Improving radiotherapy in immunosuppressive microenvironments by targeting complement receptor C5aR1

An immunosuppressive microenvironment causes poor tumor T cell infiltration and is associated with reduced patient overall survival in colorectal cancer. How to improve treatment responses in these tumors is still a challenge. Using an integrated screening approach to identify cancer-specific vulnerabilities, we identified complement receptor C5aR1 as a druggable target, which when inhibited improved radiotherapy, even in tumors displaying immunosuppressive features and poor CD8+ T cell infiltration. While C5aR1 is well-known for its role in the immune compartment, we found that C5aR1 is also robustly expressed on malignant epithelial cells, highlighting potential tumor cell-specific functions. C5aR1 targeting resulted in increased NF-κB-dependent apoptosis specifically in tumors and not normal tissues, indicating that, in malignant cells, C5aR1 primarily regulated cell fate. Collectively, these data revealed that increased complement gene expression is part of the stress response mounted by irradiated tumors and that targeting C5aR1 could improve radiotherapy, even in tumors displaying immunosuppressive features.

FXR inhibition may protect from SARS-CoV-2 infection by reducing ACE2

Preventing SARS-CoV-2 infection by modulating viral host receptors, such as angiotensin-converting enzyme 2 (ACE2)1, could represent a new chemoprophylactic approach for COVID-19 that complements vaccination2,3. However, the mechanisms that control the expression of ACE2 remain unclear. Here we show that the farnesoid X receptor (FXR) is a direct regulator of ACE2 transcription in several tissues affected by COVID-19, including the gastrointestinal and respiratory systems. We then use the over-the-counter compound z-guggulsterone and the off-patent drug ursodeoxycholic acid (UDCA) to reduce FXR signalling and downregulate ACE2 in human lung, cholangiocyte and intestinal organoids and in the corresponding tissues in mice and hamsters. We show that the UDCA-mediated downregulation of ACE2 reduces susceptibility to SARS-CoV-2 infection in vitro, in vivo and in human lungs and livers perfused ex situ. Furthermore, we reveal that UDCA reduces the expression of ACE2 in the nasal epithelium in humans. Finally, we identify a correlation between UDCA treatment and positive clinical outcomes after SARS-CoV-2 infection using retrospective registry data, and confirm these findings in an independent validation cohort of recipients of liver transplants. In conclusion, we show that FXR has a role in controlling ACE2 expression and provide evidence that modulation of this pathway could be beneficial for reducing SARS-CoV-2 infection, paving the way for future clinical trials.

Targeting Acid Ceramidase to Improve the Radiosensitivity of Rectal Cancer

Previous work utilizing proteomic and immunohistochemical analyses has identified that high levels of acid ceramidase (AC) expression confers a poorer response to neoadjuvant treatment in locally advanced rectal cancer. We aimed to assess the radiosensitising effect of biological and pharmacological manipulation of AC and elucidate the underlying mechanism. AC manipulation in three colorectal cancer cell lines (HT29, HCT116 and LIM1215) was achieved using siRNA and plasmid overexpression. Carmofur and a novel small molecular inhibitor (LCL521) were used as pharmacological AC inhibitors. Using clonogenic assays, we demonstrate that an siRNA knockdown of AC enhanced X-ray radiosensitivity across all colorectal cancer cell lines compared to a non-targeting control siRNA, and conversely, AC protein overexpression increased radioresistance. Using CRISPR gene editing, we also generated AC knockout HCT116 cells that were significantly more radiosensitive compared to AC-expressing cells. Similarly, two patient-derived organoid models containing relatively low AC expression were found to be comparatively more radiosensitive than three other models containing higher levels of AC. Additionally, AC inhibition using carmofur and LCL521 in three colorectal cancer cell lines increased cellular radiosensitivity. Decreased AC protein led to significant poly-ADP ribose polymerase-1 (PARP-1) cleavage and apoptosis post-irradiation, which was shown to be executed through a p53-dependent process. Our study demonstrates that expression of AC within colorectal cancer cell lines modulates the cellular response to radiation, and particularly that AC inhibition leads to significantly enhanced radiosensitivity through an elevation in apoptosis. This work further solidifies AC as a target for improving radiotherapy treatment of locally advanced rectal cancer.

