CDKN2A-p16 Deletion and Activated KRASG12D Drive Barrett's-Like Gland Hyperplasia-Metaplasia and Synergize in the Development of Dysplasia Precancer Lesions

BACKGROUND & AIMS

Barrett's esophagus is the precursor of esophageal dysplasia and esophageal adenocarcinoma. CDKN2A-p16 deletions were reported in 34%-74% of patients with Barrett's esophagus who progressed to dysplasia and esophageal adenocarcinoma, suggesting that p16 loss may drive neoplastic progression. KRAS activation frequently occurs in esophageal adenocarcinoma and precancer lesions. LGR5+ stem cells in the squamocolumnar-junction (SCJ) of mouse stomach contribute as Barrett's esophagus progenitors. We aimed to determine the functional effects of p16 loss and KRAS activation in Barrett's-like metaplasia and dysplasia development.

METHODS

We established mouse models with conditional knockout of CDKN2A-p16 (p16KO) and/or activated KRASG12D expression targeting SCJ LGR5+ cells in interleukin 1b transgenic mice and characterized histologic alterations (mucous-gland hyperplasia/metaplasia, inflammation, and dysplasia) in mouse SCJ. Gene expression was determined by microarray, RNA sequencing, and immunohistochemistry of SCJ tissues and cultured 3-dimensional organoids.

RESULTS

p16KO mice exhibited increased mucous-gland hyperplasia/metaplasia versus control mice (P = .0051). Combined p16KO+KRASG12D resulted in more frequent dysplasia and higher dysplasia scores (P = .0036), with 82% of p16KO+KRASG12D mice developing high-grade dysplasia. SCJ transcriptome analysis showed several activated pathways in p16KO versus control mice (apoptosis, tumor necrosis factor-α/nuclear factor-kB, proteasome degradation, p53 signaling, MAPK, KRAS, and G1-to-S transition).

CONCLUSIONS

p16 deletion in LGR5+ cell precursors triggers increased SCJ mucous-gland hyperplasia/metaplasia. KRASG12D synergizes with p16 deletion resulting in higher grades of SCJ glandular dysplasia, mimicking Barrett's high-grade dysplasia. These genetically modified mouse models establish a functional role of p16 and activated KRAS in the progression of Barrett's-like lesions to dysplasia in mice, representing an in vivo model of esophageal adenocarcinoma precancer. Derived 3-dimensional organoid models further provide in vitro modeling opportunities of esophageal precancer stages.

Erythrophagocytosis is not a reproducible finding in liver biopsies, and is not associated with clinical diagnosis of hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a rare disease with high mortality. Liver involvement is common (based on elevated liver function tests) with most patients demonstrating acute hepatitis. Liver biopsies are frequently obtained in the setting of suspected HLH for the purpose of identification of erythrophagocytosis, and if present, this finding is thought to suggest or support the diagnosis of HLH. However, there are problems with this approach; in particular, we do not know whether this finding is reproducible or whether it is specific to HLH. Therefore, we conducted a multi-institutional study in which experienced liver pathologists reviewed images taken from liver biopsies from patients with normal liver, acute hepatitis, possible HLH, and clinical HLH to determine if there was agreement about the presence or absence of erythrophagocytosis, and to ascertain whether the finding corresponds to a clinical diagnosis of HLH. Twelve liver pathologists reviewed 141 images in isolation (i.e., no clinical information or diagnosis provided). These came from 32 patients (five normal, 17 acute hepatitis, six HLH, four possible HLH). The pathologists classified each image as negative, equivocal, or positive for erythrophagocytosis. Kappa was .08 (no agreement) for case-level and 0.1 for image-level (1.4% agreement, based on two images which were universally considered negative). There was no difference in the proportion of pathologists who diagnosed erythrophagocytosis among those with different diagnoses at case or image-level (p = 0.82 and p = 0.82, respectively). Thus, erythrophagocytosis is an entirely unreliable histologic parameter in liver, as it is irreproducible and not demonstrably associated with a clinical disease (namely, HLH). Unless and until more reliable guidelines can be established, pathologists should refrain from commenting on the presence or absence of erythrophagocytosis in liver biopsy.

Chemotherapy and Immune Checkpoint Blockade for Gastric and Gastroesophageal Junction Adenocarcinoma

Importance

Combining immune checkpoint blockade (ICB) with chemotherapy improves outcomes in patients with metastatic gastric and gastroesophageal junction (G/GEJ) adenocarcinoma; however, whether this combination has activity in the perioperative setting remains unknown.

Objective

To evaluate the safety and preliminary activity of perioperative chemotherapy and ICB followed by maintenance ICB in resectable G/GEJ adenocarcinoma.

