Microsatellite Stable Colorectal Cancer Research Articles

Canonical and uncanonical pathogenic germline variants in colorectal cancer patients by next-generation sequencing in a European referral center

Despite increasing use of next-generation sequencing (NGS), data concerning the gain in germline pathogenic variants (PVs) remain scanty, especially with respect to uncanonical ones. We aimed to verify the impact of different cancer predisposition genes (CPGs) on colorectal cancer (CRC) in patients referred for genetic evaluation. We enrolled for NGS, by Illumina TruSight Cancer panel comprising 94 CPGs, 190 consecutive subjects referred for microsatellite instability (MSI) CRC, polyposis, and/or family history. Overall, 51 (26.8%) subjects carried 64 PVs; PVs coexisted in 4 (7.8%) carriers. PVs in mismatch repair (MMR) genes accounted for one-third of variant burden (31.3%). Four Lynch syndrome patients (20%) harbored additional PVs (HOXB13, CHEK2, BRCA1, NF1 plus BRIP1); such multiple PVs occurred only in subjects with PVs in mismatch syndrome genes (4/20 versus 0/31; P= 0.02). Five of 22 (22.7%) patients with MSI cancers but wild-type MMR genes harbored PVs in unconventional genes (FANCL, FANCA, ATM, PTCH1, BAP1). In 10/63 patients (15.9%) with microsatellite stable CRC, 6 had MUTYH PVs (2 being homozygous) and 4 exhibited uncanonical PVs (BRCA2, BRIP1, MC1R, ATM). In polyposis, we detected PVs in 13 (25.5%) cases: 5 (9.8%) in APC, 6 (11.8%) with biallelic PVs in MUTYH, and 2 (3.9%) in uncanonical genes (FANCM, XPC). In subjects tested for family history only, we detected two carriers (18.2%) with PVs (ATM, MUTYH). Uncanonical variants may account for up to one-third of PVs, underlining the urgent need of consensus on clinical advice for incidental findings in cancer-predisposing genes not related to patient phenotype.

Cabozantinib sensitizes microsatellite stable colorectal cancer to immune checkpoint blockade by immune modulation in human immune system mouse models.

Immune checkpoint inhibitors have been found to be effective in metastatic MSI-high colorectal cancers (CRC), however, have no efficacy in microsatellite stable (MSS) cancers, which comprise the majority of mCRC cases. Cabozantinib is a small molecule multi-tyrosine kinase inhibitor that is FDA approved in advanced renal cell, medullary thyroid, and hepatocellular carcinoma. Using Human Immune System (HIS) mice, we tested the ability of cabozantinib to prime MSS-CRC tumors to enhance the potency of immune checkpoint inhibitor nivolumab. In four independent experiments, we implanted distinct MSS-CRC patient-derived xenografts (PDXs) into the flanks of humanized BALB/c-Rag2nullIl2rγnullSirpαNOD (BRGS) mice that had been engrafted with human hematopoietic stem cells at birth. For each PDX, HIS-mice cohorts were treated with vehicle, nivolumab, cabozantinib, or the combination. In three out of the four models, the combination had a lower tumor growth rate compared to vehicle or nivolumab-treated groups. Furthermore, interrogation of the HIS in immune organs and tumors by flow cytometry revealed increased Granzyme B+, TNFα+ and IFNγ+ CD4+ T cells among the human tumor infiltrating leukocytes (TIL) that correlated with reduced tumor growth in the combination-treated HIS-mice. Notably, slower growth correlated with increased expression of the CD4+ T cell ligand, HLA-DR, on the tumor cells themselves. Finally, the cabozantinib/nivolumab combination was tested in comparison to cobimetinib/atezolizumab. Although both combinations showed tumor growth inhibition, cabozantinib/nivolumab had enhanced cytotoxic IFNγ and TNFα+ T cells. This pre-clinical in vivo data warrants testing the combination in clinical trials for patients with MSS-CRC.

T cell-inflamed gene expression profile is associated with favorable disease-specific survival in non-hypermutated microsatellite-stable colorectal cancer patients.

