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Purpose: There is increasing use of neoadjuvant chemotherapy in the management of localized pancreatic ductal adenocarcinoma (PDAC), yet there are few validated biomarkers to guide therapy selection. We aimed to determine whether somatic genomic biomarkers predict response to induction FOLFIRINOX or gemcitabine/nab-paclitaxel. Experimental Design: This single-institution cohort study included consecutive patients (N = 322) with localized PDAC (2011–2020) who received at least one cycle of FOLFIRINOX (N = 271) or gemcitabine/nab-paclitaxel (N = 51) as initial treatment. We assessed somatic alterations in four driver genes (KRAS, TP53, CDKN2A, and SMAD4) by targeted next-generation sequencing, and determined associations between these alterations and (1) rate of metastatic progression during induction chemotherapy, (2) surgical resection, and (3) complete/major pathologic response. Results: The alteration rates in driver genes KRAS, TP53, CDKN2A, and SMAD4 were 87.0%, 65.5%, 26.7%, and 19.9%, respectively. For patients receiving first-line FOLFIRINOX, SMAD4 alterations were uniquely associated with metastatic progression (30.0% vs. 14.5%; P = 0.009) and decreased rate of surgical resection (37.1% vs. 66.7%; P < 0.001). For patients receiving induction gemcitabine/nab-paclitaxel, alterations in SMAD4 were not associated with metastatic progression (14.3% vs. 16.2%; P = 0.866) nor decreased rate of surgical resection (33.3% vs. 41.9%; P = 0.605). Major pathologic response was rare (6.3%) and not associated with type of chemotherapy regimen. Conclusions: SMAD4 alterations were associated with more frequent development of metastasis and lower probability of reaching surgical resection during neoadjuvant FOLFIRINOX but not gemcitabine/nab-paclitaxel. Confirmation in a larger, diverse patient cohort will be important before prospective evaluation of SMAD4 as a genomic biomarker to guide treatment selection.

PURPOSE Appendiceal adenocarcinomas (ACs) are rare, histologically diverse malignancies treated as colorectal cancers despite having distinct biology and clinical behavior. To guide clinical decision making, we defined molecular subtypes of AC associated with patient survival, metastatic burden, and chemotherapy response. PATIENTS AND METHODS A comprehensive molecular analysis was performed in patients with AC to define molecular subtypes. Associations between molecular subtype and overall survival, intraoperative peritoneal cancer index, and first-line chemotherapy response were assessed adjusting for histopathologic and clinical variables using multivariable Cox proportional hazards, linear regression, and logistic regression models. RESULTS We defined distinct molecular lineages of mucinous appendiceal adenocarcinoma (MAAP) from co-occurring mutations in GNAS, RAS, and TP53. Of 164 MAAP tumors, 24 were RAS-mutant (mut) predominant ( RAS-mut/ GNAS-wild-type [wt]/ TP53-wt) with significantly decreased mutations and chromosomal alterations compared with tumors with GNAS mutations (GNAS-mut predominant) or TP53 mutations (TP53-mut predominant). No patient with RAS-mut predominant subtype metastatic MAAP died of cancer, and overall survival in this subgroup was significantly improved compared with patients with GNAS-mut ( P = .05) and TP53-mut ( P = .004) predominant subtypes. TP53-mut predominant subtypes were highly aneuploid; increased tumor aneuploidy was independently ( P = .001) associated with poor prognosis. The findings retained significance in patients with any metastatic AC. RAS-mut predominant metastases exhibited reduced peritoneal tumor bulk ( P = .04) and stromal invasion ( P < .001) compared with GNAS-mut or TP53-mut predominant tumors, respectively. Patients with RAS-mut predominant MAAP responded more to first-line chemotherapy (50%) compared with patients with GNAS-mut predominant tumors (6%, P = .03). CONCLUSION AC molecular patterns identify distinct molecular subtypes: a clinically indolent RAS-mut/GNAS-wt/TP53-wt subtype; a chemotherapy-resistant GNAS-mut predominant subtype; and an aggressive, highly aneuploid TP53-mut predominant subtype. Each subtype exhibits conserved clinical behavior irrespective of histopathology.

