Dominique Guenot

Marked Activity of Irinotecan and Rapamycin Combination toward Colon Cancer Cells In vivo and In vitro Is Mediated through Cooperative Modulation of the Mammalian Target of Rapamycin/Hypoxia-Inducible Factor-1α Axis

Purpose: Despite recent progress, colon cancer is often resistant to combination chemotherapy, highlighting the need for development of novel therapeutic approaches. An attractive target is hypoxia-inducible factor-1α (HIF-1α), a key transcription factor with a pivotal role in tumor cell metabolism. One potential class of therapeutic agents targeting HIF-1α are mammalian target of rapamycin inhibitors such as rapamycin. A second class are topoisomerase I inhibitors, such as irinotecan, which are able to inhibit the accumulation of HIF-1α. We here investigated whether combination of rapamycin and irinotecan was active in human colon cancer models. Experimental Design: Human metastatic tumors were xenografted in nude mice and treated with low doses of irinotecan alone, rapamycin alone, or combination of both drugs. The cellular effects of irinotecan and rapamycin were further characterized for HT-29 and HCT-116 colon cancer cells in vitro. Results: In contrast to single-agent therapy, xenografted tumors treated with combination of irinotecan and rapamycin showed potent inhibition of the mammalian target of rapamycin/HIF-1α axis, which was accompanied by a dramatic reduction in tumor volume. In vitro experiments showed that exposure to low concentrations of the two drugs resulted in massive HT-29 cell death under hypoxic, but not normoxic, conditions, in full agreement with a cytotoxic effect mediated through HIF-1α rather than through induction of genotoxic lesions. HCT-116 cells were less sensitive to the combined treatment due to constitutive activation of phosphatidylinositol 3-kinase/Akt and Ras/mitogen-activated protein kinase pathways. Conclusion: These results identify HIF-1α as a promising target and provide a rationale for clinical trials of low-dose irinotecan and rapamycin combination toward metastatic colon cancer.

IR spectral imaging for histopathological characterization of xenografted human colon carcinomas.

This study aims to develop IR imaging of tumor tissues for generating an automated IR-based histology. Formalin-fixed paraffin-embedded xenografts of human colon carcinomas were analyzed. Chemometric and statistical multivariate treatments of spectral data permitted to probe the intrinsic chemical composition of tissues, directly from paraffinized sections without previous dewaxing. Reconstructed color-coded spectral images revealed a marked tumor heterogeneity. We identified three spectral clusters associated to tumoral tissues, whereas HE staining revealed only a single structure. Nine other clusters were assigned to either necrotic or host tissues. This spectral histology proved to be consistent over multiple passages of the same xenografted tumor confirming that intratumoral heterogeneity was maintained over time. In addition, developing an innovative image analysis, based on the quantification of neighboring pixels, permitted the identification of two main sequences of spectral clusters related to the tissue spatial organization. Molecular attribution of the spectral differences between the tumor clusters revealed differences of transcriptional activity within these tumor tissue subtypes. In conclusion, IR spectral imaging proves to be highly effective both for reproducible tissue subtype recognition and for tumor heterogeneity characterization. This may represent an attractive tool for routine high throughput diagnostic challenges, independent from visual morphology.

Integrin α5β1 Plays a Critical Role in Resistance to Temozolomide by Interfering with the p53 Pathway in High-Grade Glioma

Integrins play a role in the resistance of advanced cancers to radiotherapy and chemotherapy. In this study, we show that high expression of the α5 integrin subunit compromises temozolomide-induced tumor suppressor p53 activity in human glioblastoma cells. We found that depletion of the α5 integrin subunit increased p53 activity and temozolomide sensitivity. However, when cells were treated with the p53 activator nutlin-3a, the protective effect of α5 integrin on p53 activation and cell survival was lost. In a functional p53 background, nutlin-3a downregulated the α5 integrin subunit, thereby increasing the cytotoxic effect of temozolomide. Clinically, α5β1 integrin expression was associated with a more aggressive phenotype in brain tumors, and high α5 integrin gene expression was associated with decreased survival of patients with high-grade glioma. Taken together, our findings indicate that negative cross-talk between α5β1 integrin and p53 supports glioma resistance to temozolomide, providing preclinical proof-of-concept that α5β1 integrin represents a therapeutic target for high-grade brain tumors. Direct activation of p53 may remain a therapeutic option in the subset of patients with high-grade gliomas that express both functional p53 and a high level of α5β1 integrin.