The anti-tumor immune response plays a key role in colorectal cancer (CRC) progression and survival. The T cell-inflamed gene expression profile (GEP) is a biomarker predicting response to checkpoint inhibitor immunotherapy across immunogenic cancer types, but the prognostic value in CRC is unknown. We evaluated associations with disease-specific survival, somatic mutations, and examined its differentially expressed genes and pathways among 84 sporadic CRC patients from the Seattle Colon Cancer Family Registry. Gene expression profiling was performed using Nanostring's nCounter PanCancer IO 360 panel. Somatic mutations were identified by a targeted DNA sequencing panel. The T cell-inflamed GEP was positively associated with tumor mutation burden and microsatellite instability high (MSI-H). Higher T cell-inflamed GEP had favorable CRC-specific survival (hazard ratio [HR] per standard deviation unit=0.50, p=0.004) regardless of hypermutation or MSI status. Analysis of recurrently mutated genes having at least 10 mutation carriers, suggested that the T cell-inflamed GEP is positively associated with RYR1, and negatively associated with APC. However, these associations were attenuated after adjusting for hypermutation or MSI status. We also found that expression of genes RPL23, EPCAM, AREG and ITGA6, and the Wnt signaling pathway was negatively associated with the T cell-inflamed GEP, which might indicate immune-inhibitory mechanisms. Our results show that the T cell-inflamed GEP is a prognostic biomarker in non-hypermutated microsatellite-stable CRC. This also suggests that patient stratification for immunotherapy within this CRC subgroup should be explored further. Moreover, reported immune-inhibitory gene expression signals may suggest targets for therapeutic combination with immunotherapy.

Single-cell transcriptome analysis of tumor immune microenvironment characteristics in colorectal cancer liver metastasis.

Liver metastasis is the leading cause of death in colorectal cancer (CRC) patients, and the precise mechanisms remain unclear. In this study, single-cell RNA sequencing (scRNA-seq) was used to analyze the cellular and molecular heterogeneity between CRC primary lesion and corresponding liver metastasis, and to clarify the characteristics of the tumor microenvironment (TME) in synchronous liver metastasis of CRC. A case of microsatellite stable (MSS) sigmoid carcinoma with synchronous liver metastasis was selected, and tissues from the primary tumor and the liver metastasis were collected for scRNA-seq. The EdgeR package software was used to identify the differentially expressed genes between cells. Gene Set Enrichment Analysis (GSEA) was performed and the clusterProfiler R package was used for Gene Ontology (GO) enrichment analysis. The SCENIC and CellphoneDB packages were used to reconstruct the transcriptional regulatory networks and to analyze the intercellular interaction network, respectively. Compared to the primary tumor, the proportion of myeloid cells in the metastatic tumor was significantly increased, while B cells and plasma cells were decreased. In the metastatic tumor, the myeloid-derived suppressor cell (MDSC) characteristic gene, mannose receptor C-type 1 (MRC1) and tumor associated macrophage 2 (TAM2)-related gene, were highly expressed. Furthermore, angiogenesis, oxidative phosphorylation, and endothelial mesenchymal transition (EMT) of myeloid cells were also significantly enhanced. There were less myeloid cells in primary tumors, and these were mainly monocytes and TAM1; while the number of TAM2 was significantly upregulated in the metastatic samples. In liver metastasis, the T cell population was exhausted, and this was accompanied by a significant increase in the number of CD4+ T cells and a decrease in the number of CD8+ T cells. Furthermore, some immune checkpoint molecules were highly expressed. Interactions between myeloid cells and other cell populations appeared to be strong. The TME of CRC liver metastasis is significantly immunosuppressed. Interactions between myeloid cells and other cell populations in the TME contribute to the establishment of a pro-metastatic niche that promotes colonization and growth of CRC cells in the liver. TAMs may be a potential immunotherapeutic target for MSS CRC.

WIN Symposium 2022 - Abstract Poster Presentations.

WIN Symposium 2022 - Abstract Poster Presentations.

CXD101 and nivolumab in patients with metastatic microsatellite-stable colorectal cancer (CAROSELL): a multicentre, open-label, single-arm, phase II trial

