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Patients with both BRAF V600E mutations and microsatellite instability-high (MSI-H)/mismatch repair-deficient (dMMR) metastatic colorectal cancer (mCRC) have poor prognosis. Currently, there are no specifically targeted first-line treatment options indicated for patients with mCRC whose tumors harbor both molecular aberrations. Pembrolizumab is a checkpoint inhibitor approved for the treatment of MSI-H/dMMR mCRC, and the BRAF inhibitor encorafenib, in combination with cetuximab, is approved for previously treated BRAF V600E-mutant mCRC. Combination of pembrolizumab with encorafenib and cetuximab may synergistically enhance antitumor activity in patients with BRAF V600E-mutant, MSI-H/dMMR mCRC. SEAMARK is a randomized phase II study comparing the efficacy of the combination of pembrolizumab with encorafenib and cetuximab versus pembrolizumab alone in patients with previously untreated BRAF V600E-mutant, MSI-H/dMMR mCRC.

Background: This study aims to assess predictive markers for response to immunotherapy in dMMR/MSI-H metastatic colorectal cancer (mCRC) patients., Materials and Methods: A study using two prospective cohorts from MD Anderson Cancer Center and Sheba Medical Center of consecutive patients with dMMR/MSI-H mCRC that were treated with immunotherapy between 2014-2022. Primary outcome was progression-free survival (PFS) and secondary outcome was overall response rate (ORR). Evaluated predictors included ECOG-PS score, RAS/BRAF status, single-agent versus doublet immunotherapy, metastatic sites, disease burden, and CEA levels prior to treatment initiation. Kaplan-Meier analysis and Cox proportional hazard regression model were used to analyze the effect of exposure variables on PFS., Results: The study included 153 patients. Median follow-up time was 26 months (IQR 11-48). Median PFS was 51.6 months (95%CI 38.1-NR) and ORR was 58.1%. In a univariate analysis, male sex was associated with worse PFS with a HR of 1.67 (95% CI 1.00-2.79); Right-sided tumors were associated with improved PFS with a HR of 0.56 (95% CI 0.32-0.97); Liver or lung metastasis were associated with worse PFS with HRs of 2.35 (95%CI 1.43-3.88) and 2.30 (95%CI 1.31-4.04), respectively; ECOG-PS score ≥ 2, CEA levels ˃5 μg/L prior to treatment initiation and ≥ 3 metastatic sites were associated with worse PFS with HRs of 2.09 (95%CI 0.98-4.47), 2.23 (95%CI 1.30-3.81) and 3.11 (95%CI 1.61-6.03), respectively. Liver or lung metastasis remained significant in a multivariable model., Conclusions: Extent of disease (worse PFS with high CEA, poor ECOG-PS and ≥3 metastatic sites) and disease location (worse PFS with liver or lung metastasis and left sided tumor) were associated with immunotherapy outcome in dMMR/MSI-H mCRC., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Oncogenic KRAS (KRAS*) contributes to many cancer hallmarks. In colorectal cancer, KRAS* suppresses antitumor immunity to promote tumor invasion and metastasis. Here, we uncovered that KRAS* transforms the phenotype of carcinoma-associated fibroblasts (CAF) into lipid-laden CAFs, promoting angiogenesis and tumor progression. Mechanistically, KRAS* activates the transcription factor CP2 (TFCP2) that upregulates the expression of the proadipogenic factors BMP4 and WNT5B, triggering the transformation of CAFs into lipid-rich CAFs. These lipid-rich CAFs, in turn, produce VEGFA to spur angiogenesis. In KRAS*-driven colorectal cancer mouse models, genetic or pharmacologic neutralization of TFCP2 reduced lipid-rich CAFs, lessened tumor angiogenesis, and improved overall survival. Correspondingly, in human colorectal cancer, lipid-rich CAF and TFCP2 signatures correlate with worse prognosis. This work unveils a new role for KRAS* in transforming CAFs, driving tumor angiogenesis and disease progression, providing an actionable therapeutic intervention for KRAS*-driven colorectal cancer., Significance: This study identified a molecular mechanism contributing to KRAS*-driven colorectal cancer progression via fibroblast transformation in the tumor microenvironment to produce VEGFA driving tumor angiogenesis. In preclinical models, targeting the KRAS*-TFCP2-VEGFA axis impaired tumor progression, revealing a potential novel therapeutic option for patients with KRAS*-driven colorectal cancer. This article is featured in Selected Articles from This Issue, p. 2489., (©2023 American Association for Cancer Research.)

Immune checkpoint inhibitors improve survival in patients with mismatch repair deficiency/microsatellite instability-high (MSI-H) colorectal cancer. The recurrence outcomes following discontinuation of immunotherapy after prolonged disease control have not been definitively reported in large series. Records from patients with advanced MSI-H colorectal cancer from The University of Texas - MD Anderson Cancer Center who received immunotherapy between 2014 and 2022 and stopped after prolonged clinical benefit were reviewed. Median progression-free and overall survival were estimated. Associations between the event of recurrence and coexisting mutations (KRAS/NRAS, BRAFV600E), metastatic organ involvement (lung, liver, lymph node, or peritoneum), metastatic timing (synchronous vs. metachronous), prior immunotherapy [anti-PD-(L)1 alone or in combination with anti-CTLA antibodies], etiology of MSI status (sporadic vs. hereditary non-polyposis colorectal cancer), and duration of immunotherapy were assessed. Sixty-four patients with MSI-H colorectal cancer without progression on immunotherapy were reviewed. Of these 48 and 16 received anti-PD(L)1 antibody alone or in combination with anti-CTLA-4 antibody, respectively. Median exposure to immunotherapy was 17.6 months (range, 1.3-51.9). After a median follow-up of 22.6 months (range, 0.3-71.7) after stopping immunotherapy, 56 of 64 patients (88%) remained without disease progression. Lung metastases were associated with recurrence/progression (OR, 6.1; P = 0.04), but coexisting mutation, primary tumor sidedness, and immunotherapy were not. These data provide a retrospective, single-institution analysis that showed that most patients with advanced MSI-H colorectal cancer do not recur after treatment cessation, regardless of the reason for stopping treatment or a variety of patient and disease features, supporting an optimistic prognosis of sustained disease control., Significance: Outcomes for patients with MSI-H colorectal cancer stopping immunotherapy after disease control remain unknown. Sixty-four patients with MSI-H colorectal cancer from our institution stopping treatment for sustained benefit or toxicity were retrospectively assessed. After median follow up of 22 months and median immunotherapy exposure of 18 months, 88% patients remained without progression. All patients who recurred or progressed and were rechallenged with immunotherapy have continued to experience disease control., (© 2023 The Authors; Published by the American Association for Cancer Research.)