Cdx2 Controls Expression of the Protocadherin Mucdhl, an Inhibitor of Growth and β-Catenin Activity in Colon Cancer Cells

BACKGROUND & AIMS The intestine-specific homeobox transcription factor Cdx2 is an important determinant of intestinal identity in the embryonic endoderm and regulates the balance between proliferation and differentiation in the adult intestinal epithelium. Human colon tumors often lose Cdx2 expression, and heterozygous inactivation of Cdx2 in mice increases colon tumorigenesis. We sought to identify Cdx2 target genes to determine how it contributes to intestinal homeostasis. METHODS We used expression profiling analysis to identify genes that are regulated by Cdx2 in colon cancer cells lines. Regulation and function of a potential target gene were further investigated using various cell assays. RESULTS In colon cancer cell lines, Cdx2 directly regulated the transcription of the gene that encodes the protocadherin Mucdhl. Mucdhl localized to the apex of differentiated cells in the intestinal epithelium, and its expression was reduced in most human colon tumors. Overexpression of Mucdhl inhibited low-density proliferation of colon cancer cells and reduced tumor formation in nude mice. One isoform of Mucdhl interacted with β-catenin and inhibited its transcriptional activity. CONCLUSIONS The transcription factor Cdx2 activates expression of the protocadherin Mucdhl, which interacts with β-catenin and regulates activities of intestinal cells. Loss of Cdx2 expression in colon cancer cells might reduce expression of Mucdhl and thereby lead to tumor formation.

KRAS and BRAF mutations are prognostic biomarkers in patients undergoing lung metastasectomy of colorectal cancer

Background:We evaluated KRAS (mKRAS (mutant KRAS)) and BRAF (mBRAF (mutant BRAF)) mutations to determine their prognostic potential in assessing patients with colorectal cancer (CRC) for lung metastasectomy.Methods:Data were reviewed from 180 patients with a diagnosis of CRC who underwent a lung metastasectomy between January 1998 and December 2011.Results:Molecular analysis revealed mKRAS in 93 patients (51.7%), mBRAF in 19 patients (10.6%). In univariate analyses, overall survival (OS) was influenced by thoracic nodal status (median OS: 98 months for pN−, 27 months for pN+, P<0.0001), multiple thoracic metastases (75 months vs 101 months, P=0.008) or a history of liver metastases (94 months vs 101 months, P=0.04). mBRAF had a significantly worse OS than mKRAS and wild type (WT) (P<0.0001). The 5-year OS was 0% for mBRAF, 44% for mKRAS and 100% for WT, with corresponding median OS of 15, 55 and 98 months, respectively (P<0.0001). In multivariate analysis, WT BRAF (HR: 0.005 (95% CI: 0.001–0.02), P<0.0001) and WT KRAS (HR: 0.04 (95% CI: 0.02–0.1), P<0.0001) had a significant impact on OS.Conclusions:mKRAS and mBRAF seem to be prognostic factors in patients with CRC who undergo lung metastasectomy. Further studies are necessary.

In Vivo Topoisomerase I Inhibition Attenuates the Expression of Hypoxia-Inducible Factor 1α Target Genes and Decreases Tumor Angiogenesis

Topoisomerase I is a privileged target for widely used anticancer agents such as irinotecan. Although these drugs are classically considered to be DNA-damaging agents, increasing evidence suggests that they might also influence the tumor environment. This study evaluates in vivo cellular and molecular modifications induced by irinotecan, a topoisomerase I-directed agent, in patient-derived colon tumors subcutaneously implanted in athymic nude mice. Irinotecan was given intraperitoneally at 40 mg/kg five times every 5 d, and expression profiles were evaluated at d 25 in tumors from treated and untreated animals. Unexpectedly, the in vivo antitumor activity of irinotecan was closely linked to a downregulation of hypoxia-inducible factor-1α (HIF1A) target genes along with an inhibition of HIF1A protein accumulation. The consequence was a decrease in tumor angiogenesis leading to tumor size stabilization. These results highlight the molecular basis for the antitumor activity of a widely used anticancer agent, and the method used opens the way for mechanistic studies of the in vivo activity of other anticancer therapies.

Prognostic value of the KRAS G12V mutation in 841 surgically resected Caucasian lung adenocarcinoma cases

Background:Identifying patients who will experience lung cancer recurrence after surgery remains a challenge. We aimed to evaluate whether mutant forms of epidermal growth factor receptor (EGFR) and Kirsten rat sarcoma viral oncogene homolog (KRAS) (mEGFR and mKRAS) are useful biomarkers in resected non-small cell lung cancer (NSCLC).Methods:We retrospectively reviewed data from 841 patients who underwent surgery and molecular testing for NSCLC between 2007 and 2012.Results:mEGFR was observed in 103 patients (12.2%), and mKRAS in 265 (31.5%). The median overall survival (OS) and time to recurrence (TTR) were significantly lower for mKRAS (OS: 43 months; TTR: 19 months) compared with mEGFR (OS: 67 months; TTR: 24 months) and wild-type patients (OS: 55 months; disease-free survival (DFS): 24 months). Patients with KRAS G12V exhibited worse OS and TTR compared with the entire cohort (OS: KRAS G12V: 26 months vs Cohort: 60 months; DFS: KRAS G12V: 15 months vs Cohort: 24 months). These results were confirmed using multivariate analyses (non-G12V status, hazard ratio (HR): 0.43 (confidence interval: 0.28–0.65), P<0.0001 for OS; HR: 0.67 (0.48–0.92), P=0.01 for TTR). Risk of recurrence was significantly lower for non-KRAS G12V (HR: 0.01, (0.001–0.08), P<0.0001).Conclusions:mKRAS and mEGFR may predict survival and recurrence in early stages of NSCLC. Patients with KRAS G12V exhibited worse OS and higher recurrence incidences.