Patients with microsatellite stable (MSS) colorectal carcinoma (CRC) do not respond to immune checkpoint inhibitors. Preclinical models suggested synergistic anti-tumour activity combining CXD101 and anti-programmed cell death protein 1 treatment; therefore, we assessed the clinical combination of CXD101 and nivolumab in heavily pre-treated patients with MSS metastatic CRC (mCRC). This single-arm, open-label study enrolled patients aged 18 years or older with biopsy-confirmed MSS CRC; at least two lines of systemic anticancer therapies (including oxaliplatin and irinotecan); at least one measurable lesion; Eastern Cooperative Oncology Group performance status of 0, 1 or 2; predicted life expectancy above 3 months; and adequate organ and bone marrow function. Nine patients were enrolled in a safety run-in study to define a tolerable combination schedule of CXD101 and nivolumab, followed by 46 patients in the efficacy assessment phase. Patients in the efficacy assessment cohort were treated orally with 20 mg CXD101 twice daily for 5 consecutive days every 3 weeks, and intravenously with 240 mg nivolumab every 2 weeks. The primary endpoint was immune disease control rate (iDCR). Between 2018 and 2020, 55 patients were treated with CXD101 and nivolumab. The combination therapy was well tolerated with the most frequent grade 3 or 4 adverse events being neutropenia (18%) and anaemia (7%). Immune-related adverse reactions commonly ascribed to checkpoint inhibitors were surprisingly rare although we did see single cases of pneumonitis, hypothyroidism and hypopituitarism. There were no treatment-related deaths. Of 46 patients assessable for efficacy, 4 (9%) achieved partial response and 18 (39%) achieved stable disease, translating to an immune disease control rate of 48%. The median overall survival (OS) was 7.0 months (95% confidence interval 5.13-10.22 months). The primary endpoint was met in this phase II study, which showed that the combination of CXD101 and nivolumab, at full individual doses in the treatment of advanced or metastatic MSS CRC, was both well tolerated and efficacious.

Potentiating effect of reovirus on immune checkpoint inhibition in microsatellite stable colorectal cancer.

The majority of colorectal cancers (CRCs) are microsatellite stable (MSS) and resistant to immunotherapy. The current study explores the possibility of using oncolytic reovirus to sensitize MSS CRC to immune checkpoint inhibition. While reovirus reduced metabolic activity among KRAS Mut cells, microarray/computational analysis revealed microsatellite status-oriented activation of immune-response pathways. Reovirus plus anti-PD-1 treatment increased cell death among MSS cells ex vivo. Reduced tumorigenicity and proliferative index, and increased apoptosis were evident among CT26 [MSS, KRAS Mut], but not in MC38 [microsatellite unstable/MSI, KRAS Wt] syngeneic mouse models under combinatorial treatment. PD-L1-PD-1 signaling axis were differentially altered among CT26/MC38 models. Combinatorial treatment activated the innate immune system, pattern recognition receptors, and antigen presentation markers. Furthermore, we observed the reduction of immunosuppressive macrophages and expansion of effector T cell subsets, as well as reduction in T cell exhaustion. The current investigation sheds light on the immunological mechanisms of the reovirus-anti-PD-1 combination to reduce the growth of MSS CRC.

PD-1 Inhibitor Combined with Radiotherapy and GM-CSF with or not IL-2 (PRaG regimen) in Patients with Microsatellite Stable Metastatic Colorectal Cancer

<h3>Purpose/Objective(s)</h3> Immunotherapy has improved outcomes for metastatic colorectal cancer(mCRC) patients with MSI-H/dMMR but has not been effective in MSS/pMMR tumors, which comprise 95% of mCRC. Radiotherapy is able to stimulate tumor specific immune response and improve the efficacy of PD-1/PD-L1 inhibitors in metastatic cancers. The synergistic effects of radiotherapy and PD-1/PD-L1 inhibitors can be reinforced by adding cytokines like granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-2(IL-2). Our previous PRaG trial demonstrated that radiotherapy in combination with PD-1 inhibitors and GM-CSF could improve clinical response in patients with advanced refractory solid tumors, which was presented at the ASTRO congress 2021. We found that mCRC patients with MSS/pMMR could also benefit from the PRaG regimen. <h3>Materials/Methods</h3> Patients of mCRC with MSS/pMMR were collected from the PRaG trial and PRaG 2.0 trial. A treatment cycle consisted of radiotherapy (5 or 8 Gy × 2-3f) delivered for one metastatic lesion, PD-1 inhibitor dosing within one week after completion of radiotherapy, GM-CSF 200μg subcutaneous (SC) injection once daily for 14 days(d1-14), or GM-CSF 200μg (d1-7), and then sequentially followed by IL-2 200 million IU SC once daily for 7 days(d8-14). PRaG regimen was repeated every 21 days for at least 2 cycles until no appropriate lesions for irradiation or reached the tolerance dose. Pooled analysis of response rate (ORR), median progression-free survival (PFS), and treatment-related adverse events were calculated. The PRaG trial was registered in chictr.org.cn (No. ChiCTR1900020175) and the PRaG 2.0 trial was registered in clinicaltrials.gov (NCT04892498). <h3>Results</h3> With the cutoff date of 15 February 2022, a total of 12 mCRC patients with MSS/pMMR were enrolled. All of the patients completed at least 2 cycles of PRaG therapy and one evaluation. The median follow-up was 7.0 months (95%CI, 4.7, 9.3). The ORR was 25%, and the disease control rate (DCR) was 58.3%. The median PFS was 4.7 months (95%CI, 0.9 to 8.5). One patient got complete remission, with PFS over 18 months. Treatment-related adverse events (TRAE) occurred in 10 of 12 (83.3%) patients. One patient (8.3%) occurred Grade3 TRAE of renal insufficiency. <h3>Conclusion</h3> Our preliminary results suggest that the PRaG regimen could improve clinical outcomes in mCRC patients with MSS/pMMR with acceptable toxicity. Radiotherapy could have radiosensitization effect on immunotherapy of mCRC with MSS/pMMR.