Design, Setting, and Participants

This investigator-initiated, multicenter, open-label, single-stage, phase 2 nonrandomized controlled trial screened 49 patients and enrolled 36 patients with resectable G/GEJ adenocarcinoma from February 10, 2017, to June 17, 2021, with a median (range) follow-up of 35.2 (17.4-73.0) months. Thirty-four patients were deemed evaluable for efficacy analysis, with 28 (82.4%) undergoing curative resection. This study was performed at 4 referral institutions in the US.

Interventions

Patients received 3 cycles of capecitabine, 625 mg/m2, orally twice daily for 21 days; oxaliplatin, 130 mg/m2, intravenously and pembrolizumab, 200 mg, intravenously with optional epirubicin, 50 mg/m2, every 3 weeks before and after surgery with an additional cycle of pembrolizumab before surgery. Patients received 14 additional doses of maintenance pembrolizumab.

Main Outcomes and Measures

The primary end point was pathologic complete response (pCR) rate. Secondary end points included overall response rate, disease-free survival (DFS), overall survival (OS), and safety.

Results

A total of 34 patients (median [range] age, 65.5 [25-90] years; 23 [67.6%] male) were evaluable for efficacy. Of these patients, 28 (82.4%) underwent curative resection, 7 (20.6%; 95% CI, 10.1%-100%) achieved pCR, and 6 (17.6%) achieved a pathologic near-complete response. Of the 28 patients who underwent resection, 4 (14.3%) experienced disease recurrence. The median DFS and OS were not reached. The 2-year DFS was 67.8% (95% CI, 0.53%-0.87%) and the OS was 80.6% (95% CI, 0.68%-0.96%). Treatment-related grade 3 or higher adverse events for evaluable patients occurred in 20 patients (57.1%), and 12 (34.3%) experienced immune-related grade 3 or higher adverse events.

Conclusion and Relevance

In this trial of unselected patients with resectable G/GEJ adenocarcinoma, capecitabine, oxaliplatin, and pembrolizumab resulted in a pCR rate of 20.6% and was well tolerated. This trial met its primary end point and supports the development of checkpoint inhibition in combination with perioperative chemotherapy in locally advanced G/GEJ adenocarcinoma.

Trial Registration

ClinicalTrials.gov Identifier: NCT02918162.

A 52-Year-Old Man With Chest Pain and Dyspnea

CASE PRESENTATION

A 52-year-old man came to the cardiac surgery clinic for pulmonary thromboendarterectomy (PTE) evaluation. He had initially appeared at an outside hospital 1 year earlier, with chest pain and shortness of breath. He had no known chronic conditions. A CT pulmonary angiogram (CTPA) at that time showed a filling defect at the bifurcation of the main pulmonary artery. A transthoracic echocardiogram revealed mild mitral valve regurgitation, but otherwise the results were normal. As he was hemodynamically stable and not hypoxemic, he was treated solely by anticoagulation. Despite adhering to prescribed apixaban, he developed progressive dyspnea and reduced exercise tolerance over the subsequent year. A repeat CTPA performed 12 months after the initial presentation showed a persistent filling defect at the level of the pulmonary artery bifurcation, with a new extension now completely occluding the right main pulmonary artery. A pulmonary angiogram confirmed this complete occlusion, and right heart catheterization revealed precapillary pulmonary hypertension, with a mean pulmonary artery pressure of 50 mm Hg. His anticoagulation was transitioned to enoxaparin for presumed apixaban treatment failure, and an investigation for hypercoagulable conditions was initiated. His lupus anticoagulant test result was positive, but he did not meet the criteria for antiphospholipid syndrome because he was negative for anticardiolipin and β2-glycoprotein antibodies. Assays for antithrombin III, protein C, prothrombin gene, and factor V Leiden mutations produced normal results.

Abstract CT009: Phase II trial of perioperative pembrolizumab plus capecitabine and oxaliplatin followed by adjuvant pembrolizumab for resectable gastric and gastroesophageal junction (GC/GEJ) adenocarcinoma

Background: Perioperative therapy for locally advanced (LA) GC/GEJ adenocarcinoma is standard of care. Although immune checkpoint blockade (ICB) following chemoradiotherapy and resection significantly improves disease free survival (DFS) for esophageal cancer, the effectiveness of ICB together with chemotherapy in LA GC/GEJ cancer is unknown.

