Irinotecan induces steroid and xenobiotic receptor (SXR) signaling to detoxification pathway in colon cancer cells

<p>Abstract</p> <p>Background</p> <p>Resistance to chemotherapy remains one of the principle obstacles to the treatment of colon cancer. In order to identify the molecular mechanism of this resistance, we investigated the role of the steroid and xenobiotic receptor (SXR) in the induction of drug resistance. Indeed, this nuclear receptor plays an important role in response to xenobiotics through the upregulation of detoxification genes. Following drug treatments, SXR is activated and interacts with the retinoid X receptor (RXR) to induce expression of some genes involved in drug metabolism such as phase I enzyme (like CYP), phase II enzymes (like UGT) and transporters (e.g. MDR1).</p> <p>Results</p> <p>In this study, we have shown that endogenous SXR is activated in response to SN-38, the active metabolite of the anticancer drug irinotecan, in human colon cancer cell lines. We have found that endogenous SXR translocates into the nucleus and associates with RXR upon SN-38 treatment. Using ChIP, we have demonstrated that endogenous SXR, following its activation, binds to the native promoter of the CYP3A4 gene to induce its expression. RNA interference experiments confirmed SXR involvement in CYP3A4 overexpression and permitted us to identify CYP3A5 and MRP2 transporter as SXR target genes. As a consequence, cells overexpressing SXR were found to be less sensitive to irinotecan treatment.</p> <p>Conclusions</p> <p>Altogether, these results suggest that the SXR pathway is involved in colon cancer irinotecan resistance in colon cancer cell line via the upregulation of select detoxification genes.</p

Antibodies against endogenous retroviruses promote lung cancer immunotherapy

B cells are frequently found in the margins of solid tumours as organized follicles in ectopic lymphoid organs called tertiary lymphoid structures (TLS)$^{1,2}$. Although TLS have been found to correlate with improved patient survival and response to immune checkpoint blockade (ICB), the underlying mechanisms of this association remain elusive$^{1,2}$. Here we investigate lung-resident B cell responses in patients from the TRACERx 421 (Tracking Non-Small-Cell Lung Cancer Evolution Through Therapy) and other lung cancer cohorts, and in a recently established immunogenic mouse model for lung adenocarcinoma$^{3}$. We find that both human and mouse lung adenocarcinomas elicit local germinal centre responses and tumour-binding antibodies, and further identify endogenous retrovirus (ERV) envelope glycoproteins as a dominant anti-tumour antibody target. ERV-targeting B cell responses are amplified by ICB in both humans and mice, and by targeted inhibition of KRAS(G12C) in the mouse model. ERV-reactive antibodies exert anti-tumour activity that extends survival in the mouse model, and ERV expression predicts the outcome of ICB in human lung adenocarcinoma. Finally, we find that effective immunotherapy in the mouse model requires CXCL13-dependent TLS formation. Conversely, therapeutic CXCL13 treatment potentiates anti-tumour immunity and synergizes with ICB. Our findings provide a possible mechanistic basis for the association of TLS with immunotherapy response

Antibodies against endogenous retroviruses promote lung cancer immunotherapy

B cells are frequently found in the margins of solid tumours as organized follicles in ectopic lymphoid organs called tertiary lymphoid structures (TLS)1,2. Although TLS have been found to correlate with improved patient survival and response to immune checkpoint blockade (ICB), the underlying mechanisms of this association remain elusive1,2. Here we investigate lung-resident B cell responses in patients from the TRACERx 421 (Tracking Non-Small-Cell Lung Cancer Evolution Through Therapy) and other lung cancer cohorts, and in a recently established immunogenic mouse model for lung adenocarcinoma3. We find that both human and mouse lung adenocarcinomas elicit local germinal centre responses and tumour-binding antibodies, and further identify endogenous retrovirus (ERV) envelope glycoproteins as a dominant anti-tumour antibody target. ERV-targeting B cell responses are amplified by ICB in both humans and mice, and by targeted inhibition of KRAS(G12C) in the mouse model. ERV-reactive antibodies exert anti-tumour activity that extends survival in the mouse model, and ERV expression predicts the outcome of ICB in human lung adenocarcinoma. Finally, we find that effective immunotherapy in the mouse model requires CXCL13-dependent TLS formation. Conversely, therapeutic CXCL13 treatment potentiates anti-tumour immunity and synergizes with ICB. Our findings provide a possible mechanistic basis for the association of TLS with immunotherapy respons

