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Colorectal cancer (CRC) is the third most frequent neoplastic disorder and is a main cause of tumor-related mortality, as many patients progress to stage IV metastatic CRC. Standard care consists of combination chemotherapy (FOLFIRI or FOLFOX). Patients with WT KRAS typing are eligible to receive anti-EGFR therapy combined with chemotherapy. Unfortunately, predicting efficacy of CRC anti-EGFR therapy has remained challenging. Here we uncovered that the EGFR pathway component RasGRP1 acts as a CRC tumor suppressor in the context of aberrant Wnt signaling. We found that RasGRP1 suppresses EGF-driven proliferation of colonic epithelial organoids. Having established that RasGRP1 dosage levels impact biology, we next focused on CRC patients. Mining 5 different data platforms, we establish that RasGRP1 expression levels decrease with CRC progression and predict poor clinical outcome of patients. Last, deletion of 1 or 2 Rasgrp1 alleles made CRC spheroids more susceptible to EGFR inhibition. Retrospective analysis of the CALGB 80203 clinical trial showed that addition of anti-EGFR therapy to chemotherapy significantly improved outcome for CRC patients when tumors expressed low levels of RasGRP1 suppressor. In sum, our data support RasGRP1 as a biomarker in the EGFR pathway that has potential relevance to anti-EGFR therapy for CRC patients.

Background:Iberdomide (IBER) is a novel cereblon (CRBN) E3 ligase modulatory compound (CELMoD) that is being investigated as monotherapy, in combination with dexamethasone (DEX), and in combination with DEX and daratumumab or bortezomib in a phase 1b/2a dose‐escalation study in relapsed/refractory multiple myeloma (RRMM). IBER modulates CRBN, which induces ubiquitination of Aiolos, Ikaros and ZFP91, increases their proteasome‐dependent degradation, and thereby inhibits myeloma cell growth. IBER binds more potently to CRBN and is more efficient at degrading Aiolos and Ikaros than the immunomodulatory agents (IMiDs) lenalidomide (LEN) and pomalidomide (POM) and it can overcome IMiD drug resistance in pre‐clinical models.Aims:To determine if IBER is pharmacodynamically (PD) active in multiple myeloma patients refractory to POM and/or LEN, and to establish pharmacokinetic (PK)/PD and PD/dose relationships.Methods:As of Jan 11, 2019, 83 patients received IBER as monotherapy or in combination with DEX; 61 (74%) were LEN refractory and 47 (57%) were POM refractory. Longitudinal immunohistochemistry (IHC) data on CRBN, Aiolos, Ikaros and ZFP91 expression was obtained from bone marrow samples from 14 patients dosed with 0.3–0.9 mg IBER daily ± DEX. PD analysis of immune activity by TruCulture® (n = 45) and by peripheral blood flow cytometry (n = 60) was completed on a subset of patients dosed up to 1.0 mg IBER ± DEX. A population PK approach was used to estimate exposure (area under the concentration curve over the 24 hr dosing interval [AUCτ]) on 59 patients dosed up to 1.0 mg IBER ± DEX.Results:IBER AUCτ increased in a dose‐proportional manner in RRMM patients over the dose range 0.3–1.0 mg (22.4–65.31 ng∗hr/mL, respectively). In patient biopsies analyzed to date, CRBN expression was observed in all tumors by IHC at baseline and did not significantly change while on‐treatment. Furthermore, no significant decrease in baseline CRBN expression was observed in patients refractory to POM. In MM cells, significant decreases in Aiolos (median 37% decrease, P < 0.001), Ikaros (median 12% decrease, P = 0.006), and ZFP91 (median 47% decrease, P < 0.001) protein expression were observed on‐treatment across all dose levels; these decreases were unrelated to levels of CRBN expression at screening or prior LEN or POM refractoriness. In TruCulture® samples, dose‐dependent increases were observed in IL‐2 and IFN‐γ, with median increases of 78% and 66%, respectively, 5 hours post 0.9 mg dose of IBER. A dose‐ and exposure‐dependent decrease in B‐cells was detected (median 74% decrease at cycle 2 day 15, IBER 0.9 mg). These observations are consistent with the proposed IBER mechanism of action. Immunoprofiling showed significant increases in total and proliferating NK cells in RRMM patients treated with IBER, and a dose‐dependent increase in proliferating, activated, and effector memory T‐cells. These trends were consistent in RRMM patients treated with IBER monotherapy and in combination with DEX.Summary/Conclusion:These translational analyses from IBER treated RRMM patients indicate it is pharmacodynamically active at the lowest dose (0.3 mg) and exhibits dose‐ and exposure‐dependent immunostimulatory activity, supporting further dose‐escalation beyond 1.0 mg, which is currently ongoing. These results also suggest that prior refractoriness to LEN or POM is not associated with significant loss of CRBN or IBER PD activity, supporting continued investigation of IBER in RRMM patients refractory to IMiD drugs.