In managing patients with solid tumors, the value of detecting the status of tumor DNA mismatch repair function is widely recognized. Mismatch repair protein immunohistochemistry and molecular microsatellite instability testing constitute the two major test modalities currently in use, yet each is associated with caveats and limitations that can be consequential. Most notably, the traditional approach of defining mismatch repair protein immunohistochemistry abnormality by complete loss of staining in all tumor cells is evolving. Partial or clonal loss is becoming recognized as a manifestation of gene abnormality; in some cases, such clonal loss is associated with germline pathogenic variants. The current criteria and cutoff values for defining microsatellite instability-high are developed primarily according to colorectal tumors. Non-colorectal cases, and occasionally even colorectal tumors, that are mismatch repair-deficient by immunohistochemistry but not microsatellite instability-high by current standards are being recognized. Emerging data suggest that these immunohistochemistry abnormal / non-microsatellite instability-high cases warrant further genetic workup for Lynch syndrome detection. Whether these tumors respond to immunotherapy is a question still to be addressed. It is imperative that pathologists as well as clinicians and investigators be aware of such intricacies regarding routine immunohistochemistry and microsatellite instability testing and the results they generate. This review summarizes our current understanding of the advantages and limitations of these tests and offer our view on what constitutes the most optimal strategy in test selection and how best to utilize case context to enhance the interpretation of the test results.

There is increased use of neoadjuvant fluorouracil, leucovorin, irinotecan, and oxaliplatin (FOLFIRINOX) in the management of localized pancreatic ductal adenocarcinoma (PDAC), yet there are few validated biomarkers of treatment response.Consecutive patients (n = 196) with resectable, borderline resectable or locally advanced PDAC (2012-2019) receiving FOLFIRINOX as initial treatment and with targeted sequencing of a pretreatment biopsy were identified in a prospective institutional database. Genomic alterations were determined in the 4 driver mutations (KRAS, TP53, CDKN2A, SMAD4), and associations between genomic alterations and clinical outcomes were assessed.Alterations in KRAS (n = 172, 87.8%) and TP53 (n = 131, 66.8%) were common; alterations in CDKN2A (n = 49, 25.0%) and SMAD4 (n = 36, 18.4%) were less frequently observed. A total of 105 patients (53.6%) were able to undergo resection, of whom 8 (7.6%) had a complete/near-complete pathologic response. There were no somatic alterations associated with major pathologic response. Alterations in SMAD4 were associated with a lower rate of surgical resection (27.8% vs 59.4%, p0.001); this was additionally observed in a multivariable regression model accounting for resectability status (OR 0.35, 95% confidence interval [CI] 0.15-0.85). Thirty-three patients (16.8%) developed metastatic disease while on neoadjuvant therapy. SMAD4 alterations were associated with a significant risk of metastatic progression on therapy when controlling for resectability status (OR 3.31, 95% CI 1.44-7.60).SMAD4 alterations are associated with more frequent development of metastasis during neoadjuvant FOLFIRINOX and lower probability of reaching surgical resection. Evaluation of alternative chemotherapy regimens in patients with SMAD4 alterations will be important to distinguish whether this represents a prognostic or predictive biomarker.

The incidence of rectal cancer is increasing in patients younger than 50 years. Locally advanced rectal cancer is still treated with neoadjuvant radiation, chemotherapy and surgery, but recent evidence suggests that patients with a complete response can avoid surgery permanently. To define correlates of response to neoadjuvant therapy, we analyzed genomic and transcriptomic profiles of 738 untreated rectal cancers. APC mutations were less frequent in the lower than in the middle and upper rectum, which could explain the more aggressive behavior of distal tumors. No somatic alterations had significant associations with response to neoadjuvant therapy in a treatment-agnostic manner, but KRAS mutations were associated with faster relapse in patients treated with neoadjuvant chemoradiation followed by consolidative chemotherapy. Overexpression of IGF2 and L1CAM was associated with decreased response to neoadjuvant therapy. RNA-sequencing estimates of immune infiltration identified a subset of microsatellite-stable immune hot tumors with increased response and prolonged disease-free survival.

