Molecular screening with liquid biopsy for anti-EGFR retreatment in metastatic colorectal cancer: preliminary data from the randomized phase 2 PARERE trial

Background

Retreatment with anti-EGFR monoclonal antibodies is a promising strategy in patients with RAS/BRAF wild-type (wt) metastatic colorectal cancer (mCRC) who achieved benefit from previous anti-EGFR exposure upon exclusion of mutations in RAS/BRAF genes according to circulating tumor DNA (ctDNA) analysis by means of liquid biopsy (LB). This treatment approach is now being investigated in the randomized phase II trial PARERE (NCT04787341). We here present preliminary findings of molecular screening.

Methods

Patients with RAS/BRAFV600E wt mCRC according to tissue genotyping who benefited from previous anti-EGFR-based treatment (fluoropyrimidines, oxaliplatin, irinotecan, and antiangiogenics) and then experienced disease progression to EGFR targeting were eligible for screening in the PARERE trial. The next-generation sequencing (NGS) panel Oncomine™ was employed for ctDNA testing.

Results

A total of 218 patients underwent LB, and ctDNA sequencing was successful in 201 of them (92%). RAS/BRAFV600E mutations were found in 68 (34%) patients and were mainly subclonal (median variant allele fraction [VAF] for KRAS, NRAS, and BRAF mutant clones: 0.52%, 0.62%, and 0.12%, respectively; p = 0.01), with KRASQ61H being the most frequently detected (31%). Anti-EGFR-free intervals did not predict ctDNA molecular status (p = 0.12). Among the 133 patients with RAS/BRAFV600E wt tumors according to LB, 40 (30%) harbored a mutation in at least another gene potentially implied in anti-EGFR resistance, mainly with subclonal expression (median VAF, 0.56%). In detail, alterations in PIK3CA, FBXW7, GNAS, MAP2K, ERBB2, BRAF (class I and II non-BRAFV600E), SMAD, EGFR, AKT1, and CTNNB1 occurred in 13%, 8%, 7%, 3%, 2%, 2%, 1%, 1%, 1%, and 1% cases, respectively. Co-mutations were detected in 13 (33%) out of 40 patients.

Conclusions

This is the largest prospective cohort of mCRC patients screened with LB for anti-EGFR retreatment in a randomized study. ctDNA genotyping reveals that at least one out of three patients candidate for retreatment should be excluded from this therapy, and other potential drivers of anti-EGFR resistance are found in approximately one out of three patients with RAS/BRAFV600E wt ctDNA.

Exploring the Role of Immunotherapy-Based Treatments for Advanced Non-Small-Cell Lung Cancer With Novel Driver Alterations

BACKGROUND

Immunotherapy (IO) single agent or combined with chemotherapy (CT-IO) is the standard treatment for advanced non-small-cell lung cancer (aNSCLC) without driver alterations. IO efficacy in patients with novel driver alterations is not well reported.

MATERIALS AND METHODS

Data of aNSCLC patients treated with IO or CT-IO in any line from January 2016 to September 2022 were retrospectively collected. Patients harboring novel driver alterations (m-cohort), including MET exon 14 skipping, BRAF (V600E or atypical), RET rearrangements, HER2 point mutations/exon 20 insertions or uncommon EGFR mutations/EGFR exon 20 insertions, and wild type patients (wt-cohort) were eligible. Clinico-pathological data were extracted from Institutional databases and compared through chi square or Fisher's exact test. Survivals were estimated through Kaplan-Meier method and compared by log-rank test.

RESULTS

m-cohort and wt-cohort included 84 and 444 patients, respectively. Progression free survival (PFS) was 5.53 vs. 4.57 months (P= .846) and overall survival (OS) was 25.1 vs. 9.37 months, (P < .0001) for m-cohort compared to wt-cohort. Within the m-cohort, BRAF atypical mutations had the better outcomes (Overall Response Rate [ORR], PFS), targeted agents timing did not affect response to IO and CT-IO had better ORR and disease control rate (DCR) compared to IO single agent (P = .0160 and P = .0152). In the PD-L1≥50% group, first line IO single agent resulted in inferior ORR (P = .027) and PFS (P = .022) in m-cohort compared to wt-cohort.

