ObjectiveRegorafenib demonstrated efficacy in patients with metastatic colorectal cancer (mCRC). Lack of predictive biomarkers, potential toxicities and cost-effectiveness concerns highlight the unmet need for better patient selection.DesignPatients with RAS mutant mCRC with biopsiable metastases were enrolled in this phase II trial. Dynamic contrast-enhanced (DCE) MRI was acquired pretreatment and at day 15 post-treatment. Median values of volume transfer constant (Ktrans), enhancing fraction (EF) and their product KEF (summarised median values of Ktrans× EF) were generated. Circulating tumour (ct) DNA was collected monthly until progressive disease and tested for clonal RAS mutations by digital-droplet PCR. Tumour vasculature (CD-31) was scored by immunohistochemistry on 70 sequential tissue biopsies.ResultsTwenty-seven patients with paired DCE-MRI scans were analysed. Median KEF decrease was 58.2%. Of the 23 patients with outcome data, >70% drop in KEF (6/23) was associated with higher disease control rate (p=0.048) measured by RECIST V. 1.1 at 2 months, improved progression-free survival (PFS) (HR 0.16 (95% CI 0.04 to 0.72), p=0.02), 4-month PFS (66.7% vs 23.5%) and overall survival (OS) (HR 0.08 (95% CI 0.01 to 0.63), p=0.02). KEF drop correlated with CD-31 reduction in sequential tissue biopsies (p=0.04). RAS mutant clones decay in ctDNA after 8 weeks of treatment was associated with better PFS (HR 0.21 (95% CI 0.06 to 0.71), p=0.01) and OS (HR 0.28 (95% CI 0.07–1.04), p=0.06).ConclusionsCombining DCE-MRI and ctDNA predicts duration of anti-angiogenic response to regorafenib and may improve patient management with potential health/economic implications.
There are limited data on circulating, cell-free, tumour (ct)DNA analysis in locally advanced rectal cancer (LARC). Digital droplet (dd)PCR was used to investigate KRAS/BRAF mutations in ctDNA from baseline blood samples of 97 LARC patients who were treated with CAPOX followed by chemoradiotherapy, surgery and adjuvant CAPOX ± cetuximab in a randomised phase II trial. KRAS mutation in G12D, G12V or G13D was detected in the ctDNA of 43% and 35% of patients with tumours that were mutant and wild-type for these hotspot mutations, respectively, according to standard PCR-based analyses on tissue. The detection rate in the ctDNA of 10 patients with less common mutations was 50%. In 26 cases ctDNA analysis revealed KRAS mutations that were not previously found in tissue. Twenty-two of these (84.6%) were detected following repeat tissue testing by ddPCR. Overall, the ctDNA detection rate in the KRAS mutant population was 66%. Detection of KRAS mutation in ctDNA failed to predict prognosis or refine patient selection for cetuximab. While this study confirms the feasibility of ctDNA analysis in LARC and the high sensitivity of ddPCR, larger series are needed to better address the role of ctDNA as a prognostic or predictive tool in this setting.
Trastuzumab in combination with chemotherapy represents the standard of care in HER2-positive advanced gastro-esphageal cancer (GOC), but development of resistance limits response. MicroRNAs (miRs) modulate key pathways in GOC. Identification of miRs responsible for resistance to HER2 inhibition may help stratify patients, predict response and define novel strategies to restore drug sensitivity. A high-throughput LNA™ miR-inhibitor screen in HER2-positive NCI-N87 and HER2-negative FLO-1 GOC cell lines was performed in order to identify potential miRs involved in trastuzumab sensitivity/resistance. Cells were treated with a combination of cisplatin, 5FU, and trastuzumab. MiRs were considered significant if LNAs caused >40% reduction in cell viability 72 hours post treatment relative to controls with a t-test p-value of <0.001 across 3 biological replicates. Putative hits with higher baseline miR levels on nCounter® NCI-N87 cell line analysis were validated in two HER2-positive cell lines by calculating the difference (Δ) in cell viability between cells treated with trastuzumab+chemotherapy versus ‘no drug' control. MiR levels in translational samples from ten HER2-positive GOC patients recruited to the FOrMAT trial (NCT02112357) were analysed by ddPCR. MiR levels were categorized as ‘low' or ‘high' relative to median expression and correlated with clinical response. Kaplan-Meier curves for PFS and OS were generated. In NCI-N87 and FLO-1 cell lines, 59 and 37 LNAs respectively caused >40% reduction in cell viability compared to controls (p<0.001). Eighteen miRs were significant exclusively in the NCI-N87 cell line screen, suggesting potential involvement in the HER2-signaling pathway. nCounter® analysis showed 6 of these were elevated at baseline in NCI-N87: miR-1260, miR-148-3p, miR-28-3p, miR-331-3p, miR-7-5p and miR-365. Inhibition of miR-148a-3p increased sensitivity to trastuzumab + 5FU+cisplatin in both the NCI-N87 cell line (Δ 67% versus Δ 55% in the control) and OACP4C cell line (Δ 50% versus Δ 47% in the control). Patients who responded to trastuzumab + chemotherapy in FOrMAT had a trend towards lower average miR-148a-3p plasma levels than those who failed to respond. Median PFS for plasma miR-148a-3p ‘low' subgroup was 146 days versus 154 days in ‘high' subgroup. Median OS for plasma miR-148a-3p ‘low' subgroup was 357 days versus 226 days for miR-148a-3p ‘high' subgroup. Our screen identified a panel of miRs associated with GOC resistance to HER2 inhibitors in combination with chemotherapy. Inhibition of these miRs affects GOC cell viability and restores sensitivity. MiR-148a-3p emerged as a potential biomarker of resistance and further evaluation is underway in the PLATFORM trial (NCT02678182). Citation Format: Hazel Lote, Andrea Lampis, George Vlachogiannis, Jens Hahne, Sing-Yu Moorcraft, Michael Davidson, Carolin Fong, Ruwaida Begum, Matteo Fassan, Sheela Rao, David Watkins, Naureen Starling, Ian Chau, David Cunningham, Nicola Valeri. MicroRNAs as biomarkers of resistance to HER2 inhibition in combination with chemotherapy in gastro-esophageal cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 258.
