SMARCB1/INI1-deficient undifferentiated tumour of the thorax: a case report and review of the literature.

The 5th WHO classification of thoracic tumours includes thoracic SMARCA4-deficient undifferentiated tumour (SMARCA4-UT) among the "other epithelial tumours of the lung" chapter. Herein, we present a case of undifferentiated thoracic neoplasm with retention of SMARCA4 expression, lack of NUT fusion protein and loss of SMARCB1/INI1 expression. After presenting the clinical and pathological features of the tumour, we carried out a review of the literature on the same topic. Albeit very rare, we believe this entity should be included in the heterogeneous group of undifferentiated neoplasms of the thorax.

Biphenotypic lung carcinoma with coexpression of TTF-1 and ΔNP63/P40 within most of the same individual cells: a further case confirming poor prognosis and a review of literature.

The WHO Classification of Tumors, Thoracic Tumors, 5th edition, has outlined the use of TTF-1 and ΔNP63/P40 to discriminate between adenocarcinoma and squamous cell carcinoma. In 2015, the first description of a rare non-small cell lung carcinoma featuring co-expression of glandular and squamous differentiation within most of the same individual tumor cells was reported on, with ultrastructural and molecular demonstration of such a biphenotypic differentiation. We herein describe an additional case of this rare tumor entity, which is confirmed to be an aggressive neoplasm despite potential targets of therapy.

Clinicopathological characterisation of MTAP alterations in gastrointestinal cancers.

BACKGROUND: Methylthioadenosine phosphorylase (MTAP) is an essential metabolic enzyme in the purine and methionine salvage pathway. In cancer, MTAP gene copy number loss (MTAP loss) confers a selective dependency on the related protein arginine methyltransferase 5. The impact of MTAP alterations in gastrointestinal (GI) cancers remains unknown although hypothetically druggable. Here, we aim to investigate the prevalence, clinicopathological features and prognosis of MTAP loss GI cancers. METHODS: Cases with MTAP alterations were retrieved from The Cancer Genome Atlas (TCGA) and a real-world cohort of GI cancers profiled by next-generation sequencing. If MTAP alterations other than loss were found, immunohistochemistry was performed. Finally, we set a case-control study to assess MTAP loss prognostic impact. RESULTS: Findings across the TCGA dataset (N=1363 patients) and our cohort (N=508) were consistent. Gene loss was the most common MTAP alteration (9.4%), mostly co-occurring with CDKN2A/B loss (97.7%). Biliopancreatic and gastro-oesophageal cancers had the highest prevalence of MTAP loss (20.5% and 12.7%, respectively), being mostly microsatellite stable (99.2%). In colorectal cancer, MTAP loss was rare (1.1%), while most MTAP alterations were mutations (5/7, 71.4%); among the latter, only MTAP-CDKN2B truncation led to protein loss, thus potentially actionable. MTAP loss did not confer worse prognosis. CONCLUSIONS: MTAP alterations are found in 5%-10% of GI cancers, most frequently biliopancreatic and gastro-oesophageal. MTAP loss is the most common alteration, identified almost exclusively in MSS, CDKN2A/B loss, upper-GI cancers. Other MTAP alterations were found in colorectal cancer, but unlikely to cause protein loss and drug susceptibility.

Unique Patterns of Heterogeneous Mismatch Repair Protein Expression in Colorectal Cancer Unveil Different Degrees of Tumor Mutational Burden and Distinct Tumor Microenvironment Features.