Methods: This is a multicenter, single-arm, phase II clinical trial of pembrolizumab 200 mg every 3 weeks with capecitabine 625 mg/m2 twice daily and oxaliplatin 130 mg/m2 every 3 weeks (CAPOX) in patients with resectable GC/GEJ adenocarcinoma. Subjects with ECOG PS of 0-1 received CAPOX with pembrolizumab for 3 cycles prior to and 3 cycles following surgery with an additional cycle of pembrolizumab just prior to surgery and 12 months of maintenance pembrolizumab following adjuvant chemoimmunotherapy. The primary endpoint was pathologic complete response (pCR) rate. The study had 80% power to detect an increase in pCR rate from 3% to 15% with a one-sided alpha of 0.05. Secondary endpoints included overall response rate, DFS, and overall survival (OS). This study was registered with ClinicalTrials.gov (NCT02918162).

Results: Between 02/10/2017 and 06/17/2021, 36 patients were enrolled with 34 (21 gastric and 13 GEJ) evaluable for efficacy. The median age was 65 years and 17 (50%) patients had an ECOG PS of 1. In total, 29 (85%) patients underwent resection. Seven patients achieved a pCR (20.6% of evaluable patients and 24.1% of those who underwent resection). An additional 6 (17.6%) patients achieved a near CR and 8 (23.5%) demonstrated a significant treatment effect on pathologic review. One patient was deemed unfit for surgery, 2 expired prior to surgery, and 2 were found to have metastatic disease during surgery. At the time of data cut-off, the median follow-up was 19 mo. Of those who underwent resection, 4 (13.7%) experienced disease recurrence and 5 (17.2%) expired. The probability of survival at 1 and 2 years was 0.91 (0.82-1.0) and 0.80 (0.64-0.99), respectively. The median DFS and OS have not been reached. Of the 35 patients who received treatment, treatment related adverse events (AEs) of grade greater than or equal to 3 were reported in 18 (51%) patients. Grade greater than or equal to 3 immune-related AEs were reported in 10 (29%) patients. Three grade 5 AEs occurred, two possibly treatment-related (gastric hemorrhage and gastric perforation) and one unrelated to treatment (cardiac arrest).

Conclusion: In LA GC/GEJ adenocarcinoma, the combination CAPOX and pembrolizumab resulted in a pCR rate of 20.6%. The combination was well tolerated and 85.3% of patients underwent surgical resection. This trial met its primary endpoint supporting further investigation of this regimen as an alternative for patients who are unlikely to tolerate triple combination chemotherapy. Correlative studies are in progress.

Citation Format: Alexander Grenander Raufi, Shing Lee, Michael May, Armando Del Portillo, Naomi Sender, Sarah Sta Ana, Katarzyna Gautier, Emily Alouani, Haeseong Park, Paul Oberstein, Manish Shah, Gulam A. Manji. Phase II trial of perioperative pembrolizumab plus capecitabine and oxaliplatin followed by adjuvant pembrolizumab for resectable gastric and gastroesophageal junction (GC/GEJ) adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT009.

Multiplexed single-cell analysis reveals prognostic and nonprognostic T cell types in human colorectal cancer

Clinical outcomes in colorectal cancer (CRC) correlate with T cell infiltrates, but the specific contributions of heterogenous T cell types remain unclear. To investigate the diverse function of T cells in CRC, we profiled 37,931 T cells from tumors and adjacent normal colon of 16 patients with CRC with respect to transcriptome, TCR sequence, and cell surface markers. Our analysis identified phenotypically and functionally distinguishable effector T cell types. We employed single-cell gene signatures from these T cell subsets to query the TCGA database to assess their prognostic significance. We found 2 distinct cytotoxic T cell types. GZMK+KLRG1+ cytotoxic T cells were enriched in CRC patients with good outcomes. GNLY+CD103+ cytotoxic T cells with a dysfunctional phenotype were not associated with good outcomes, despite coexpression of CD39 and CD103, markers that denote tumor reactivity. We found 2 distinct Treg subtypes associated with opposite outcomes. While total Tregs were associated with good outcomes, CD38+ Tregs were associated with bad outcomes independently of stage and possessed a highly suppressive phenotype, suggesting that they inhibit antitumor immunity in CRC. These findings highlight the potential utility of these subpopulations in predicting outcomes and support the potential for novel therapies directed at CD38+ Tregs or CD8+CD103+ T cells.

Doxycycline-induced cholestatic liver injury

Doxycycline-induced liver injury is a rare phenomenon, with an unclear clinical course and etiopathogenesis. The onset of injury may be acute-to-subacute, with a pattern ranging from hepatocellular or cholestatic to mixed, and it often lasts up to several weeks. We present a case of cholestatic liver injury secondary to doxycycline use in a middle-aged woman. In patients with a history of doxycycline exposure and subsequent hepatic injury, an adverse drug reaction due to doxycycline should remain on the differential, and immediate removal of the offending agent with close monitoring of the clinical condition should be pursued.

