Tyrosine Kinase Inhibition Activates Intratumoral γδ T Cells in Gastrointestinal Stromal Tumor.

γδ T cells are a rare but potent subset of T cells with pleiotropic functions. They commonly reside within tumors but the response of γδ T cells to tyrosine kinase inhibition is unknown. To address this, we studied a genetically engineered mouse model of gastrointestinal stromal tumor (GIST) driven by oncogenic Kit signaling that responds to the Kit inhibitor imatinib. At baseline, γδ T cells were antitumoral, as blockade of either γδ T-cell receptor or IL17A increased tumor weight and decreased antitumor immunity. However, imatinib therapy further stimulated intratumoral γδ T cells, as determined by flow cytometry and single-cell RNA sequencing (scRNA-seq). Imatinib expanded a highly activated γδ T-cell subset with increased IL17A production and higher expression of immune checkpoints and cytolytic effector molecules. Consistent with the mouse model, γδ T cells produced IL17A in fresh human GIST specimens, and imatinib treatment increased γδ T-cell gene signatures, as measured by bulk tumor RNA-seq. Furthermore, tumor γδ T cells correlated with survival in patients with GIST. Our findings highlight the interplay between tumor cell oncogene signaling and antitumor immune responses and identify γδ T cells as targets for immunotherapy in GIST.

Multiple intratumoral sources of kit ligand promote gastrointestinal stromal tumor.

Gastrointestinal stromal tumor (GIST) is the most common human sarcoma and is typically driven by a single mutation in the Kit or PDGFRA receptor. While highly effective, tyrosine kinase inhibitors (TKIs) are not curative. The natural ligand for the Kit receptor is Kit ligand (KitL), which exists in both soluble and membrane-bound forms. While KitL is known to stimulate human GIST cell lines in vitro, we used a genetically engineered mouse model of GIST containing a common human KIT mutation to investigate the intratumoral sources of KitL, importance of KitL during GIST oncogenesis, and contribution of soluble KitL to tumor growth in vivo. We discovered that in addition to tumor cells, endothelia and smooth muscle cells produced KitL in KitV558Δ/+ tumors, even after imatinib therapy. Genetic reduction of total KitL in tumor cells of KitV558Δ/+ mice impaired tumor growth in vivo. Similarly, genetic reduction of tumor cell soluble KitL in KitV558Δ/+ mice decreased tumor size. By RNA sequencing, quantitative PCR, and immunohistochemistry, KitL expression was heterogeneous in human GIST specimens. In particular, PDGFRA-mutant tumors had much higher KitL expression than Kit-mutant tumors, suggesting the benefit of Kit activation in the absence of mutant KIT. Serum KitL was higher in GIST patients with tumors resistant to imatinib and in those with tumors expressing more KitL RNA. Overall, KitL supports the growth of GIST at baseline and after imatinib therapy and remains a potential biomarker and therapeutic target.

Immunotherapy for GI Malignancies, Ready for Prime Time?

Gastrointestinal (GI) cancers include esophageal, gastric, pancreatic, hepatobiliary, and colorectal malignancies. Immunotherapy has proved to be an important treatment method for cancer, and its use for a wide range of GI malignancies has been evaluated recently. This article discusses the type and mechanism of various immunotherapies under investigation in GI cancer. The study also reviews recent clinical trials, with a particular focus on overall survival, and discusses their achievements and limitations. Immunotherapy has shown efficacy for microsatellite instability high colorectal cancer and some promise in some gastroesophageal junction and gastric cancers. Meanwhile, it has not been effective for pancreatic or neuroendocrine tumors. The identification of novel biomarkers likely will guide selection of therapy for individual patients. Nevertheless, immunotherapy for GI cancers is in its infancy, and many other classes of immune therapies are being developed besides anti-PD1 and anti-PDL1. Thus, although immunotherapy has not seen a dramatic advance to date, it still has great potential.

Tyrosine Kinase Inhibition Alters Intratumoral CD8+ T-cell Subtype Composition and Activity.

