Federica Morano

Inactivation of DNA repair triggers neoantigen generation and impairs tumour growth

Molecular alterations in genes involved in DNA mismatch repair (MMR) promote cancer initiation and foster tumour progression. Cancers deficient in MMR frequently show favourable prognosis and indolent progression. The functional basis of the clinical outcome of patients with tumours that are deficient in MMR is not clear. Here we genetically inactivate MutL homologue 1 (MLH1) in colorectal, breast and pancreatic mouse cancer cells. The growth of MMR-deficient cells was comparable to their proficient counterparts in vitro and on transplantation in immunocompromised mice. By contrast, MMR-deficient cancer cells grew poorly when transplanted in syngeneic mice. The inactivation of MMR increased the mutational burden and led to dynamic mutational profiles, which resulted in the persistent renewal of neoantigens in vitro and in vivo, whereas MMR-proficient cells exhibited stable mutational load and neoantigen profiles over time. Immune surveillance improved when cancer cells, in which MLH1 had been inactivated, accumulated neoantigens for several generations. When restricted to a clonal population, the dynamic generation of neoantigens driven by MMR further increased immune surveillance. Inactivation of MMR, driven by acquired resistance to the clinical agent temozolomide, increased mutational load, promoted continuous renewal of neoantigens in human colorectal cancers and triggered immune surveillance in mouse models. These results suggest that targeting DNA repair processes can increase the burden of neoantigens in tumour cells; this has the potential to be exploited in therapeutic approaches.

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.

Heterogeneity of acquired resistance to anti-EGFR monoclonal antibodies in patients with metastatic colorectal cancer

Purpose: Even if RAS-BRAF wild-type and HER2/MET–negative metastatic colorectal cancer (mCRC) patients frequently respond to anti-EGFR mAbs, acquired resistance almost invariably occurs. Mechanisms of resistance to EGFR blockade include the emergence of KRAS, NRAS, and EGFR extracellular domain mutations as well as HER2/MET alterations. However, these findings derive from retrospective studies that analyzed one single resistance mechanism at a time; moreover, it is still unclear how molecular heterogeneity affects clonal evolution in patients. In this work, we aimed at extensively characterizing and correlating the molecular characteristics of tissue- and blood-based data in a prospective cohort of patients with mCRC who received anti-EGFR antibodies. Experimental design: Twenty-two RAS-BRAF wild-type, HER2/MET–negative mCRC patients progressing on anti-EGFR therapy after initial response underwent rebiopsy. Next-generation sequencing and silver in situ hybridization (SISH)/IHC analyses were performed both on archival tumors and postprogression samples. Circulating tumor (ctDNA) molecular profiles were obtained in matched tissue–plasma samples. Results: RAS mutations and HER2/MET amplification were the most frequently detected resistance mechanisms in both tissue and blood sample analysis. On the other hand, BRAF and EGFR ectodomain mutations were much rarer. Patients with acquired MET amplification showed worse PFS on anti-EGFRs. We detected both intralesion heterogeneity, as suggested by co-occurrence of different resistance mechanisms in the same sample, and interlesion heterogeneity. The combined analysis of tissue and blood (ctDNA) results highlights the complexity of clonal evolution triggered by EGFR blockade. Conclusions: Our results indicate that it may be extremely challenging to target the complex landscape of molecular heterogeneity associated with emergence of resistance to targeted therapies in patients with mCRC. Clin Cancer Res; 23(10); 2414–22. ©2016 AACR.

HER2 loss in HER2-positive gastric or gastroesophageal cancer after trastuzumab therapy : Implication for further clinical research

Mechanisms of acquired resistance to trastuzumab‐based treatment in gastric cancer are largely unknown. In this study, we analyzed 22 pairs of tumor samples taken at baseline and post‐progression in patients receiving chemotherapy and trastuzumab for advanced HER2‐positive [immunohistochemistry (IHC) 3+ or 2+ with in‐situ hybridization (ISH) amplification] gastric or gastroesophageal cancers. Strict clinical criteria for defining acquired trastuzumab resistance were adopted. Loss of HER2 positivity and loss of HER2 over‐expression were defined as post‐trastuzumab IHC score <3+ and absence of ISH amplification, and IHC “downscoring” from 2+/3+ to 0/1+, respectively. HER2 IHC was always performed, while ISH was missing in 3 post‐progression samples. Patients with initial HER2 IHC score 3+ and 2+ were 14 (64%) and 8 (36%), respectively. Loss of HER2 positivity and HER2 over‐expression was observed in 32 and 32% samples, respectively. The chance of HER2 loss was not associated with any of the baseline clinicopathological variables. The only exception was in patients with initial IHC score 2+ versus 3+, for both endpoints of HER2 positivity (80 vs. 14%; p = 0.008) and HER2 over‐expression (63 vs. 14%; p = 0.025). As already shown in breast cancer, loss of HER2 may be observed also in gastric cancers patients treated with trastuzumab‐based chemotherapy in the clinical practice. This phenomenon may be one of the biological reasons explaining the failure of anti‐HER2 second‐line strategies in initially HER2‐positive disease.

