Association of wnt signalling with metachronous colonic polyp risk

232

Background: Following colorectal polypectomy, 20-50% of patients develop metachronous polyps, and a proportion have increased colorectal cancer (CRC) risk. However, there are currently no molecular biomarkers for predicting metachronous polyp risk. Constitutive activation of the Wnt signalling cascade is a hallmark of polyp development and carcinogenesis, therefore biomarkers from this pathway were investigated for association with detection of metachronous polyps. Methods: A retrospective study was performed on a tissue microarray (TMA) of left sided colonic polyps from 279 patients undergoing screening polypectomy (May’09-Dec’16) followed by surveillance colonoscopy (up to 6 years). Mutational analysis was performed using the GPOL cancer plus panel, protein expression by Immunohistochemistry and RNA-sequencing by TempO-Seq (BioClavis). Log rank statistics determined associations with time to detection of metachronous polyp. Index polyp number, histology and size were compared to metachronous lesion outcome using χ2/ANOVA and multivariate polynomial regression identified independent predictors of advanced future lesions. Results: APC (91%), KRAS (30%) and SOX9 (23%) were the most frequently mutated genes and APC and SOX9 are both implicated in Wnt signalling. Mutations in APC and co-mutations in SOX9 with ARID1 were associated with a shorter time to detection of metachronous polyps. Neither variant classification nor location of mutations were associated with metachronous polyp detection. Luminal epithelial cells with high expression of E-Cadherin or SOX9 were significantly associated with earlier detection of metachronous polyps or CRC (HR 2.3, 95%CI 1.6-3.3: p<0.001 and: HR 2.0, 95%CI 1.3-3.0; p=0.001 respectively). By χ2/ANOVA analysis, E-Cadherin and SOX9 expression was associated with detection of metachronous polyp (p>0.001, p=0.037 respectively). On multivariate regression, number of polyps (HR 1.2, 95%CI 1.1-1.3; p<0.001), and E-Cadherin expression (HR 2.1, 95%CI 1.5-3; p<0.001), independently predicted metachronous lesions. Gene set enrichment analysis (GSEA) was used to explore differential biology between high and low E-Cadherin or SOX9 expression. For E-Cadherin, all seven immune-annotated MSigDB hallmarks had negative enrichment, however Wnt--catenin signaling was positively enriched (NES=1.50, p-adj<0.1). The top signature enriched for SOX9 was ‘NFB signaling via TNF (NES=1.70, p-adj<0.001). The LGR5 stemness signature was enriched in both high E-Cadherin (NES=1.97 p-adj<0.0001) and high SOX9 (NES=1.48, p-adj<0.0001) groups. Conclusions: Wnt signalling-associated protein expression within index polyp tissue is valuable for predicting metachronous polyp risk. In addition, expression of E-Cadherin and SOX9 in colonic polyps are linked to immune and stemness signatures, suggesting immune and stemness biology may be an underlying driver of metachronous polyp development.

Durvalumab (MEDI 4736) with extended neoadjuvant regimens in rectal cancer: A randomised phase II trial (PRIME-RT)

TPS282

Background: Advances in multi-modality treatment of locally advanced rectal cancer (LARC) have resulted in low local recurrence rates, but many patients still die from distant disease. There is increasing recognition that with neoadjuvant treatment some patients achieve a complete response and may avoid surgical resection. PRIME-RT tests the inclusion of neoadjuvant immunotherapy with the aim of enhancing complete response rates, improving stoma-free survival and reducing distant relapse. Methods: PRIME-RT is a multi-centre, open label, phase II, randomised trial for patients with newly diagnosed LARC. Eligible patients are randomised to Arm A: short course radiotherapy (25 Gray in 5 fractions) with concomitant durvalumab, followed by durvalumab and FOLFOX chemotherapy, or Arm B: long course chemoradiotherapy (50 Gray to primary tumour, 45 Gray to elective nodes, in 25 fractions with capecitabine) with concomitant durvalumab followed by FOLFOX and durvalumab. The primary endpoint is complete response rate in each arm. Bio-specimens including serial tumour biopsies and peripheral blood samples are collected prior to, during, and following treatment to explore the molecular and immunological factors underpinning treatment response. The main trial will recruit up to 42 patients and commence after a safety run-in which is recruiting patients with metastatic disease. After opening in January 2021, the four patients completed the safety run in and the main trial commenced in March 2022. The trial is currently open across 5 UK sites. Up to date recruitment details will be provided at the time of presentation but at the time of writing this is ahead of target. Early recruitment to PRIME-RT has shown that adding immunotherapy in the neoadjuvant setting for LARC is feasible. Furthermore, on treatment biospecimen collection is also feasible across multiple sites. The expectation is that the trial will provide efficacy and safety information which allows the optimal treatment approach to be tested within a larger phase clinical trial. Core funding (Glasgow CRUK CTU) and trial-specific funding (Astrazeneca). Clinical trial: NCT04621370; ISRCTN18138369. Clinical trial information: ISRCTN18138369 .