Targeted therapy with a tyrosine kinase inhibitor (TKI) such as imatinib is effective in treating gastrointestinal stromal tumor (GIST), but it is rarely curative. Despite the presence of a robust immune CD8+ T-cell infiltrate, combining a TKI with immune-checkpoint blockade (ICB) in advanced GIST has achieved only modest effects. To identify limitations imposed by imatinib on the antitumor immune response, we performed bulk RNA sequencing (RNA-seq), single-cell RNA-seq, and flow cytometry to phenotype CD8+ T-cell subsets in a genetically engineered mouse model of GIST. Imatinib reduced the frequency of effector CD8+ T cells and increased the frequency of naïve CD8+ T cells within mouse GIST, which coincided with altered tumor chemokine production, CD8+ T-cell recruitment, and reduced CD8+ T-cell intracellular PI3K signaling. Imatinib also failed to induce intratumoral T-cell receptor (TCR) clonal expansion. Consistent with these findings, human GISTs sensitive to imatinib harbored fewer effector CD8+ T cells but more naïve CD8+ T cells. Combining an IL15 superagonist (IL15SA) with imatinib restored intratumoral effector CD8+ T-cell function and CD8+ T-cell intracellular PI3K signaling, resulting in greater tumor destruction. Combination therapy with IL15SA and ICB resulted in the greatest tumor killing and maintained an effector CD8+ T-cell population in the presence of imatinib. Our findings highlight the impact of oncogene inhibition on intratumoral CD8+ T cells and support the use of agonistic T-cell therapy during TKI and/or ICB administration.

Pulling Back from the Brink: A Multi-Pronged Approach to Address General Surgery Resident Clinical Work Hour Adherence.

PURPOSE: The conflict between prioritizing education for surgical trainees, promoting trainee wellness, and maintaining optimal patient care has remained challenging since the introduction of the Accreditation Council for Graduate Medical Education (ACGME) work hour restrictions in 2003. There is still a dearth of research examining which interventions successfully enable duty hour adherence. This study assessed the impact of a combination of strategic interventions on improving clinical work hour adherence. METHODS: Monthly clinical work hour submission rates were assessed for all general surgery residents at a single university-based residency program over a 3-year period (2018-2021). Interventions targeted 3 domains and were implemented between academic years 2018 to 2019 (control) and 2020 to 2021 (intervention): 1) improving the accuracy and transparency of work hour reporting, 2) facilitating more timely interventions, and 3) structural scheduling changes. All 80-hour work week and continuous work hour violations were assessed. Findings were also compared to the corresponding ACGME Resident Survey results. RESULTS: There was no significant difference in the rate of monthly work hour submissions pre- and postintervention (78% vs 75%, p = 0.057). However, the number of total reported monthly violations decreased significantly (mean 13.8 vs 2.4, p < 0.01), including decreases in both 80-hour work week and continuous work hour violations (mean 4.7 vs 1.6, p < 0.001 and 9.1 vs 0.8, p < 0.001, respectively). Reported compliance also increased on the annual ACGME resident surveys, where 61% vs 95% of residents felt they were compliant with the 80-hour work week and 71% vs 95% felt they were compliant with the continuous work hours (2018-19 vs 2020-21). CONCLUSION: Innovative strategies addressing schedule changes, the culture of work hour reporting, and early intervention significantly decreased the number of duty hour violations at our institution. Reported resident compliance also improved based on ACGME Resident Survey data. These data may inform similar multifaceted approaches at other institutions to improve overall work hour adherence.

Molecular and Immunologic Techniques in a Genetically Engineered Mouse Model of Gastrointestinal Stromal Tumor.

Gastrointestinal stromal tumor (GIST) is the most common human sarcoma and is typically driven by a single mutation in the KIT receptor. Across tumor types, numerous mouse models have been developed in order to investigate the next generation of cancer therapies. However, in GIST, most in vivo studies use xenograft mouse models which have inherent limitations. Here, we describe an immunocompetent, genetically engineered mouse model of gastrointestinal stromal tumor harboring a KitV558Δ/+ mutation. In this model, mutant KIT, the oncogene responsible for most GISTs, is driven by its endogenous promoter leading to a GIST which mimics the histological appearance and immune infiltrate seen in human GISTs. Furthermore, this model has been used successfully to investigate both targeted molecular and immune therapies. Here, we describe the breeding and maintenance of a KitV558Δ/+ mouse colony. Additionally, this paper details the treatment and procurement of GIST, draining mesenteric lymph node, and adjacent cecum in KitV558Δ/+ mice, as well as sample preparation for molecular and immunologic analyses.

Hiatal Hernia after Esophagectomy: An Underappreciated Complication?