Tumor Ablation by Irreversible Electroporation Augments PD-1 Checkpoint Inhibitor Immunotherapy in Colon Adenocarcinoma

INTRODUCTION: Programmed Cell Death Protein 1 (PD-1) checkpoint inhibitors have recently been approved for microsatellite instability high (MSI-H) or mismatch repair deficient (dMMR) colorectal cancer (CRC). Response rates are promising in MSI-H-dMMR CRC but remain dismal for microsatellite-stable (MSS) or mismatch repair proficient (pMMR) CRC. >80% of CRCs are MSS-pMMR. Increasing tumor-infiltrating lymphocytes (TILs) may improve checkpoint inhibitor efficacy in CRC. New data suggest irreversible electroporation (IRE) therapy whereby electric pulses cause tumor necrosis and apoptosis; increase tumor-associated protein uptake by dendritic cells, subsequently boosting neoantigen presentation and TILs. We hypothesized that IRE combined with anti–PD-1 antibody, when compared with IRE or anti–PD-1 antibody alone, would increase survival, cause tumor regression by increasing TILs, and guard against secondary tumor challenge by increasing tumor antigen-specific CD8 T cells. METHODS: Using the MC38 cell line derived from murine colon adenocarcinoma, immunohistochemistry, and anti-CD8 antibodies, we evaluated antitumor immune responses in mice. RESULTS: IRE with anti–PD-1 antibody showed statistically significant survival, tumor regression, and increased TILs compared with IRE or anti–PD-1 antibody alone. Seventeen of 18 mice treated with IRE and anti–PD-1 antibody rejected a secondary tumor challenge. Conversely, IRE with anti–PD-1 antibody failed to protect against tumor rechallenge in mice that underwent CD8 T-cell depletion. Zero of 10 CD8 T-cell–depleted mice survived after secondary tumor challenge (Figure).FigureCONCLUSION: These data suggest IRE and anti–PD-1 antibody work in concert to bolster tumor-specific CD8 T-cell immune responses, serving as a pragmatic strategy for overcoming clinical challenges in checkpoint inhibitor immunotherapy for CRC.

Tumour break load is a biologically relevant feature of genomic instability with prognostic value in colorectal cancer

BackgroundClinically implemented prognostic biomarkers are lacking for the 80% of colorectal cancers (CRCs) that exhibit chromosomal instability (CIN). CIN is characterised by chromosome segregation errors and double-strand break repair defects that lead to somatic copy number aberrations (SCNAs) and chromosomal rearrangement-associated structural variants (SVs), respectively. We hypothesise that the number of SVs is a distinct feature of genomic instability and defined a new measure to quantify SVs: the tumour break load (TBL). The present study aimed to characterise the biological impact and clinical relevance of TBL in CRC. MethodsDisease-free survival and SCNA data were obtained from The Cancer Genome Atlas and two independent CRC studies. TBL was defined as the sum of SCNA-associated SVs. RNA gene expression data of microsatellite stable (MSS) CRC samples were used to train an RNA-based TBL classifier. Dichotomised DNA-based TBL data were used for survival analysis. ResultsTBL shows large variation in CRC with poor correlation to tumour mutational burden and fraction of genome altered. TBL impact on tumour biology was illustrated by the high accuracy of classifying cancers in TBL-high and TBL-low (area under the receiver operating characteristic curve [AUC]: 0.88; p < 0.01). High TBL was associated with disease recurrence in 85 stages II–III MSS CRCs from The Cancer Genome Atlas (hazard ratio [HR]: 6.1; p = 0.007) and in two independent validation series of 57 untreated stages II–III (HR: 4.1; p = 0.012) and 74 untreated stage II MSS CRCs (HR: 2.4; p = 0.01). ConclusionTBL is a prognostic biomarker in patients with non-metastatic MSS CRC with great potential to be implemented in routine molecular diagnostics.