Mismatch repair (MMR) protein expression in colorectal cancer (CRC) cells is usually homogeneously retained or lost. Rare lesions may show a heterogeneous pattern of MMR protein expression. We evaluated MMR protein expression (MLH1, MSH2, MSH6, and PMS2) in 200 CRCs, identifying 3 groups with proficient MMR protein expression (MMRp), deficient MMR protein expression (MMRd), and heterogeneous MMR protein expression (MMRh). MMRh tumors were microdissected on the basis of the expression of the heterogeneous marker. DNA was extracted and subjected to targeted sequencing. RNA was purified from bulk tumors of all MMRh cases and in a control series of 15 MMRp and 10 MMRd CRCs and analyzed using the PanCancer IO 360 Panel (NanoString Technologies). Twenty-nine of the 200 cases (14.5%) were MMRd. Nine cases (4.5%) showed a heterogeneous pattern of MMR expression, with 6 tumors harboring concomitant loss of one of the other MMR proteins, thus featuring areas with double loss at immunohistochemistry (IHC) testing (MMRh double-loss cases). Four of the 6 MMRh double-loss cases were suitable for a separate sequence variant analysis of IHC double-negative and IHC single-negative components of the tumor. In all lesions, both components exhibited a high tumor mutation burden (TMB). Nevertheless, a significant increase in TMB in the double-negative components was observed (mean TMB: negative, 70 mut/Mb vs positive, 59 mut/Mb) because of a higher number of subclonal variants compared with the other component. Comparative gene expression analyses among MMRd, MMRp, and MMRh CRCs highlighted differential gene expression patterns and an increased number of tumor-infiltrating lymphocytes in MMRh lesions, which is also characterized by a substantial population of exhausted CD8+ lymphocytes. We describe a unique subgroup of CRCs showing heterogeneous expression of MMR proteins in a background of concomitant loss of one of the other markers.

Temozolomide Treatment Alters Mismatch Repair and Boosts Mutational Burden in Tumor and Blood of Colorectal Cancer Patients.

The majority of metastatic colorectal cancers (mCRC) are mismatch repair (MMR) proficient and unresponsive to immunotherapy, whereas MMR-deficient (MMRd) tumors often respond to immune-checkpoint blockade. We previously reported that the treatment of colorectal cancer preclinical models with temozolomide (TMZ) leads to MMR deficiency, increased tumor mutational burden (TMB), and sensitization to immunotherapy. To clinically translate these findings, we designed the ARETHUSA clinical trial whereby O6-methylguanine-DNA-methyltransferase (MGMT)-deficient, MMR-proficient, RAS-mutant mCRC patients received priming therapy with TMZ. Analysis of tissue biopsies and circulating tumor DNA (ctDNA) revealed the emergence of a distinct mutational signature and increased TMB after TMZ treatment. Multiple alterations in the nucleotide context favored by the TMZ signature emerged in MMR genes, and the p.T1219I MSH6 variant was detected in ctDNA and tissue of 94% (16/17) of the cases. A subset of patients whose tumors displayed the MSH6 mutation, the TMZ mutational signature, and increased TMB achieved disease stabilization upon pembrolizumab treatment. SIGNIFICANCE: MMR-proficient mCRCs are unresponsive to immunotherapy. We provide the proof of concept that inactivation of MMR genes can be achieved pharmacologically with TMZ and molecularly monitored in the tissue and blood of patients with mCRC. This strategy deserves additional evaluation in mCRC patients whose tumors are no longer responsive to standard-of-care treatments. See related commentary by Willis and Overman, p. 1612. This article is highlighted in the In This Issue feature, p. 1599.

Long-term Clinical Outcome of Trastuzumab and Lapatinib for HER2-positive Metastatic Colorectal Cancer.

