Involvement of Bcl-2 Family Proteins in Tetraploidization-Related Senescence.

The B-cell lymphoma 2 (Bcl-2) family of proteins is the main regulator of apoptosis. However, multiple emerging evidence has revealed that Bcl-2 family proteins are also involved in cellular senescence. On the one hand, the different expression of these proteins determines the entry into senescence. On the other hand, entry into senescence modulates the expression of these proteins, generally conferring resistance to apoptosis. With some exceptions, senescent cells are characterized by the upregulation of antiapoptotic proteins and downregulation of proapoptotic proteins. Under physiological conditions, freshly formed tetraploid cells die by apoptosis due to the tetraploidy checkpoint. However, suppression of Bcl-2 associated x protein (Bax), as well as overexpression of Bcl-2, favors the appearance and survival of tetraploid cells. Furthermore, it is noteworthy that our laboratory has shown that the joint absence of Bax and Bcl-2 antagonist/killer (Bak) favors the entry into senescence of tetraploid cells. Certain microtubule inhibitory chemotherapies, such as taxanes and vinca alkaloids, induce the generation of tetraploid cells. Moreover, the combined use of inhibitors of antiapoptotic proteins of the Bcl-2 family with microtubule inhibitors increases their efficacy. In this review, we aim to shed light on the involvement of the Bcl-2 family of proteins in the senescence program activated after tetraploidization and the possibility of using this knowledge to create a new therapeutic strategy targeting cancer cells.

Multiomics insights on the onset, progression, and metastatic evolution of breast cancer.

Breast cancer is the most common malignant neoplasm in women. Despite progress to date, 700,000 women worldwide died of this disease in 2020. Apparently, the prognostic markers currently used in the clinic are not sufficient to determine the most appropriate treatment. For this reason, great efforts have been made in recent years to identify new molecular biomarkers that will allow more precise and personalized therapeutic decisions in both primary and recurrent breast cancers. These molecular biomarkers include genetic and post-transcriptional alterations, changes in protein expression, as well as metabolic, immunological or microbial changes identified by multiple omics technologies (e.g., genomics, epigenomics, transcriptomics, proteomics, glycomics, metabolomics, lipidomics, immunomics and microbiomics). This review summarizes studies based on omics analysis that have identified new biomarkers for diagnosis, patient stratification, differentiation between stages of tumor development (initiation, progression, and metastasis/recurrence), and their relevance for treatment selection. Furthermore, this review highlights the importance of clinical trials based on multiomics studies and the need to advance in this direction in order to establish personalized therapies and prolong disease-free survival of these patients in the future.

ACBP/DBI protein neutralization confers autophagy-dependent organ protection through inhibition of cell loss, inflammation, and fibrosis.

Acyl-coenzyme A (CoA)-binding protein (ACBP), also known as diazepam-binding inhibitor (DBI), is an extracellular feedback regulator of autophagy. Here, we report that injection of a monoclonal antibody neutralizing ACBP/DBI (α-DBI) protects the murine liver against ischemia/reperfusion damage, intoxication by acetaminophen and concanavalin A, and nonalcoholic steatohepatitis caused by methionine/choline-deficient diet as well as against liver fibrosis induced by bile duct ligation or carbon tetrachloride. α-DBI downregulated proinflammatory and profibrotic genes and upregulated antioxidant defenses and fatty acid oxidation in the liver. The hepatoprotective effects of α-DBI were mimicked by the induction of ACBP/DBI-specific autoantibodies, an inducible Acbp/Dbi knockout or a constitutive Gabrg2F77I mutation that abolishes ACBP/DBI binding to the GABAA receptor. Liver-protective α-DBI effects were lost when autophagy was pharmacologically blocked or genetically inhibited by knockout of Atg4b. Of note, α-DBI also reduced myocardium infarction and lung fibrosis, supporting the contention that it mediates broad organ-protective effects against multiple insults.

Paradoxical implication of BAX/BAK in the persistence of tetraploid cells.