Abstract Context von Hippel-Lindau (VHL) disease, comprising renal cancer, hemangioblastoma, and/or pheochromocytoma (PHEO), is caused by missense or truncating variants of the VHL tumor-suppressor gene, which is involved in degradation of hypoxia-inducible factors (HIFs). However, the role of synonymous VHL variants in the disease is unclear. Objective We evaluated a synonymous VHL variant in patients with familial PHEO or VHL disease without a detectable pathogenic VHL mutation. Design We performed genetic and transcriptional analyses of leukocytes and/or tumors from affected and unaffected individuals and evaluated VHL splicing in existing cancer databases. Results We identified a synonymous VHL variant (c.414A>G, p.Pro138Pro) as the driver event in five independent individuals/families with PHEOs or VHL syndrome. This variant promotes exon 2 skipping and hence, abolishes expression of the full-length VHL transcript. Exon 2 spans the HIF-binding domain required for HIF degradation by VHL. Accordingly, PHEOs carrying this variant display HIF hyperactivation typical of VHL loss. Moreover, other exon 2 VHL variants from the The Cancer Genome Atlas pan-cancer datasets are biased toward expression of a VHL transcript that excludes this exon, supporting a broader impact of this spliced variant. Conclusion A recurrent synonymous VHL variant (c.414A>G, p.Pro138Pro) confers susceptibility to PHEO and VHL disease through splice disruption, leading to VHL dysfunction. This finding indicates that certain synonymous VHL variants may be clinically relevant and should be considered in genetic testing and surveillance settings. The observation that other coding VHL variants can exclude exon 2 suggests that dysregulated splicing may be an underappreciated mechanism in VHL-mediated tumorigenesis.

AbstractBackgroundSarcopenia, characterized by low muscle mass, associates with mortality in patients with cirrhosis. Skeletal muscle area in a single computed tomography image at the level of the third lumbar vertebrate (L3) is a valid representative of whole body muscle mass. Controversy remains regarding applicability of psoas muscle to identify patients at greater risk of mortality. We aimed to determine psoas muscle index (PMI) association with skeletal muscle index (SMI) and to evaluate the capacity of PMI to predict liver transplant waitlist mortality.MethodsWe evaluated listed adult patients with cirrhosis from 2012 to 2013 at four North American liver transplant centres. From L3 computed tomography images within 3 months of listing, we determined SMI and PMI expressed by cm2/m2. Low SMI was defined as SMI <39 cm2/m2 in women and <50 cm2/m2 in men as published by us earlier. Cut‐offs for PMI to predict mortality were established using a receiver‐operating characteristic analysis. Mortality predictors were determined using competing‐risk analysis with reported results as subdistribution hazard ratios (sHRs).ResultsOf 353 waitlist candidates, 68% were men, mean age 56 ± 9 years, and Model for End‐stage Liver Disease of 16 ± 8 points. Low SMI was present more frequently in men than women (51 vs. 36%, P = 0.02). Moderately strong correlation between SMI and PMI was observed (r > 0.7, P < 0.001). Low PMI (males < 5.1 cm2/m2; females < 4.3 cm2/m2) yielded poor and moderate concordance with low SMI in men and women, respectively (Kappa coefficient 0.31 and 0.63). SMI (39 ± 9 vs. 43 ± 7 cm2/m2; P = 0.009) and PMI (4.4 ± 1.3 vs. 5.2 ± 1.1 cm2/m2; P = 0.001) were lower in women who died and/or were delisted (compared with non‐deceased patients) whereas men who died and/or were delisted had only lower SMI (47 ± 7 vs. 51 ± 9 cm2/m2; P = 0.003), but not PMI compared with non‐deceased patients. In women, both SMI (sHR 0.94, P = 0.048) and PMI (sHR 0.58, P = 0.002) were predictors of mortality, while in men, SMI was significant (sHR 0.95, P = 0.001) and PMI showed a trend to be (sHR 0.85, P = 0.09) associated with mortality. Overall, 104 patients (29%) were misclassified between SMI and PMI categories. Using PMI cut‐offs, 66% and 28% of low SMI men and women, who have a higher risk of mortality, were incorrectly classified as low risk.ConclusionsSkeletal muscle index is a more complete and robust measurement than PMI, especially in men with cirrhosis. Low PMI identifies an incomplete subset of patients at increased risk of mortality indicated by low SMI. Given the poor performance of PMI, SMI should not be substituted by PMI.