BACKGROUND: ERBB2 amplification occurs in 5% of RAS wild-type metastatic colorectal cancer (mCRC) and it has been shown to be a target for treatment with 2 HER2-directed combinations of trastuzumab and lapatinib or trastuzumab and pertuzumab. We present long-term clinical results of trastuzumab and lapatinib (HERACLES-A trial) at 6.7 years (82 months) follow-up and focus on central nervous system (CNS) recurrences. PATIENTS AND METHODS: Patients had histologically confirmed KRAS exon 2 (codons 12 and 13) wild-type and HER2-positive mCRC. HER2 positivity was assessed by immunohistochemistry and in situ hybridization HERACLES diagnostic criteria. Patients were treated with intravenous trastuzumab 4 mg/kg loading dose, then 2 mg/kg once per week, and oral lapatinib 1000 mg per day until disease progression or toxicity. Patients who presented with symptoms or signs of CNS disease received brain computed tomography scan or magnetic resonance imaging. RESULTS: A total of 35 patients received trastuzumab and lapatinib and 32 were evaluable for response. One patient (3%) achieved complete response (CR), 8 (25%) partial response, and 13 (41%) stable disease. Therefore, response rate was 28%. Median progression-free survival was 4.7 months (95% confidence interval [CI] 3.7-6.1). Median overall survival was 10.0 months (95% CI 7.9-15.8). One patient achieved sustained CR still maintained at 7 years of follow-up. Progression in the central nervous system (CNS) occurred in 6 (19%) of 32 patients. CONCLUSIONS: Long-term (6.7 years) follow-up analysis of HERACLES-A supports using of trastuzumab and lapatinib as treatment reference for KRAS wild-type, chemorefractory HER2-positive mCRC. In this subset of patients, prolongation of survival is accompanied by CNS recurrences that will require diagnostic and therapeutic attention in future studies. Clinicaltrials. Gov identifier: NCT 03225937.

Pertuzumab and trastuzumab emtansine in patients with HER2-amplified metastatic colorectal cancer: the phase II HERACLES-B trial.

BACKGROUND: HER2 is a therapeutic target for metastatic colorectal cancer (mCRC), as demonstrated in the pivotal HERACLES-A (HER2 Amplification for Colo-rectaL cancer Enhanced Stratification) trial with trastuzumab and lapatinib. The aim of HERACLES-B trial is to assess the efficacy of the combination of pertuzumab and trastuzumab-emtansine (T-DM1) in this setting. METHODS: HERACLES-B was a single-arm, phase II trial, in patients with histologically confirmed RAS/BRAF wild-type and HER2+ mCRC refractory to standard treatments. HER2 positivity was assessed by immunohistochemistry and in situ hybridisation according to HERACLES criteria. Patients were treated with pertuzumab (840 mg intravenous load followed by 420 mg intravenous every 3 weeks) and T-DM1 (3.6 mg/kg every 3 weeks) until disease progression or toxicity. Primary and secondary end points were objective response rate (ORR) and progression-free survival (PFS). With a Fleming/Hern design (H0=ORR 10%; α=0.05; power=0.85), 7/30 responses were required to demonstrate an ORR ≥30% (H1). RESULTS: Thirty-one patients, 48% with ≥4 lines of previous therapies, were treated and evaluable. ORR was 9.7% (95% CI: 0 to 28) and stable disease (SD) 67.7% (95% CI: 50 to 85). OR/SD ≥4 months was associated with higher HER2 immunohistochemistry score (3+ vs 2+) (p = 0.03). Median PFS was 4.1 months (95% CI: 3.6 to 5.9). Drug-related grade (G) 3 adverse events were observed in two patients (thrombocytopaenia); G≤2 AE in 84% of cycles (n = 296), mainly nausea and fatigue. CONCLUSIONS: HERACLES-B trial did not reach its primary end point of ORR; however, based on high disease control, PFS similar to other anti-HER2 regimens, and low toxicity, pertuzumab in combination with T-DM1 can be considered for HER2+mCRC as a potential therapeutic resource. TRIAL REGISTRATION NUMBER: 2012-002128-33 and NCT03225937.

The Reproducibility of the Immunohistochemical PD-L1 Testing in Non-Small-Cell Lung Cancer: A Multicentric Italian Experience.