In this work, we investigated the oncogenic role of Streptococcus gallolyticus subsp. gallolyticus (SGG), a gut bacterium associated with colorectal cancer (CRC). We showed that SGG UCN34 accelerates colon tumor development in a chemically induced CRC murine model. Full proteome and phosphoproteome analysis of murine colons chronically colonized by SGG UCN34 revealed that 164 proteins and 725 phosphorylation sites were differentially regulated. Ingenuity Pathway Analysis (IPA) indicates a pro-tumoral shift specifically induced by SGG UCN34, as ~ 90% of proteins and phosphoproteins identified were associated with digestive cancer. Comprehensive analysis of the altered phosphoproteins using ROMA software revealed up-regulation of several cancer hallmark pathways such as MAPK, mTOR and integrin/ILK/actin, affecting epithelial and stromal colonic cells. Importantly, an independent analysis of protein arrays of human colon tumors colonized with SGG showed up-regulation of PI3K/Akt/mTOR and MAPK pathways, providing clinical relevance to our findings. To test SGG's capacity to induce pre-cancerous transformation of the murine colonic epithelium, we grew ex vivo organoids which revealed unusual structures with compact morphology. Taken together, our results demonstrate the oncogenic role of SGG UCN34 in a murine model of CRC associated with activation of multiple cancer-related signaling pathways., (© 2023. Springer Nature Limited.)

Purpose: In metastatic colorectal cancer, the detection of RAS mutations by circulating tumor DNA (ctDNA) has emerged as a valid and noninvasive alternative approach to determining RAS status. However, some RAS mutations may be missed, that is, false negatives can occur, possibly compromising important treatment decisions. We propose a statistical model to assess the probability of false negatives when performing ctDNA testing for RAS., Methods: Cohorts of 172 subjects with tissue and multipanel ctDNA testing from MD Anderson Cancer Center and 146 subjects from Massachusetts General Hospital were collected. We developed a Bayesian model that uses observed frequencies of reference mutations (the maximum of APC and TP53 ) to provide information about the probability of KRAS false negatives. The model was alternatively trained on one cohort and tested on the other. All data were collected on Guardant assays., Results: The model suggests that negative KRAS findings are believable when the maximum of APC and TP53 frequencies is at least 8% (corresponding posterior probability of false negative <5%). Validation studies demonstrated the ability of our tool to discriminate between false-negative and true-negative subjects. Simulations further confirmed the utility of the proposed approach., Conclusion: We suggest clinicians use the tool to more precisely quantify KRAS false-negative ctDNA results when at least one of the reference mutations ( APC , TP53 ) is observed; usage may be especially important for subjects with a maximum reference frequency of <8%. Extension of the methodology to predict false negatives of other genes is possible. Additional reference genes can also be considered. Use of personal training data sets is supported. An open-source R Shiny application is available for public use.

Mutations in KRAS are found in more than 50% of tumors from patients with metastatic colorectal cancer (mCRC). However, direct targeting of most KRAS mutations is difficult; even the recently developed KRASG12C inhibitors failed to show significant benefit in patients with mCRC. Single agents targeting mitogen-activated protein kinase kinase (MEK), a downstream mediator of RAS, have also been ineffective in colorectal cancer. To identify drugs that can enhance the efficacy of MEK inhibitors, we performed unbiased high-throughput screening using colorectal cancer spheroids. We used trametinib as the anchor drug and examined combinations of trametinib with the NCI-approved Oncology Library version 5. The initial screen, and following focused validation screens, identified vincristine as being strongly synergistic with trametinib. In vitro, the combination strongly inhibited cell growth, reduced clonogenic survival, and enhanced apoptosis compared with monotherapies in multiple KRAS-mutant colorectal cancer cell lines. Furthermore, this combination significantly inhibited tumor growth, reduced cell proliferation, and increased apoptosis in multiple KRAS-mutant patient-derived xenograft mouse models. In vivo studies using drug doses that reflect clinically achievable doses demonstrated that the combination was well tolerated by mice. We further determined that the mechanism underlying the synergistic effect of the combination was due to enhanced intracellular accumulation of vincristine associated with MEK inhibition. The combination also significantly decreased p-mTOR levels in vitro, indicating that it inhibits both RAS-RAF-MEK and PI3K-AKT-mTOR survival pathways. Our data thus provide strong evidence that the combination of trametinib and vincristine represents a novel therapeutic option to be studied in clinical trials for patients with KRAS-mutant mCRC., Significance: Our unbiased preclinical studies have identified vincristine as an effective combination partner for the MEK inhibitor trametinib and provide a novel therapeutic option to be studied in patients with KRAS-mutant colorectal cancer., (©2023 American Association for Cancer Research.)

Purpose: Encorafenib + cetuximab (E+C) is an effective therapeutic option in chemorefractory BRAFV600E metastatic colorectal cancer (mCRC). However, there is a need to improve the efficacy of this molecular-targeted therapy and evaluate regimens suitable for untreated BRAFV600E in patients with mCRC., Experimental Design: We performed a series of in vivo studies using BRAFV600E mCRC tumor xenografts. Mice were randomized to receive 5-fluoruracil (5-FU), irinotecan, or oxaliplatin regimens (FOLFIRI or FOLFOX), (E+C) or the combination. Patients received long-term treatment until disease progression, with deescalation strategies used to mimic maintenance therapy. Transcriptomic changes after progression on cytotoxic chemotherapy or targeted therapy were assessed., Results: Antitumor activity of either FOLFIRI or E+C was better as first-line treatment as compared with second-line, with partial cross-resistance seen between a cytotoxic regimen and targeted therapy with an average 62% loss of efficacy for FOLFIRI after E+C and a 45% loss of efficacy of E+C after FOLFIRI (P < 0.001 for both). FOLFIRI-treated models had upregulation of epithelial-mesenchymal transition (EMT) and MAPK pathway activation, where E+C treated models had suppressed MAPK signaling. In contrast, with chemotherapy with E+C, EMT and MAPK signaling remained suppressed. FOLFOX or FOLFIRI, each in combination with E+C, were the most active first-line treatments as compared with E+C or to chemotherapy alone. Furthermore, FOLFOX in combination with E+C as first-line induction therapy, followed by E+C ± 5-FU as maintenance therapy, was the most effective strategy for long-term disease control., Conclusions: These results support the combination of cytotoxic chemotherapy and molecular-targeted therapy as a promising therapeutic approach in the first-line treatment of BRAFV600E mCRC., (©2023 The Authors; Published by the American Association for Cancer Research.)

Background: Immune checkpoint blockade (ICB) has improved outcomes for patients with microsatellite instability high (MSI-H)/deficient mismatch repair (dMMR) tumors. However, not all MSI-H/dMMR patients will exhibit the same ICB efficacy. Previous studies suggest that concomitant antibiotic use while receiving ICB may result in poorer outcomes. We aimed to evaluate this association in patients with MSI-H/dMMR metastatic colorectal cancer (mCRC)., Materials and Methods: A single-site, retrospective review of 57 patients with MSI-H/dMMR mCRC that received ICB was completed. Data collected included patient demographics, ICB information, and antibiotic use. Antibiotic exposure was considered from 90 days prior to ICB through 6 weeks after initiation. Primary endpoint was overall response rate (ORR)., Results: The majority of patients received pembrolizumab (27 [47%]) or nivolumab (17 [30%]) monotherapy as their ICB agent. Of the 57 patients, 19 (33.3%) had antibiotic exposure from 90 days prior to ICB initiation through 6 weeks after initiation with most (13 [68%]) having antibiotic use in the 30 days preceding ICB initiation. Similar ORRs were seen in both groups (P-value > .99). No difference was observed in OS (P-value .29) or PFS (P-value .36) between groups., Conclusion: Our data show no association of lower response rates or survival in those MSI-H/dMMR patients with mCRC who receive antibiotics around the initiation of ICB. This information needs to be confirmed in a larger prospective cohort., (© The Author(s) 2022. Published by Oxford University Press.)

