Cell Death Signaling and Anticancer Therapy

For a long time, it was commonly believed that efficient anticancer regimens would either trigger the apoptotic demise of tumor cells or induce a permanent arrest in the G1 phase of the cell cycle, i.e., senescence. The recent discovery that necrosis can occur in a regulated fashion and the increasingly more precise characterization of the underlying molecular mechanisms have raised great interest, as non-apoptotic pathways might be instrumental to circumvent the resistance of cancer cells to conventional, pro-apoptotic therapeutic regimens. Moreover, it has been shown that some anticancer regimens engage lethal signaling cascades that can ignite multiple oncosuppressive mechanisms, including apoptosis, necrosis, and senescence. Among these signaling pathways is mitotic catastrophe, whose role as a bona fide cell death mechanism has recently been reconsidered. Thus, anticancer regimens get ever more sophisticated, and often distinct strategies are combined to maximize efficacy and minimize side effects. In this review, we will discuss the importance of apoptosis, necrosis, and mitotic catastrophe in the response of tumor cells to the most common clinically employed and experimental anticancer agents

PO-300 Unveiling and exploiting cancer stem cell editing and immunogenicity for precision medicine

Introduction Immunogenic chemotherapy (IC) induces immunogenic cell death (ICD), which, similar to viral infection, leads to a cancer-cell autonomous Type-I-Interferon (IFN-I) signalling. This immunological signature is crucial for effective antitumor responses but may paradoxically promote the emergence of a rare population of cancer stem cells (CSCs) acting as a chemoresistant niche within the tumour and roots for metastasis and relapse. In this study, we have investigated the role of IFN-I during IC in inducing a cancer editing program resulting in the appearance of poor immunogenic CSCs. Material and methods Human and murine tumour cell lines were treated in vitro with ICD-inducers or IFN-I as control and the induction of CSC were analysed by cytofluorometry, quantitative real time (qRT)-PCR, 3D culture and functional assays. Free and vesicle-mediated nucleic acid transfer during ICD has been characterised by co-culture experiments. IC-induced CSC immunogenicity has been studied through cytofluorometry, microfluidic devices and in vivo experiments. All experiments have been done in triplicate and statistical significance evaluated by two-tailed Student's t test and two-way ANOVA. Results and discussions The transient/acute induction of IFN-I during ICD is followed by the appearance of a rare population of CSCs. Both free nucleic acids and extracellular vesicles are released during tumour ICD constituting the upstream inducers of IFN-I-mediated reprogramming of neighbouring cells. IC-induced CSCs display epithelial-to-mesenchymal transition traits, multidrug resistance and regenerative properties, and a significant tumorigenic potential when inoculated in immunodeficient and immunocompetent mice. As expected, tumour growth and size are reduced in the presence of an intact immune system. Experiments on microfluidic devices reveal a poor immunogenic potential of CSCs, further confirmed by the expression of immune checkpoint blockers. Conclusion Our results pinpoint a surprising link between ICD, IFN-I and CSCs. Elucidating the mechanisms of CSC editing together with a deep characterisation of CSC (immune) properties could be crucial to prevent tumour relapse. This could undoubtedly have dramatic implications for the clinical management of cancer in an era of terrific development of precision combined chemo-immune therapy

Relative Information Gain: Shannon entropy-based measure of the relative structural conservation in RNA alignments

Structural characterization of RNAs is a dynamic field, offeringmanymodelling possibilities. RNA secondary structure models are usually characterized by an encoding that depicts structural information of the molecule through string representations or graphs. In this work, we provide a generalization of the BEAR encoding (a context-aware structural encoding we previously developed) by expanding the set of alignments used for the construction of substitution matrices and then applying it to secondary structure encodings ranging from fine-grained to more coarse-grained representations. We also introduce a re-interpretation of the Shannon Information applied on RNA alignments, proposing a new scoring metric, the Relative Information Gain (RIG). The RIG score is available for any position in an alignment, showing how different levels of detail encoded in the RNA representation can contribute differently to convey structural information. The approaches presented in this study can be used alongside state-ofthe-art tools to synergistically gain insights into the structural elements that RNAs and RNA families are composed of. This additional information could potentially contribute to their improvement or increase the degree of confidence in the secondary structure of families and any set of aligned RNAs