CONCLUSION

IO based treatments seem not detrimental for patients harboring novel driver alteration. Adding CT could improve modest responses to IO alone. Confirmation on larger datasets is required.

Breast implant associated anaplastic large cell lymphoma: Evidence for an efficient diagnostic workup

INTRODUCTION

During the last few years it has been shown that an anaplastic T cell lymphoma can develop as a rare and late sequelae of implant-based breast reconstruction. This malignancy was recognized in the 2017 by WHO and named breast implant associated anaplastic large T cell lymphoma (BIA-ALCL). BIA-ALCL usually presents as abundant effusion around the implant, thus, in addition to cytology smears, its diagnosis also requires immunohistochemistry, T cells clonality and cytometry. Due to the increasing attention of clinicians, it is likely that the number of the BIA-ALCL suspected cases will grow in the future, implying the necessity of a reliable and cost-effective diagnostic procedure.

METHODS

To achieve this goal, we retrospectively analyzed the results of laboratory investigations performed at our Institute (Fondazione IRCCS Istituto Nazionale dei Tumori Milan, Italy) on 44 effusions obtained from 31 women suspected for BIA-ALCL.

RESULTS

Through cytology, eight out of 44 effusions showed the presence of BIA-ALCL cells. Lymphoma cells were than confirmed in seven samples by immunohistochemistry and/or T cell clonality and/or cytometry. Overall, cytology showed 100% sensitivity, 97% specificity and positive and negative predictive values of 87.5% and 100% respectively. Further analyses were particularly useful in effusions showing small percentages of BIA-ALCL cells. Moreover, an extended cytometric profile that can be applied when fast confirmation of the cytologic result is required was also identified.

CONCLUSIONS

Our results evidenced a central role of cytopathology in the management of BIA-ALCL suspected effusions and suggested that further laboratory investigations might be applied only in cases showing atypical/activated lymphoid cells through cytology.

The Revolution of Immunotherapy in Gynecological Cancers: The Lazarus Effect in Endometrial Cancer

Patients with solid tumors and mismatch repair deficiency (dMMR) or microsatellite instability-high (MSI-H) are eligible for immunotherapy. Recently, different reports described patients with poor performance status (PS), unrelated to comorbidities, which showed a rapid improvement of their clinical conditions under immunotherapy, which evoked a Lazarus response. Very few data on the efficacy and safety of immunotherapy in patients with gynecological malignancies and poor PS are available. Based on the GARNET trial, Dostarlimab, a monoclonal antibody anti-programmed death receptor-1 (PD-1), has been approved in advanced or recurrent mismatch repair deficient endometrial cancer (EC) which progressed after platinum-based therapy. For the first time, in gynecological oncology, an immune checkpoint inhibitor drastically changed the clinical practice. We collected a multicenter case series of six patients with advanced endometrial carcinoma and PS ECOG 3-4 treated with Dostarlimab, showing exceptionally quick responses and significant improvement of PS to configure a Lazarus response.

A2AR Expression and Immunosuppressive Environment Independent of KRAS and GNAS Mutations in Pseudomyxoma Peritonei