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.

Platinum-Fluoropyrimidine and Paclitaxel-Based Chemotherapy in the Treatment of Advanced Anal Cancer Patients.

BACKGROUND Although treatment of localized anal cancer (AC) is well established, very little evidence is available to inform the management of advanced tumors, and the prognosis of these patients remains poor. We have analyzed treatment pathways and outcomes of a single-institution series of advanced AC patients in order to provide insight into the management of this rare condition. MATERIALS AND METHODS Inclusion criteria included epidermoid histology, inoperable locally recurrent or metastatic disease, and availability of full medical records. The primary objective was overall survival (OS). Prognostic factors were analyzed in univariate models. RESULTS Sixty-four patients (1997-2014) were included: 16 (25.0%) with inoperable locally advanced and 48 (75.0%) with metastatic tumors. Fifty-one (79.7%) received at least one line of chemotherapy; of these, 37% underwent multimodality treatment. A combination of a platinum agent plus a fluoropyrimidine was the most common first-line regimen (74.5%), with an objective response rate (ORR) of 34.4% (95% confidence interval [CI], 18.6%-53.2%). Paclitaxel-based chemotherapy was used in 15 patients as front-line or salvage treatment, and the overall ORR was 53.3% (95% CI, 26.6%-78.7%). Median progression-free survival (PFS) after first- and second-line chemotherapy was 5.8 (interquartile range [IQR], 2.8-7.6) and 3.2 (IQR, 2.5-7.1) months, respectively. Five-year OS in the overall population was 15% (95% CI, 7.0%-25.0%). Age ≤65 years and liver metastases were predictive of better PFS (hazard ratio [HR], 0.39; 95% CI, 0.16-0.97; p = .04) and worse OS (HR, 2.25; 95% CI, 1.25-4.03; p = .01), respectively. CONCLUSION A platinum agent plus a fluoropyrimidine and paclitaxel-based chemotherapy are active regimens for advanced AC. Clinical trials are needed to standardize treatment pathways, investigate the potential of novel therapeutics, and improve the poor prognosis of this rare condition. The Oncologist 2017;22:402-408Implications for Practice: Because of the lack of randomized trials, the optimal management of advanced anal cancer is uncertain. Despite its retrospective analysis and relatively small sample size, this is the second largest study ever conducted in this setting, and, as such, it has the potential to serve as a valuable source of information for everyday clinical practice. These findings suggest that chemotherapy with a platinum agent plus a fluoropyrimidine or paclitaxel-containing regimens are reasonable treatment options for patients with inoperable locally recurrent or metastatic anal carcinoma.

RET fusions in a small subset of advanced colorectal cancers at risk of being neglected

Background Recognition of rare molecular subgroups is a challenge for precision oncology and may lead to tissue-agnostic approval of targeted agents. Here we aimed to comprehensively characterize the clinical, pathological and molecular landscape of RET rearranged metastatic colorectal cancer (mCRC). Patients and methods In this case series, we compared clinical, pathological and molecular characteristics of 24 RET rearranged mCRC patients with those of a control group of 291 patients with RET negative tumors. RET rearranged and RET negative mCRCs were retrieved by systematic literature review and by taking advantage of three screening sources: (i) Ignytas phase 1/1b study on RXDX-105 (NCT01877811), (ii) cohorts screened at two Italian and one South Korean Institutions and (iii) Foundation Medicine Inc. database. Next-generation sequencing data were analyzed for RET rearranged cases. Results RET fusions were more frequent in older patients (median age of 66 versus 60 years, P = 0.052), with ECOG PS 1-2 (90% versus 50%, P = 0.02), right-sided (55% versus 32%, P = 0.013), previously unresected primary tumors (58% versus 21%, P < 0.001), RAS and BRAF wild-type (100% versus 40%, P < 0.001) and MSI-high (48% versus 7%, P < 0.001). Notably, 11 (26%) out of 43 patients with right-sided, RAS and BRAF wild-type tumors harbored a RET rearrangement. At a median follow-up of 45.8 months, patients with RET fusion-positive tumors showed a significantly worse OS when compared with RET-negative ones (median OS 14.0 versus 38.0 months, HR: 4.59; 95% CI, 3.64-32.66; P < 0.001). In the multivariable model, RET rearrangements were still associated with shorter OS (HR: 2.97; 95% CI, 1.25-7.07; P = 0.014), while primary tumor location, RAS and BRAF mutations and MSI status were not. Conclusions Though very rare, RET rearrangements define a new subtype of mCRC that shows poor prognosis with conventional treatments and is therefore worth of a specific management.