548 Background: RAS status in tissue and/or liquid biopsies and tumour location (sidedness) are predictive markers of patients’ response to anti-EGFR mABs. MiR-31-3p expression has been correlated with clinical benefit from anti-EGFR mABs with chemotherapy. We aimed to validate the predictive power of miR-31-3p in a prospective cohort of chemo-refractory mCRC patients treated with single agent anti-EGFR mABs in the PROSPECT-C trial (NCT02994888). Methods: MiR-31-3p was tested by in-situ hybridization in 91 pre-treatment (PT) core biopsies from 45 mCRC patients. Sequential tissue biopsies obtained PT, at time of best response and at disease progression were tested to monitor changes in miR-31-3p expression over treatment. In 34 patients miR-31-3p, gender, sidedness, previous lines of treatment and RAS status in PT cell free (cf) DNA were evaluated in multivariate Cox and logistic regression models. Results: Patients with low miR-31-3p expression in PT biopsies showed better overall response rate (ORR: 58.3% vs 22.2%), median progression free survival (mPFS: 4.21 vs 2.27 months) and overall survival (mOS: 4.21 vs 2.27 mo) compared to those with high miR-31-3p expression (Hazard Ratio for PFS high vs low: 1.96; 95% CI: 0.98-3.88; p: 0.06 and HR for OS high vs low: 2.14; 95% CI: 1.04- 4.40; p: 0.04) adjusting for age, gender and sidedness. There was significant association between ORR and miR-31-3p expression (χ2 test p: 0.029). MiR-31-3p expression was an independent predictor of response, adjusting for gender, previous treatment lines and RAS (odds ratio: 0.14; 95% CI: 0.02-1.00, p: 0.048). A trend towards improved mPFS (5.10 vs 2.27 mo) and mOS (15.23 vs 4.67 mo) was noted in miR31-3p low vs high group in cfDNA RAS wild-type patients. No significant change in miR-31-3p expression were observed in archival tissue and sequential tissue biopsies. Conclusions: Our study validates the role of miR-31-3p as potential predictive biomarker of selection for anti-EGFR mABs. Further studies are needed to test if miR-31-3p combined with cfDNA RAS test can identify best responders in specific clinical niches.
Despite showing clinical activity in BRAF-mutant melanoma, the MEK inhibitor (MEKi) trametinib failed to show clinical benefit in KRAS-mutant colorectal cancer. To identify mechanisms of resistance to MEK inhibition we identified gene expression differences between MEKi-sensitive and MEKi-resistant colorectal cancer cell lines. Strikingly, inflammation-related gene sets were the most significantly enriched in cell lines exhibiting intrinsic or acquired resistance to MEK inhibition. The bromodomain inhibitor JQ1 suppressed inflammatory gene expression and in combination with MEK inhibitors displayed synergistic anti-proliferative activity, inhibited colony formation and induced apoptosis in colorectal cancer cell lines. NFkB activation was greater in cell lines resistant to MEK inhibition and JQ1 treatment suppressed TNF-induced translocation of NFkB to the nucleus. Resistance to MEK inhibition could be induced by inflammatory cytokines or by conditioned medium from macrophage cultures and was associated with greater NFkB activation. In 2-dimensional cell culture and in 3-dimensional spheroid models of colorectal cancer, resistance to trametinib was readily established; however, co-treatment of cells with JQ1 and trametinib suppressed the emergence of resistant populations. Notably, high inflammatory gene expression was confirmed in patient-derived organoid (PDO) models of colorectal cancer, which displayed resistance to trametinib. JQ1 treatment of PDOs suppressed inflammatory gene expression and showed synergistic anti-proliferative activity in combination with trametinib. Combination treatment of in vivo models of KRAS-mutant colorectal cancer significantly suppressed tumor growth. Our findings provide a potential explanation for the limited response to MEK inhibitors in KRAS-mutant colorectal cancer, where a highly inflammatory environment may prime cells to be resistant to MEK inhibition. Moreover, the high expression of inflammatory genes was associated with significantly reduced survival of colorectal cancer patients. Excitingly, this opens novel therapeutic opportunities to overcome intrinsic and acquired resistance to MEK inhibition in colorectal cancer. Citation Format: Steve Wagner, George Vlachogiannis, Alexis de Haven Brandon, Melanie Valenti, Gary Box, Liam Jenkins, Caterina Mancusi, Annette Self, Ritika Chauhan, Alistair Rust, Nik Matthews, Kate Eason, Anguraj Sadanandam, Clare Isacke, Vladimir Kirkin, Nicola Valeri, Steven R. Whittaker. Suppression of inflammatory gene expression overcomes resistance to MEK inhibition in KRAS-mutant colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-094.
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