Purpose: Over 10% of assessed patients with appendiceal adenocarcinoma (AC) have a pathogenic (P) or likely pathogenic (LP) germline variant, including genes implicated in heritable gastrointestinal cancer syndromes, such as Lynch Syndrome. We defined the clinical and molecular impact of heritable alterations in AC to evaluate the need for dedicated appendiceal screening and prevention strategies in patients with LP/P germline variants. Experimental Design: We performed an integrated germline and somatic molecular analysis for patients with confirmed AC. Patients underwent paired tumor-normal sequencing for up to 90 hereditary cancer-risk genes and 505 genes for somatic mutation profiling. We defined the co-occurrence of LP/P germline variants and second-hit pathogenic somatic alterations. The associations between germline variants and patient clinicopathologic features were also evaluated. Results: Twenty-five out of 237 patients (10.5%) carried pathogenic or likely pathogenic germline variants in cancer susceptibility genes. Clinicopathologic characteristics and AC-specific survival were similar in patients with or without germline variants. Most (92%, N=23/25) patients with germline variants demonstrated no second-hit somatic alterations, including loss of heterozygosity. Two patients with a germline APC I1307K low-penetrance founder variant exhibited secondary somatic pathogenic alterations in APC. However only one patient tumor exhibited APC-mediated WNT-signaling dysregulation; a plausible consequence of multiple somatic APC mutations with no germline variant contribution. Four patients had germline variants in PMS2 or MSH2 associated with Lynch Syndrome, yet their cancers were microsatellite-stable. Conclusions: Germline variants are likely incidental without a contributory driver role in AC. AC screening in patients with germline variants is not clearly merited.

Supplementary Video from Reprogrammed Schwann Cells Organize into Dynamic Tracks that Promote Pancreatic Cancer Invasion

Supplementary Data from Reprogrammed Schwann Cells Organize into Dynamic Tracks that Promote Pancreatic Cancer Invasion

Nerves are a component of the tumor microenvironment contributing to cancer progression, but the role of cells from nerves in facilitating cancer invasion remains poorly understood. Here we show that Schwann cells (SC) activated by cancer cells collectively function as tumor-activated Schwann cell tracks (TAST) that promote cancer cell migration and invasion. Nonmyelinating SCs form TASTs and have cell gene expression signatures that correlate with diminished survival in patients with pancreatic ductal adenocarcinoma. In TASTs, dynamic SCs form tracks that serve as cancer pathways and apply forces on cancer cells to enhance cancer motility. These SCs are activated by c-Jun, analogous to their reprogramming during nerve repair. This study reveals a mechanism of cancer cell invasion that co-opts a wound repair process and exploits the ability of SCs to collectively organize into tracks. These findings establish a novel paradigm of how cancer cells spread and reveal therapeutic opportunities.Significance:How the tumor microenvironment participates in pancreatic cancer progression is not fully understood. Here, we show that SCs are activated by cancer cells and collectively organize into tracks that dynamically enable cancer invasion in a c-Jun–dependent manner.See related commentary by Amit and Maitra, p. 2240.This article is highlighted in the In This Issue feature, p. 2221

Supplementary Figure from Reprogrammed Schwann Cells Organize into Dynamic Tracks that Promote Pancreatic Cancer Invasion

Supplementary Tables 1 and 2 PDF file 91K, Table 1 contains clinical and genotypic data from the patient cohort referred to in Fig. 6. Table 2 contains shRNA target sequences