Pro-apoptotic multi-domain proteins of the BCL2 family such as BAX and BAK are well known for their important role in the induction of mitochondrial outer membrane permeabilization (MOMP), which is the rate-limiting step of the intrinsic pathway of apoptosis. Human or mouse cells lacking both BAX and BAK (due to a double knockout, DKO) are notoriously resistant to MOMP and cell death induction. Here we report the surprising finding that BAX/BAK DKO cells proliferate less than control cells expressing both BAX and BAK (or either BAX or BAK) when they are driven into tetraploidy by transient exposure to the microtubule inhibitor nocodazole. Mechanistically, in contrast to their BAX/BAK-sufficient controls, tetraploid DKO cells activate a senescent program, as indicated by the overexpression of several cyclin-dependent kinase inhibitors and the activation of ß-galactosidase. Moreover, DKO cells manifest alterations in ionomycin-mobilizable endoplasmic reticulum (ER) Ca2+ stores and store-operated Ca2+ entry that are affected by tetraploidization. DKO cells manifested reduced expression of endogenous sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (Serca2a) and transfection-enforced reintroduction of Serca2a, or reintroduction of an ER-targeted variant of BAK into DKO cells reestablished the same pattern of Ca2+ fluxes as observed in BAX/BAK-sufficient control cells. Serca2a reexpression and ER-targeted BAK also abolished the tetraploidy-induced senescence of DKO cells, placing ER Ca2+ fluxes downstream of the regulation of senescence by BAX/BAK. In conclusion, it appears that BAX/BAK prevent the induction of a tetraploidization-associated senescence program. Speculatively, this may contribute to the low incidence of cancers in BAX/BAK DKO mice and explain why human cancers rarely lose the expression of both BAX and BAK.

Everolimus and plicamycin specifically target chemoresistant colorectal cancer cells of the CMS4 subtype.

Colorectal cancers (CRC) can be classified into four consensus molecular subtypes (CMS), among which CMS1 has the best prognosis, contrasting with CMS4 that has the worst outcome. CMS4 CRC is notoriously resistant against therapeutic interventions, as demonstrated by preclinical studies and retrospective clinical observations. Here, we report the finding that two clinically employed agents, everolimus (EVE) and plicamycin (PLI), efficiently target the prototypic CMS4 cell line MDST8. As compared to the prototypic CMS1 cell line LoVo, MDST8 cells treated with EVE or PLI demonstrated stronger cytostatic and cytotoxic effects, increased signs of apoptosis and autophagy, as well as a more pronounced inhibition of DNA-to-RNA transcription and RNA-to-protein translation. Moreover, nontoxic doses of EVE and PLI induced the shrinkage of MDST8 tumors in mice, yet had only minor tumor growth-reducing effects on LoVo tumors. Altogether, these results suggest that EVE and PLI should be evaluated for their clinical activity against CMS4 CRC.

Quantification of eIF2α Phosphorylation Associated with Mitotic Catastrophe by Immunofluorescence Microscopy.

Mitotic catastrophe is an oncosuppressive mechanism that drives cells toward senescence or death when an error occurs during mitosis. Eukaryotic cells have developed adaptive signaling pathways to cope with stress. The phosphorylation on serine 51 of the eukaryotic translation initiation factor (eIF2α) is a highly conserved event in stress responses, including the one that is activated upon treatment with mitotic catastrophe inducing agents, such as microtubular poisons or actin blockers. The protocol described herein details a method to quantify the phosphorylation of eIF2α by high-throughput immunofluorescence microscopy. This method is useful to capture the 'integrated stress response', which is characterized by eIF2α phosphorylation in the context of mitotic catastrophe.

Clonogenic Assays to Detect Cell Fate in Mitotic Catastrophe.

Mitotic catastrophe (MC) is a cell death modality induced by DNA damage that involves the activation of cell cycle checkpoints such as the "DNA structure checkpoint" and "spindle assembly checkpoint" (SAC) leading to aberrant mitosis. Depending on the signal, MC can drive the cell to death or to senescence. The suppression of MC favors aneuploidy. Several cancer therapies, included microtubular poisons and radiations, trigger MC. The clonogenic assay has been used to study the capacity of single cells to proliferate and to generate macroscopic colonies and to evaluate the efficacy of anticancer drugs. Nevertheless, this method cannot analyze MC events. Here, we report an improved technique based on the use of human colon cancer HCT116 stable expressing histone H2B-GFP and DsRed-centrin proteins, allowing to determine the capacity of cells to proliferate, and to determine changes in the nucleus and centrosomes.

In Vivo Imaging of Orthotopic Lung Cancer Models in Mice.