An important harmonization effort was produced by the scientific community to standardize both the preanalytical and interpretative phases of programmed death-ligand 1 (PD-L1) immunohistochemical (IHC) testing in non-small-cell lung cancer (NSCLC). This analysis is crucial for the selection of patients with advanced-stage tumors eligible for treatment with pembrolizumab and potentially with other anti-PD-1/PD-L1 checkpoint inhibitors. This multicentric retrospective study evaluated the reproducibility of PD-L1 testing in the Italian scenario both for closed and open platforms. In the evaluation of the well-known gold-standard combinations (Agilent 22C3 PharmDx on Dako Autostainer versus Roche's Ventana SP263 on BenchMark), the results confirmed the literature data and showed complete overlapping between the two methods. With regard to the performances by using open platforms, the combination of 22C3 with Dako Omnis or Benchmark obtained good results basically, while the 28,8 clone seemed to be associated with worse scores.

HER2 Positivity Predicts Unresponsiveness to EGFR-Targeted Treatment in Metastatic Colorectal Cancer.

BACKGROUND: HER2 amplification is detected in 3% of patients with colorectal cancer (CRC), making tumors in the metastatic setting vulnerable to double pharmacological HER2 blockade. Preclinical findings show that it also might impair response to anti-epidermal growth factor receptor (EGFR) treatment. SUBJECTS AND METHODS: Patients with KRAS exon 2 wild-type metastatic CRC underwent molecular screening of HER2 positivity by HERACLES criteria (immunohistochemistry 3+ or 2+ in ≥50% of cells, confirmed by fluorescence in situ hybridization). A sample of consecutive HER2-negative patients was selected as control. A regression modeling strategy was applied to identify predictors explaining the bulk of HER2 positivity and the association with response to previous anti-EGFR treatment. RESULTS: From August 2012 to April 2018, a total of 100 HER2-positive metastatic CRC tumors were detected out of 1,485 KRAS exon 2 wild-type screened patients (6.7%). HER2-positive patients show more frequently lung metastases (odds ratio [OR], 2.04; 95% confidence interval [CI], 1.15-3.61; p = .014) and higher tumor burden (OR, 1.48; 95% CI, 1.10-2.01; p = .011), and tumors were more likely to be left sided (OR, 0.50; 95% CI, 0.22-1.11; p = .088). HER2-positive patients who received treatment with anti-EGFR agents (n = 79) showed poorer outcome (objective response rate, 31.2% vs. 46.9%, p = .031; progression-free survival, 5.7 months vs. 7 months, p = .087). CONCLUSION: Testing for HER2 should be offered to all patients with metastatic CRC because the occurrence of this biomarker is unlikely to be predicted based on main clinicopathological features. Patients with HER2-amplified metastatic CRC are less likely to respond to anti-EGFR therapy. IMPLICATIONS FOR PRACTICE: Patients with HER2-amplified/overexpressed metastatic colorectal cancer (mCRC) harbor a driver actionable molecular alteration that has been shown in preclinical models to hamper efficacy of the anti-epidermal growth factor receptor (EGFR) targeted therapies. The present study confirmed that this molecular feature was associated with worse objective tumor response and shorter progression-free survival in response to previous anti-EGFR therapies. Moreover, it was found that the occurrence of this biomarker is unlikely to be predicted based on main clinicopathological features. Therefore, HER2 status assessment should be included in the molecular diagnostic workup of all mCRC for speedy referral to clinical trials encompassing HER2-targeted double blockade independently of previous anti-EGFR treatment.

Combined Low Densities of FoxP3+ and CD3+ Tumor-Infiltrating Lymphocytes Identify Stage II Colorectal Cancer at High Risk of Progression.