Role of autophagy in the maintenance and function of cancer stem cells

Recent advances in experimental technologies and cancer models have made possible to demonstrate that the tumor is a dynamic system comprising heterogeneous populations of cancer cells organized in a hierarchical fashion with cancer stem cells (CSCs) at the apex. CSCs are immature cells characterized by self-renewal property and long-term repopulation potential. CSCs have been causally linked to cancer initiation, propagation, spreading, recurrence and relapse as well as to resistance to anticancer therapy. A growing body of evidence suggests that the function and physiology of CSCs may be influenced by genetic/epigenetic factors and tumor environment. In this context, macroautophagy is a lysosomal degradative process (herein referred to as autophagy) critical for the adaptive response to stress and the preservation of cellular and tissue homeostasis in all eukaryotes that may have a crucial role of in the origin, maintenance and invasiveness of CSCs. The activation of the autophagic machinery is also considered as an adaptive response of CSCs to perturbation of tumor microenvironment, caused for instance by anticancer therapy. Nevertheless, compelling preclinical and clinical evidence on the cytoprotective role of autophagy for CSCs is still missing. Here, we summarize the results on the contribution of autophagy in CSCs and how it impacts tumorigenesis and tumor progression. We also discuss the therapeutical potential of the modulation of autophagy as a means to eradicate CSCs

DNA Damage in Stem Cells

Both embryonic and adult stem cells are endowed with a superior capacity to prevent the accumulation of genetic lesions, repair them, or avoid their propagation to daughter cells, which would be particularly detri- mental to the whole organism. Inducible pluripotent stem cells also display a robust DNA damage response, but the stability of their genome is often conditioned by the mutational history of the cell population of origin, which constitutes an obstacle to clinical applications. Cancer stem cells are particularly tolerant to DNA dam- age and fail to undergo senescence or regulated cell death upon accumulation of genetic lesions. Such a resistance contributes to the genetic drift of evolving tumors as well as to their limited sensitivity to chemo- and radiotherapy. Here, we discuss the pathophysiological and therapeutic implications of the molecular pathways through which stem cells cope with DNA damage

BRIO: a web server for RNA sequence and structure motif scan

The interaction between RNA and RNA-binding proteins (RBPs) has a key role in the regulation of gene expression, in RNA stability, and in many other biological processes. RBPs accomplish these functions by binding target RNA molecules through specific sequence and structure motifs. The identification of these binding motifs is therefore fundamental to improve our knowledge of the cellular processes and how they are regulated. Here, we present BRIO (BEAM RNA Interaction mOtifs), a new web server designed for the identification of sequence and structure RNA-binding motifs in one or more RNA molecules of interest. BRIO enables the user to scan over 2508 sequence motifs and 2296 secondary structure motifs identified in Homo sapiens and Mus musculus, in three different types of experiments (PAR-CLIP, eCLIP, HITS). The motifs are associated with the binding of 186 RBPs and 69 protein domains. The web server is freely available at http://brio.bio.uniroma2.it

Inhibition of Chk1 Kills Tetraploid Tumor Cells through a p53-Dependent Pathway

Tetraploidy constitutes an adaptation to stress and an intermediate step between euploidy and aneuploidy in oncogenesis. Tetraploid cells are particularly resistant against genotoxic stress including radiotherapy and chemotherapy. Here, we designed a strategy to preferentially kill tetraploid tumor cells. Depletion of checkpoint kinase-1 (Chk1) by siRNAs, transfection with dominant-negative Chk1 mutants or pharmacological Chk1 inhibition killed tetraploid colon cancer cells yet had minor effects on their diploid counterparts. Chk1 inhibition abolished the spindle assembly checkpoint and caused premature and abnormal mitoses that led to p53 activation and cell death at a higher frequency in tetraploid than in diploid cells. Similarly, abolition of the spindle checkpoint by knockdown of Bub1, BubR1 or Mad2 induced p53-dependent apoptosis of tetraploid cells. Chk1 inhibition reversed the cisplatin resistance of tetraploid cells in vitro and in vivo, in xenografted human cancers. Chk1 inhibition activated p53-regulated transcripts including Puma/BBC3 in tetraploid but not in diploid tumor cells. Altogether, our results demonstrate that, in tetraploid tumor cells, the inhibition of Chk1 sequentially triggers aberrant mitosis, p53 activation and Puma/BBC3-dependent mitochondrial apoptosis