A molecular single-cell lung atlas of lethal COVID-19

Respiratory failure is the leading cause of death in patients with severe SARS-CoV-2 infection^1,2, but the host response at the lung tissue level is poorly understood. Here we performed single-nucleus RNA sequencing of about 116,000 nuclei from the lungs of nineteen individuals who died of COVID-19 and underwent rapid autopsy and seven control individuals. Integrated analyses identified substantial alterations in cellular composition, transcriptional cell states, and cell-to-cell interactions, thereby providing insight into the biology of lethal COVID-19. The lungs from individuals with COVID-19 were highly inflamed, with dense infiltration of aberrantly activated monocyte-derived macrophages and alveolar macrophages, but had impaired T cell responses. Monocyte/macrophage-derived interleukin-1β and epithelial cell-derived interleukin-6 were unique features of SARS-CoV-2 infection compared to other viral and bacterial causes of pneumonia. Alveolar type 2 cells adopted an inflammation-associated transient progenitor cell state and failed to undergo full transition into alveolar type 1 cells, resulting in impaired lung regeneration. Furthermore, we identified expansion of recently described CTHRC1⁺ pathological fibroblasts³ contributing to rapidly ensuing pulmonary fibrosis in COVID-19. Inference of protein activity and ligand-receptor interactions identified putative drug targets to disrupt deleterious circuits. This atlas enables the dissection of lethal COVID-19, may inform our understanding of long-term complications of COVID-19 survivors, and provides an important resource for therapeutic development.

Invasive carcinoma versus pseudoinvasion: interobserver variability in the assessment of left-sided colorectal polypectomies

OBJECTIVES

Misplaced epithelium in adenomas can occasionally be difficult to distinguish from invasive adenocarcinoma. We evaluated interobserver variability in the assessment of left-sided colon polypectomies for pseudoinvasion versus invasive adenocarcinoma and further investigated relevant histological findings.

METHODS

28 consecutive left-sided colon polyps with the keywords "pseudoinvasion", "epithelial misplacement", "herniation", "prolapse" or "invasive adenocarcinoma" were collected from 28 patients and reviewed by eight gastrointestinal pathologists. Participants assessed stromal hemosiderin, lamina propria/eosinophils surrounding glands, desmoplasia, high grade dysplasia/intramucosal adenocarcinoma and margin status and rendered a diagnosis of pseudoinvasion, invasive adenocarcinoma, or both.

RESULTS

Agreement among pathologists was substantial for desmoplasia (κ=0.70), high grade dysplasia/intramucosal adenocarcinoma (κ=0.66), invasive adenocarcinoma (κ=0.63) and adenocarcinoma at the margin (κ=0.65). There was moderate agreement for hemosiderin in stroma (κ=0.53) and prolapse/pseudoinvasion (κ=0.50). Agreement was low for lamina propria/eosinophils around glands (κ=0.12). For invasive adenocarcinoma, seven or more pathologists agreed in 24 of 28 cases (86%), and there was perfect agreement in 19/28 cases (68%). For pseudoinvasion, seven or more pathologists agreed in 19 of 28 cases (68%), and there was perfect agreement in 16/28 cases (57%).

CONCLUSION

Moderate to substantial, though imperfect, agreement was achieved in the distinction of pseudoinvasion from invasive carcinoma.

Randomized Controlled Trial of the Gastrin/CCK2 Receptor Antagonist Netazepide in Patients with Barrett's Esophagus

Hypergastrinemia has been associated with high-grade dysplasia and adenocarcinoma in patients with Barrett's esophagus, and experimental studies suggest proinflammatory and proneoplastic effects of gastrin on Barrett's esophagus. This is of potential concern, as patients with Barrett's esophagus are treated with medications that suppress gastric acid production, resulting in increased physiologic levels of gastrin. We aimed to determine whether treatment with the novel gastrin/CCK₂ receptor antagonist netazepide reduces expression of markers associated with inflammation and neoplasia in Barrett's esophagus. This was a randomized, double-blind, placebo-controlled trial of netazepide in patients with Barrett's esophagus without dysplasia. Subjects were treated for 12 weeks, with endoscopic assessment at baseline and at end of treatment. The primary outcome was within-individual change in cellular proliferation as assessed by Ki67. Secondary analyses included changes in gene expression, assessed by RNA-sequencing, and safety and tolerability. A total of 20 subjects completed the study and were included in the analyses. There was no difference between arms in mean change in cellular proliferation (netazepide: +35.6 Ki67+ cells/mm², SD 620.7; placebo: +307.8 Ki67+ cells/mm², SD 640.3; P = 0.35). Netazepide treatment resulted in increased expression of genes related to gastric phenotype (TFF2, MUC5B) and certain cancer-associated markers (REG3A, PAX9, MUC1), and decreased expression of intestinal markers MUC2, FABP1, FABP2, and CDX1 No serious adverse events related to study drug occurred. The gastrin/CCK₂ receptor antagonist netazepide did not reduce cellular proliferation in patients with nondysplastic Barrett's esophagus. Further research should focus on the biological effects of gastrin in Barrett's esophagus.Prevention Relevance: Treatment of patients with Barrett's esophagus with a gastrin/CCK₂ receptor antagonist did not have obvious chemopreventive effects.