The role of APOBEC3B in lung tumor evolution and targeted cancer therapy resistance

In this study, the impact of the apolipoprotein B mRNA-editing catalytic subunit-like (APOBEC) enzyme APOBEC3B (A3B) on epidermal growth factor receptor (EGFR)-driven lung cancer was assessed. A3B expression in EGFR mutant (EGFRmut) non-small-cell lung cancer (NSCLC) mouse models constrained tumorigenesis, while A3B expression in tumors treated with EGFR-targeted cancer therapy was associated with treatment resistance. Analyses of human NSCLC models treated with EGFR-targeted therapy showed upregulation of A3B and revealed therapy-induced activation of nuclear factor kappa B (NF-κB) as an inducer of A3B expression. Significantly reduced viability was observed with A3B deficiency, and A3B was required for the enrichment of APOBEC mutation signatures, in targeted therapy-treated human NSCLC preclinical models. Upregulation of A3B was confirmed in patients with NSCLC treated with EGFR-targeted therapy. This study uncovers the multifaceted roles of A3B in NSCLC and identifies A3B as a potential target for more durable responses to targeted cancer therapy.</p

Genomic–transcriptomic evolution in lung cancer and metastasis

Intratumour heterogeneity (ITH) fuels lung cancer evolution, which leads to immune evasion and resistance to therapy. Here, using paired whole-exome and RNA sequencing data, we investigate intratumour transcriptomic diversity in 354 non-small cell lung cancer tumours from 347 out of the first 421 patients prospectively recruited into the TRACERx study. Analyses of 947 tumour regions, representing both primary and metastatic disease, alongside 96 tumour-adjacent normal tissue samples implicate the transcriptome as a major source of phenotypic variation. Gene expression levels and ITH relate to patterns of positive and negative selection during tumour evolution. We observe frequent copy number-independent allele-specific expression that is linked to epigenomic dysfunction. Allele-specific expression can also result in genomic–transcriptomic parallel evolution, which converges on cancer gene disruption. We extract signatures of RNA single-base substitutions and link their aetiology to the activity of the RNA-editing enzymes ADAR and APOBEC3A, thereby revealing otherwise undetected ongoing APOBEC activity in tumours. Characterizing the transcriptomes of primary–metastatic tumour pairs, we combine multiple machine-learning approaches that leverage genomic and transcriptomic variables to link metastasis-seeding potential to the evolutionary context of mutations and increased proliferation within primary tumour regions. These results highlight the interplay between the genome and transcriptome in influencing ITH, lung cancer evolution and metastasis

Antibodies against endogenous retroviruses promote lung cancer immunotherapy

B cells are frequently found in the margins of solid tumours as organized follicles in ectopic lymphoid organs called tertiary lymphoid structures (TLS). Although TLS have been found to correlate with improved patient survival and response to immune checkpoint blockade (ICB), the underlying mechanisms of this association remain elusive. Here we investigate lung-resident B cell responses in patients from the TRACERx 421 (Tracking Non-Small-Cell Lung Cancer Evolution Through Therapy) and other lung cancer cohorts, and in a recently established immunogenic mouse model for lung adenocarcinoma. We find that both human and mouse lung adenocarcinomas elicit local germinal centre responses and tumour-binding antibodies, and further identify endogenous retrovirus (ERV) envelope glycoproteins as a dominant anti-tumour antibody target. ERV-targeting B cell responses are amplified by ICB in both humans and mice, and by targeted inhibition of KRAS(G12C) in the mouse model. ERV-reactive antibodies exert anti-tumour activity that extends survival in the mouse model, and ERV expression predicts the outcome of ICB in human lung adenocarcinoma. Finally, we find that effective immunotherapy in the mouse model requires CXCL13-dependent TLS formation. Conversely, therapeutic CXCL13 treatment potentiates anti-tumour immunity and synergizes with ICB. Our findings provide a possible mechanistic basis for the association of TLS with immunotherapy response

Oncogène RAS et Cancer Colorectal : Étude de la Réponse au Stress Oncogénique et de l'Échappement à la Sénescence