Microsatellite stable metastatic colorectal cancer without liver metastasis may be preferred population for regorafenib or fruquintinib plus sintilimab as third-line or above therapy:A real-world study.

ObjectivesThe antitumor activity of nivolumab plus regorafenib in colorectal cancer from a phase Ib REGONIVO study is encouraging. The present study was conducted to evaluate the efficacy and safety of regorafenib or fruquintinib plus sintilimab as third-line or above therapy in patients with microsatellite stable (MSS) metastatic colorectal cancer.MethodsPatients with MSS metastatic colorectal cancer who have failed from prior treatment and received regorafenib or fruquintinib plus sintilimab as third-line or above therapy from January 2019 to December 2020 were prospectively analyzed based on real-world clinical practice. The primary end point was progression free survival (PFS). Secondary end points included objective response rate (ORR), disease control rate (DCR), overall survival (OS), and safety.Results42 patients received regorafenib plus sintilimab(RS), and the other 30 patients received fruquintinib plus sintilimab(FS). In the general population, the ORR and DCR were 13.9% and 70.8%, and the median PFS and OS was 4.2(95% CI=2.9-5.5) and 10.5 (95% CI=8.6-12.4) months, respectively. There were no statistically significant differences between RS and FS group in PFS (3.5(2.2-4.8) vs. 5.5(3.5-7.5) months, P=0.434) and OS (11.0(7.0-15.0) vs. 10.5(3.8-17.2) months, P=0.486). Subgroup analysis suggested that patients without liver metastasis responded well to this combination regimen (ORR: 21.4% vs. 9.1%) and obtained better OS (26(8.8-43.2) vs. 10.0(7.4-12.6) months, P=0.016). The incidence of Grade 3-4 adverse events (AEs) was 15.3% and the toxicities were generally tolerable and manageable.ConclusionsRegorafenib or fruquintinib plus sintilimab as third-line or above therapy provide a feasible treatment regimen for MSS metastatic colorectal cancer with tolerated toxicity. Patients without liver metastasis may be the preferred population for this combination regimen.

MAP7D2 reduces CD8+ cytotoxic T lymphocyte infiltration through MYH9-HMGB1 axis in colorectal cancer

Immune checkpoint inhibitors (ICIs) represent a new paradigm in cancer immunotherapy, but can be largely restricted by the limited presence of CD8+ cytotoxic T lymphocytes (CTLs) in colorectal cancer (CRC) patients with microsatellite stable (MSS) tumors. Here, through next-generation sequencing, we identify microtubule-associated protein 7 domain 2 (MAP7D2) as an exploitable therapeutic maneuver to improve the efficacy of ICIs for MSS CRC therapy. In human CRC tissues, MAP7D2 expression is significantly increased in MSS CRC, and MAP7D2 adversely correlates with the presence of antitumor T lymphocytes. Invitro and in vivo experiments demonstrate that MAP7D2 knockdown significantly increases the infiltration of CD8+ CTLs, thereby inhibiting tumor progression and improving the efficacy of ICIs in MSS CRC murine models. Mechanistically, MAP7D2 interacts with MYH9 and protects it from ubiquitin-mediated degradation, subsequently decreasing the secretion of HMGB1, which suppresses the infiltration of CD8+ CTLs in MSS CRC. These findings highlight the importance of MAP7D2 in determining the infiltration of CD8+ CTLs and indicate that targeting MAP7D2 in MSS CRC may present a novel antitumor immunotherapy.