Background: The ability to detect circulating tumor DNA (ctDNA), a novel surrogate for minimal residual disease (MRD) for patients with solid tumors, has significantly evolved over the past decade. Several studies have shown that ctDNA may provide clinical insight into the biological dynamics of MRD. The CIRCULATE-US (NRG-GI008; NCT05174169) trial will aim to address the role of ctDNA for risk stratification to intensify and deintensify adjuvant chemotherapy for patients with early-stage colon cancer., Methods: CIRCULATE-US, a prospective phase 2/3 randomized trial, is investigating the molecular dynamics and prognostic role of ctDNA (evaluated by Natera's Signatera assay) for patients with resected colon cancer. Patients with negative postoperative ctDNA will be enrolled in cohort A and randomized to receive either immediate treatment with 5-fluorouracil and folinic acid or capecitabine plus oxaliplatin (FOLFOX6 or CAPEOX; Arm 1) or serial ctDNA surveillance with delayed adjuvant therapy (Arm 2). Patients randomized to Arm 2 with subsequent positive ctDNA results will be enrolled in cohort B for a second randomization to receive either FOLFOX6/CAPEOX (Arm 3) or 5-fluorouracil, folinic acid, oxaliplatin, and irinotecan (FOLFIRINOX; Arm 4) for 6 months. Patients with positive postoperative ctDNA results will be directly enrolled in cohort B and randomized to receive either FOLFOX6/CAPEOX (Arm 3) or FOLFIRINOX (Arm 4). Patients with stage II or stage IIIC colon cancer with positive ctDNA results (tested as standard of care with commercial testing) will be eligible for enrollment in cohort B. The primary end point for cohort A is time to positive ctDNA status for phase 2 and disease-free survival for phase 3 with a noninferiority design. The primary end point for cohort B is disease-free survival for both phase 2 and phase 3 with a superiority design., Discussion: CIRCULATE-US will aim to understand postoperative ctDNA dynamics in early-stage colon cancer and will investigate escalation and de-escalation approaches by using ctDNA status as a surrogate for MRD status.