DNA damage and repair biomarkers in cervical cancer patients treated with neoadjuvant chemotherapy: An exploratory analysis

Cervical cancer cells commonly harbour a defective G1/S checkpoint owing to the interaction of viral oncoproteins with p53 and retinoblastoma protein. The activation of the G2/M checkpoint may thus become essential for protecting cancer cells from genotoxic insults, such as chemotherapy. In 52 cervical cancer patients treated with neoadjuvant chemotherapy, we investigated whether the levels of phosphorylated Wee1 (pWee1), a key G2/M checkpoint kinase, and y-H2AX, a marker of DNA double-strand breaks, discriminated between patients with a pathological complete response (pCR) and those with residual disease. We also tested the association between pWee1 and phosphorylated Chk1 (pChk1), a kinase acting upstream Wee1 in the G2/M checkpoint pathway. pWee1, y-H2AX and pChk1 were retrospectively assessed in diagnostic biopsies by immunohistochemistry. The degrees of pWee1 and pChk1 expression were defined using three different classification methods, i.e., staining intensity, Allred score, and a multiplicative score. y-H2AX was analyzed both as continuous and categorical variable. Irrespective of the classification used, elevated levels of pWee1 and y-H2AX were significantly associated with a lower rate of pCR. In univariate and multivariate analyses, pWee1 and y-H2AX were both associated with reduced pCR. Internal validation conducted through a re-sampling without replacement procedure confirmed the robustness of the multivariate model. Finally, we found a significant association between pWee1 and pChk1. The message conveyed by the present analysis is that biomarkers of DNA damage and repair may predict the efficacy of neoadjuvant chemotherapy in cervical cancer. Further studies are warranted to prospectively validate these encouraging findings

DNA damage repair and survival outcomes in advanced gastric cancer patients treated with first-line chemotherapy

The DNA damage response (DDR) network is exploited by cancer cells to withstand chemotherapy. Gastric cancer (GC) carries deregulation of the DDR and harbors genetic defects that fuel its activation. The ATM-Chk2 and ATR-Chk1-Wee1 axes are deputed to initiate DNA repair. Overactivation of these pathways in cancer cells may represent an adaptive response for compensating genetic defects deregulating G1-S transition (e.g., TP53) and ATM/ATR-initiated DNA repair (e.g., ARID1A). We hypothesized that DDR-linked biomarkers may predict clinical outcomes in GC patients treated with chemotherapy. Immunohistochemical assessment of DDR kinases (pATM, pChk2, pChk1 and pWee1) and DNA damage markers (\uce\ub3-H2AX and pRPA32) was performed in biological samples from 110 advanced GC patients treated with first-line chemotherapy, either in phase II trials or in routine clinical practice. In 90 patients, this characterization was integrated with targeted ultra-deep sequencing for evaluating the mutational status of TP53 and ARID1A. We recorded a positive association between the investigated biomarkers. The combination of two biomarkers (\uce\ub3-H2AXhigh/pATMhigh) was an adverse factor for both progression-free survival (multivariate Cox: HR 2.23, 95%CI: 1.47\ue2\u80\u933.40) and overall survival (multivariate Cox: HR: 2.07, 95%CI: 1.20\ue2\u80\u933.58). The relationship between the \uce\ub3-H2AXhigh/pATMhigh model and progression-free survival was consistent across the different TP53 backgrounds and was maintained in the ARID1A wild-type setting. Conversely, this association was no longer observed in an ARID1A-mutated subgroup. The \uce\ub3-H2AXhigh/pATMhigh model negatively impacted survival outcomes in GC patients treated with chemotherapy. The mutational status of ARID1A, but apparently not TP53 mutations, affects its predictive significance