The success of anticancer interventions relies on their ability to ignite an anticancer immune response and to reinstate cancer immunosurveillance. Thus, high dose crizotinib can induce immunogenic cell death (ICD) in cancer cells. If combined with cisplatin, crizotinib sensitizes non-small cell lung cancers (NSCLC) to subsequent (but not simultaneous) immunotherapy with PD-1 immune checkpoint blockade, facilitating the cure of more than 90% of established orthotopic cancers in mice. Here, we detail protocols for the establishment and monitoring of transplantable orthotopic NSCLCs in syngeneic immunocompetent animals. Indeed, TC1 cells establish lung cancer upon their intravenous injection into the tail vein, while Lewis lung carcinoma (LLC) cells can be implanted intrathoracically to generate lung cancers. If transduced with luciferase, both TC1 and LLC cells form tumors that can be conveniently monitored by chemiluminescence. This type of NSCLC model is highly useful for the development of novel curative anticancer therapies.

Publisher Correction: Immunoprophylactic and immunotherapeutic control of hormone receptor-positive breast cancer.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Immunoprophylactic and immunotherapeutic control of hormone receptor-positive breast cancer.

Hormone receptor (HR)+ breast cancer (BC) causes most BC-related deaths, calling for improved therapeutic approaches. Despite expectations, immune checkpoint blockers (ICBs) are poorly active in patients with HR+ BC, in part reflecting the lack of preclinical models that recapitulate disease progression in immunocompetent hosts. We demonstrate that mammary tumors driven by medroxyprogesterone acetate (M) and 7,12-dimethylbenz[a]anthracene (D) recapitulate several key features of human luminal B HR+HER2- BC, including limited immune infiltration and poor sensitivity to ICBs. M/D-driven oncogenesis is accelerated by immune defects, demonstrating that M/D-driven tumors are under immunosurveillance. Safe nutritional measures including nicotinamide (NAM) supplementation efficiently delay M/D-driven oncogenesis by reactivating immunosurveillance. NAM also mediates immunotherapeutic effects against established M/D-driven and transplantable BC, largely reflecting increased type I interferon secretion by malignant cells and direct stimulation of immune effector cells. Our findings identify NAM as a potential strategy for the prevention and treatment of HR+ BC.

Suppression of tumor antigen presentation during aneuploid tumor evolution contributes to immune evasion.

Anti-tumor immune responses impede tumor formation, and cancers have evolved many mechanisms of immune evasion. Confirming earlier findings, we show that human tumors with high chromosomal instability (CIN+) are significantly less immunogenic, as judged by tumor lymphocyte infiltration, compared to those with more stable genomes (CIN-). This finding is paradoxical, as genomic instability is expected to evoke an innate immune response. Importantly, CIN+ tumors and cell lines exhibited suppressed expression of proteins involved in MHC class I antigen presentation at least partly due to DNA hypermethylation of the corresponding genes. Using a mouse model of the in vivo evolution of aneuploid tumors, we found that the induction of chromosomal instability in tumor cells is highly immunogenic due to the activation of the STING/TBK1 pathway and consequent increased interferon signaling and antigen presentation. However, tumors evolving under immune pressure suppress the STING/TBK1 and antigen presentation pathways and evade anti-tumor immune responses. In contrast, CIN+ tumors that develop under low immune pressure in both humans and mice retain efficient MHC class I antigen presentation and immunogenicity. Altogether, this study identifies an important mechanism of immune evasion in chromosomally unstable tumors.

Lurbinectedin synergizes with immune checkpoint blockade to generate anticancer immunity.

Systemic treatment with the active transcription inhibitor lurbinectedin aims at inducing tumor cell death in hyperproliferative neoplasms. Here we show that cell death induced by lurbinectedin reinstates and enhances systemic anticancer immune responses. Lurbinectedin treatment showed traits of immunogenic cell death, including the exposure of calreticulin, the release of ATP, the exodus of high mobility group box 1 (HMGB1) and type 1 interferon responses in vitro. Lurbinectedin treated cells induced antitumor immunity when injected into immunocompetent animals and treatment of transplanted fibrosarcomas reduced tumor growth in immunocompetent yet not in immunodeficient hosts. Anticancer effects resulting from lurbinectedin treatment were boosted in combination with PD-1 and CTLA-4 double immune checkpoint blockade (ICB), and lurbinectedin combined with double ICB exhibited strong antineoplastic effects. Cured animals exhibited long term immune memory effects that rendered them resistant to rechallenge with syngeneic tumors underlining the potency of combination therapy with lurbinectedin.

Crizotinib-induced immunogenic cell death in non-small cell lung cancer.