The densities of CD3+ and CD8+ tumor-infiltrating lymphocytes (TILs), combined with tumor-node-metastasis (TNM) staging, have prognostic value for patients with nonmetastatic colorectal cancer. We compared the prognostic value of CD3+ and FoxP3+ TILs at the invasive front, TNM classifiers, and microsatellite (MS) status in a trial set of patients with stage II and III colorectal cancer (n = 413), by recursive partitioning with a classification and regression tree (CART). Significant prognostic factors and interactions were reassessed by logistic regression and Cox proportional-hazards modeling in the trial and a validation set (n = 215) of patients with stage II colorectal cancer. In the trial set, CART indicated that TIL numbers were of value only in predicting recurrence risk for stage II cancers, where low densities of FoxP3+ TILs ranked first and low densities of CD3+ TILs further stratifying risk. Multivariate analysis showed that TILs interacted with tumor stage (FoxP3+, P = 0.06; CD3+, P = 0.02) and MS instability (MSI; FoxP3+; P = 0.02). In stage II MS-stable cancers, concomitant low densities of both FoxP3+ and CD3+ TILs identified patients with the highest progression risk in the trial [HR 7.24; 95% confidence interval (CI), 3.41-15.4; P < 0.001] and the validation (HR 15.16; 95% CI, 3.43-66.9; P < 0.001) sets. FoxP3+ and CD3+ TIL load in colorectal cancer was more informative than other prognostic factors before the cancer progressed to lymph nodes. This prognostic information about TILs, including FoxP3+ cells, suggests that randomized controlled trials might be refined to include interactions between TNM status, molecular classifiers, and postsurgical treatments.

Radiologic and Genomic Evolution of Individual Metastases during HER2 Blockade in Colorectal Cancer.

Targeting HER2 is effective in 24% of ERBB2 amplified metastatic colorectal cancer; however, secondary resistance occurs in most of the cases. We studied the evolution of individual metastases during treatment to discover spatially resolved determinants of resistance. Circulating tumor DNA (ctDNA) analysis identified alterations associated with resistance in the majority of refractory patients. ctDNA profiles and lesion-specific radiographic reports revealed organ- or metastasis-private evolutionary patterns. When radiologic assessments documented progressive disease in target lesions, response to HER2 blockade was retained in other metastases. Genomic and functional analyses on samples and cell models from eight metastases of a patient co-recruited to a postmortem study unveiled lesion-specific evolutionary trees and pharmacologic vulnerabilities. Lesion size and contribution of distinct metastases to plasma ctDNA were correlated.

TRKA expression and NTRK1 gene copy number across solid tumours.

AIMS: Neurotrophic Tropomyosin Kinase Receptor 1 (NTRK1) gene encodes for the protein Tropomyosin-related kinase A (TRKA). Deregulated activity of TRKA has been shown to have oncogenic potential. We present here the results of an immunohistochemical (IHC) observational cohort study of TRKA expression together with gene copy number (GCN) assessment in various solid tumours. METHODS: Formalin-fixed, paraffin-embedded consecutive samples of different tumour types were tested for TRKA expression. Samples showing TRKA IHC staining in at least 10% of cells were analysed by fluorescence in situ hybridisation to assess NTRK1 gene rearrangements and/or individual GCN gain. All patients underwent this molecular assessment within the phase I ALKA-001 clinical trial. RESULTS: 1043 samples were tested and annotation for histology was available in 1023. Most of the samples were colorectal adenocarcinoma (CRC) (n=550, 52.7%) and lung adenocarcinoma (n=312, 29.9%). 24 samples (2.3%) were biliary tract carcinoma (BTC). Overall, 17 (1.6%) samples were characterised by TRKA IHC expression (four weak, eight moderate, five strong): 9/17 lung adenocarcinoma, 3/17 CRC, 3/17 BTC, 1/17 thyroid cancer and 1/17 cancer of unknown primary. Of these, 1/17 with strong TRKA IHC staining displayed NTRK1 gene rearrangement and 15/17 NTRK1 GCN gain by FISH. No correlation was found between intensity of TRKA IHC staining and number of copies of NTRK1. CONCLUSIONS: TRKA expression can be found in 1.6% of solid tumours and can be paralleled by NTRK1 gene rearrangements or mostly GCN gain. The prognostic and translational therapeutic impact of the latter remains to be established.