Inhibition of YAP/TAZ-driven TEAD activity prevents growth of NF2-null schwannoma and meningioma

Schwannoma tumours typically arise on the 8th cranial nerve and are mostly caused by loss of the tumour suppressor Merlin (NF2). There are no approved chemotherapies for these tumours and the surgical removal of the tumour carries a high risk of damage to the 8th or other close cranial nerve tissue. New treatments for schwannoma and other NF2-null tumours such as meningioma are urgently required. Using a combination of human primary tumour cells and mouse models of schwannoma, we have examined the role of the Hippo signalling pathway in driving tumour cell growth. Using both genetic ablation of the Hippo effectors YAP and TAZ as well as novel TEAD palmitoylation inhibitors, we show that Hippo signalling may be successfully targeted in vitro and in vivo to both block and, remarkably, regress schwannoma tumour growth. In particular, successful use of TEAD palmitoylation inhibitors in a pre-clinical mouse model of schwannoma points to their potential future clinical use. We also identify the cancer stem cell marker aldehyde dehydrogenase 1A1 (ALDH1A1) as a Hippo signalling target, driven by the TAZ protein in human and mouse NF2-null schwannoma cells, as well as in NF2-null meningioma cells, and examine the potential future role of this new target in halting schwannoma and meningioma tumour growth.

Abstract 5957: Roles for the cancer stem cell marker Aldh1A1 in Merlin null nervous system tumors

Our lab is interested in the development and growth of schwannoma and meningioma tumors of the nervous system. Approximately 70% of these tumors arise due to loss of the tumor suppressor Merlin. In a mouse model of schwannoma (P0-CRE NF2fl/fl), we observed increased mRNA levels of the cancer stem cell marker Aldehyde dehydrogenase 1A1 (Aldh1A1) in Merlin-null Schwann cells. Immunostaining showed elevated levels of Aldh1A1 protein in this mouse model and in another mouse model (Postn-CRE NF2fl/fl), in which schwannoma tumors arise spontaneously within the vestibulocochlear nerve and dorsal root ganglia of the nervous system. Similarly, staining of human schwannoma samples also showed a strong elevation of Aldh1A1 protein in all tumor cells. Parallel analysis of meningioma tumor samples, in which Merlin loss also occurs, also showed a strong increase of Aldh1A1 protein levels. Western blotting enabled identification of the mechanism by which Merlin loss regulates Aldh1A1. Merlin/TAZ double knockout, but not Merlin/YAP double knockout, sciatic nerves show reduced Aldh1A1 expression. This implicates Hippo signalling through the TAZ effector as the mechanism of Aldh1A1 upregulation both in vitro and in vivo in both tumor types. Chemical inhibition with Aldh1a1-specific inhibitor (NCT-505) or shRNA knockdown of Aldh1A1 in Merlin-null schwannoma and meningioma cells in culture attenuated tumor cell growth, proving Aldh1A1 has a role in tumor cell proliferation; studies using Aldh1A1 null mice to test this in vivo are ongoing. A major target of Aldh1A1 signalling is the regulation of retinoic acid (RA) signalling. We are examining expression and activation of components of RA signalling in both schwannoma and meningioma tumor cells to identify whether this may be of therapeutic use in the future for these two tumor types. In conclusion, the TAZ-dependent upregulation of Aldh1A1 in Merlin-null schwannoma and meningioma tumor cells has a functional role in driving cell proliferation in these two clinically important tumor types. Further work will seek to identify the mechanism by which Aldh1A1 activity contributes to tumor growth.

Citation Format: Lily Hillson, Liyam Laraba, Aditya G. Shivane, Philip Edwards, Ganesha Bantukallu, Anton Simeonov, Natalia J. Martinez, Shyh-Ming Yang, David B. Parkinson. Roles for the cancer stem cell marker Aldh1A1 in Merlin null nervous system tumors [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 5957.