Chen, Wei

Enteroblastic, hepatoid, and clear cell carcinomas are rare subtypes of colorectal carcinoma (CRC) with histologic and immunohistochemical (IHC) overlap. We assessed 37 CRCs that possibly represent these subtypes. Provisional criteria for each subtype, along with case photomicrographs and IHC data, were circulated among the authors to provide diagnostic interpretations. Based on plurality consensus, the carcinomas were classified as enteroblastic (n=13), hepatoid (n=6), and clear cell (n=18). Unanimous agreement was reached in 18% (3 clear cell, 3 hepatoid). Interobserver analysis revealed a mean pairwise Cohen κ of 0.63 (range: 0.32 to 0.91), with the hepatoid subtype eliciting the greatest consensus. Clear cell areas were the most likely to intermix with areas of conventional CRC ( P <0.001). Seven patients (20%) had inflammatory bowel disease (mostly linked to enteroblastic CRC). Twenty-three of 34 patients (68%) had nodal metastasis, and 12 (32%) had distant metastasis (mostly to the liver) at presentation. Median recurrence-free survival was 17 months, with enteroblastic cases the most likely to recur (54%, P =0.015). Median follow-up length was 27 months, with 14 patients (40%) dying of disease (representing 7 enteroblastic, 4 hepatoid, and 3 clear cell CRC). Mutations were identified in TP53 (n=8) , APC (n=3) , FBXW7 (n=2), and KRAS (n=1). Inflammatory bowel disease significantly worsened recurrence-free survival on multivariate analysis, while distant metastasis significantly worsened both recurrence-free and overall survival on multivariate analysis. Enteroblastic, hepatoid, and clear cell CRC demonstrate morphologic and IHC overlap, leading to interobserver variability in diagnosis. Given potential differences in clinical correlations and outcomes, more refined criteria are likely necessary.

AimsWe compiled two cohorts of colorectal adenosquamous carcinoma (ASC) to describe its histologic and molecular aspects using modern parameters to compare them with literature reports using meta‐analysis of cohorts and individual case series.Methods and ResultsWe identified 53 colorectal ASC from 19 North American academic medical centres, in addition to national database reports on 94 Dutch cases. We analysed available clinical, histologic, and immunohistochemical features and patient outcome. ASC comprised 0.02% of colorectal cancers in the Dutch database. The median cohort patient ages at resection were 65 and 69 years (North American and Dutch cohorts, respectively), with a roughly equal male:female ratio. The squamous component represented between 5% and 95% of each tumour, with a median of 50%. Tumour‐infiltrating lymphocytes (TILs) were generally low (66%), and tumour budding was often Bd1 (64%). Most cases were pT3 (55%) or pT4 (40%), with nodal metastases in more than half (58%). Twenty‐three cases (43%) metastasized distantly, most commonly to the liver. Mismatch repair (MMR) deficiency was identified in 34% of the cases. Follow‐up was available for 48 patients; 13 (27%) had recurrent disease and 29 (60%) died. A total of 31 patients progressed, with median time to progression of 18 months. Available data for the Dutch cohort revealed largely similar findings, as did review of cases in the literature.ConclusionColorectal ASC usually presents at an advanced stage. Despite high rates of MMR deficiency and low tumour budding, TILs were generally low, and there is a high recurrence rate and poor prognosis.