PD-1 Signaling Promotes Tumor-Infiltrating Myeloid-Derived Suppressor Cells and Gastric Tumorigenesis in Mice

BACKGROUND & AIMS

Immune checkpoint inhibitors have limited efficacy in many tumors. We investigated mechanisms of tumor resistance to inhibitors of programmed cell death-1 (PDCD1, also called PD-1) in mice with gastric cancer, and the role of its ligand, PD-L1.

METHODS

Gastrin-deficient mice were given N-methyl-N-nitrosourea (MNU) in drinking water along with Helicobacter felis to induce gastric tumor formation; we also performed studies with H/K-ATPase-hIL1B mice, which develop spontaneous gastric tumors at the antral-corpus junction and have parietal cells that constitutively secrete interleukin 1B. Mice were given injections of an antibody against PD-1 or an isotype control before tumors developed, or anti-PD-1 and 5-fluorouracil and oxaliplatin, or an antibody against lymphocyte antigen 6 complex locus G (also called Gr-1), which depletes myeloid-derived suppressor cells [MDSCs]), after tumors developed. We generated knock-in mice that express PD-L1 specifically in the gastric epithelium or myeloid lineage.

RESULTS

When given to gastrin-deficient mice before tumors grew, anti-PD-1 significantly reduced tumor size and increased tumor infiltration by T cells. However, anti-PD-1 alone did not have significant effects on established tumors in these mice. Neither early nor late anti-PD-1 administration reduced tumor growth in the presence of MDSCs in H/K-ATPase-hIL-1β mice. The combination of 5-fluorouracil and oxaliplatin reduced MDSCs, increased numbers of intra-tumor CD8⁺ T cells, and increased the response of tumors to anti-PD-1; however, this resulted in increased tumor expression of PD-L1. Expression of PD-L1 by tumor or immune cells increased gastric tumorigenesis in mice given MNU. Mice with gastric epithelial cells that expressed PD-L1 did not develop spontaneous tumors, but they developed more and larger tumors after administration of MNU and H felis, with accumulation of MDSCs.

CONCLUSIONS

In mouse models of gastric cancer, 5-fluorouracil and oxaliplatin reduce numbers of MDSCs to increase the effects of anti-PD-1, which promotes tumor infiltration by CD8⁺ T cells. However, these chemotherapeutic agents also induce expression of PD-L1 by tumor cells. Expression of PD-L1 by gastric epithelial cells increases tumorigenesis in response to MNU and H felis, and accumulation of MDSCs, which promote tumor progression. The timing and site of PD-L1 expression is therefore important in gastric tumorigenesis and should be considered in design of therapeutic regimens.

SATB2 in Neoplasms of Lung, Pancreatobiliary, and Gastrointestinal Origins

OBJECTIVES

Special AT-rich binding protein 2 (SATB2) immunohistochemistry (IHC) has high sensitivity and specificity for colorectal adenocarcinoma (CRC), but data on its expression in specific subsets of pulmonary, gastric, small bowel, and pancreatobiliary adenocarcinomas (ADCAs) are relatively limited or discordant. We assessed SATB2 expression in a large cohort of ADCAs from these sites to determine its reliability in distinguishing CRC from them.

METHODS

SATB2 IHC was performed on 335 neoplasms, including 40 lung ADCAs, 165 pancreatobiliary neoplasms (34 intraductal papillary mucinous neoplasms [IPMNs], 19 pancreatic ADCAs, 112 cholangiocarcinomas [CCs]), and 35 gastric, 13 small bowel, 36 ampullary (AMP), and 46 CRC ADCAs. The cases were evaluated for positivity (defined as ≥5% nuclear staining), and an H-score was calculated based on the percentage of SATB2+ cells and staining intensity. Analysis was performed to determine the optimal H-score threshold to separate CRC and non-CRC.

RESULTS

SATB2 was positive in 3% of lung, 2% of CC, 17% of gastric, 38% of small bowel, and 6% of AMP ADCAs. All pancreatic ADCA/IPMNs were negative, and 87% CRCs were positive.

