MHC Class II is Induced by IFNγ and Follows Three Distinct Patterns of Expression in Colorectal Cancer Organoids.

Tumor-specific MHC class II (tsMHC-II) expression impacts tumor microenvironmental immunity. tsMHC-II positive cancer cells may act as surrogate antigen-presenting cells and targets for CD4+ T cell-mediated lysis. In colorectal cancer, tsMHC-II negativity is common, in cell lines due to CIITA promoter methylation. To clarify mechanisms of tsMHC-II repression in colorectal cancer, we analyzed colorectal cancer organoids which are epigenetically faithful to tissue of origin. 15 primary colorectal cancer organoids were treated with IFNγ ± epigenetic modifiers: flow cytometry was used for tsMHC-II expression. qRT-PCR, total RNA sequencing, nanopore sequencing, bisulfite conversion/pyrosequencing, and Western blotting was used to quantitate CIITA, STAT1, IRF1, and JAK1 expression, mutations and promoter methylation and chromatin immunoprecipitation to quantitate H3K9ac, H3K9Me2, and EZH2 occupancy at CIITA. We define three types of response to IFNγ in colorectal cancer: strong, weak, and noninducibility. Delayed and restricted expression even with prolonged IFNγ exposure was due to IFNγ-mediated EZH2 occupancy at CIITA. tsMHC-II expression was enhanced by EZH2 and histone deacetylase inhibition in the weakly inducible organoids. Noninducibility is seen in three consensus molecular subtype 1 (CMS1) organoids due to JAK1 mutation. No organoid demonstrates CIITA promoter methylation. Providing IFNγ signaling is intact, most colorectal cancer organoids are class II inducible. Upregulation of tsMHC-II through targeted epigenetic therapy is seen in one of fifteen organoids. Our approach can serve as a blueprint for investigating the heterogeneity of specific epigenetic mechanisms of immune suppression across individual patients in other cancers and how these might be targeted to inform the conduct of future trials of epigenetic therapies as immune adjuvants more strategically in cancer. Significance: Cancer cell expression of MHC class II significantly impacts tumor microenvironmental immunity. Previous studies investigating mechanisms of repression of IFNγ-inducible class II expression using cell lines demonstrate epigenetic silencing of IFN pathway genes as a frequent immune evasion strategy. Unlike cell lines, patient-derived organoids maintain epigenetic fidelity to tissue of origin. In the first such study, we analyze patterns, dynamics, and epigenetic control of IFNγ-induced class II expression in a series of colorectal cancer organoids.

Patient Derived Organoids Confirm That PI3K/AKT Signalling Is an Escape Pathway for Radioresistance and a Target for Therapy in Rectal Cancer.

Objectives: Partial or total resistance to preoperative chemoradiotherapy occurs in more than half of locally advanced rectal cancer patients. Several novel or repurposed drugs have been trialled to improve cancer cell sensitivity to radiotherapy, with limited success. We aimed to understand the mechanisms of resistance to chemoradiotherapy in rectal cancer using patient derived organoid models. Design: To understand the mechanisms underlying this resistance, we compared the pre-treatment transcriptomes of patient-derived organoids (PDO) with measured radiotherapy sensitivity to identify biological pathways involved in radiation resistance coupled with single cell sequencing, genome wide CRISPR-Cas9 and targeted drug screens. Results: RNA sequencing enrichment analysis revealed upregulation of PI3K/AKT/mTOR and epithelial mesenchymal transition pathway genes in radioresistant PDOs. Single-cell sequencing of pre & post-irradiation PDOs showed mTORC1 and PI3K/AKT upregulation, which was confirmed by a genome-wide CRSIPR-Cas9 knockout screen using irradiated colorectal cancer (CRC) cell lines. We then tested the efficiency of dual PI3K/mTOR inhibitors in improving cancer cell sensitivity to radiotherapy. After irradiation, significant AKT phosphorylation was detected (p=0.027) which was abrogated with dual PI3K/mTOR inhibitors and lead to significant radiosensitisation of the HCT116 cell line and radiation resistant PDO lines. Conclusions: The PI3K/AKT/mTOR pathway upregulation contributes to radioresistance and its targeted pharmacological inhibition leads to significant radiosensitisation in CRC organoids, making it a potential target for clinical trials.

Paradox breaker BRAF inhibitors have comparable potency and MAPK pathway reactivation to encorafenib in BRAF mutant colorectal cancer.

The BEACON CRC trial demonstrated a survival advantage over chemotherapy for a combination of targeted agents comprising the potent BRAF inhibitor encorafenib together with cetuximab and binimetinib. Resistance to BRAF inhibition in CRC arises in part through the generation and activation of RAF dimers resulting in MEK-ERK pathway reactivation. Paradox breaker BRAF inhibitors, such as PLX8394, are designed to inhibit RAF dimer formation. We analyzed whether paradox breakers reduce pathway reactivation and so have enhanced potency compared with encorafenib in BRAF mutant CRC. The potency of encorafenib and PLX8394 was greater than vemurafenib and the degree of pathway reactivation somewhat less. However, dose response curves for encorafenib and PLX8394 were similar and there was no significant differences in degree of pathway reactivation. To our knowledge these data represent the first comparative data of encorafenib and paradox breaker inhibitors in BRAF mutant CRC. Whilst these results support further investigation of PLX8394, all three agents tested reactivated the pathway in melanoma cells, a disease in which monotherapy is effective. Strategies focused on restricting RAF dimerization fail to address the impact that specific context of BRAF mutation in CRC has on targeted therapy outcomes.

Immune checkpoint blockade: releasing the breaks or a protective barrier to COVID-19 severe acute respiratory syndrome?

The rapid emergence of COVID-19 has sent shockwaves through healthcare systems globally, with cancer patients at increased risk. The interplay of the virus and host immune system has been implicated in the development of ARDS. Immunotherapy agents have the potential to adversely potentiate this phenomenon, requiring careful real-world observation.

Follow-up of potential novel Graves' disease susceptibility loci, identified in the UK WTCCC genome-wide nonsynonymous SNP study.

A recent association scan using a genome-wide set of nonsynonymous coding single-nucleotide polymorphisms (nsSNPs) conducted in four diseases including Graves' disease (GD), identified nine novel possible regions of association with GD. We used a case-control approach in an attempt to replicate association of these nine regions in an independent collection of 1578 British GD patients and 1946 matched Caucasian controls. Although none of these loci showed evidence of association with GD in the independent data set, when combined with the original Wellcome Trust Case-Control Consortium study group, minor differences in allele frequencies (P>or=10(-3)) remained in the combined collection of 5924 subjects for four of the nsSNPs, present within HDLBP, TEKT1, JSRP1 and UTX. An additional 29 Tag SNPs were screened within these four gene regions to determine if further associations could be detected. Similarly, minor differences only (P=0.042-0.002) were detected in two HDLBP and two TEKT1 Tag SNPs in the combined UK GD collection. In conclusion, it is unlikely that the SNPs selected in this replication study have a significant effect on the risk of GD in the United Kingdom. Our study confirms the need for large data sets and stringent analysis criteria when searching for susceptibility loci in common diseases.