Identification and characterization of a novel SCYL3-NTRK1 rearrangement in a colorectal cancer patient.

In colorectal cancer patients, chromosomal rearrangements involving NTRK1 gene (encoding the TRKA protein) are shown in a small subset of patients and are associated with the constitutive activation of the kinase domain of TRKA. In turn, activated TRKA-fusion proteins are associated with proliferation and survival in colorectal cancer tumors. Here we report the identification and functional characterization of a new SCYL3-NTRK1 fusion gene in a 61-year-old colorectal cancer patient. To our knowledge, this fusion protein has never been previously documented in oncological patients. We show that this novel fusion is oncogenic and sensitive to TRKA inhibitors. As suggested by other pieces of evidence, entrectinib - an orally available pan-TRK, ROS1 and ALK inhibitor - may have particular efficacy in patients with NTRK rearrangements. Therefore, screening for rearrangements involving NTRK genes may help identifying a subset of patients able to derive benefit from treatment with entrectinib or other targeted inhibitors.

Pooled Analysis of Clinical Outcome of Patients with Chemorefractory Metastatic Colorectal Cancer Treated within Phase I/II Clinical Studies Based on Individual Biomarkers of Susceptibility: A Single-Institution Experience.

BACKGROUND: Patients with metastatic colorectal cancer (mCRC) refractory to standard therapies have a poor prognosis. In this setting, recruitment into clinical trials is warranted, and studies driven by selection according to individual tumor molecular characteristics are expected to provide added value. OBJECTIVE: We retrospectively analyzed data from patients with mCRC refractory to or following failure of standard therapies who were enrolled into phase I/II clinical studies at the Niguarda Cancer Center based on the presence of a specific molecular profile expected to represent the target of susceptibility to the experimental drug(s). PATIENTS AND METHODS: From June 2011 to May 2016, 2044 patients with mCRC underwent molecular screening. Eighty patients (3.9%) were enrolled in ad hoc studies; the median age was 60 years (range 36-86) and the median number of previous treatment lines was five (range 2-8). Molecular characteristics exploited within these studies were MGMT promoter hypermethylation (48.7%), HER2 amplification (28.8%), BRAF V600E mutation (20%), and novel gene fusions involving ALK or NTRK (2.5%). RESULTS: One patient (1%) had RECIST (Response Evaluation Criteria In Solid Tumors) complete response (CR), 13 patients (16.5%) experienced a partial response (PR), and 28 (35%) stable disease (SD). Median progression-free survival (PFS) was 2.8 months (range 2.63-3.83), with 24% of patients displaying PFS >5 months. Median growth modulation index (GMI) was 0.85 (range 0-15.61) and 32.5% of patients had GMI >1.33. KRAS exon 2 mutations were found in 38.5% of patients, and among the 78 patients with known KRAS status, those with wild-type tumors had longer PFS than those with mutated tumors (3.80 [95% CI 2.80-5.03] vs. 2.13 months [95% CI 1.77-2.87], respectively, p = 0.001). Median overall survival (OS) was 7.83 months (range 7.17-9.33) for all patients, and patients with KRAS wild-type tumors had longer OS than those with mutated tumors (7.83 [95% CI 7.33-10.80] vs. 7.18 months [95% CI 5.63-9.33], respectively, p = 0.06). CONCLUSIONS: This single-institution retrospective study indicates that in a heavily pretreated population approximately 4% of mCRC tumors display a potential actionable molecular context suitable for therapeutic intervention. Application of molecular selection is challenging but improves clinical outcome even in later lines of treatment.

Emergence of MET hyper-amplification at progression to MET and BRAF inhibition in colorectal cancer.