Oncogene-Induced Senescence (OIS) is a tumor suppressor mechanism which prevent uncontrolled cells proliferation during oncogenic stress. During tumorigenesis, this process is inhibited by inactivation of tumor suppressor genes to allow proliferation and cell transformation. The OIS is described in primary cells, however, we have observed that this mechanism is conserved in transformed cells following the expression of H-RasV12. We investigated the regulation of this line of response in a colorectal adenoma cell line that have already inactivated tumor suppressors p16INK4a and p53. We observed that Ras oncogene induces p53-independent p21Waf1 expression which promotes senescence establishment. Under these conditions, we observed that p21Waf1 inhibits proliferation by transcriptional regulation of cell cycle genes Cdc25A and Plk1. In this work we noticed that some cells escaped to this arrest. By studying the presence of Senescence-Associated Heterochromatin Foci (SAHF), we observed that these cells loss senescence phenotype, and exhibit mesenchymal and dedifferentiation markers. These results suggests that upon expression of the oncogene Ras, some cells escape the OIS and this bypass exhaust is associated with an Epithelial-Mesenchymal Transition (EMT) and emergence of dedifferentiated cells. The bypass of Ras mediated OIS is associated to EMT and dedifferentiation. This mechanism might contribute to tumorigenesis.La sénescence induite par l'oncogène, ou OIS (Oncogene-Induced Senescence), est un mécanisme permettant d'empêcher la prolifération anarchique des cellules lors du stress oncogénique. Lors de la tumorigenèse, ce processus est inhibé par l'inactivation des gènes suppresseurs de tumeurs pour permettre la prolifération et la transformation cellulaire. L'OIS est un processus conservé dans les cellules primaires, cependant, nous l'avons observé dans des cellules transformées à la suite de l'expression de H-RasV12. Nous avons étudié les acteurs de cette réponse dans une lignée d'adénome colorectal ayant déjà inactivé les suppresseurs de tumeurs p16Ink4a et p53. Nous avons observé que l'oncogène Ras induisait l'expression de p21Waf1 et conduisait à la mise en place de la sénescence. Dans ces conditions, nous avons vu que p21Waf1 inhibait la transcription des gènes du cycle cellulaire Cdc25A et Plk1 pour permettre l'arrêt de la prolifération. Au cours de ce travail nous avons remarqué que certaines cellules échappaient à cet arrêt. Par l'étude de la présence de SAHF (Senescence- Associated Heterochromatine Foci), nous avons observé que ces cellules ne présentaient plus ce phénotype caractéristique de la sénescence, mais des marqueurs de cellules mésenchymateuses, et que certaines d'entre elles avaient subi une dédifférenciation. Les résultats que nous avons obtenus indiquent que lors de l'expression de l'oncogène Ras, certaines cellules échappent à l'OIS et que cet échappement est associé à une EMT (Epithelial-Mesenchymal Transition) et à l'émergence de cellules dédifférenciées. L'EMT contribuerait à l'échappement des cellules à l'arrêt du cycle cellulaire

BCL-XL directly modulates RAS signalling to favour cancer cell stemness

In tumours, accumulation of chemoresistant cells that express high levels of anti-apoptotic proteins such as BCL-XL is thought to result from the counter selection of sensitive, low expresser clones during progression and/or initial treatment. We herein show that BCL-XL expression is selectively advantageous to cancer cell populations even in the absence of pro-apoptotic pressure. In transformed human mammary epithelial cells BCL-XL favours full activation of signalling downstream of constitutively active RAS with which it interacts in a BH4-dependent manner. Comparative proteomic analysis and functional assays indicate that this is critical for RAS-induced expression of stemness regulators and maintenance of a cancer initiating cell (CIC) phenotype. Resistant cancer cells thus arise from a positive selection driven by BCL-XL modulation of RAS-induced self-renewal, and during which apoptotic resistance is not necessarily the directly selected trait

Tight Sequestration of BH3 Proteins by BCL-xL at Subcellular Membranes Contributes to Apoptotic Resistance

Anti-apoptotic BCL-2 family members bind to BH3-only proteins and multidomain BAX/BAK to preserve mitochondrial integrity and maintain survival. Whereas inhibition of these interactions is the biological basis of BH3-mimetic anti-cancer therapy, the actual response of membrane-bound protein complexes to these compounds is currently ill-defined. Here, we find that treatment with BH3 mimetics targeting BCL-xL spares subsets of cells with the highest levels of this protein. In intact cells, sequestration of some pro-apoptotic activators (including PUMA and BIM) by full-length BCL-xL is much more resistant to derepression than previously described in cell-free systems. Alterations in the BCL-xL C-terminal anchor that impacts subcellular membrane-targeting and localization dynamics restore sensitivity. Thus, the membrane localization of BCL-xL enforces its control over cell survival and, importantly, limits the pro-apoptotic effects of BH3 mimetics by selectively influencing BCL-xL binding to key pro-apoptotic effectors