1688P Selection of PD-L1 escape variants in microsatellite stable metastatic colorectal cancer on avelumab treatment

In patients with microsatellite stable (MSS) metastatic colorectal cancer (mCRC), immune checkpoint blockade is ineffective. However, data from the AVETUX trial suggests PD-L1 epitope escape upon avelumab treatment in MSS-mCRC patients expressing the high affinity SNP of FcγR3a (rs396991).

375P The co-mutations and genetic features of BRAF-mutated gene mutations in a large Chinese MSS colorectal cancer cohort

BRAF p.V600E is a known prognostic factor for poor progression-free survival and overall survival in colorectal cancer (CRC), occurring in 5%-8% patients. This is a special population resistant to chemotherapies. A combined regimen of targeted drugs including MEK inhibitor, BRAF inhibitor and EGFR inhibitor is effective in BRAF V600E mutated patients, while it is only authorized as second-line treatment. BRAF V600E mutation was also considered correlated with sporadic MSI-H. However, studies on other alterations in the BRAF gene are few, and the differences of comprehensive genetic features between BRAF mutated and BRAF wild-type in microsatellite stable (MSS) CRC remain unclear.

423P Fruquintinib plus sintilimab in refractory repair-proficient (pMMR)/microsatellite stable (MSS) metastatic colorectal cancer (mCRC): Preliminary clinical results and biomarker analyses from a phase II study

Addition of immune checkpoint inhibitor to anti-angiogenesis inhibitors is expected to have the potential to improve efficacy in pMMR/MSS refractory mCRC. This study aimed to evaluate the efficacy and safety of fruquintinib plus sintilimab in refractory mCRC, and to explore the potential biomarker associated with efficacy and prognosis. This is a prospective, single arm phase II trial (NCT04695470). Patients with pMMR/MSS mCRCs who had failed with at least 2 lines of standard therapy including bevacizumab were treated with fruquintinib (5mg/day, orally, d1-14, Q3w) plus sintilimab (sintilimab 200mg, intravenous infusion, d1, Q3w). The primary endpoint was the 6-month PFS rate, and secondary endpoints included ORR, PFS, OS and safety, with biomarker analyses from ctDNA being the exploratory endpoint. Between Sep 18, 2020 and Apr 19, 2022, 55 patients (pts) were enrolled. 43 pts with a follow-up time of at least 3 months (median 9.8 m) were included in this analysis. The median age was 57 (IQR, 34-73); 69% were male. 7 pts achieved PR and 26 achieved SD, the ORR was 16% (95% CI, 7%-31%), and DCR was 77% (95% CI, 61%-88%). Pts with liver metastases had lower ORR than those without (7.1% vs 33.3%, P=0.0398). The 6-month PFS rate was 31% with a median PFS of 4.1 m and an estimated OS of 13.3 m, respectively. The present of liver metastasis was associated with shorter PFS (4.1 vs 6.4 m, P=0.0364). The most common adverse events were proteinuria (53.4%), palmar-plantar erythrodysesthesia syndrome (46.5%) and hypothyroidism (37.2%). 18.6% of the pts had grade 3 or 4 treatment-related adverse events. The median bTMB was 11.35 muts/Mb (IQR: 5.03-177.85muts/Mb). No statistically significant differences in ORR and PFS were observed according to bTMB status. Three pts with MYC amplification in ctDNA seemed to have worse PFS (1.3 m, 1.3 m, 2.1 m) and OS (3.0 m, 3.7 m, 5.4 m). Fruquintinib plus sintilimab showed promising efficacy and favorable safety profile in refractory MSS mCRC. MYC amplification identified by ctDNA sequencing seemed to associate with poor prognosis, which warrants future study.

426P Assessing nivolumab in class II expressing microsatellite stable (pMMR) colorectal cancer (CRC): Results of the ANICCA-Class II trial