In pseudomyxoma peritonei (PMP), KRAS and GNAS mutations are frequent. We hypothesized that these mutations may contribute to the suppression of antitumor immunity: KRAS may induce GMCSF expression, while GNAS may enhance the expression of cyclic adenosine monophosphate and A2AR signaling. This study aimed to explore possible mechanisms facilitated by KRAS and GNAS mutations for escaping immune surveillance. Additionally, we looked for new potential therapeutic and prognostic targets in this rare disease which is poorly characterized at the molecular level. GM-CSF, A2AR, CD73, CD39, and PD-L1 expression was investigated by immunohistochemistry in 40 PMPs characterized for GNAS and KRAS mutational status. Immune cell populations were studied by immunohistochemistry and nanostring nCounter^®. Following the criteria of a prognostic nomogram reported for PMP, we stratified the patients into two different risk groups, with 28 "low-risk" and 12 "high-risk" patients. We observed the expression of GM-CSF (74%); CD39 (37%); CD73 (53%); A2AR (74%); and PD-L1 (16%) which was unrelated to GNAS or KRAS status. The tumor microenvironment showed the presence of CD4+ T cells (86%); CD8+ T cells (27%); CD20+ B (67%); CD15+ cells (86%); and CD163+ M2 macrophages (67%), while CD56+ NK cells were absent. CD163 expression (27%) in PMP tumor cells was associated with poor prognosis. GNAS mutation and A2AR expression were not associated with a specific immune transcriptional signature. However, the expression assay revealed 21 genes associated with prognosis. The "high-risk" patients exhibited worse progression-free survival (HR = 2.3, CI 95%: 1.1-5.1, p = 0.034) and significant downregulation of MET, IL8, PPARG, DTX4, HMGA1, ZIC2, WNT5B, and CCRL2. In conclusion, we documented the presence of immunosuppressive factors such as GM-CSF, A2AR, and PD-L1 in PMP. These factors were not associated with GNAS and KRAS status and could be explored as therapeutic molecular targets. Additionally, a set of potential prognostic biomarkers, including CD163 expression in tumor cells, deserve further investigation.

Molecular Tumor Board as a Clinical Tool for Converting Molecular Data Into Real-World Patient Care

PURPOSE

The investigation of multiple molecular targets with next-generation sequencing (NGS) has entered clinical practice in oncology, yielding to a paradigm shift from the histology-centric approach to the mutational model for personalized treatment. Accordingly, most of the drugs recently approved in oncology are coupled to specific biomarkers. One potential tool for implementing the mutational model of precision oncology in daily practice is represented by the Molecular Tumor Board (MTB), a multidisciplinary team whereby molecular pathologists, biologists, bioinformaticians, geneticists, medical oncologists, and pharmacists cooperate to generate, interpret, and match molecular data with personalized treatments.

PATIENTS AND METHODS

Since May 2020, the institutional MTB set at Fondazione IRCCS Istituto Nazionale Tumori of Milan met weekly via teleconference to discuss molecular data and potential therapeutic options for patients with advanced/metastatic solid tumors.

RESULTS

Up to October 2021, among 1,996 patients evaluated, we identified >10,000 variants, 43.2% of which were functionally relevant (pathogenic or likely pathogenic). On the basis of functionally relevant variants, 711 patients (35.6%) were potentially eligible to targeted therapy according to European Society of Medical Oncology Scale for Clinical Actionability of Molecular Targets tiers, and 9.4% received a personalized treatment. Overall, larger NGS panels (containing >50 genes) significantly outperformed small panels (up to 50 genes) in detecting actionable gene targets across different tumor types.

CONCLUSION

Our real-world data provide evidence that MTB is a valuable tool for matching NGS data with targeted treatments, eventually implementing precision oncology in clinical practice.