CONCLUSIONS

SATB2 is not entirely specific for colorectal origin and can be expressed in a subset of gastrointestinal ADCAs. It is most useful in the differential of CRC vs lung and pancreatobiliary ADCAs.

Neuronophagia and microglial nodules in a SARS-CoV-2 patient with cerebellar hemorrhage

We document the neuropathologic findings of a 73-year old man who died from acute cerebellar hemorrhage in the context of relatively mild SARS-CoV2 infection. The patient developed sudden onset of headache, nausea, and vomiting, immediately followed by loss of consciousness on the day of admission. Emergency medical services found him severely hypoxemic at home, and the patient suffered a cardiac arrest during transport to the emergency department. The emergency team achieved return of spontaneous circulation after over 17 min of resuscitation. A chest radiograph revealed hazy bilateral opacities; and real-time-PCR for SARS-CoV-2 on the nasopharyngeal swab was positive. Computed tomography of the head showed a large right cerebellar hemorrhage, with tonsillar herniation and intraventricular hemorrhage. One day after presentation, he was transitioned to comfort care and died shortly after palliative extubation. Autopsy performed 3 h after death showed cerebellar hemorrhage and acute infarcts in the dorsal pons and medulla. Remarkably, there were microglial nodules and neuronophagia bilaterally in the inferior olives and multifocally in the cerebellar dentate nuclei. This constellation of findings has not been reported thus far in the context of SARS-CoV-2 infection.

Radiomics of MRI for pretreatment prediction of pathologic complete response, tumor regression grade, and neoadjuvant rectal score in patients with locally advanced rectal cancer undergoing neoadjuvant chemoradiation: an international multicenter study

OBJECTIVE

To investigate whether pretreatment MRI-based radiomics of locally advanced rectal cancer (LARC) and/or the surrounding mesorectal compartment (MC) can predict pathologic complete response (pCR), neoadjuvant rectal (NAR) score, and tumor regression grade (TRG).

METHODS

One hundred thirty-two consecutive patients with LARC who underwent neoadjuvant chemoradiation and total mesorectal excision (TME) were retrospectively collected from 2 centers in the USA and Italy. The primary tumor and surrounding MC were segmented on the best available T2-weighted sequence (axial, coronal, or sagittal). Three thousand one hundred ninety radiomic features were extracted using a python package. The most salient radiomic features as well as MRI parameter and clinical-based features were selected using recursive feature elimination. A logistic regression classifier was built to distinguish between any 2 binned categories in the considered endpoints: pCR, NAR, and TRG. Repeated k-fold validation was performed and AUCs calculated.

RESULTS

There were 24, 87, and 21 T4, T3, and T2 LARCs, respectively (median age 63 years, 32 to 86). For NAR and TRG, the best classification performance was obtained using both the tumor and MC segmentations. The AUCs for classifying NAR 0 versus 2, pCR, and TRG 0/1 versus 2/3 were 0.66 (95% CI, 0.60-0.71), 0.80 (95% CI, 0.74-0.85), and 0.80 (95% CI, 0.77-0.82), respectively.

CONCLUSION

Radiomics of pretreatment MRIs can predict pCR, TRG, and NAR score in patients with LARC undergoing neoadjuvant treatment and TME with moderate accuracy despite extremely heterogenous image data. Both the tumor and MC contain important prognostic information.

KEY POINTS

• Machine learning of rectal cancer on images from the pretreatment MRI can predict important patient outcomes with moderate accuracy. • The tumor and the tissue around it both contain important prognostic information.

Low Frequency of Lymph Node Metastases in Patients in the United States With Early-stage Gastric Cancers That Fulfill Japanese Endoscopic Resection Criteria

BACKGROUND & AIMS

In the West, early gastric cancer is increasingly managed with endoscopic resection (ER). This is, however, based on the assumption that the low prevalence and risk of lymph node metastases observed in Asian patients is applicable to patients in the United States. We sought to evaluate the frequency of and factors associated with metastasis of early gastric cancers to lymph nodes, and whether the Japanese ER criteria are applicable to patients in the US.

METHODS

We performed a retrospective study of 176 patients (mean age 68.5 years; 59.1% male; 58.5% white) who underwent surgical resection with lymph node dissection of T1 and Tis gastric adenocarcinomas, staged by pathologists, at 7 tertiary care centers in the US from January 1, 1999, through December 31, 2016. The frequency of lymph node metastases and associated risk factors were determined.