BACKGROUND: The natural history of hiatal herniation of small and/or large bowel post-esophagectomy (HHBPE) in the current era of improving long-term survival and evolving surgical technique is unknown. The aim of this study was to describe the rate and risk factors of HHBPE at our hospital. METHODS: Patients undergoing esophagectomy between January 2011 and June 2017 were included if both follow-up information and axial imaging were available beyond 3 months post-esophagectomy. Patient characteristics, disease information, and treatment factors were all included in univariate analysis comparing patients with and without HHBPE, and multivariate regression was used to identify significant independent risk factors associated with HHBPE. RESULTS: Of 310 esophagectomy patients analyzed, 258 patients were included in the study, with 79 patients (31%) showing evidence of an HHBPE and an overall median follow-up of 24 months; 44 of 79 patients (56%) had symptoms possibly referable to HHBPE and 17 of 79 patients (22%) underwent surgical repair. On univariate analysis, neoadjuvant therapy (n = 176), higher clinical stage, minimally invasive approach (n = 154), and transhiatal esophagectomy (n = 189) were significant predictors of HHBPE (p < 0.05). On multivariate analysis, neoadjuvant therapy and transhiatal approach remained significant independent predictors (p < 0.05). The rate of HHBPE was 44% in the 131 patients (51%) that had both factors. CONCLUSIONS: HHBPE in the current era of neoadjuvant therapy and minimally invasive esophagectomy is common. HHBPE can cause gastrointestinal symptoms, but operation to repair HHBPE is uncommon on intermediate follow-up. Additional study and long-term follow-up are required to fully assess the impact of HHBPE and to potentially modify surgical practice to prevent or minimize HHBPE.

Relationship between age and likelihood of lymph node metastases in patients with intermediate thickness melanoma (1.01-4.00 mm): A National Cancer Database study.

BACKGROUND: There is large variability in the risk of sentinel lymph node (SLN) positivity among patients with intermediate thickness melanoma (ITM), with a subgroup of patients exhibiting a low risk of nodal disease. OBJECTIVE: To identify a group of patients with ITM for whom the risk of nodal disease is low. METHODS: A retrospective cohort of patients with ITM who underwent wide excision and nodal evaluation from 2010 to 2013 was identified by using the National Cancer Database and analyzed for the presence of nodal disease. Classification and regression tree analysis identified the most important factors used in a model to identify groups at low risk of SLN positivity. RESULTS: Of 23,440 patients, 14.7% were found to have nodal metastasis. On classification and regression tree analysis, patients older than 55 years without lymphovascular invasion and with a lesion thickness less than 1.7 mm had an SLN positivity rate of 4.9%. A model using age and thickness in nonulcerated patients identified a low-risk subgroup with a corresponding SLN positivity rate of 4.7%. LIMITATIONS: This was a retrospective study, and the model developed requires prospective validation. CONCLUSIONS: Patient age is an important factor in estimating risk of SLN in patients with ITM and may help identify patients without ulceration who may be safely spared an SLN biopsy.

Laparoscopic Heller Myotomy vs Per Oral Endoscopic Myotomy: Patient-Reported Outcomes at a Single Institution.

BACKGROUND: Although laparoscopic Heller myotomy (LHM) has been the standard of care for achalasia, per oral endoscopic myotomy (POEM) has gained popularity as a viable alternative. This retrospective study aimed to compare patient-reported outcomes between LHM and POEM in a consecutive series of achalasia patients with more than 1 year of follow-up. STUDY DESIGN: We reviewed demographic and procedure-related data for patients who underwent either LHM or POEM for achalasia between January 2011 and May 2016. Phone interviews were conducted assessing post-procedure achalasia symptoms via the Eckardt score and achalasia severity questionnaire (ASQ). Demographics, disease factors, and survey results were compared between LHM and POEM patients using univariate analysis. Significant predictors of procedure failure were analyzed using univariate and multivariate analysis. RESULTS: There were no serious complications in 110 consecutive patients who underwent LHM or POEM during the study period, and 96 (87%) patients completed phone surveys. There was a nonsignificant trend toward better patient-reported outcomes with POEM. There were significant differences in patient characteristics including sex, achalasia type, mean residual lower esophageal pressure (rLESP), and follow-up time. The only univariate predictors of an unsatisfactory Eckardt score or ASQ were longer follow-up and lower rLESP, with follow-up length being the only predictor on multivariate analysis. CONCLUSIONS: There were significant demographic and clinical differences in patient selection for POEM vs LHM in our group. Although the 2 procedures have similar patient-reported effectiveness, subjective outcomes seem to decline as a result of time rather than procedure type.