AbstractObjectiveThe prognostic value of cerebrospinal fluid neurofilament light chain, total tau, phosphorylated tau181, and amyloid beta1‐42was examined in frontotemporal dementia subtypes.MethodsWe compared baseline biomarkers between 49 controls, 40 patients with behavioral variant frontotemporal dementia, 24 with semantic variant primary progressive aphasia, and 26 with nonfluent variant primary progressive aphasia. Linear mixed effect models were used to assess the value of baseline biomarkers in predicting clinical and radiographic change in patient cohorts over multiple yearly follow up visits.ResultsNeurofilament light chain concentrations were lowest in controls. Elevated baseline neurofilament light chain predicted faster worsening in clinical severity, frontotemporal volume and frontotemporal fractional anisotropy in patients with behavioral variant frontotemporal dementia and nonfluent variant primary progressive aphasia. High total tau similarly predicted faster progression in nonfluent variant primary progressive aphasia. In behavioral variant frontotemporal dementia, higher phosphorylated tau181predicted faster clinical progression whereas lower amyloid beta1‐42predicted faster volumetric and fractional anisotropy reduction. Neurofilament light chain and phosphorylated tau181were of greater predictive value in patients with tau pathology as compared toTDP‐43 pathology. Baseline neurofilament light chain correlated with baseline clinical severity and frontotemporal volume in behavioral variant frontotemporal dementia. Baseline total tau correlated with baseline clinical severity in semantic variant primary progressive aphasia.InterpretationHigh cerebrospinal fluid neurofilament light chain predicts more aggressive disease in behavioral variant frontotemporal dementia and nonfluent variant primary progressive aphasia. Total tau, phosphorylated tau181, and amyloid beta1‐42also predict some measures of disease aggressiveness in frontotemporal dementia.

The TP53 tumor-suppressor gene is mutated in >50% of human tumors and Li-Fraumeni patients with germ line inactivation are predisposed to developing cancer. Here, we generated tp53 deleted zebrafish that spontaneously develop malignant peripheral nerve-sheath tumors, angiosarcomas, germ cell tumors, and an aggressive Natural Killer cell-like leukemia for which no animal model has been developed. Because the tp53 deletion was generated in syngeneic zebrafish, engraftment of fluorescent-labeled tumors could be dynamically visualized over time. Importantly, engrafted tumors shared gene expression signatures with predicted cells of origin in human tissue. Finally, we showed that tp53del/del enhanced invasion and metastasis in kRASG12D-induced embryonal rhabdomyosarcoma (ERMS), but did not alter the overall frequency of cancer stem cells, suggesting novel pro-metastatic roles for TP53 loss-of-function in human muscle tumors. In summary, we have developed a Li-Fraumeni zebrafish model that is amenable to large-scale transplantation and direct visualization of tumor growth in live animals.