miR-31-3p Expression and Benefit from Anti-EGFR Inhibitors in Metastatic Colorectal Cancer Patients Enrolled in the Prospective Phase II PROSPECT-C Trial

PURPOSE

Anti-EGFR mAbs are effective in the treatment of metastatic colorectal cancer (mCRC) patients. RAS status and tumor location (sidedness) are predictive markers of patients' response to anti-EGFR mAbs. Recently, low miR-31-3p expression levels have been correlated with clinical benefit from the anti-EGFR mAb cetuximab. Here, we aimed to validate the predictive power of miR-31-3p in a prospective cohort of chemorefractory mCRC patients treated with single-agent anti-EGFR mAbs.

EXPERIMENTAL DESIGN

miR-31-3p was tested by in situ hybridization (ISH) in 91 pretreatment core biopsies from metastatic deposits of 45 patients with mCRC. Sequential tissue biopsies obtained before treatment, at the time of partial response, and at disease progression were tested to monitor changes in miR-31-3p expression overtreatment. miR-31-3p expression, sidedness, and RAS status in pretreatment cell-free DNA were combined in multivariable regression models to assess the predictive value of each variable alone or in combination.

RESULTS

Patients with low miR-31-3p expression in pretreatment biopsies showed better overall response rate, as well as better progression-free survival and overall survival, compared to those with high miR-31-3p expression. The prognostic effect of miR-31-3p was independent from age, gender, and sidedness. No significant changes in the expression of miR-31-3p were observed when sequential tissue biopsies were tested in long-term or poor responders to anti-EGFR mAbs. miR-31-3p scores were similar when pretreatment biopsies were compared with treatment-naïve archival tissues (often primary colorectal cancer).

CONCLUSIONS

Our study validates the role of miR-31-3p as potential predictive biomarker of selection for anti-EGFR mAbs.

Patient-derived organoids model treatment response of metastatic gastrointestinal cancers

Patient-derived organoids (PDOs) have recently emerged as robust preclinical models; however, their potential to predict clinical outcomes in patients has remained unclear. We report on a living biobank of PDOs from metastatic, heavily pretreated colorectal and gastroesophageal cancer patients recruited in phase 1/2 clinical trials. Phenotypic and genotypic profiling of PDOs showed a high degree of similarity to the original patient tumors. Molecular profiling of tumor organoids was matched to drug-screening results, suggesting that PDOs could complement existing approaches in defining cancer vulnerabilities and improving treatment responses. We compared responses to anticancer agents ex vivo in organoids and PDO-based orthotopic mouse tumor xenograft models with the responses of the patients in clinical trials. Our data suggest that PDOs can recapitulate patient responses in the clinic and could be implemented in personalized medicine programs.

Abstract 3589: Validation of the role of circulating tumor DNA (ctDNA) in tracking mechanisms of resistance to anti-EGFR monoclonal antibodies (AE-mABs): preliminary results of the PROSPECT-C prospective trial

Background: AE-mABs (cetuximab and/or panitumumab) have been approved for the treatment of RAS wild-type (WT) metastatic colorectal cancer (mCRC) patients (pts). Indeed, previous studies have identified mutations (MTs)/amplifications in RAS/RAF/MEK kinase pathway as the main genetic events promoting primary and acquired resistance to these mABs. RAS status is frequently established on archival material, as tumour re-biopsy may not be always feasible. PROSPECT-C is a prospective trial aiming to define novel and known mechanisms of resistance to AE-mABs by obtaining repeated biopsies and sequential bloods from pts receiving AE-mABs for chemo-refractory mCRC.

Here we present the preliminary results of the PROSPECT-C liquid biopsy study where the goals were to: 1) confirm the ability of ctDNA to determine RAS status prior to treatment; 2) determine any discordance of RAS status between archival material and ctDNA; 3) confirm the ability of ctDNA to track emerging MTs in the RAS pathway.