Predictive biomarkers for immune checkpoint blockade (ICB) are desperately needed. Retrospective studies demonstrate that tsMHC-II positivity is a strong predictive biomarker for anti-PD-1 activity in melanoma, Hodgkins disease and breast cancer. Deficient mismatch repair (dMMR) CRC responds readily to anti-PD-1 and has significantly higher tsMHC-II expression than pMMR CRC but some pMMR patients have strong primary tsMHC-II positivity and it is prognostic. We report here a prospective trial of nivolumab in locally advanced and metastatic tsMHC-II positive pMMR CRC (NCT03981146). pMMR CRC patients who had progressed on all standard of care therapies and whose tumors exhibited >1% tsMHC-II were prospectively treated with 480mg nivolumab every 4 weeks. Primary outcome measure was durable clinical benefit (DCB – no progression at 27 weeks), key secondary outcomes were objective response (OR), progression-free survival time (PFS) and overall survival (OS). Of 455 patients screened, 12.8% were tsMHC-II positive (8.6% ≥5% and 0.7% >50% staining). Of 35 patients treated, 65.7% has tsMHC-II ≥5%, 2.9% >50%. Liver metastases were present in 62.9%. At a median follow-up time of 57 weeks, only 1 patient was still on treatment. 3/35 (8.6%) had DCB, none of whom had liver metastases; of 9 patients remaining on therapy >18 weeks, 7 had no liver metastases. The OR was 0%. Currently mPFS is 9.1 weeks (95% Confidence Interval (CI): 9.0, 9.8) and mOS 29.6 weeks (95% CI: 17.3, 42.1). The one patient with tsMHC-II expression >50% remained on treatment for one cycle. Staining of matched primaries and secondaries showed discordance is common with <40% tsMHC-II positive primaries giving rise to positive secondaries. There were no new safety signals. In this first prospective trial of tsMHC-II as a predictive biomarker for anti-PD-1 we show that tsMHC-II expression is not a useful stratifier in advanced pMMR CRC. We discuss likely reasons for this which include the liver predominance of metastatic CRC, the discordance of tsMHC-II status by site and the nature of the IFNg producing T cells in those with tsMHC-II positive pMMR primaries that subsequently relapse.

Efficacy, safety and predictors of combined fruquintinib with programmed death-1 inhibitors for advanced microsatellite-stable colorectal cancer: A retrospective study.

BackgroundResearch findings have revealed that combining anti-angiogenesis inhibitors with programmed death-1(PD-1) inhibitors can reverse the immunosuppressive tumor microenvironment and enhance the antitumor immune response. To explore the therapeutic options for breaking immune tolerance in microsatellite stability (MSS) or mismatch repair-proficiency (pMMR) advanced colorectal cancer (CRC), we assessed the efficacy, safety and predictors of the fruquintinib and PD-1 inhibitors combination in patients with MSS/pMMR advanced CRC in a real-world environment.MethodsWe conducted a single-center retrospective study by collecting relevant data on patients with MSS/pMMR advanced CRC who received fruquintinib coupled with PD-1 inhibitors in the First Affiliated Hospital of Zhengzhou University between August 2019 and November 2021, focusing on progression-free survival.ResultsWe enrolled 110 eligible patients in this study between August 2019 and November 2021. At the deadline (January 20, 2022), 13 patients had objective responses. The objective response rate was 11.8% (13/110, 95% confidence interval [CI]: 6.4-18.2), the disease control rate was 70.0% (82/110, 95% CI: 60.9-78.2), and the progression-free survival was 5.4 months (95% CI: 4.0-6.8). Liver metastases (hazard ratio [HR]: 0.594, 95% CI: 0.363-0.973, P<0.05), alkaline phosphatase elevation (ALP>160U/L) (HR: 0.478, 95%CI: 0.241-0.948, P<0.05), fibrinogen elevation (FIB>4g/L) (HR: 0.517, 95% CI: 0.313-0.855, P<0.05), and an increase in the ALP level from the baseline after treatment (HR: 1.673, 95% CI: 1.040-2.690, P<0.05) were negative predictors of the progression-free survival. A total of 101 of 110 patients experienced treatment-related adverse events, including 14 who experienced grade 3 or above treatment-related adverse events, and no treatment-related deaths occurred. Hypertension was the most frequently encountered grade 3 treatment-related adverse event.ConclusionFruquintinib combined with PD-1 inhibitors has antitumor activity and manageable safety in treating patients with MSS/pMMR advanced CRC. Liver metastases, ALP level and FIB level might be a prediction of the patient response to this therapy.