RESULTS

The mean size of gastric adenocarcinomas was 23.0 ± 16.6 mm-most were located in the lower-third of the stomach (67.0%), invading the submucosa (55.1%), and moderately differentiated (31.3%). Lymphovascular invasion was observed in 18.2% of lesions. Overall, 20.5% of patients had lymph node metastases. Submucosal invasion (odds ratio, 3.9; 95% CI, 1.4-10.7) and lymphovascular invasion (odds ratio, 4.6; 95% CI, 1.8-12.0) were independently associated with increased risk of metastasis to lymph nodes. The frequency of lymph node metastases among patients fulfilling standard and expanded Japanese criteria for ER were 0 and 7.5%, respectively.

CONCLUSIONS

The frequency of lymph node metastases among patients with early gastric cancer in a US population is higher than that of published Asian series. However, early gastric cancer lesions that meet the Japanese standard criteria for ER are associated with negligible risk of metastasis to lymph nodes, so ER can be recommended for definitive therapy. Expanded criteria cancers appear to have a higher risk of metastasis to lymph nodes, so ER may be considered for select cases.

Downregulation of Friend Leukemia Integration 1 (FLI1) follows the stepwise progression to gastric adenocarcinoma

Gastric adenocarcinoma (GC) is a leading cause of cancer-related deaths worldwide. The transcription factor gene Friend Leukemia Integration 1 (FLI1) is methylated and downregulated in human GC tissues. Using human GC samples, we determined which cells downregulate FLI1, when FLI1 downregulation occurs, if FLI1 downregulation correlates with clinical-pathologic characteristics, and whether FLI1 plays a role in invasion and/or proliferation of cultured cells. We analyzed stomach tissues from 98 patients [8 normal mucosa, 8 intestinal metaplasia (IM), 7 dysplasia, 91 GC] by immunohistochemistry for FLI1. Epithelial cells from normal, IM, and low-grade dysplasia (LGD) showed strong nuclear FLI1 staining. GC epithelial cells showed significantly less nuclear FLI1 staining as compared to normal epithelium, IM and LGD (P=1.2×10^-5, P=1.4×10^-6 and P=0.006, respectively). FLI1 expression did not correlate with tumor stage or differentiation, but was associated with patient survival, depending on tumor differentiation. We tested the functional role of FLI1 by assaying proliferation and invasion in cultured GC cells. Lentiviral-transduced FLI1 overexpression in GC AGS cells inhibited invasion by 73.5% (P = 0.001) and proliferation by 31.5% (P = 0.002), as compared to controls. Our results support a combined role for FLI1 as a suppressor of invasiveness and proliferation in gastric adenocarcinoma, specifically in the transition from pre-cancer lesions and dysplasia to invasive adenocarcinoma, and suggest that FLI1 may be a prognostic biomarker of survival in gastric cancers.

High-resolution genomic alterations in Barrett's metaplasia of patients who progress to esophageal dysplasia and adenocarcinoma

The main risk factor for esophageal dysplasia and adenocarcinoma (DAC) is Barrett's esophagus (BE), characterized by intestinal metaplasia. The critical genomic mechanisms that lead to progression of nondysplastic BE to DAC remain poorly understood and require analyses of longitudinal patient cohorts and high-resolution assays. We tested BE tissues from 74 patients, including 42 nonprogressors from two separate groups of 21 patients each and 32 progressors (16 in a longitudinal cohort before DAC/preprogression-BE and 16 with temporally concurrent but spatially separate DAC/concurrent-BE). We interrogated genome-wide somatic copy number alterations (SCNAs) at the exon level with high-resolution SNP arrays in DNA from formalin-fixed samples histologically confirmed as nondysplastic BE. The most frequent abnormalities were SCNAs involving FHIT exon 5, CDKN2A/B or both in 88% longitudinal BE progressors to DAC vs. 24% in both nonprogressor groups (p = 0.0004). Deletions in other genomic regions were found in 56% of preprogression-BE but only in one nonprogressor-BE (p = 0.0004). SCNAs involving FHIT exon 5 and CDKN2A/B were also frequently detected in BE temporally concurrent with DAC. TP53 losses were detected in concurrent-BE but not earlier in preprogression-BE tissues of patients who developed DAC. CDKN2A/p16 immunohistochemistry showed significant loss of expression in BE of progressors vs. nonprogressors, supporting the genomic data. Our data suggest a role for CDKN2A/B and FHIT in early progression of BE to dysplasia and adenocarcinoma that warrants future mechanistic research. Alterations in CDKN2A/B and FHIT by high-resolution assays may serve as biomarkers of increased risk of progression to DAC when detected in BE tissues.