Materials and Methods: Plasma was collected at baseline (BL), every 4 weeks and at progression (PD). ctDNA was isolated using the QIAamp Circulating Nucleic Acid Kit (Qiagen) and analyzed by digital droplet PCR (QX200 Bio-Rad) for MTs in KRAS-G12D, KRAS-G13D, KRAS-G12V, KRAS-Q61HA>T, KRAS-Q61HA>C, and BRAF-V600E. In the next steps, plasma samples with no MTs in the first series of hotspots will be tested for the remaining KRAS hotspots, NRAS, EGFR, PIK3CA MTs and KRAS, c-MET and HER-2 amplifications (Data to be presented).

Results: Twenty-four pts (all treated with AE-mAB monotherapy) with KRAS WT tumors (from archival tissue) have been treated on this ongoing study; 16/24 had ctDNA analysis (mean age 62 years, 62.5% males) so far. All pts were heavily pre-treated; 58.3%, 31.3% and 12.5% received 2, 3 and 4 lines of prior therapies respectively. Of 15 pts with BL samples, 5 had MTs at BL; 2 with KRAS-G12D, 1 with KRAS Q61HA>T and 2 pts with BRAF-V600E (in the latter case concordance was found with the archival material). Best response was found to be PD in 4/5 pts and stable disease in 1/5pt with BL MTs; 2 with BRAF MTs progressed in <2 months (mo). The median progression free survival (PFS) for pts with BL MTs was 1.8 mo. Five pts with no MT at BL developed one or more MTs later; those included 4 with KRAS-G12D, 3 with KRAS-G13D and 2 with KRASQ61HA>T (median PFS = 4.8 mo). 3/15 (20%) pts showed discordance in RAS MTs between archival material (WT) and baseline bloods (MT); all of them progressed within 3 mo.

Conclusions: Liquid biopsies can be a useful tool in determining and tracking RAS MTs in pts undergoing anti-EGFR therapy for mCRC. ctDNA analysis to assess RAS mutational status prior to receiving AE-mABs in our series showed 20% discordance between the archival solid and BL liquid biopsies, which may account for resistance to these therapies.

Citation Format: Khurum Khan, George Vlachogianis, David Cunningham, Jens Hahne, Mahnaz Darvish-Damavandi, Sarah Barton, Francesco Trevisani, Giulia Mentrast, Clare Peckitt, Andrea Lampis, Chiara Braconi, Nasir Khan, Ruwaida Begum, Naureen Starling, Sheela Rao, David Watkins, Annette Bryant, Ian Chau, Nicola Valeri. Validation of the role of circulating tumor DNA (ctDNA) in tracking mechanisms of resistance to anti-EGFR monoclonal antibodies (AE-mABs): preliminary results of the PROSPECT-C prospective trial. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3589. doi:10.1158/1538-7445.AM2015-3589

A systematic review of efficacy and tolerability of mebeverine in irritable bowel syndrome

We evaluated the efficacy and tolerability of mebeverine, a musculotropic antispasmodic agent, in irritable bowel syndrome (IBS) and compared its usual dosages by meta-analysis. Medical databases and all relevant literature were searched from 1965 to June 2009 for any placebo-controlled clinical trials of mebeverine, using search terms such as mebeverine, clinical trials, and IBS. Eight randomized trials met our criteria, including six trials that compared mebeverine with placebo and two that compared mebeverine tablets with capsules. These eight trials included 555 patients randomized to receive either mebeverine or placebo with 352 (63%) women and 203 (37%) men in all subtypes of IBS. The pooled relative risk (RR) for clinical improvement of mebeverine was 1.13 (95% CI: 0.59-2.16, P = 0.7056) and 1.33 (95% CI: 0.92-1.93, P = 0.129) for relief of abdominal pain. The efficacy of mebeverine 200 mg compared to mebeverine 135 mg indicated RRs of 1.12 (95% CI: 0.96-1.3, P = 0.168) for clinical or global improvement and 1.08 (95% CI: 0.87-1.34, P = 0.463) for relief of abdominal pain. Thus, mebeverine is mostly well tolerated with no significant adverse effects; however, its efficacy in global improvement of IBS is not statistically significant.