Background: In the phase II multicohort CheckMate 142 study, nivolumab plus low-dose (1 mg/kg) ipilimumab provided robust and durable clinical benefit with a manageable safety profile in previously treated patients with microsatellite instability-high/mismatch repair-deficient (MSI-H/dMMR) metastatic colorectal cancer (mCRC) at 13.4- and 25.4-month median follow-up (Overman MJ, Lonardi S, Wong KYM et al. Durable clinical benefit with nivolumab plus ipilimumab in DNA mismatch repair-deficient/microsatellite instability-high metastatic colorectal cancer. J Clin Oncol. 2018;36:773-779. Overman MJ, Lonardi S, Wong KYM, et al. Nivolumab plus low-dose ipilimumab in previously treated patients with microsatellite instability-high/mismatch repair deficient metastatic colorectal cancer: long-term follow-up. J Clin Oncol. 2019;37:635). Here, we present results from the 4-year follow-up of these patients., Patients and Methods: Patients received nivolumab (3 mg/kg) plus low-dose (1 mg/kg) ipilimumab every 3 weeks (four doses) followed by nivolumab (3 mg/kg) every 2 weeks until disease progression. Primary endpoint was investigator-assessed objective response rate (ORR; as per RECIST version 1.1)., Results: A total of 119 patients were treated; 76% had ≥2 prior lines of therapy. Median follow-up was 50.9 months (range 46.9-62.7 months). Median duration of therapy was 24.9 months [95% confidence interval (CI) 15.8-33.2 months]. Investigator-assessed ORR increased from 55% (95% CI 45% to 64%) at 13.4 months to 65% (95% CI 55% to 73%) at 50.9 months with a disease control rate of 81% (95% CI 72% to 87%). The complete response rate increased from 3% at 13.4 months to 13% at 50.9 months. Partial responses were observed in 52% of patients; 21% had stable disease, and 12% had progressive disease. Median time to response was 2.8 months (range 1.1-37.1 months), and median duration of response was not reached (range 1.4+ to 58.0+ months). At data cut-off, 37 (48%) patients had ongoing responses. Median progression-free survival was not reached [95% CI 38.4 months-not estimable (NE)], and median overall survival was not reached (95% CI NE). Grade 3-4 treatment-related adverse events (TRAEs) were observed in 32% of patients; 13% of patients had any-grade TRAEs leading to discontinuation., Conclusions: The results confirm long-term benefit of nivolumab plus low-dose ipilimumab for previously treated patients with MSI-H/dMMR mCRC. The safety profile was manageable with no new safety signals., Competing Interests: Disclosure TA reports support for the present manuscript from Bristol Myers Squibb; consulting roles for Bristol Myers Squibb, Gritstone Oncology, GlaxoSmithKline, Merck & Co., Pierre Fabre, Seagen, and Servier; honoraria from AstraZeneca, Bristol Myers Squibb, GlaxoSmithKline, Merck & Co., Pierre Fabre, Roche/Ventana, Sanofi, and Servier; travel/meetings funding from Bristol Myers Squibb and Roche; and participation in advisory boards for Amgen, Astellas Pharma, Bristol Myers Squibb, Gritstone Oncology, Haliodx, Kaleido Biosciences, Merck & Co., Pierre Fabre, and Servier. SL reports research funding from Amgen, Merck Serono, Bayer, Roche, Eli Lilly, AstraZeneca, and Bristol Myers Squibb; honoraria from Roche, Eli Lilly, Bristol Myers Squibb, Servier, Merck Serono, Pierre Fabre, GlaxoSmithKline, and Amgen; and participation in advisory boards for Amgen, Merck Serono, Eli Lilly, AstraZeneca, Incyte, Daiichi Sankyo, Bristol Myers Squibb, Servier, and Merck Sharp & Dohme. KYMW reports consulting roles for Merck & Co., Novartis, Ipsen, and Sirtex. FG reports honoraria for speaker/advisory roles from Servier, Eli Lilly, IQVIA, Merck Serono, Amgen, and Bristol Myers Squibb, outside the present work. HJL reports consulting roles for Bayer, Merck & Co., Roche, Bristol Myers Squibb, Merck KGaA, Oncocyte, Fulgent, Jazz Therapeutics, and 3T Bioscience. MAM reports support for the present manuscript from Bristol Myers Squibb; grants from Merck & Co. and Amal; and honoraria from Genentech/Roche. EVC reports participation in advisory boards for AbbVie, Array, Astellas, AstraZeneca, Bayer, Beigene, Biocartis, Boehringer Ingelheim, Bristol Myers Squibb, Celgene, Daiichi Sankyo, Halozyme, GlaxoSmithKline, Helsinn, Incyte, Ipsen, Janssen Research, Eli Lilly, Merck Sharp & Dohme, Merck KGaA, Mirati, Novartis, Pierre Fabre, Roche, Seattle Genetics, Servier, Sirtex, Terumo, Taiho, TRIGR, and Zymeworks; and research grants from Amgen, Bayer, Boehringer Ingelheim, Bristol Myers Squibb, Celgene, Ipsen, Eli Lilly, Merck Sharp & Dohme, Merck KGaA, Novartis, Roche, and Servier, paid to his institution. RMD reports personal fees and non-financial support from Pfizer and Janssen; grants from Amgen, Bristol Myers Squibb, and Merck; grants and personal fees from Bayer; non-financial support from Celgene; and personal fees from Clovis. MBS reports support for the present manuscript from Bristol Myers Squibb; grants from AstraZeneca, Alberta Cancer Foundation, Alberta Health Services Strategic Network (Seed Grant Competition), Rexahn, Eli Lilly, Canadian Institutes of Health Research, Bristol Myers Squibb, and Celgene; consulting fees from Ipsen, Bristol Myers Squibb, and Merck & Co.; honoraria from Mylan, Ipsen, Bristol Myers Squibb, and AstraZeneca; support for meetings and travel from Novartis; and holds a patent (number 61/406,856). BN reports support for the present manuscript from Bristol Myers Squibb. SA reports owning stocks and being an employee of Bristol Myers Squibb. AM and MD report being employees of Bristol Myers Squibb. ML reports being an employee of, owning stock in, and being an inventor of patents filed/owned by Bristol Myers Squibb. SK reports consulting or advisory role from Genentech, Merck, Amal Therpeutics, Holy Stone, Novartis, Eli Lilly, Boehringer Ingelheim, Boston Biomedical, AstraZeneca/MedImmune, Bayer Health, Pierre Fabre, EMD Serono, Redx Pharma, Jacobio, Natera, Repare Therapeutics, Daiichi Sankyo, Lutris, Pfizer, Ipsen, HalioDx, Inivata, GlaxoSmithKline, Jazz Pharmaceuticals, Iylon, Xilis, AbbVie, Gilead Sciences, Mirati Therapeutics, Flame Biosciences, Servier, Carina Biotechnology, Bicara Therapeutics, Endeavor BioMedicines, Numab Pharma, Johnson & Johnson/Janssen, Genomic Health, Frontier Medicines, Replimune, and Taiho Pharmaceutical; research funding from Sanofi, Biocartis, Guardant Health, Array BioPharma, Genentech/Roche, EMD Serono, MedImmune, Novartis, Amgen, Eli Lilly, and Daiichi Sankyo; and stock and other ownership interests from MolecularMatch, Lutris, Iylon, and Frontier Medicines. MJO reports consulting fees from Merck Sharp & Dohme, AbbVie, Agilvax, Takeda, Acrotech Biopharma, and Novartis. All other authors have declared no conflicts of interest. Data sharing BMS policy on data sharing can be found at https://www.bms.com/researchers-and-partners/independent-research/data-sharing-request-process.html., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Identification of circulating tumor DNA (ctDNA) following curative intent therapies is a surrogate for microscopic residual disease for patients with metastatic colorectal cancer (mCRC). Preclinically, in micrometastatic microsatellite stable (MSS) CRC, increased TGF-β signaling results in exclusion of anti-tumor cytotoxic T cells from the tumor microenvironment. Bintrafusp alfa (BA) is a bifunctional fusion protein composed of the extracellular domain of the TGF-βRII receptor ("TGF-β trap") and anti-PD-L1 antibody., Methods: Patients with liver-limited, MSS mCRC and with detected ctDNA after complete resection of all known tumors and standard-of-care therapy were treated with 1200 mg of BA intravenously every 14 days for six doses. The primary endpoint was ctDNA clearance. Radiographic characteristics at recurrence were compared using independent t-tests to historical data from a similar cohort of patients with liver-limited mCRC who underwent observation., Results: Only 4 of 15 planned patients received BA before the study was stopped early for loss of equipoise. There was no grade ≥3 AE. None of the patients cleared ctDNA. All patients developed radiographic recurrence by the first planned restaging. Although not detectable at prior to treatment, TGFβ3 was found in circulation in all patients at cycle 2 day 1. Compared to a historical cohort, patients administered BA developed more metastases (15 versus 2, p=0.005) and greater tumor volumes (9 cm vs 2 cm, p=0.05)., Conclusions: Treatment with BA in patients with ctDNA-detected, liver-limited mCRC did not clear ctDNA and was associated with large-volume recurrence, highlighting the potential context-specific complexity of dual TGF-β and PD-L1 inhibition.

Background: The KRAS p.G12C mutation has recently become an actionable drug target. To further understand KRAS p.G12C disease, we describe clinicopathologic characteristics, treatment patterns, overall survival (OS), and real-world progression-free survival (rwPFS) in patients with metastatic colorectal cancer (mCRC), KRAS p.G12C mutations (KRAS G12C), and other KRAS mutations (KRAS non-G12C) using a de-identified database., Patients and Methods: Clinical and tumor characteristics, including treatments received, genomic profile, and clinical outcomes were assessed for patients from a US clinical genomic database with mCRC diagnosed between January 1, 2011, and March 31, 2020, with genomic sequencing data available., Results: Of 6477 patients with mCRC (mCRC cohort), 238 (3.7%) had KRAS G12C and 2947 (45.5%) had KRAS non-G12C mutations. Treatment patterns were generally comparable across lines of therapy (LOT) in KRAS G12C versus KRAS non-G12C cohorts. Median (95% CI) OS after the first LOT was 16.1 (13.0-19.0) months for the KRAS G12C cohort versus 18.3 (17.2-19.3) months for the KRAS non-G12C cohort, and 19.2 (18.5-19.8) months for the mCRC overall cohort; median (95% CI) rwPFS was 7.4 (6.3-9.5), 9.0 (8.2-9.7), and 9.2 (8.6-9.7) months, respectively. The different KRAS non-G12C mutations examined did not affect clinical outcomes. Median OS and rwPFS for all cohorts declined with each subsequent LOT., Conclusions: Patients with KRAS p.G12C-mutant mCRC have poor treatment outcomes, and outcomes appear numerically worse than for those without this mutation, indicating potential prognostic implications for KRAS p.G12C mutations and an unmet medical need in this population., (© The Author(s) 2022. Published by Oxford University Press.)