BACKGROUND: Combined MET and BRAF inhibition showed clinical benefit in a patient with rectal cancer carrying BRAFV600E and MET amplification. However after 4 months, acquired resistance emerged and the patient deceased shortly after disease progression. The mechanism of resistance to this drug combination is unknown. METHODS: We analysed plasma circulating tumour DNA obtained at progression by exome sequencing and digital PCR. MET gene and mRNA in situ hybridisation analyses in two bioptic specimens obtained at progression were used to confirm the plasma data. RESULTS: We identified in plasma MET gene hyper-amplification as a potential mechanism underlying therapy resistance. Increased MET gene copy and transcript levels were detected in liver and lymph node metastatic biopsies. Finally, transduction of MET in BRAF mutant colorectal cancer cells conferred refractoriness to BRAF and MET inhibition. CONCLUSIONS: We identified in a rectal cancer patient MET gene hyper-amplification as mechanism of resistance to dual BRAF and MET inhibition.

Acquired RAS or EGFR mutations and duration of response to EGFR blockade in colorectal cancer.

Blockade of the epidermal growth factor receptor (EGFR) with the monoclonal antibodies cetuximab or panitumumab is effective in a subset of colorectal cancers (CRCs), but the emergence of resistance limits the efficacy of these therapeutic agents. At relapse, the majority of patients develop RAS mutations, while a subset acquires EGFR extracellular domain (ECD) mutations. Here we find that patients who experience greater and longer responses to EGFR blockade preferentially develop EGFR ECD mutations, while RAS mutations emerge more frequently in patients with smaller tumour shrinkage and shorter progression-free survival. In circulating cell-free tumour DNA of patients treated with anti-EGFR antibodies, RAS mutations emerge earlier than EGFR ECD variants. Subclonal RAS but not EGFR ECD mutations are present in CRC samples obtained before exposure to EGFR blockade. These data indicate that clonal evolution of drug-resistant cells is associated with the clinical outcome of CRC patients treated with anti-EGFR antibodies.

Molecular Landscape of Acquired Resistance to Targeted Therapy Combinations in BRAF-Mutant Colorectal Cancer.

Although recent clinical trials of BRAF inhibitor combinations have demonstrated improved efficacy in BRAF-mutant colorectal cancer, emergence of acquired resistance limits clinical benefit. Here, we undertook a comprehensive effort to define mechanisms underlying drug resistance with the goal of guiding development of therapeutic strategies to overcome this limitation. We generated a broad panel of BRAF-mutant resistant cell line models across seven different clinically relevant drug combinations. Combinatorial drug treatments were able to abrogate ERK1/2 phosphorylation in parental-sensitive cells, but not in their resistant counterparts, indicating that resistant cells escaped drug treatments through one or more mechanisms leading to biochemical reactivation of the MAPK signaling pathway. Genotyping of resistant cells identified gene amplification of EGFR, KRAS, and mutant BRAF, as well as acquired mutations in KRAS, EGFR, and MAP2K1 These mechanisms were clinically relevant, as we identified emergence of a KRAS G12C mutation and increase of mutant BRAF V600E allele frequency in the circulating tumor DNA of a patient at relapse from combined treatment with BRAF and MEK inhibitors. To identify therapeutic combinations capable of overcoming drug resistance, we performed a systematic assessment of candidate therapies across the panel of resistant cell lines. Independent of the molecular alteration acquired upon drug pressure, most resistant cells retained sensitivity to vertical MAPK pathway suppression when combinations of ERK, BRAF, and EGFR inhibitors were applied. These therapeutic combinations represent promising strategies for future clinical trials in BRAF-mutant colorectal cancer. Cancer Res; 76(15); 4504-15. ©2016 AACR.

MET-Driven Resistance to Dual EGFR and BRAF Blockade May Be Overcome by Switching from EGFR to MET Inhibition in BRAF-Mutated Colorectal Cancer.