Immunogenic cell death (ICD) converts dying cancer cells into a therapeutic vaccine and stimulates antitumor immune responses. Here we unravel the results of an unbiased screen identifying high-dose (10 µM) crizotinib as an ICD-inducing tyrosine kinase inhibitor that has exceptional antineoplastic activity when combined with non-ICD inducing chemotherapeutics like cisplatin. The combination of cisplatin and high-dose crizotinib induces ICD in non-small cell lung carcinoma (NSCLC) cells and effectively controls the growth of distinct (transplantable, carcinogen- or oncogene induced) orthotopic NSCLC models. These anticancer effects are linked to increased T lymphocyte infiltration and are abolished by T cell depletion or interferon-γ neutralization. Crizotinib plus cisplatin leads to an increase in the expression of PD-1 and PD-L1 in tumors, coupled to a strong sensitization of NSCLC to immunotherapy with PD-1 antibodies. Hence, a sequential combination treatment consisting in conventional chemotherapy together with crizotinib, followed by immune checkpoint blockade may be active against NSCLC.

Author Correction: Crizotinib-induced immunogenic cell death in non-small cell lung cancer.

The original version of this Article contained an error in the spelling of the author Lin Xia, which was incorrectly given as Xia Lin. This has now been corrected in both the PDF and HTML versions of the Article.

Immune effectors responsible for the elimination of hyperploid cancer cells.

The immune system avoids oncogenesis and slows down tumor progression through a mechanism called immunosurveillance. Nevertheless, some malignant cells manage to escape from immune control and form clinically detectable tumors. Tetraploidy, which consists in the intrinsically unstable duplication of the genome, is considered as a (pre)-cancerous event that can result in aneuploidy and contribute to oncogenesis. We previously described the fact that tetraploid cells can be eliminated by the immune system. Here, we investigate the role of different innate and acquired immune effectors by inoculating hyperploid cancer cells into wild type or mice bearing different immunodeficient genotypes (Cd1d-/-, FcRn-/-, Flt3l-/-, Foxn1nu/nu, MyD88-/-, Nlrp3-/-, Ighmtm1Cgn, Rag2-/-), followed by the monitoring of tumor incidence, growth and final ploidy status. Our results suggest that multiple different immune effectors including B, NK, NKT and T cells, as well as innate immune responses involving the interleukine-1 receptor and the Toll-like receptor systems participate to the immunoselection against hyperploid cells. Hence, optimal anticancer immunosurveillance likely involves the contribution of multiple arms of the immune system.

eIF2α phosphorylation is pathognomonic for immunogenic cell death.

The phosphorylation of eIF2α is essential for the endoplasmic reticulum (ER) stress response, the formation of stress granules, as well as macroautophagy. Several successful anticancer chemotherapeutics have the property to induce immunogenic cell death (ICD), thereby causing anticancer immune responses. ICD is accompanied by the translocation of calreticulin (CALR) from the ER lumen to the plasma membrane, which facilitates the transfer of tumor-associated antigens to dendritic cells. Here we systematically investigated the capacity of anticancer chemotherapeutics to induce signs of ER stress. ICD inducers including anthracyclines and agents that provoke tetraploidization were highly efficient in enhancing the phosphorylation of eIF2α, yet failed to stimulate other signs of ER stress including the transcriptional activation of activating transcription factor 4 (ATF4), the alternative splicing of X-box binding protein 1 (XBP1s) mRNA and the proteolytic cleavage of activating transcription factor 6 (ATF6) both in vitro and in cancers established in mice. Systematic analyses of clinically used anticancer chemotherapeutics revealed that only eIF2α phosphorylation, but none of the other signs of ER stress, correlated with CALR exposure. eIF2α phosphorylation induced by mitoxantrone, a prototype ICD-inducing anthracyline, was mediated by eIF2α kinase-3 (EIF2AK3). Machine-learning approaches were used to determine the physicochemical properties of drugs that induce ICD, revealing that the sole ER stress response relevant to the algorithm is eIF2α phosphorylation with its downstream consequences CALR exposure, stress granule formation and autophagy induction. Importantly, this approach could reduce the complexity of compound libraries to identify ICD inducers based on their physicochemical and structural characteristics. In summary, it appears that eIF2α phosphorylation constitutes a pathognomonic characteristic of ICD.

Calcium signaling and cell cycle: Progression or death.