Patient-derived xenografts (PDXs) and patient-derived organoids (PDOs) have been shown to model clinical response to cancer therapy. However, it remains challenging to use these models to guide timely clinical decisions for cancer patients. Here, we used droplet emulsion microfluidics with temperature control and dead-volume minimization to rapidly generate thousands of micro-organospheres (MOSs) from low-volume patient tissues, which serve as an ideal patient-derived model for clinical precision oncology. A clinical study of recently diagnosed metastatic colorectal cancer (CRC) patients using an MOS-based precision oncology pipeline reliably assessed tumor drug response within 14 days, a timeline suitable for guiding treatment decisions in the clinic. Furthermore, MOSs capture original stromal cells and allow T cell penetration, providing a clinical assay for testing immuno-oncology (IO) therapies such as PD-1 blockade, bispecific antibodies, and T cell therapies on patient tumors., Competing Interests: Declaration of interests X.S., D.H., and H.C. are cofounders of Xilis Inc. H.C. is an employee of Roche and on the advisory board of Cell Stem Cell. H.C.’s full disclosure is given at https://www.uu.nl/staff/JCClevers/. S.D. and Z.W. performed the majority of the study at Duke University and now are employees of Xilis Inc. Patents WO2020242594 and US 2021/0285054 are related to this work., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: Cetuximab 500 mg/m2 biweekly (Q2W) plus chemotherapy is commonly used and recommended by NCCN guidelines. This meta-analysis compares efficacy and safety between Q2W versus weekly (Q1W) cetuximab dosing., Methods: A systematic literature review was performed on Pubmed and RightFind (2007-2017) for patients with KRAS wild-type mCRC who received Q2W or Q1W cetuximab and other treatments. Observational studies and case reports were excluded. Randomized trials comparing Q2W and Q1W dosing, and single-arm trials with only Q2W schedule were included. CRYSTAL, a phase 3 randomized study with Q1W cetuximab dosing was paired with each single-arm study with a Q2W schedule and reweighted to achieve similar demographic/baseline characteristics. Overall survival (OS) and progression-free survival (PFS) with hazard ratios (HR), overall response rate (ORR) with odds ratios, and risk difference of adverse events of special interest (AESI) between Q2W versus Q1W cetuximab were analyzed., Results: Five phase 2 studies with cetuximab Q2W/Q1W dosing schedules were identified: CECOG (phase 2; Q2W, n = 77; Q1W, n = 75), NORDIC 7.5 (phase 2; Q2W, n = 152) and NORDIC 7 (arm C of phase 3; Q1W, n = 109), CELINE (n = 60), OPTIMIX (n = 99), and APEC (n = 289) all phase 2, Q2W, single-arm studies paired with CRYSTAL Q1W dosing (n = 303). Efficacy was similar between Q2W versus Q1W administration; OS HR = 0.96, 95% confidence interval (CI) [0.89, 1.04]; PFS HR = 0.96, 95% CI [0.87, 1.05]; ORR odds ratio 1.16, 95% CI [0.96, 1.41]. Mean differences (Q2W-Q1W) across AESI rates were not clinically meaningful with no obvious directionality., Conclusion: This meta-analysis demonstrated no significant differences in efficacy and safety between Q2W versus Q1W cetuximab administration in mCRC patients., (© The Author(s) 2022. Published by Oxford University Press.)

Background: The past 20 years have seen advances in colorectal cancer management. We sought to determine whether survival in patients undergoing resection of colorectal liver metastases (CLM) has improved in association with three landmark advances: introduction of irinotecan- and/or oxaliplatin-containing regimens, molecular targeted therapy, and multigene alteration testing., Methods: Patients undergoing CLM resection during 1998-2014 were identified and grouped by resection year. The influence of alterations in RAS, TP53, and SMAD4 was evaluated and validated in an external cohort including patients with unresectable metastatic colorectal cancer., Results: Of 1961 patients, 1599 met the inclusion criteria. Irinotecan- and/or oxaliplatin-containing regimens and molecular targeted therapy were used for more than 50% of patients starting in 2001 and starting in 2006, respectively, so patients were grouped as undergoing resection during 1998-2000, 2001-2005, or 2006-2014. Liver resectability indications expanded over time. The 5-year overall survival (OS) rate was significantly better in 2006-2014, vs. 2001-2005 (56.5% vs. 44.1%, P < 0.001). RAS alteration was associated with worse 5-year OS than RAS wild-type (44.8% vs. 63.3%, P < 0.001). However, OS did not differ significantly between patients with RAS alteration and wild-type TP53 and SMAD4 and patients with RAS wild-type in our cohort (P = 0.899) or the external cohort (P = 0.932). Of 312 patients with genetic sequencing data, 178 (57.1%) had clinically actionable alterations., Conclusion: OS after CLM resection has improved with advances in medical therapy and surgical technique. Multigene alteration testing is useful for prognostication and identification of potential therapeutic targets., (© 2021. The Society for Surgery of the Alimentary Tract.)

Background: The aim of this study was to compare the stage-for-stage overall (OS) and recurrence-free (RFS) survival between adult and pediatric/adolescent colon cancer patients., Study Design: A retrospective review of pediatric/adolescent patients less than 25 years old, treated between 1991 and 2017 at University of Texas MD Anderson Cancer Center, was compared with a prospectively maintained database of adult patients. Outcomes variables were compared, and OS and RFS were estimated using the Kaplan-Meier method and compared between groups using the log rank test and multivariable Cox models., Results: The cohort contained 94 pediatric patients and 765 adult patients. Overall, the 3-year OS rates for adult and pediatric patients, respectively, were 90% and 41.92% (95% CI 87% to 92%) (p < 0.0001), and the 3-year RFS rates were 78% and 32% (p < 0.0001). The stage-for-stage 5-year OS rates for adult vs pediatric patients were: Stage 1: 96% vs 100% (p = 0.793); stage 2: 90% vs 64% (p < 0.0001); stage 3: 85% vs 58% (p < 0.0001); stage 4; 55% vs 16% (p < 0.0001). The stage-for-stage 5-year RFS rates for adults vs children were: stage 1: 95% vs 100%; stage 2: 85% vs 55% (p = 0.0002); stage 3: 73% vs 31% (p < 0.0001); stage 4: 27% vs 5% (p < 0.0001). Pediatric/adolescent patients had a higher risk of recurrence or death than adult patients on multivariate analysis (hazard ratio [HR] 2.312, 95% CI: 1.615 to 3.313 (p < 0.0001). Peritoneal metastasis was significantly higher in pediatric patients. (p = 0.00001) CONCLUSIONS: Stage-for-stage, pediatric/adolescent patients had shorter 3- and 5-year OS and RFS rates than adult patients. Peritoneal disease and carcinomatosis were significantly higher in pediatric, adolescent, and young adult patients less than 25 years old. Predisposing conditions, such as polyposis or congenital colon disease, did not contribute to this difference., (Copyright © 2020. Published by Elsevier Inc.)