Prevalence of BRCA homopolymeric indels in an ION Torrent-based tumour-to-germline testing workflow in high-grade ovarian carcinoma

Tumour DNA sequencing is essential for precision medicine since it guides therapeutic decisions but also fosters the identification of patients who may benefit from germline testing. Notwithstanding, the tumour-to-germline testing workflow presents a few caveats. The low sensitivity for indels at loci with sequences of identical bases (homopolymers) of ion semiconductor-based sequencing techniques represents a well-known limitation, but the prevalence of indels overlooked by these techniques in high-risk populations has not been investigated. In our study, we addressed this issue at the homopolymeric regions of BRCA1/2 in a retrospectively selected cohort of 157 patients affected with high-grade ovarian cancer and negative at tumour testing by ION Torrent sequencing. Variant allele frequency (VAF) of indels at each of the 29 investigated homopolymers was systematically revised with the IGV software. Thresholds to discriminate putative germline variants were defined by scaling the VAF to a normal distribution and calculating the outliers that exceeded the mean + 3 median-adjusted deviations of a control population. Sanger sequencing of the outliers confirmed the occurrence of only one of the five putative indels in both tumour and blood from a patient with a family history of breast cancer. Our results indicated that the prevalence of homopolymeric indels overlooked by ion semiconductor techniques is seemingly low. A careful evaluation of clinical and family history data would further help minimise this technique-bound limitation, highlighting cases in which a deeper look at these regions would be recommended.

Evaluation of clinical benefit and progression-free survival ratio of targeted treatments in a prospective cohort study of patients with biliary tract cancers

590

Background: Biliary Tract Cancers (BTC) have poor prognosis and limited therapeutic options. There is mounting evidence for biomarker-directed therapy for BTC, with several potentially actionable molecular targets reported in up to ~50% of patients and significant biological differences between intrahepatic (ICC) and extrahepatic (ECC) cholangiocarcinoma and Gallbladder cancer (GBC). ESMO and ASCO recommends the use of tumour multigene next generation sequencing (NGS) for CCA. Methods: This was a monocentric study assessing real-life clinical actionability of molecular alterations identified with expanded NGS for patients (pts) affected by advanced BTCs treated at Fondazione IRCCS Istituto Nazionale dei Tumori of Milan from January 2016 to July 2022. NGS was performed either via the “Hotspot Cancer Panel, Ion Torrent”, the “Oncomine Comprehensive Assay Plus” or the FoundationOne CDx panel; FGFR2 testing was also performed via fluorescence in situ hybridisation. Molecular alterations were classified according to ESMO Scale for Clinical Actionability of Molecular Targets (ESCAT) and correlated with targeted treatments administered and efficacy endpoints. Benefit from targeted treatment was evaluated by means of progression-free survival (PFS) ratio, as defined as the ratio of each patient’s PFS2 (i.e. PFS on molecularly informed therapy) to the PFS1 (PFS on his/her most recent previous treatment), with d for efficacy equal to 1. Results: Out of 340 pts with adequate tissue for NGS, 231 (68%) were affected by ICC, 61 (32%) by ECC and 48 (14%) by GBC. Actionable alterations as per ESCAT I-III were found in 33 % of pts (N= 113, including IDH1 mutation, FGFR2 fusions/rearrangement/mutations, MSI-H, BRAFV600E mutations, ERBB2 mutations/amplifications, BRCA1/2 mutations); 88% of these alterations were found in pts with ICC. Targeted therapy was actually started for 48 pts (14 %), with 9 pts treated with ivosidenib, 32 with FGFR2 inhibitors, 2 with PD-L1 inhibitor, 6 with BRAF+MEK inhibitor and 1 with an HER2 inhibitor). Overall response rate and disease control rate were 18% and 62%, respectively.Median PFS was 5.4 months(95% CI 3.0 - 6.4) overall and 10.12 months on BRAF+MEK inhibitors, 5.55 months on FGFR2 inhibitors, 2.92 months on ivosidenib and 6.23 months on PD-L1 inhibitors. Median PFS ratio was 1.1 (95%CI 0.7 - 1.4), with benefit rate of 51%. Of note, 5 (10%) received targeted therapy as > III line. Median overall survival of targeted therapy was 10 months. Conclusions: Expanded sequencing for BTCs is feasible in real-life and can improve treatment strategy. Analysis of PFS ratio and of treatment outcomes shows clinically meaningful benefit of targeted treatment in pretreated patients.