Selective aminopeptidase-N (CD13) inhibitors with relevance to cancer chemotherapy.

Aminopeptidase-N (APN/CD13) is highly expressed on the surface of numerous types of cancer cells and particularly on the endothelial cells of neoangiogenic vessels during tumourigenesis. This metallo-aminopeptidase has been identified as a potential target for cancer chemotherapy. In this work, we evaluated the efficacy of a novel series of benzosuberone analogues, which were previously reported to be highly potent, selective APN inhibitors with Ki values in the micromolar to sub-nanomolar range. Endothelial cell morphogenesis as well as cell motility were inhibited in vitro in a dose-dependent manner at concentrations that correlated with the potency of the compounds, thus confirming the key role of APN in these established models of angiogenesis. We report toxicity studies in mice showing that these compounds are well tolerated. We report the effects of the compounds, used alone or in combination with rapamycin, on the growth of a select panel of tumours that were subcutaneously xenografted onto Swiss nude mice. Our data indicate that the in vivo efficacy of these new APN inhibitors during the initial phase of tumour growth can be ascribed to their anti-angiogenic activities. However, we also provide evidence that these compounds are effective against established solid tumours. For colonic tumours, the anti-tumour effect depends on the level of APN expression in epithelial cells, and APN expression is associated with down-regulation of the transcription factor HIF-1α. These effects seem to be distinct from those of rapamycin. Our finding that the anti-tumour effect of the inhibitors in the colon requires APN expression strongly suggests that APN plays a crucial function in tumour cells that is distinct from its known role in neovascularisation.

Involvement of the TGFβ pathway in the regulation of α5β1 integrins by caveolin-1 in human glioblastoma

Caveolin‐1 plays a crucial role in the development of cancer and its progression. We previously reported that glioblastoma cells expressing low levels of caveolin‐1 exerted a more aggressive phenotype than cells expressing high levels. Such phenotype was due to the induction of α5β1 integrin subsequent to the depletion of caveolin‐1. Caveolin‐1 was identified as a transcriptional repressor of α5β1 integrin. The current study was designed to identify in vitro, the molecular mechanisms by which caveolin‐1 controls α5β1 integrin expression and to determine if a negative correlation between caveolin‐1 and α5β1 integrins also exists in biopsies and xenografted human brain tumors. We showed that depletion of caveolin‐1 lead to the activation of the TGFβ/TGFβRI/Smad2 pathway which in turn induced the expression of α5β1 integrins. We showed that cells expressing the lowest levels of caveolin‐1 but the highest levels of α5β1 integrins and TGFβRI were the most sensitive to a α5β1 integrin antagonist and a TGFβRI inhibitor. Screening human glioma biopsies and human glioblastoma xenografts, we isolated subgroups with either low levels of caveolin‐1 but high levels of α5β1 integrin and TGFβRI or high levels of caveolin‐1 but low levels of α5β1 integrin and TGFβRI. In conclusion, caveolin‐1 controls α5β1 integrin expression through the TGFβ/TGFβRI/Smad2 pathway. The status of caveolin‐1/α5β1 integrins/TGFβRI might be a useful marker of the tumor evolution/prognosis as well as a predictor of anti‐TGFβ or anti‐α5β1 integrin therapies.

Impact of EGFR mutations and KRAS amino acid substitution on the response to radiotherapy for brain metastasis of non-small-cell lung cancer

BACKGROUND Our study aimed to evaluate response rate (RR) to brain metastasis radiotherapy (RT), depending on the genomic status of non-small-cell lung cancer. MATERIAL & METHODS We retrospectively reviewed 1971 non-small-cell lung cancer files of patients with EGFR and KRAS testing and focused on 157 patients who had undergone RT for brain metastasis. RESULTS A total of 16 patients (10.2%) harbored EGFR mutations (mEGFR) and 45 patients (28.7%) KRAS (mKRAS). In univariate analysis, RR was significantly higher for mEGFR compared with wild-type EGFR/KRAS (odds ratio [OR]: 4.96; p = 0.05) or mKRAS (OR: 1.81; p = 0.03). In multivariate analysis, KRAS G12V or G12C status was associated with both poor RR (OR: 0.1; p < 0.0001) and overall survival (OR: 3.41; p < 0.0001). CONCLUSION mEGFR are associated with higher RR to brain RT than wild-type EGFR/RAS or mKRAS.