Background: The International Duration Evaluation of Adjuvant Chemotherapy (IDEA) collaboration aimed to evaluate whether 3 months of adjuvant chemotherapy are noninferior to 6 months. Our study objectives were to characterize medical oncologists' perspectives toward the results of the IDEA collaboration and to evaluate how IDEA impacted prescribing patterns of adjuvant FOLFOX and CAPOX in colon cancer., Materials and Methods: A list of questions developed by four medical oncologists regarding IDEA results were formulated and distributed online to gastrointestinal medical oncologists globally. Descriptive statistics and chi-square tests were used to summarize information., Results: Of 174 responses, 145 were complete and analyzed. Responses were obtained globally from South America (53%); the U.S. and Canada (28%); Europe, Australia, and New Zealand (12%); and Asia (7%). Most clinicians (98%) were aware of the IDEA study. Prior to IDEA, clinicians preferred FOLFOX over CAPOX (81% vs. 19%). Subsequent to IDEA, 55% of clinicians preferred CAPOX over FOLFOX (odds ratio, 5.0; 95% confidence interval, 3.0-8.5; p < .01 compared with pre-IDEA). Two thirds (68%) of responders tailored duration of adjuvant therapy based on risk stratification. Most oncologists (76%) were more willing to discontinue oxaliplatin early if toxicities develop after the results of IDEA. Half of responders (50%) found that IDEA increased their confidence in decision making for adjuvant treatment; 36% were unchanged, and 15% indicated decreased confidence. Less than half (48%) were comfortable communicating the study results and the concept of a noninferiority trial with patients., Conclusion: IDEA appears to have shifted clinician preference from FOLFOX to CAPOX for adjuvant therapy, and most clinicians now use a risk-stratified approach in determining duration of adjuvant therapy. Patient education resources may facilitate better communication of IDEA results to patients., Implications for Practice: This global survey illustrates that most gastrointestinal medical oncologists now use a risk-stratified approach for determining the duration of adjuvant chemotherapy for stage III colon cancer. Clinicians are five times more likely to choose CAPOX over FOLFOX after the International Duration Evaluation of Adjuvant Chemotherapy (IDEA) collaboration results., (© AlphaMed Press 2019.)

Background: Mouse and human studies support the promise of dry beans to improve metabolic health and to lower cancer risk. In overweight/obese patients with a history of colorectal polyps or cancer, the Beans to Enrich the Gut microbiome vs. Obesity's Negative Effects (BE GONE) trial will test whether and how an increase in the consumption of pre-cooked, canned dry beans within the context of usual diet and lifestyle can enhance the gut landscape to improve metabolic health and reduce cancer risk., Methods/design: This randomized crossover trial is designed to characterize changes in (1) host markers spanning lipid metabolism, inflammation, and obesity-related cancer risk; (2) compositional and functional profiles of the fecal microbiome; and (3) host and microbial metabolites. With each subject serving as their own control, the trial will compare the participant's usual diet with (intervention) and without (control) dry beans. Canned, pre-cooked dry beans are provided to participants and the usual diet continually assessed and monitored. Following a 4-week run-in and equilibration period, each participant provides a total of 5 fasting blood and 6 stool samples over a total period of 16 weeks. The intervention consists of a 2-week ramp-up of dry bean intake to 1 cup/d, which is then continued for an additional 6 weeks. Intra- and inter-individual outcomes are assessed across each crossover period with consideration of the joint or modifying effects of the usual diet and baseline microbiome., Discussion: The BE GONE trial is evaluating a scalable dietary prevention strategy targeting the gut microbiome of high-risk patients to mitigate the metabolic and inflammatory effects of adiposity that influence colorectal cancer risk, recurrence, and survival. The overarching scientific goal is to further elucidate interactions between diet, the gut microbiome, and host metabolism. Improved understanding of the diet-microbiota interplay and effective means to target these relationships will be key to the future of clinical and public health approaches to cancer and other major diet- and obesity-related diseases., Trial Registration: This protocol is registered with the U.S. National Institutes of Health trial registry, ClinicalTrials.gov, under the identifier NCT02843425. First posted July 25, 2016; last verified January 25, 2019.

Pseudoprogression has been observed in patients with various tumor types treated with immunotherapy. However, the frequency of pseudoprogression is unknown in gastrointestinal malignancies. Metastatic colorectal cancer (mCRC) and advanced pancreatic ductal adenocarcinoma (PDAC) patients who progressed on treatment with immunotherapy beyond RECIST version 1.1 criteria were analyzed. Degree of progression, tumor markers, time to progression, overall survival, Eastern Cooperative Oncology Group Performance Status (ECOG PS), and costs were analyzed for patients treated beyond progression (TBP) and not treated beyond progression. Fifty-nine of 159 (37%) patients with mCRC or PDAC were TBP (31 mCRC, 28 PDAC). Fifty-four of 59 (92%) patients were microsatellite stable. Zero of these 59 patients with initial treatment beyond progression demonstrated subsequent radiographic tumor shrinkage at a median 42 days from first scan documenting progression. A pseudoprogression rate of >6% could be excluded with 95% confidence. Compared with baseline, median growth on the first and second scan that showed progression was 29.8% and 43%, respectively. In those not treated beyond progression, median growth at first restaging was 31.2%. The trend in change in tumor size positively correlated with the trend in tumor markers in all patients TBP. Fifteen patients (25%) experienced grade 3/4 adverse events by continuing treatment beyond progression, whereas 19 (32%) experienced deterioration in ECOG PS. Pseudoprogression was not seen in microsatellite stable patients with mCRC or PDAC treated with immunotherapy. Changes in tumor markers correlated with changes in tumor volume. This data may help inform future treatment decisions and/or trial design in patients with mCRC or advanced PDAC treated with immunotherapy.

Background: Percutaneous ablation is a common treatment for colorectal liver metastasis (CLM). However, the effect of rat sarcoma viral oncogene homologue (RAS) mutation on outcome after ablation of CLMs is unclear., Methods: Patients who underwent image-guided percutaneous ablation of CLMs from 2004 to 2015 and had known RAS mutation status were analysed. Patients were evaluated for local tumour progression as observed on imaging of CLMs treated with ablation. Multivariable Cox regression analysis was performed to determine factors associated with local tumour progression-free survival., Results: The study included 92 patients who underwent ablation of 137 CLMs. Thirty-six patients (39 per cent) had mutant RAS. Rates of local tumour progression were 14 per cent (8 of 56) for patients with wild-type RAS and 39 per cent (14 of 36) for patients with mutant RAS (P = 0·007). The actuarial 3-year local tumour progression-free survival rate after percutaneous ablation was worse in patients with mutant RAS than in those with wild-type RAS (35 versus 71 per cent respectively; P = 0·001). In multivariable analysis, negative predictors of local tumour progression-free survival were a minimum ablation margin of less than 5 mm (hazard ratio (HR) 2·48, 95 per cent c.i. 1·31 to 4·72; P = 0·006) and mutant RAS (HR 3·01, 1·60 to 5·77; P = 0·001)., Conclusion: Mutant RAS is associated with an earlier and higher rate of local tumour progression in patients undergoing ablation of CLMs., (© 2017 BJS Society Ltd Published by John Wiley & Sons Ltd.)

