Proffered papers session


Programme session type(s): Proffered papers session

Chair: Nitzan Rosenfeld, Cancer Research UK Cambridge Institute, UK
Presenter: Adam Hall, Institute of Genetics and Molecular Medicine, The University of Edinburgh, UK
Presenter: Amy Downing, University of Leeds, UK
Presenter: Arafath Najumudeen, Beatson Institute for Cancer Research, UK
Presenter: Ben O'Leary, The Institute of Cancer Research, UK
Presenter: Meda Sandu, University of Bristol, UK
Presenter: Michael Hodder, CRUK Beatson Institute, UK

13:00-14:00

Room: Carron

Proffered paper sessions are dedicated to the highest scoring abstracts chosen by the scientific committee. They are grouped by type of science presented (following the main Conference streams) and in broad terms cover basic, translational and clinical research.

The abstracts being presented in this session are:
1.A novel application of two-step Mendelian randomization: applying the results of small feasibility studies of interventions to infer causal effects on clinical endpoints – Medu Sandu

2. Effective chemoprevention strategies in APC driven mouse models of intestinal tumourigenesis – Michael Hodder

3. Patient-reported outcomes in men with advanced and localised disease: Results from the UK-wide Life After Prostate Cancer Diagnosis study – Amy Downing

4. Investigating the role of dysregulated RNA splicing in colorectal cancer initiation and progression- Adam Hall

5. Clonal evolution of breast cancer treated with palbociclib and fulvestrant: a circulating tumour DNA analysis of the PALOMA-3 trial – Ben O’Leary

6. Amino acid transporter SLC7A5 is required for growth of Kras-mutant colorectal cancer in vivo – Arafath Najumudeen

A novel application of two-step Mendelian randomization: applying the results of small feasibility studies of interventions to infer causal effects on clinical endpoints
Speaker: Meda R. Sandu
Affiliation: University of Bristol

Abstract:

Feasibility trials are preliminary trials that assess the viability and acceptability of intervention studies and the effects of the intervention on intermediate endpoints.  Due to their short duration, they are unable to establish the effects of the intervention on long-term clinical outcomes. We propose a novel method that could transform the interpretation of feasibility trials using modified two-stage randomization analyses.

Method

In this two-stage process, we explored the effects of a 6-month feasibility factorial randomised controlled trial (RCT) of lycopene and green tea dietary interventions (ProDiet) on 159 serum metabolic traits in 133 men with raised PSA levels but prostate cancer (PCA) free. In the first stage, we conducted an intention-to-treat analysis, using linear regression to examine the effects of the interventions on metabolic traits, compared to the placebo group.  In the second stage, we used a two-sample Mendelian Randomization (MR) approach to assess the causal effect of metabolic traits altered by the interventions, on PCA risk, using summary statistics data from an international PCA consortium of 44,825 cancer cases and 27,904 controls.

Results

The systemic effects of lycopene and green tea supplementation on serum metabolic profile were comparable to the effects of the respective dietary advice interventions (R2= 0.65 and 0.76 for lycopene and green tea respectively).  Metabolites which were altered in response to lycopene supplementation were acetate (standard deviation difference versus placebo (β)): 0.69; 95% CI= 0.24, 1.15; p=0.003), valine (β: -0.62; -1.03, -0.02; p=0.004), pyruvate (β: -0.56; -0.95, -0.16; p=0.006), and docosahexaenoic acid (β: -0.50; -085, -0.14; p=0.006). Using MR, a genetically instrumented SD increase in pyruvate increased the odds of PCA by 1.29 (1.03, 1.62; p=0.027).

Conclusion

Using a two-stage randomization analysis in a feasibility RCT, we found that lycopene lowered levels of pyruvate, which our Mendelian randomization analysis suggests may be causally related to reduced PCA risk.

Patient-reported outcomes in men with advanced and localised disease: Results from the UK-wide Life After Prostate Cancer Diagnosis study
Speaker: Adam Glaser
Affiliation: University of Leeds

Abstract:

Prostate cancer (PCa) outcome studies frequently focus on localised cancer and little is known regarding advanced disease.  The Life After Prostate Cancer Diagnosis (LAPCD) study is a large-scale population-wide evaluation of patient-reported outcomes in men with PCa, including all stages of disease and all treatments.  Here we report the functional outcomes and health-related quality of life (HRQL) of men with advanced and localised disease.

Method

Men diagnosed 18-42 months previously were identified through cancer registration data in each United Kingdom (UK) nation.  Postal surveys were used to collect data on functional outcomes (EPIC-26 plus interventions for sexual dysfunction) and generic HRQL (EQ-5D-5L and self-assessed health [SAH; rated 0-100]), alongside sociodemographic and treatment information.

