Pierre Saintigny

A stemness-related ZEB1-MSRB3 axis governs cellular pliancy and breast cancer genome stability.

Chromosomal instability (CIN), a feature of most adult neoplasms from their early stages onward, is a driver of tumorigenesis. However, several malignancy subtypes, including some triple-negative breast cancers, display a paucity of genomic aberrations, thus suggesting that tumor development may occur in the absence of CIN. Here we show that the differentiation status of normal human mammary epithelial cells dictates cell behavior after an oncogenic event and predetermines the genetic routes toward malignancy. Whereas oncogene induction in differentiated cells induces massive DNA damage, mammary stem cells are resistant, owing to a preemptive program driven by the transcription factor ZEB1 and the methionine sulfoxide reductase MSRB3. The prevention of oncogene-induced DNA damage precludes induction of the oncosuppressive p53-dependent DNA-damage response, thereby increasing stem cells intrinsic susceptibility to malignant transformation. In accord with this model, a subclass of breast neoplasms exhibit unique pathological features, including high ZEB1 expression, a low frequency of TP53 mutations and low CIN.

New insights into the role of EMT in tumor immune escape

Novel immunotherapy approaches have provided durable remission in a significant number of cancer patients with cancers previously considered rapidly lethal. Nonetheless, the high degree of nonresponders, and in some cases the emergence of resistance in patients who do initially respond, represents a significant challenge in the field of cancer immunotherapy. These issues prompt much more extensive studies to better understand how cancer cells escape immune surveillance and resist immune attacks. Here, we review the current knowledge of how cellular heterogeneity and plasticity could be involved in shaping the tumor microenvironment (TME) and in controlling antitumor immunity. Indeed, recent findings have led to increased interest in the mechanisms by which cancer cells undergoing epithelial‐mesenchymal transition (EMT), or oscillating within the EMT spectrum, might contribute to immune escape through multiple routes. This includes shaping of the TME and decreased susceptibility to immune effector cells. Although much remains to be learned on the mechanisms at play, cancer cell clones with mesenchymal features emerging from the TME seem to be primed to face immune attacks by specialized killer cells of the immune system, the natural killer cells, and the cytotoxic T lymphocytes. Recent studies investigating patient tumors have suggested EMT as a candidate predictive marker to be explored for immunotherapy outcome. Promising data also exist on the potential utility of targeting these cancer cell populations to at least partly overcome such resistance. Research is now underway which may lead to considerable progress in optimization of treatments.

Response to first line chemotherapy regimen is associated with efficacy of nivolumab in non-small-cell lung cancer

ABSTRACT Nivolumab, an anti PD-1 checkpoint inhibitor has demonstrated efficacy in metastatic non-small-cell lung cancer (NSCLC) patients after failure to standard chemotherapy. Standard chemotherapy agents could promote antitumor immune response. We thus examined whether the response to first line chemotherapy could impact on nivolumab benefit. One hundred and 15 patients with NSCLC were included in this retrospective study from 4 different French centers. Forty-three squamous cell carcinomas (SCC), and 72 non-SCC received nivolumab between 2015 and 2016 (3 mg/kg IV Q2W). Response to first-line chemotherapy and to nivolumab was retrospectively assessed on CT-scan by central review. The association between RECIST response to first-line chemotherapy and nivolumab efficacy were determined using Fishers exact test and Cox proportional hazard model. Respectively 46 (40%), 44 (38%) and 25 (22%) patients experienced partial response (PR), stable disease (SD), or progressive disease (PD) in response to first-line platinum- based chemotherapy. Twenty 5 (21%), 34 (30%), 56 (49%) respectively experienced PR, SD and PD in response to nivolumab. 60% (54/90) of patients who experienced clinical benefit (PR + SD) after first-line chemotherapy also had clinical benefit after nivolumab, while only 20% (5/25) of patients with initial PD subsequently experienced clinical benefit with nivolumab (Fishers exact test, P = 0.001). The type of first-line doublet chemotherapy did not influence the response rate to nivolumab. Univariate and multivariate analyses showed that patients with clinical benefit from first-line chemotherapy had higher second-line PFS (P = 0.003) (median PFS on nivolumab of 5, 3.3 and 1.9 months for patients with PR, SD and PD in response to first-line therapy, respectively). Similar results were obtained for OS. Thus this study suggests that the efficacy of first-line chemotherapy may be a valuable surrogate marker of the benefit of nivolumab in terms of PFS and OS.

The SCN9A channel and plasma membrane depolarization promote cellular senescence through Rb pathway

Oncogenic signals lead to premature senescence in normal human cells causing a proliferation arrest and the elimination of these defective cells by immune cells. Oncogene‐induced senescence (OIS) prevents aberrant cell division and tumor initiation. In order to identify new regulators of OIS, we performed a loss‐of‐function genetic screen and identified that the loss of SCN9A allowed cells to escape from OIS. The expression of this sodium channel increased in senescent cells during OIS. This upregulation was mediated by NF‐κB transcription factors, which are well‐known regulators of senescence. Importantly, the induction of SCN9A by an oncogenic signal or by p53 activation led to plasma membrane depolarization, which in turn, was able to induce premature senescence. Computational and experimental analyses revealed that SCN9A and plasma membrane depolarization mediated the repression of mitotic genes through a calcium/Rb/E2F pathway to promote senescence. Taken together, our work delineates a new pathway, which involves the NF‐κB transcription factor, SCN9A expression, plasma membrane depolarization, increased calcium, the Rb/E2F pathway and mitotic gene repression in the regulation of senescence. This work thus provides new insight into the involvement of ion channels and plasma membrane potential in the control of senescence.