UNLABELLED: A patient with metastatic BRAF-mutated colorectal cancer initially responded to combined EGFR and BRAF inhibition with panitumumab plus vemurafenib. Pre-existing cells with increased MET gene copy number in the archival tumor tissue likely underwent clonal expansion during treatment, leading to the emergence of MET amplification in the rebiopsy taken at progression. In BRAF-mutated colorectal cancer cells, ectopic expression of MET conferred resistance to panitumumab and vemurafenib, which was overcome by combining BRAF and MET inhibition. Based on tumor genotyping and functional in vitro data, the patient was treated with the dual ALK-MET inhibitor crizotinib plus vemurafenib, thus switching to dual MET and BRAF blockade, with rapid and marked effectiveness of such strategy. Although acquired resistance is a major limitation to the clinical efficacy of anticancer agents, the identification of molecular targets emerging during the first treatment may afford the opportunity to design the next line of targeted therapies, maximizing patient benefit. SIGNIFICANCE: MET amplification is here identified-clinically and preclinically-as a new mechanism of resistance to EGFR and BRAF dual/triple block combinations in BRAF-mutated colorectal cancer. Switching from EGFR to MET inhibition, while maintaining BRAF inhibition, resulted in clinical benefit after the occurrence of MET-driven acquired resistance. Cancer Discov; 6(9); 963-71. ©2016 AACR.This article is highlighted in the In This Issue feature, p. 932.

Dual-targeted therapy with trastuzumab and lapatinib in treatment-refractory, KRAS codon 12/13 wild-type, HER2-positive metastatic colorectal cancer (HERACLES): a proof-of-concept, multicentre, open-label, phase 2 trial.

BACKGROUND: We previously found that dual HER2 blockade with trastuzumab and lapatinib led to inhibition of tumour growth in patient-derived xenografts of HER2-amplified metastatic colorectal cancer. In this study, we aimed to assess the antitumour activity of trastuzumab and lapatinib in patients with HER2-positive colorectal cancer. METHODS: HERACLES was a proof-of-concept, multicentre, open-label, phase 2 trial done at four Italian academic cancer centres. We enrolled adult patients with KRAS exon 2 (codons 12 and 13) wild-type and HER2-positive metastatic colorectal cancer refractory to standard of care (including cetuximab or panitumumab), an Eastern Cooperative Oncology Group performance status of 0 or 1, and at least one measurable lesion. We defined HER2 positivity in tumour samples by use of immunohistochemistry and fluorescence in-situ hybridisation in accordance with our previously validated colorectal cancer-specific diagnostic criteria. Eligible patients received intravenous trastuzumab at 4 mg/kg loading dose followed by 2 mg/kg once per week, and oral lapatinib at 1000 mg per day until evidence of disease progression. The primary endpoint was the proportion of patients achieving an objective response (defined as complete response or partial response), which was assessed by independent central review in the intention-to-treat population. This trial is registered with EudraCT, number 2012-002128-33. FINDINGS: Between Aug 27, 2012, and May 15, 2015, we screened 914 patients with KRAS exon 2 (codons 12 and 13) wild-type metastatic colorectal cancer and identified 48 (5%) patients with HER2-positive tumours, although two died before enrolment. Of these patients, 27 were eligible for the trial. All were evaluable for response. At the time of data cutoff on Oct 15, 2015, with a median follow-up of 94 weeks (IQR 51-127), eight (30%, 95% CI 14-50) of 27 patients had achieved an objective response, with one patient (4%, 95% CI -3 to 11) achieving a complete response, and seven (26%, 95% CI 9-43) achieving partial responses; 12 (44%, 95% CI 25-63) patients had stable disease. Six (22%) of 27 patients had grade 3 adverse events, which consisted of fatigue in four patients, skin rash in one patient, and increased bilirubin concentration in one patient. No grade 4 or 5 adverse events were reported. We detected no drug-related serious adverse events. INTERPRETATION: The combination of trastuzumab and lapatinib is active and well tolerated in treatment-refractory patients with HER2-positive metastatic colorectal cancer. FUNDING: Associazione Italiana Ricerca Cancro (AIRC), Fondazione Oncologia Niguarda Onlus, and Roche.