Cytosolic Ca2+ concentration levels fluctuate in an ordered manner along the cell cycle, in line with the fact that Ca2+ is involved in the regulation of cell proliferation. Cell proliferation should be an error-free process, yet is endangered by mistakes. In fact, a complex network of proteins ensures that cell cycle does not progress until the previous phase has been successfully completed. Occasionally, errors occur during the cell cycle leading to cell cycle arrest. If the error is severe, and the cell cycle checkpoints work perfectly, this results into cellular demise by activation of apoptotic or non-apoptotic cell death programs. Cancer is characterized by deregulated proliferation and resistance against cell death. Ca2+ is a central key to these phenomena as it modulates signaling pathways that control oncogenesis and cancer progression. Here, we discuss how Ca2+ participates in the exogenous and endogenous signals controlling cell proliferation, as well as in the mechanisms by which cells die if irreparable cell cycle damage occurs. Moreover, we summarize how Ca2+ homeostasis remodeling observed in cancer cells contributes to deregulated cell proliferation and resistance to cell death. Finally, we discuss the possibility to target specific components of Ca2+ signal pathways to obtain cytostatic or cytotoxic effects.

Immunogenic stress and death of cancer cells: Contribution of antigenicity vs adjuvanticity to immunosurveillance.

Cancer cells are subjected to constant selection by the immune system, meaning that tumors that become clinically manifest have managed to subvert or hide from immunosurveillance. Immune control can be facilitated by induction of autophagy, as well as by polyploidization of cancer cells. While autophagy causes the release of ATP, a chemotactic signal for myeloid cells, polyploidization can trigger endoplasmic reticulum stress with consequent exposure of the "eat-me" signal calreticulin on the cell surface, thereby facilitating the transfer of tumor antigens into dendritic cells. Hence, both autophagy and polyploidization cause the emission of adjuvant signals that ultimately elicit immune control by CD8+ T lymphocytes. We investigated the possibility that autophagy and polyploidization might also affect the antigenicity of cancer cells by altering the immunopeptidome. Mass spectrometry led to the identification of peptides that were presented on major histocompatibility complex (MHC) class I molecules in an autophagy-dependent fashion or that were specifically exposed on the surface of polyploid cells, yet lost upon passage of such cells through immunocompetent (but not immunodeficient) mice. However, the preferential recognition of autophagy-competent and polyploid cells by the innate and cellular immune systems did not correlate with the preferential recognition of such peptides in vivo. Moreover, vaccination with such peptides was unable to elicit tumor growth-inhibitory responses in vivo. We conclude that autophagy and polyploidy increase the immunogenicity of cancer cells mostly by affecting their adjuvanticity rather than their antigenicity.

Kinetic fragility and structure of lithium borophosphate glasses analysed by 1D/2D NMR.

The macroscopic and high temperature properties of lithium borophosphate glasses were determined in this contribution. Our data, obtained on 50Li2O-xB2O3-(50-x)P2O5 glasses, confirm a continuous and linear increase of the glass transition temperature with the B/P substitution but show a two-domain evolution of the kinetic fragility with a steep decrease in the low B2O3 region (0 ≤ x ≤ 10) followed by a moderate increase for higher B2O3 contents. In order to understand this different behaviour, the glass structure was investigated in detail using 1D and 2D 11B/31P correlation solid state nuclear magnetic resonance. The local and medium orders of borate units were determined by 1D MAS-NMR, 2D 11B DQSQ- and 11B(31P) D-HMQC NMR experiments. The latter NMR technique was also used to deeply interpret the 1D 31P MAS-NMR spectra. Altogether the data allow (i) highlighting of the presence of four borate and seven phosphate units, (ii) evaluation of the number of homopolar POP and mixed POB linkages, and (iii) contribute to a better understanding of the Tg and kinetic fragility evolution.

Image Cytofluorometry for the Quantification of Ploidy and Endoplasmic Reticulum Stress in Cancer Cells.

One of the mechanisms of cancer-associated genomic instability involves a transient phase of polyploidization, in most cases tetraploidization, followed by asymmetric divisions and chromosome loss. Increases in ploidy are consistently accompanied by the activation of an endoplasmic reticulum (ER) stress response, resulting in the translocation of calreticulin to the outer surface of the plasma membrane where it stimulates anticancer immune responses. Conversely, immunoselection leads to a coordinated reduction in ploidy, ER stress, and calreticulin exposure. To simultaneously investigate the ER stress and ploidy, we developed an image cytofluorometric method that allows to measure DNA content, ER stress-associated phosphorylation of eIF2α, and calreticulin exposure at the cell surface. Here, we specify this methodology, which is useful for investigating the correlation between ploidy and ER stress at the single cell level.