ROS1 genomic rearrangements are rare actionable drivers in microsatellite stable colorectal cancer.

c-Ros oncogene 1, receptor tyrosine kinase (ROS1) genomic rearrangements have been reported previously in rare cases of colorectal cancer (CRC), yet little is known about the frequency, molecular characteristics, and therapeutic vulnerabilities of ROS1-driven CRC. We analyzed a clinical dataset of 40 589 patients with CRC for ROS1 genomic rearrangements and their associated genomic characteristics (Foundation Medicine, Inc [FMI]). We moreover report the disease course and treatment response of an index patient with ROS1-rearranged metastatic CRC. ROS1 genomic rearrangements were identified in 34 (0.08%) CRC samples. GOPC-ROS1 was the most common ROS1 fusion identified (11 samples), followed by TTC28-ROS1 (3 samples). Four novel 5' gene partners of ROS1 were identified (MCM9, SRPK1, EPHA6, P4HA1). Contrary to previous reports on fusion-positive CRC, ROS1-rearrangements were found exclusively in microsatellite stable (MSS) CRCs. KRAS mutations were significantly less abundant in ROS1-rearranged vs ROS1 wild type cases. The index patient presented with chemotherapy-refractory metastatic right-sided colon cancer harboring GOPC-ROS1. Molecularly targeted treatment with crizotinib induced a rapid and sustained partial response. After 15 months on crizotinib disseminated tumor progression occurred and KRAS Q61H emerged in tissue and liquid biopsies. ROS1 rearrangements define a small, yet therapeutically actionable molecular subgroup of MSS CRC. In summary, the high prevalence of GOPC-ROS1 and noncanonical ROS1 fusions pose diagnostic challenges. We advocate NGS-based comprehensive molecular profiling of MSS CRCs that are wild type for RAS and BRAF and patient enrollment in precision trials.

Targeting thymidine phosphorylase alleviates resistance to dendritic cell immunotherapy in colorectal cancer and promotes antitumor immunity.

T-cell exhaustion plays a pivotal role in the resistance of microsatellite-stable colorectal cancer (CRC) to immunotherapy. Identifying and targeting T-cell exhaustion-activating mechanisms is a promising strategy to augment the effects of immunotherapy. Here, we found that thymidine phosphorylase (TYMP) plays a decisive role in inducing systemic T-cell exhaustion and abrogating the efficacy of dendritic cell (DC) therapy in a CRC model. Targeting TYMP with tipiracil hydrochloride (TPI) induces immunological cell death (ICD). The combined effects of TPI and imiquimod-activated DCs turn CT26 tumors into immunologically ‘hot’ tumors by inducing ICD in vivo. High-dimensional cytometry analysis revealed T-cell and IFN-γ dependency on the therapeutic outcome. In addition, chemoimmunotherapy converts intratumoral Treg cells into Th1 effector cells and eliminates tumor-associated macrophages, resulting in higher cytotoxic T lymphocyte infiltration and activation. This effect is also associated with the downregulation of PD-L1 expression in tumors, leading to the prevention of T-cell exhaustion. Thus, cooperative and cognitive interactions between dendritic cells and immunogenic cell death induced by therapy with TPI promote the immune response and tumoricidal activities against microsatellite stable colorectal cancer. Our results support TYMP targeting to improve the effects of DC immunotherapy and outcomes in CRC.

RNA editing facilitates the enhanced production of neoantigens during the simultaneous administration of oxaliplatin and radiotherapy in colorectal cancer

Most cases of colorectal cancers (CRCs) are microsatellite stable (MSS), which frequently demonstrate lower response rates to immune checkpoint inhibitors (ICIs). RNA editing produces neoantigens by altering amino acid sequences. In this study, RNA editing was induced artificially by chemoradiation therapy (CRT) to generate neoantigens in MSS CRCs. Altogether, 543 CRC specimens were systematically analyzed, and the expression pattern of ADAR1 was investigated. In vitro and in vivo experiments were also performed. The RNA editing enzyme ADAR1 was upregulated in microsatellite instability–high CRCs, leading to their high affinity for ICIs. Although ADAR1 expression was low in MSS CRC, CRT including oxaliplatin (OX) treatment upregulated RNA editing levels by inducing ADAR1. Immunohistochemistry analyses showed the upregulation of ADAR1 in patients with CRC treated with CAPOX (capecitabine + OX) radiation therapy relative to ADAR1 expression in patients with CRC treated only by surgery (p < 0.001). Compared with other regimens, CRT with OX effectively induced RNA editing in MSS CRC cell lines (HT29 and Caco2, p < 0.001) via the induction of type 1 interferon-triggered ADAR1 expression. CRT with OX promoted the RNA editing of cyclin I, a neoantigen candidate. Neoantigens can be artificially induced by RNA editing via an OX–CRT regimen. CRT can promote proteomic diversity via RNA editing.