Pan-TRK immunohistochemistry as screening tool for NTRK fusions: A diagnostic workflow for the identification of positive patients in clinical practice

BACKGROUND

Pan-TRK inhibitors Entrectinib and Larotrectinib have been recently approved as tumor-agnostic therapies in NTRK1-2-3 rearranged patients and there is therefore an urgent need to identify reliable and accessible biomarkers for capturing NTRK fusions in the real-world practice.

OBJECTIVE

We aim to assess the analytical validity of the recently released pan-TRK assay (Ventana), running a head-to-head comparison between immunohistochemistry and Archer FusionPlex Lung Panel (ArcherDX) that is designed to detect key fusions in 13 genes, also including NTRK1-3.

METHODS

Pan-TRK IHC and NGS analysis were conducted on a retrospective/prospective cohort of 124 cancer patients (carcinomas, 93 cases; soft tissue sarcomas, 19; primary central nervous system tumours, 10; and neuroblastomas, 2). FISH data were available in most of the IHC/NGS discordant cases.

RESULTS

A comparison between IHC and NGS results was carried out in 117 cases: among 30 pan-TRK positive cases, NTRK rearrangement by NGS was found in 11 (37%), while one of the 87 (1.1%) pan-TRK negative cases (a case of NSCLC) showed a TPM3-NRTK1 rearrangement by NGS. Accordingly, sensitivity and specificity of IHC in predicting NTRK status were 91.7% and 81.9%, respectively, while negative (NPV) and positive predictive value (PPV) were 98.8% and 36.7%, respectively.

CONCLUSIONS

These data lead to suggest that IHC with VENTANA pan-TRK antibody can be a reliable screening tool for the identification of patients potentially bearing NTRK rearranged tumours.

Management of BRCA Tumour Testing in an Integrated Molecular Tumour Board Multidisciplinary Model

Tumour testing of the BRCA1/2 genes is routinely performed in patients with different cancer histological subtypes. To accurately identify patients with tumour-detected germline pathogenic variants (PVs) is a relevant issue currently under investigation. This study aims at evaluating the performance of the tumour-to-germline diagnostic flowchart model defined at our Institutional Molecular Tumour Board (MTB). Results from tumour BRCA sequencing of 641 consecutive unselected cancer patients were discussed during weekly MTB meetings with the early involvement of clinical geneticists for appropriate referral to genetic counselling. The overall tumour detection rate of BRCA1/2 PVs was 8.7% (56/641), ranging from 24.4% (31/127) in high-grade ovarian cancer to 3.9% (12/304) in tumours not associated with germline BRCA1/2 PVs. Thirty-seven patients with PVs (66%) were evaluated by a clinical geneticist, and in 24 of them (64.9%), germline testing confirmed the presence of the PV in blood. Nine of these patients (37.5%) were not eligible for germline testing according to the criteria in use at our institution. Cascade testing was subsequently performed on 18 relatives. The tumour-to-germline diagnostic pipeline, developed in the framework of our institutional MTB, compared with guideline-based germline testing following genetic counselling, proved to be effective in identifying a higher number of germline BRCA PVs carriers.

BYL719 (alpelisib) for the treatment of PIK3CA-mutated, recurrent/advanced cervical cancer

PURPOSE

Advanced/recurrent cervical cancer has limited therapeutic options, with a median progression-free survival after the failure of systemic treatments ranging between 3.5 and 4.5 months. Here, we reported our preliminary experience in the use of BYL719 (alpelisib) in advanced/recurrent cervical cancer after failure of at least 2 lines of treatment. The Istituto Nazionale dei Tumori di Milano approved this investigation.

METHODS

From April 2020 to September 2020, 17 consecutive patients with recurrent cervical cancer had Next Generation Sequencing (NGS). Of these, six patients harboring the PIK3CA mutation were included in the study. All patients had been treated with at least 2 previous lines of systemic treatment: 3 patients received >2 prior lines of treatment in the recurrent or metastatic setting; 60% had received prior bevacizumab in combination with chemotherapy. All patients started alpelisib at the daily dosage of 300 mg.

