, processes and pathways afflicted with drug resistance mechanisms in general, and specifically with vincristine significantly involving actin associated features. However, specific mode of resistance as well as underlying genotype of parental, vincristine sensitive cells apparently exhibited significant heterogeneity. No consensus profile for vincristine resistance could be derived, but resistance-associated changes on the level of individual neuroblastoma cell lines as well as individual patient profiles became clearly evident. Based on these prerequisites we utilized the concept of synthetic lethality aimed at identifying hub proteins which when inhibited promise to induce cell death due to a synthetic lethal interaction with down-regulated, chemoresistance associated features. Our screening procedure identified synthetic lethal hub proteins afflicted with actin associated processes holding synthetic lethal interactions to down-regulated features individually found in all chemoresistant cell lines tested, therefore promising an improved therapeutic window. Verification of such synthetic lethal hub candidates in human neuroblastoma tissue expression profiles indicated the feasibility of this screening approach for addressing vincristine resistance in neuroblastoma.     

Interactions of cancer cells with the microvasculature during metastasis

Metastasis of cancer via the bloodstream is a major factor in the diagnosis, treatment, and prognosis of patients with cancer. Key events in hematogenous metastasis occur in the microvasculature. This is a brief, selective review of some interactions involving cancer cells and the microvasculature in pathological sequence, specifically: 1) intravasation of cancer cells; 2) the arrest of circulating cancer in the microvasculature; 3) cancer cell trauma associated with arrest; 4) microvascular trauma; 5) the inflammatory and 6) coagulative responses associated with arrest; and 7) the fate of arrested cancer cells. The evidence shows that in addition to providing routes for cancer cell dissemination and arrest sites for cancer cell emboli, the microvasculature, through a series of complex interactions with cancer cells, controls the efficiency of and acts as a rate regulator for the metastatic process.     

SWI/SNF proteins as targets in cancer therapy

Recent identification of synthetic lethal interactions involving several proteins of the SWI/SNF complex discussed in this Research Highlight has opened the possibility of new cancer therapeutic approaches.     

“Cancer Reviews 2021” series: Cell competition in intratumoral and tumor microenvironment interactions

Tumors are complex cellular and acellular environments within which cancer clones are under continuous selection pressures. Cancer cells are in a permanent mode of interaction and competition with each other as well as with the immediate microenvironment. In the course of these competitive interactions, cells share information regarding their general state of fitness, with less‐fit cells being typically eliminated via apoptosis at the hands of those cells with greater cellular fitness. Competitive interactions involving exchange of cell fitness information have implications for tumor growth, metastasis, and therapy outcomes. Recent research has highlighted sophisticated pathways such as Flower, Hippo, Myc, and p53 signaling, which are employed by cancer cells and the surrounding microenvironment cells to achieve their evolutionary goals by means of cell competition mechanisms. In this review, we discuss these recent findings and explain their importance and role in evolution, growth, and treatment of cancer. We further consider potential physiological conditions, such as hypoxia and chemotherapy, that can function as selective pressures under which cell competition mechanisms may evolve differently or synergistically to confer oncogenic advantages to cancer.     

Chromosome instability and tumor lethality suppression in carcinogenesis

The maintenance and survival of each organism depends on its genome integrity. Alterations of essential genes, or aberrant chromosome number and structure lead to cell death. Paradoxically, cancer cells, especially in solid tumors, contain somatic gene mutations and are chromosome instability (CIN), suggesting a mechanism that cancer cells have acquired to suppress the lethal mutations and/or CIN. Herein we will discuss a tumor lethality suppression concept based on the studies of yeast genetic interactions and transgenic mice. During the early stages of the multistep process of tumorigenesis, incipient cancer cells probably have adopted genetic and epigenetic alterations to tolerate the lethal mutations of other genes that ensue, and to a larger extent CIN. In turn, CIN mediated massive gain and loss of genes provides a wider buffer for further genetic reshuffling, resulting in cancer cell heterogeneity, drug resistance and evasion of oncogene addiction, thus CIN may be both the effector and inducer of tumorigenesis. Accordingly, interfering with tumor lethality suppression could lead to cancer cell death or growth defects. Further validation of the tumor lethality suppression concept would help to elucidate the role of CIN in tumorigenesis, the relationship between CIN and somatic gene mutations, and would impact the design of anticancer drug development.