Results

35,823 (60.8%) men responded; median age 71 years.  Stage at diagnosis was known for 85.8% of respondents; 63.8% stage I/II, 23.5% stage III, 12.8% stage IV.  Overall HRQL reports were good.  Poor sexual function was common (78.9%), regardless of disease stage and few men received help for this (medication: 41.4%; devices: 22.6%; specialist services: 14.8%; 56.5% offered no intervention). Androgen deprivation therapy (ADT) use was associated with poorer HRQL, hot flushes and lack of energy. A quarter of men with stage IV disease reported no problems on any EQ-5D dimension (compared to 42.1% stage I/II, 36.4% stage III).  SAH was 6 points lower in men with stage IV disease (71.6) compared to men with localised cancer (77.8) but this difference was greater in younger men.

Conclusion

18-42 months after diagnosis of PCa, a high proportion of men report sexual dysfunction and less than half were offered intervention.  Loss of HRQL through ADT is common and is more pronounced in younger men.  The good overall HRQL allows clinicians to present positive goals for quality of survival after PCa, including for many diagnosed with advanced disease.

Investigating the role of dysregulated RNA splicing in colorectal cancer initiation and progression
Speaker: Adam Hall
Affiliation: Institute of Genetics and Molecular Medicine, The University of Edinburgh

Abstract:

Colorectal cancer is a leading cause of cancer-related mortality. Intestinal cancer is driven by loss of the APC protein and subsequent hyperactive Wnt/β-catenin signalling in the Lgr5+ stem cell population of the intestinal crypts. Recent work has shown that cancerous cells produce different RNA splicing isoforms and have altered levels of certain splicing factors.

Method

We used state-of-the-art colorectal cancer mouse models as well as 3D primary mouse intestinal organoid culture (“mini-guts”) to elucidate the mechanisms mediating hyperproliferation following APC loss.

Results

We sequenced RNA from the intestinal tissue of wild-type and Apc-/- mice. We found there was an enrichment in transcripts associated with RNA processing following APC loss which included the splicing factor SRSF1. Furthermore, we found that genes alternatively spliced following loss of APC included K-ras, as well as the stem cell marker CD44. We demonstrated the feasibility of targeting the spliceosome by treating wild-type and Apc-/- intestinal organoids with the splicing inhibitor pladienolide B, which resulted in a severely reduced level of cell viability in APC-/- organoids compared to wild-type. We then conducted a targeted CRISPR dropout screen of splicing factors in wild-type and Apc-/- intestinal organoids. This screen revealed that six splicing factors, including SRSF1, were essential for the survival of APC-deficient organoids, whereas their impairment was more tolerated in wild-type organoids. To further characterise the role of SRSF1, we compared the transcriptome profiles of Apc-/- and Apc-/- Srsf1+/- intestinal tissue and found that SRSF1 heterozygous cells had a transcriptome signature more similar to differentiated cells and had reduced ‘stemness’. Immunohistochemistry analysis revealed reduced levels of BrdU staining in the intestinal epithelium of Apc-/- Srsf1+/-. We also showed in vitro that Apc-/- Srsf1+/- organoids had impaired clonogenic capacity.

Conclusion

These results suggest that targeting individual splicing factors might be an attractive therapeutic option in concert with other chemotherapy agents.

Amino acid transporter SLC7A5 is required for growth of Kras-mutant colorectal cancer in vivo
Speaker: Arafath Najumudeen
Affiliation: Beatson Institute for Cancer Research

Abstract:

Colorectal Cancer (CRC) is the third most common cancer worldwide and Ras/MAPK pathway deregulation is strongly associated with the development of CRC, often through activating KRAS mutations (40%) and inactivation of APC (80%). Recent studies from our laboratory and others showed that expression of oncogenic Kras dramatically increases intestinal tumorigenesis initiated by the inactivation of APC in mice. However, the role of Kras mutation in metabolic rewiring of intestinal tumours is not yet fully understood.

Method

We use extensive combinations of genetically engineered mouse (GEM) models of intestinal cancer, targeted liquid chromatography/Mass spectrometry (LC/MS) metabolomics and transcriptomic analysis on intestinal organoids.

Results

Here we demonstrate in GEM models of intestinal cancer that Wnt activation (by Apc loss) and Kras mutation co-ordinately rewire intestinal metabolism in vivo and in vitro by increasing both glucose and glutamine consumption to support anabolic processes that fuel cell proliferation. From this analysis, we identified Solute carrier member 7a5 (Slc7a5) to be significantly upregulated in both mouse and human CRC to meet the increased nutrient demand of the cancer cells. This work aims to determine the mechanism by which Slc7a5 contributes to CRC. Using genetic deletion of Slc7a5 in murine models of CRC we show that Slc7a5 is functionally required for Kras driven (not wildtype) epithelial cell proliferation and tumorigenesis. Mechanistically, Slc7a5 is needed for Kras mediated nutrient sensing and subsequent mTOR1 signaling downstream. Importantly, Slc7a5 deletion sensitises Kras tumours to rapamycin (further suppressing mTORC1 signalling) causing tumour cells to undergo growth arrest. 

Conclusion

In conclusion, our results reveal a Kras mediated metabolic rewiring mechanism that couples amino acid transport by Slc7a5 and mTOR1 activation with control of intestinal tumorigenesis and further suggest that altering Slc7a5 activity may provide a therapeutic opportunity for colorectal cancer.