Temozolomide and irinotecan (TEMIRI regimen) as salvage treatment of irinotecan-sensitive advanced colorectal cancer patients bearing MGMT methylation

Background Non-randomized studies showed that temozolomide (TMZ) achieves an average 10% response rate in heavily pretreated metastatic colorectal cancer (mCRC) patients with promoter methylation of the DNA repair gene O6-methylguanine-DNA methyltransferase (MGMT). In this phase II trial, irinotecan and temozolomide (TEMIRI) combination regimen was assessed in irinotecan-sensitive, MGMT methylated/microsatellite stable (MSS) pretreated mCRC patients. Patients and methods Key inclusion criteria were centrally confirmed MGMT methylation by methylation-specific PCR, MSS mCRC, progression after at least two prior chemotherapy regimens for advanced disease and irinotecan-free interval >3 months. TEMIRI (TMZ 150 mg/m2 on days 1-5 plus irinotecan 100 mg/m2 on days 1, 15 q28 days) was administered for six cycles, followed by maintenance with TMZ. The primary end point was overall response rate (ORR). Exploratory translational analyses included MGMT immunohistochemistry (IHC) and methyl-BEAMing (MB). Results Between December 2014 and June 2017, 25 patients were enrolled. The primary end point was met, since six patients achieved a partial response [ORR 24%, 95% confidence interval (CI) 11% to 43%]. At a median follow-up of 15.6 months, median progression-free survival (mPFS) and overall survival (mOS) were 4.4 and 13.8 months, respectively. Only four (16%) patients had ≥ grade 3 (CTCAE 4.0) adverse events. All patients whose cancer was MGMT-positive IHC were non-responders. Consistently, patients with MGMT-negative/low tumors had a significantly longer mPFS than others (6.9 versus 2.0 months; hazard ratio = 0.29, 95% CI 0.02-0.41; P = 0.003) and a non-significant trend for longer mOS. MB testing showed similar accuracy. Conclusions TEMIRI regimen is a safe and active option in pre-treated, irinotecan-sensitive mCRC patients with MGMT methylation.

Vinorelbine in BRAF V600E mutated metastatic colorectal cancer: a prospective multicentre phase II clinical study

Background BRAF V600E mutation defines a specific colorectal cancer (CRC) subgroup with poor prognosis. Promising preclinical data showed synthetically lethal activity of mitotic spindle poisons on BRAF-mutated and BRAF-like CRC models. We designed a phase II trial to test the activity of vinorelbine in patients with BRAF V600E mutated metastatic CRC (mCRC). Patients and methods Patients progressed to or not deemed eligible for standard treatments received oral (60 mg/sqm) or intravenous (25 mg/sqm) vinorelbine, on days 1 and 8 every 21 days. Primary endpoint was objective response rate (ORR). Results Twenty patients were enrolled; 75% of them were highly pretreated. No responses were observed (0%); only one patient had a confirmed disease stabilisation (5%). Median progression-free survival was 1 month (95% CI 0.8 to 1.8), median overall survival was 2.1 months (95% CI 1.6 to 3.7). No serious adverse events were observed. Conclusions Despite encouraging preclinical data, our study did not show signs of clinical activity for vinorelbine in this patients’ population. Further investigations on molecular heterogeneity and dynamic evolution of BRAF V600E mutated mCRC are needed.

Bilateral parotid gland metastases from gastric signet-ring cell carcinoma

Introduction: Signet-ring cell (SRC) carcinoma is a common subtype of gastric adenocarcinoma associated with poor prognosis. Metastatic involvement of the parotid gland has been reported in gastric cancer patients, but never bilaterally nor in association with the SRC histotype. Here, we report the first case and a brief review of the literature. Case description: A 47-year-old woman was referred to our center for a signet-ring gastric carcinoma with synchronous hepatic and peritoneal metastases. After 3 lines of chemotherapy, the patient reported a progressive bilateral enlargement in the periauricolar area. An ultrasound of the salivary glands and a fine needle biopsy were diagnostic for parotid metastases of gastric origin. In the literature, only 3 cases of parotid gland metastases arising from gastric cancer are described – none with a feature of SRC carcinoma. Conclusions: To the best of our knowledge, this is the first report of gastric SRC carcinoma with bilateral parotid metastases. This case highlights the importance of considering a parotid enlargement as a possible sign of disease progression in a patient with gastric cancer. Fine-needle biopsy and immunocytochemistry are essential in establishing the origin of the secondary lesion.