The incidence of esophagogastric cancer is rapidly rising, but only a minority of patients derive durable benefit from current therapies. Chemotherapy as well as anti-HER2 and PD-1 antibodies are standard treatments. To identify predictive biomarkers of drug sensitivity and mechanisms of resistance, we implemented prospective tumor sequencing of patients with metastatic esophagogastric cancer. There was no association between homologous recombination deficiency defects and response to platinum-based chemotherapy. Patients with microsatellite instability–high tumors were intrinsically resistant to chemotherapy but more likely to achieve durable responses to immunotherapy. The single Epstein–Barr virus–positive patient achieved a durable, complete response to immunotherapy. The level of ERBB2 amplification as determined by sequencing was predictive of trastuzumab benefit. Selection for a tumor subclone lacking ERBB2 amplification, deletion of ERBB2 exon 16, and comutations in the receptor tyrosine kinase, RAS, and PI3K pathways were associated with intrinsic and/or acquired trastuzumab resistance. Prospective genomic profiling can identify patients most likely to derive durable benefit to immunotherapy and trastuzumab and guide strategies to overcome drug resistance.Significance: Clinical application of multiplex sequencing can identify biomarkers of treatment response to contemporary systemic therapies in metastatic esophagogastric cancer. This large prospective analysis sheds light on the biological complexity and the dynamic nature of therapeutic resistance in metastatic esophagogastric cancers. Cancer Discov; 8(1); 49–58. ©2017 AACR.See related commentary by Sundar and Tan, p. 14.See related article by Pectasides et al., p. 37.This article is highlighted in the In This Issue feature, p. 1

Supplementary Figure S3 PDF file 66K,Additional data related to the proliferative and apoptotic phenotypes of CRC cells expressing mutant Ras

Concordance between copy-number inferred from next generation sequencing and protein overexpression by IHC or gene amplification by FISH.

Additional results for dual probe EGFR and ERBB2 FISH from Patients 9, 30 and 32.

Supplementary Figure 2

Detected RTK alterations and MAP2K1 mutations in sequenced colorectal carcinomas.

Supplementary Figure 1

Text legends for Supplementary Figures S1-S4.

Supplementary Figure

Supplementary Figure 3

Supplementary Figure Legends PDF file 72K, Legends for Supplementary Figures 1-6

Supplementary Table 3

Supplementary Figure 4

Supplementary Table 2

Supplementary Table 1: Comprehensive clinical data and sample IDs. Supplementary Table 2: Summary of baseline patient and sample characteristics. Supplementary Table 3: List of somatic mutations identified in all samples. Supplementary Table 4: Detailed data for assesment of ERBB2 amplification. Supplementary Table 5: Genes included on MSK-IMPACT platform

Supplementary Table 1

Most patients with KRASG12C–mutant non–small cell lung cancer (NSCLC) experience clinical benefit from selective KRASG12C inhibition, whereas patients with colorectal cancer bearing the same mutation rarely respond. To investigate the cause of the limited efficacy of KRASG12C inhibitors in colorectal cancer, we examined the effects of AMG510 in KRASG12C colorectal cancer cell lines. Unlike NSCLC cell lines, KRASG12C colorectal cancer models have high basal receptor tyrosine kinase (RTK) activation and are responsive to growth factor stimulation. In colorectal cancer lines, KRASG12C inhibition induces higher phospho-ERK rebound than in NSCLC cells. Although upstream activation of several RTKs interferes with KRASG12C blockade, we identify EGFR signaling as the dominant mechanism of colorectal cancer resistance to KRASG12C inhibitors. The combinatorial targeting of EGFR and KRASG12C is highly effective in colorectal cancer cells and patient-derived organoids and xenografts, suggesting a novel therapeutic strategy to treat patients with KRASG12C colorectal cancer.Significance:The efficacy of KRASG12C inhibitors in NSCLC and colorectal cancer is lineage-specific. RTK dependency and signaling rebound kinetics are responsible for sensitivity or resistance to KRASG12C inhibition in colorectal cancer. EGFR and KRASG12C should be concomitantly inhibited to overcome resistance to KRASG12C blockade in colorectal tumors.See related commentary by Koleilat and Kwong, p. 1094.This article is highlighted in the In This Issue feature, p. 1079

Supplementary Figure Legends

A.Immunofluorescence microscopy was performed on control or shCdc42 MiaPaCa2 murine sciatic nerve tumors. Slides were stained with DAPI (blue) nuclear staining and primary antibodies (green) targeting total Cdc42, �-Pix, RET, and phospho-RET. B. Hematoxylin and eosin staining and GTP-Cdc42 immunohistochemistry of a control MiaPaCa2 murine sciatic nerve tumor.