Although clinical management of colon cancer generally has not accounted for the primary tumor site, left-sided and right-sided colon cancers harbor different clinical and biologic characteristics. Right-sided colon cancers are more likely to have genome-wide hypermethylation via the CpG island methylator phenotype (CIMP), hypermutated state via microsatellite instability, and BRAF mutation. There are also differential exposures to potential carcinogenic toxins and microbiota in the right and left colon. Gene expression analyses further shed light on distinct biologic subtypes of colorectal cancers (CRCs), with 4 consensus molecular subtypes (CMSs) identified. Importantly, these subtypes are differentially distributed between right- and left-sided CRCs, with greater proportions of the "microsatellite unstable/immune" CMS1 and the "metabolic" CMS3 subtypes found in right-sided colon cancers. This review summarizes important biologic distinctions between right- and left-sided CRCs that likely impact prognosis and may predict for differential responses to biologic therapy. Given the inferior prognosis of stage III-IV right-sided CRCs and emerging data suggesting that anti-epidermal growth factor receptor antibody therapy is associated with worse survival in right-sided stage IV CRCs compared with left-sided cancers, these biologic differences between right- and left-sided CRCs provide critical context and may provide opportunities to personalize therapy., (Copyright © 2017 by the National Comprehensive Cancer Network.)

Despite marked tumor shrinkage after 5-FU treatment, the frequency of colon cancer relapse indicates that a fraction of tumor cells survives treatment causing tumor recurrence. The majority of cancer cells divert metabolites into anabolic pathways through Warburg behavior giving an advantage in terms of tumor growth. Here, we report that treatment of colon cancer cell with 5-FU selects for cells with mesenchymal stem-like properties that undergo a metabolic reprogramming resulting in addiction to OXPHOS to meet energy demands. 5-FU treatment-resistant cells show a de novo expression of pyruvate kinase M1 (PKM1) and repression of PKM2, correlating with repression of the pentose phosphate pathway, decrease in NADPH level and in antioxidant defenses, promoting PKM2 oxidation and acquisition of stem-like phenotype. Response to 5-FU in a xenotransplantation model of human colon cancer confirms activation of mitochondrial function. Combined treatment with 5-FU and a pharmacological inhibitor of OXPHOS abolished the spherogenic potential of colon cancer cells and diminished the expression of stem-like markers. These findings suggest that inhibition of OXPHOS in combination with 5-FU is a rational combination strategy to achieve durable treatment response in colon cancer.

Posttranslational modifications to the intracellular domain of the EGFR are known to regulate EGFR functions; however, modifications to the extracellular domain and their effects remain relatively unexplored. Here, we determined that methylation at R198 and R200 of the EGFR extracellular domain by protein arginine methyltransferase 1 (PRMT1) enhances binding to EGF and subsequent receptor dimerization and signaling activation. In a mouse orthotopic colorectal cancer xenograft model, expression of a methylation-defective EGFR reduced tumor growth. Moreover, increased EGFR methylation sustained signaling activation and cell proliferation in the presence of the therapeutic EGFR monoclonal antibody cetuximab. In colorectal cancer patients, EGFR methylation level also correlated with a higher recurrence rate after cetuximab treatment and reduced overall survival. Together, these data indicate that R198/R200 methylation of the EGFR plays an important role in regulating EGFR functionality and resistance to cetuximab treatment.

Purpose: This study aimed to detect cell-surface vimentin (CSV) on the surface of epithelial-mesenchymal transitioned (EMT) circulating tumor cells (CTC) from blood of patients with epithelial cancers., Experimental Design: In this study, 101 patients undergoing postsurgery adjuvant chemotherapy for metastatic colon cancer were recruited. EMT CTCs were detected from blood of patients using the 84-1 monoclonal antibody against CSV as a marker. EMT CTCs isolated were characterized further using EMT-specific markers, fluorescent in situ hybridization, and single-cell mutation analysis., Results: Using the 84-1 antibody, we detected CSV exclusively on EMT CTCs from a variety of tumor types but not in the surrounding normal cells in the blood. The antibody exhibited very high specificity and sensitivity toward different epithelial cancer cells. With this antibody, we detected and enumerated EMT CTCs from patients. From our observations, we defined a cutoff of <5 or ≥5 EMT CTCs as the optimal threshold with respect to therapeutic response using ROC curves. Using this defined threshold, the presence of ≥5 EMT CTCs was associated with progressive disease, whereas patients with <5 EMT CTCs showed therapeutic response., Conclusion: Taken together, the number of EMT CTCs detected correlated with the therapeutic outcome of the disease. These results establish CSV as a universal marker for EMT CTCs from a wide variety of tumor types and thus provide the foundation for emerging CTC detection technologies and for studying the molecular regulation of these EMT CTCs., (©2014 American Association for Cancer Research.)

Farnesoid X receptor (FXR) is a bile acid nuclear receptor described through mouse knockout studies as a tumor suppressor for the development of colon adenocarcinomas. This study investigates the regulation of FXR in the development of human colon cancer. We used immunohistochemistry of FXR in normal tissue (n = 238), polyps (n = 32), and adenocarcinomas, staged I-IV (n = 43, 39, 68, and 9), of the colon; RT-quantitative PCR, reverse-phase protein array, and Western blot analysis in 15 colon cancer cell lines; NR1H4 promoter methylation and mRNA expression in colon cancer samples from The Cancer Genome Atlas; DNA methyltransferase inhibition; methyl-DNA immunoprecipitation (MeDIP); bisulfite sequencing; and V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) knockdown assessment to investigate FXR regulation in colon cancer development. Immunohistochemistry and quantitative RT-PCR revealed that expression and function of FXR was reduced in precancerous lesions and silenced in a majority of stage I-IV tumors. FXR expression negatively correlated with phosphatidylinositol-4, 5-bisphosphate 3 kinase signaling and the epithelial-to-mesenchymal transition. The NR1H4 promoter is methylated in ~12% colon cancer The Cancer Genome Atlas samples, and methylation patterns segregate with tumor subtypes. Inhibition of DNA methylation and KRAS silencing both increased FXR expression. FXR expression is decreased early in human colon cancer progression, and both DNA methylation and KRAS signaling may be contributing factors to FXR silencing. FXR potentially suppresses epithelial-to-mesenchymal transition and other oncogenic signaling cascades, and restoration of FXR activity, by blocking silencing mechanisms or increasing residual FXR activity, represents promising therapeutic options for the treatment of colon cancer.

The functional roles of SNPs within the 8q24 gene desert in the cancer phenotype are not yet well understood. Here, we report that CCAT2, a novel long noncoding RNA transcript (lncRNA) encompassing the rs6983267 SNP, is highly overexpressed in microsatellite-stable colorectal cancer and promotes tumor growth, metastasis, and chromosomal instability. We demonstrate that MYC, miR-17-5p, and miR-20a are up-regulated by CCAT2 through TCF7L2-mediated transcriptional regulation. We further identify the physical interaction between CCAT2 and TCF7L2 resulting in an enhancement of WNT signaling activity. We show that CCAT2 is itself a WNT downstream target, which suggests the existence of a feedback loop. Finally, we demonstrate that the SNP status affects CCAT2 expression and the risk allele G produces more CCAT2 transcript. Our results support a new mechanism of MYC and WNT regulation by the novel lncRNA CCAT2 in colorectal cancer pathogenesis, and provide an alternative explanation of the SNP-conferred cancer risk.