Background: Optimal patient selection for radiotherapy in pancreatic ductal adenocarcinoma (PDAC) is unestablished. Molecular profiling may select patients at high risk for locoregional recurrence (LRR) who would benefit from radiation. Methods: We included resectable pancreatic cancer (R-PDAC) patients, divided into training and validation cohorts, treated among three institutions with surgery and adjuvant chemotherapy, and borderline resectable or locally advanced pancreatic cancer (BR/LA-PDAC) patients treated with chemotherapy with or without radiation at the primary study institution. We isolated RNA from R-PDAC surgical specimens. Using NanoString, we identified miRNAs differentially expressed between normal and malignant pancreatic tissue. ElasticNet regression identified two miRNAs most predictive of LRR in the training cohort, miR-181b/d and miR-575, which were used to generate a risk score (RS). We evaluated the association of the median-dichotomized RS with recurrence and overall survival (OS). Results: We identified 183 R-PDAC and 77 BR/LA-PDAC patients with median follow up of 37 months treated between 2001 and 2014. On multivariable analysis of the R-PDAC training cohort (n = 90), RS was associated with worse LRR (HR = 1.34; 95%CI 1.27–11.38; p = 0.017) and OS (HR = 2.89; 95%CI 1.10–4.76; p = 0.027). In the R-PDAC validation cohort, RS was associated with worse LRR (HR = 2.39; 95%CI 1.03–5.54; p = 0.042), but not OS (p = 0.087). For BR/LA-PDAC, RS was associated with worse LRR (HR = 2.71; 95%CI 1.14–6.48; p = 0.025), DR (HR = 1.93; 95%CI 1.10–3.38; p = 0.022), and OS (HR = 1.97; 95%CI 1.17–3.34; p = 0.011). Additionally, after stratifying by RS and receipt of radiation in BR/LA-PDAC patients, high RS patients who did not receive radiation had worse LRR (p = 0.018), DR (p = 0.006), and OS (p < 0.001) compared to patients with either low RS or patients who received radiation, irrespective of RS. Conclusions: RS predicted worse LRR and OS in R-PDAC and worse LRR, DR, and OS in BR/LA-PDAC. This may select patients who would benefit from radiation and should be validated prospectively.

Abstract KRAS-activating mutations are oncogenic drivers and are correlated with radioresistance of multiple cancers, including colorectal cancer, but the underlying precise molecular mechanisms remain elusive. Herein we model the radiosensitivity of isogenic HCT116 and SW48 colorectal cancer cell lines bearing wild-type or various mutant KRAS isoforms. We demonstrate that KRAS mutations indeed lead to radioresistance accompanied by reduced radiotherapy-induced mitotic catastrophe and an accelerated release from G2/M arrest. Moreover, KRAS mutations result in increased DNA damage response and upregulation of 53BP1 with associated increased non-homologous end-joining (NHEJ) repair. Remarkably, KRAS mutations lead to activation of NRF2 antioxidant signaling to increase 53BP1 gene transcription. Furthermore, genetic silencing or pharmacological inhibition of KRAS, NRF2 or 53BP1 attenuates KRAS mutation-induced radioresistance, especially in G1 phase cells. These findings reveal an important role for a KRAS-induced NRF2-53BP1 axis in the DNA repair and survival of KRAS-mutant tumor cells after radiotherapy, and indicate that targeting NRF2, 53BP1 or NHEJ may represent novel strategies to selectively abrogate KRAS mutation-mediated radioresistance.

Abstract Purpose: The RAS/RAF/MEK/ERK signaling pathway is critical to the development of colorectal cancers, and KRAS, NRAS, and BRAF mutations foster resistance to radiation. We performed a phase I trial to determine the safety of trametinib, a potent MEK1/2 inhibitor, with 5-fluorouracil (5-FU) chemoradiation therapy (CRT) in patients with locally advanced rectal cancer (LARC). Patients and Methods: Patients with stage II/III rectal cancer were enrolled on a phase I study with 3+3 study design, with an expansion cohort of 9 patients at the MTD. Following a 5-day trametinib lead-in, with pre- and posttreatment tumor biopsies, patients received trametinib and CRT, surgery, and adjuvant chemotherapy. Trametinib was given orally daily at 3 dose levels: 0.5 mg, 1 mg, and 2 mg. CRT consisted of infusional 5-FU 225 mg/m2/day and radiation dose of 28 daily fractions of 1.8 Gy (total 50.4 Gy). The primary endpoint was to identify the MTD and recommended phase II dose. IHC staining for phosphorylated ERK (pERK) and genomic profiling was performed on the tumor samples. Results: Patients were enrolled to all dose levels, and 18 patients were evaluable for toxicities and responses. Treatment was well tolerated, and there was one dose-limiting toxicity of diarrhea, which was attributed to CRT rather than trametinib. At the 2 mg dose level, 25% had pathologic complete response. IHC staining confirmed dose-dependent decrease in pERK with increasing trametinib doses. Conclusions: The combination of trametinib with 5-FU CRT is safe and well tolerated, and may warrant additional study in a phase II trial, perhaps in a RAS/RAF-mutant selected population.