Table S2. Oncogenic/Likely-oncogenic structural variants in GBC

Purpose:Gallbladder carcinoma (GBC) is an uncommon and aggressive disease, which remains poorly defined at a molecular level. Here, we aimed to characterize the molecular landscape of GBC and identify markers with potential prognostic and therapeutic implications.Experimental Design:GBC samples were analyzed using the MSK-IMPACT (Memorial Sloan Kettering–Integrated Mutation Profiling of Actionable Cancer Targets) platform (targeted NGS assay that analyzes 505 cancer-associated genes). Variants with therapeutic implications were identified using OncoKB database. The associations between recurrent genetic alterations and clinicopathologic characteristics (Fisher exact tests) or overall survival (univariate Cox regression) were evaluated. P values were adjusted for multiple testing.Results:Overall, 244 samples (57% primary tumors and 43% metastases) from 233 patients were studied (85% adenocarcinomas, 10% carcinomas with squamous differentiation, and 5% neuroendocrine carcinomas). The most common oncogenic molecular alterations appeared in the cell cycle (TP53 63% and CDKN2A 21%) and RTK_RAS pathways (ERBB2 15% and KRAS 11%). No recurrent structural variants were identified. There were no differences in the molecular landscape of primary and metastasis samples. Variants in SMAD4 and STK11 independently associated with reduced survival in patients with metastatic disease. Alterations considered clinically actionable in GBC or other solid tumor types (e.g., NTRK1 fusions or oncogenic variants in ERBB2, PIK3CA, or BRCA1/2) were identified in 35% of patients; 18% of patients with metastatic disease were treated off-label or enrolled in a clinical trial based on molecular findings.Conclusions:GBC is a genetically diverse malignancy. This large-scale genomic analysis revealed alterations with potential prognostic and therapeutic implications and provides guidance for the development of targeted therapies.

Figure S1. Mutation signatures and altered canonical pathways in GBC.

Table S3. Therapy regimens

Table S1. Sample list (cBioPortal identifiers, ‘DMP_SAMPLE_ID’). Only the primary tumor (if available) or the earliest collected metastasis are included (n=233)

Detailed statistical results

Purpose: BRAF-mutant metastatic colorectal cancer (mCRC) forms an aggressive subset of colorectal cancer with minimal response to selective RAF inhibitors. Preclinical data show that reactivation of EGFR signaling occurs in colorectal tumor cells treated with RAF inhibitors and that the addition of an EGFR inhibitor enhances antitumor activity. These data suggest that combined therapy with RAF and EGFR inhibitors could be an effective strategy for treating BRAF V600E mCRC.Experimental Design: We undertook a pilot trial to assess the response rate and safety of the BRAF inhibitor vemurafenib combined with anti-EGFR antibody panitumumab in patients with BRAF-mutant mCRC. Patients received standard approved doses of panitumumab and vemurafenib.Results: Fifteen patients were treated. Performance status was Eastern Cooperative Oncology Group (ECOG) 0 in 4 patients (27%) and ECOG 1 in 11 patients (73%). All patients had progressed through at least one standard treatment regimen, and 8 (53%) had received previous fluoropyrimidine, oxaliplatin, and irinotecan chemotherapy. Treatment was well tolerated, with less cutaneous toxicity than would be expected with either agent, and no cases of keratoacanthomas/squamous cell carcinomas. Tumor regressions were seen in 10 of 12 evaluable patients with partial responses in 2 patients (100% and 64% regression lasting 40 and 24 weeks, respectively), and stable disease lasting over 6 months in 2 patients.Conclusions: Combined RAF and EGFR inhibition is well tolerated, with less cutaneous toxicity than would be expected with either agent, and results in modest clinical activity in this highly aggressive and chemoresistant subset of CRC. Clin Cancer Res; 21(6); 1313–20. ©2015 AACR.

Nerve mediated inflammatory monocyte recruitment in perineural invasion.

Flow dot plots