Abstract 5532: Functional role of Friend Leukemia Integration-1 (FLI1) in gastric carcinogenesis

Gastric adenocarcinoma (GC) is the 5th most common cancer worldwide but is the 3rd leading cause of cancer death. FLI1 (Friend leukemia integration-1) is an ETS family transcription factor that regulates genes involved in proliferation and differentiation. FLI1 is implicated in tumorigenesis, such as in Ewing’s sarcoma where a translocation creates an EWS-FLI1 oncogenic fusion protein. However, few studies have examined the role of FLI1 in carcinomas. In human breast cancer, overexpression of FLI1 led to inhibition of apoptosis, thereby promoting survival and malignant potential. In functional studies in a murine breast cancer model, however, downregulation of FLI1 increased malignant potential. In human GCs, we recently reported that FLI1 expression is inversely correlated with its promoter CpG methylation of the FLI1.

To determine if decreased expression occurs in GC epithelial cells or background non-epithelial cells, we analyzed 91 human GC tumors by immunohistochemistry (IHC) for FLI1 and compared them to normal gastric mucosa and intestinal metaplasia (IM) using an IHC composite scoring system accounting for intensity and percentage of epithelial cells expressing FLI1. We found that FLI1 is strongly expressed in normal gastric glandular epithelium and in IM, and that decreased expression was seen in most human GCs (P < 1x10-17 vs normal, P < 1x10-26 vs IM). These findings suggest that FLI1 acts as a tumor suppressor gene in GC. To test this hypothesis, we used an invasion assay and the human GC cell lines NUGC3 and SNU638, which have little to no FLI1 expression, respectively. Cultured GC cells were transduced to overexpress FLI1 or control, along with an eGFP reporter from an IRES (Lv203, Genecopoeia). After selection by puromycin, these GC cells were plated in serum-free media in the upper chamber on a Matrigel coated 8µm pore opaque membrane. Complete media with 10% fetal calf serum was plated in the lower chamber. Images were obtained of the lower membrane with an inverted fluorescent microscope and cellSens imaging software. Overexpression of FLI1 significantly decreased invasion by NUGC3 cells at 24 hours (P = 0.013) but not at 48 hours (P = 0.268) as compared to control. Overexpression of FLI1 significantly decreased invasion by SNU638 cells at both 24 and 48 hours (P = 0.027 and 0.012, respectively) as compared to control. Since NUGC3 cells have low FLI1 expression, we knocked down FLI1 by using a FLI1 shRNA lentiviral system with mCherry from an IRES as a reporter (LvRU6MP, Genecopoeia). Using the same invasion assay, knockdown of FLI1 trended towards a significant increase in invasion as compared to control at 48 hrs (P = 0.14), but not at 24 hrs (P = 0.73).

In summary, the combined observations in human GC tissue samples and the functional analyses in GC cells support a tumor suppressor role for FLI1 in human GC and also suggest that FLI1 and/or its target genes may be involved in regulatory mechanisms driving invasive properties of GC.

Citation Format: Armando Del Portillo, Elena V. Komissarova, Anne Koehne de Gonzalez, Aqiba Bokhari, Helen Remotti, Jorge Sepulveda, Antonia Sepulveda. Functional role of Friend Leukemia Integration-1 (FLI1) in gastric carcinogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5532. doi:10.1158/1538-7445.AM2017-5532

Multiple Gastrointestinal Polyps in Patients Treated with BRAF Inhibitors

PURPOSE

BRAF inhibitors (BRAFi) extend survival in BRAF-mutant melanoma but can promote the growth of Ras-mutant neoplasms. This study determined if gastrointestinal polyps found in BRAFi-treated patients harbored Ras mutations.

EXPERIMENTAL DESIGN

Colonic and gastric polyps were identified and resected from BRAFi-treated melanoma patients. Next-generation sequencing (NGS) was performed on polyps. The ability of BRAFi to promote polyp formation was functionally characterized in Apc Min(+/-) mice. MAPK and β-catenin pathway activity was assessed by immunohistochemistry in mouse and human polyps.

RESULTS

Fourteen patients treated with BRAFi underwent endoscopy to assess for polyps. Seven out of 7 patients >40 years of age and treated for >2 years were found to have colonic tubular adenomas with 4 out of the 7 patients having 5 or more polyps. One patient presented with bleeding from hyperplastic gastric polyps that recurred 6 months after BRAFi rechallenge. NGS performed on polyps found no mutations in MAPK pathway genes, but found APC mutations in all tubular adenomas. A significant increase in the number of polyps was observed in BRAFi-treated compared with control-treated Apc Min(+/-) mice (20.8 ± 9.2 vs 12.8 ± 0.1; P = 0.016). No polyps were observed in BRAFi-treated wild-type mice.

CONCLUSIONS

BRAFi may increase the risk of developing hyperplastic gastric polyps and colonic adenomatous polyps. Due to the risk of gastrointestinal bleeding and the possibility of malignant transformation, further studies are needed to determine whether or not endoscopic surveillance should be recommended for patients treated with BRAFi.