Purpose: Vemurafenib, a selective inhibitor of BRAF(V600), has shown significant activity in BRAF(V600) melanoma but not in less than 10% of metastatic BRAF(V600) colorectal cancers (CRC), suggesting that studies of the unique hypermethylated phenotype and concurrent oncogenic activation of BRAF(mut) CRC may provide combinatorial strategies., Experimental Design: We conducted comparative proteomic analysis of BRAF(V600E) melanoma and CRC cell lines, followed by correlation of phosphoinositide 3-kinase (PI3K) pathway activation and sensitivity to the vemurafenib analogue PLX4720. Pharmacologic inhibitors and siRNA were used in combination with PLX4720 to inhibit PI3K and methyltransferase in cell lines and murine models., Results: Compared with melanoma, CRC lines show higher levels of PI3K/AKT pathway activation. CRC cell lines with mutations in PTEN or PIK3CA were less sensitive to growth inhibition by PLX4720 (P = 0.03), and knockdown of PTEN expression in sensitive CRC cells reduced growth inhibition by the drug. Combined treatment of PLX4720 with PI3K inhibitors caused synergistic growth inhibition in BRAF-mutant CRC cells with both primary and secondary resistance. In addition, methyltransferase inhibition was synergistic with PLX4720 and decreased AKT activation. In vivo, PLX4720 combined with either inhibitors of AKT or methyltransferase showed greater tumor growth inhibition than PLX4720 alone. Clones with acquired resistance to PLX4720 in vitro showed PI3K/AKT activation with EGF receptor (EGFR) or KRAS amplification., Conclusions: We show that activation of the PI3K/AKT pathway is a mechanism of both innate and acquired resistance to BRAF inhibitors in BRAF(V600E) CRC and suggest combinatorial approaches to improve outcomes in this poor prognosis subset of patients.

Background: Because of its rarity, adenocarcinoma of the small intestine is frequently compared to adenocarcinoma of the colon, although the validity of this comparison is not known., Methods: Patients with small and large bowel adenocarcinoma (SBA and LBA) diagnosed between 1988 and 2007 were identified from the Surveillance, Epidemiology, and End Results registry. Age-standardized incidence and mortality rates were determined. Cancer-specific survival (CSS) stratified by stage and by number of assessed lymph nodes was calculated., Results: A total of 4518 and 261,521 patients with SBA and LBA, respectively, were identified. In comparison to LBA, patients with SBA were younger and presented with disease of higher stage and histologic grade. The age-standardized incidence rates decreased for LBA (-1.24% per year) but increased for SBA (+1.47% per year). Although age-standardized mortality rates decreased for both LBA and SBA, the decreases were more pronounced for LBA. Five-year CSS was worse for resected SBA compared with resected LBA, although this difference diminished when comparing cases having eight or more lymph nodes assessed. The relative reduction in CSS when selecting eight or more lymph nodes was much greater for duodenal as opposed to jejunal/ileal subsite of the small bowel. With nodal selection the absolute difference in CSS between LBA and SBA for stages I, II, and III was 13, 15.9, and 18.5%, respectively., Conclusions: Adequate nodal assessment is much less common in SBA than LBA; and it appears that SBA, in particular duodenal adenocarcinoma, is understaged. Even after corrections to minimize the effect of stage migration and inadequate lymph node evaluation, SBA demonstrated distinctly worse CSS than LBA.

Chemotherapeutic regimens for the treatment of colorectal cancer generally include oxaliplatin, although inherent and acquired resistance is common. One potential mediator of oxaliplatin sensitivity is the nonreceptor protein tyrosine kinase, Src, the activity of which correlates with disease stage and patient survival. Therefore, we investigated the effects of Src inhibition using the tyrosine kinase inhibitor dasatinib on oxaliplatin sensitivity. We show that oxaliplatin acutely activates Src and that combination treatment with dasatinib is synergistic in a cell-line dependent manner, with the level of Src activation correlating with extent of synergy in a panel of six cell lines. Intracellular reactive oxygen species (ROS) are generated after oxaliplatin treatment, and ROS potently activates Src. Pretreatment with antioxidants inhibits oxaliplatin-induced Src activation. In oxaliplatin-resistant cell lines, Src activity is constitutively increased. In a mouse model of colorectal liver metastases, treatment with oxaliplatin also results in chronic Src activation. The combination of dasatinib and oxaliplatin results in significantly smaller tumors compared with single-agent treatment, corresponding with reduced proliferation and angiogenesis. Therefore, we conclude that oxaliplatin activates Src through a ROS-dependent mechanism. Src inhibition increases oxaliplatin activity both in vitro and in vivo. These results suggest that Src inhibitors combined with oxaliplatin may have efficacy in metastatic colon cancer and may provide the first indication of a molecular phenotype that might be susceptible to such combinations.

The use of adjuvant chemotherapy following resection for all patients with stage III colon cancer is now part of the standard of care around the world. Recent trials have led to changes in the standard regimens, which now include the use of oxaliplatin (Eloxatin) for most patients with stage III colon cancer. The addition of oxaliplatin has resulted in a 23% reduction in the risk of recurrence compared with fluorouracil/leucovorin alone, with a small but statistically significant survival benefit. Unfortunately, no adequately powered trial has determined whether adjuvant chemotherapy is beneficial for stage II patients, and its use is much more controversial. Most investigators agree that adjuvant chemotherapy has some activity against stage II disease. However, its impact on progression-free and overall survival remains highly controversial. Despite the lack of data, there is growing acceptance of an informal classification system, which stratifies stage II patients by risk on the basis of clinical data, as a guide for deciding whether to use adjuvant therapy. The only phase III clinical trial for stage II patients currently ongoing in the United States uses molecular classification as the basis for patient randomization.

Background: Improved survival of patients with metastatic colorectal cancer (CRC) has been shown to correlate with increased utilization of the 3 active cytotoxic chemotherapeutic agents: 5-fluorouracil (5-FU), irinotecan, and oxaliplatin, usually administered in 2 lines of therapy. However, it is unclear which patient, disease, and treatment characteristics are associated with the utilization of a second-line regimen., Patients and Methods: We performed a retrospective chart review. Patients with metastatic CRC treated with bevacizumab outside of a clinical trial and any infusional 5-FU/leucovorin (LV) regimen off-protocol (ie, 5-FU/LV/irinotecan [FOLFIRI]/bevacizumab or 5-FU/LV/oxaliplatin [FOLFOX]/bevacizumab) at the University of Texas M. D. Anderson Cancer Center between February 2004 and September 2005 were included. Prespecified characteristics of age, tumor burden, severe toxicity, and front-line regimen efficacy were compared with exploratory analyses of additional patient, disease, and treatment characteristics., Results: Eighty-seven sequential patients treated with the specified front-line regimens were identified. Seventy-six percent of the eligible patients were treated with a second-line regimen. Despite equal treatment durations, patients with a better response of stable disease were significantly less likely to receive a third cytotoxic agent than patients with a partial response (68% vs. 95%; odds ratio, 8.2; P = .02) due to declining performance status (86%) or patient preference (14%). This was associated with a decreased 2-year overall survival (86% vs. 55%). Neither age, tumor burden, nor development of toxicities were associated with a different utilization of a second-line regimen., Conclusion: Failure to obtain a response to initial chemotherapy for metastatic disease appears to be associated with decreased utilization of a second-line regimen.