RESULTS

Investigator-assessed confirmed objective response rate (ORR) was 33%. The disease control rate (DCR) was 100%. According to RECIST 1.1, two patients had a partial response (PR), and four patients had stable disease (SD). No complete response was observed. The mean duration of response (DOR) was 11.5 (SD 3.75) months; five patients had PR lasting for >9 months. One patient stopped the treatment at 0.82 months due to the onset of a grade 2 adverse event (AE) (skin rash). Grade 3 treatment-related AEs included: lymphoedema (n = 1, 17%) and rash (n = 1, 17%). No treatment-related grade 4-5 AEs occurred.

CONCLUSIONS

Our preliminary data highlighted a high level of efficacy in this setting of patients. Further trials are needed to assess the safety and effectiveness of alpelisib in PIK3CA-mutated recurrent/advanced cervical cancer.

Temozolomide Followed by Combination With Low-Dose Ipilimumab and Nivolumab in Patients With Microsatellite-Stable, O6-Methylguanine-DNA Methyltransferase-Silenced Metastatic Colorectal Cancer: The MAYA Trial

This is a multicenter, single-arm phase II trial evaluating the efficacy and safety of an immune-sensitizing strategy with temozolomide priming followed by a combination of low-dose ipilimumab and nivolumab in patients with microsatellite-stable (MSS) and O⁶-methylguanine–DNA methyltransferase (MGMT)–silenced metastatic colorectal cancer (mCRC).

MAYA shows that temozolomide priming followed by Ipi/Nivo combo induces durable benefit in MSS/MGMT-silenced mCRC.

Targeted RNA-sequencing analysis for fusion transcripts detection in tumor diagnostics: assessment of bioinformatic tools reliability in FFPE samples

Aim:

Diagnostic laboratories are progressively introducing next-generation sequencing (NGS) technologies in the routine workflow to meet the increasing clinical need for comprehensive molecular characterization in cancer patients for diagnosis and precision medicine, including fusion-transcripts detection. Nevertheless, the low quality of messenger RNA (mRNA) extracted from formalin-fixed paraffin-embedded (FFPE) samples may affect the transition from traditional single-gene testing approaches [like fluorescence in situ hybridization (FISH), immunohistochemistry (IHC), or polymerase chain reaction (PCR)] to NGS. The present study is aimed at assessing the overall accuracy of RNA fusion transcripts detection by NGS analysis in FFPE samples in real-world diagnostics.

Methods:

Herein, NGS data from 190 soft tissue tumors (STTs) and carcinoma cases, discussed in the context of the institutional Molecular Tumor Board, are reported and analyzed by FusionPlex^© Solid tumor kit through the manufacturer’s pipeline and by two well-known fast and accurate open-source tools [Arriba (ARR) and spliced transcripts alignment to reference (STAR)-fusion (SFU)].

Results:

The combination of FusionPlex^© Solid tumor with ArcherDX^® Analysis suite (ADx) analysis package has been proven to be sensitive and specific in STT samples, while partial loss of sensitivity has been found in carcinoma specimens.

Conclusions:

Albeit ARR and SFU showed lower sensitivity, the use of additional fusion-detection tools can contribute to reinforcing or extending the output obtained by ADx, particularly in the case of low-quality input data. Overall, our results sustain the clinical use of NGS for the detection of fusion transcripts in FFPE material.

Time-domain diffuse optics with 8.6 mm2 fast-gated SiPM for extreme light harvesting

Fast time-gated single-photon detectors demonstrated high depth sensitivity in the detection of localized absorption perturbations inside scattering media, but their use for in vivo clinical applications-such as functional imaging of brain activation-was impaired by their small (<0.04mm²) active area. Here, we demonstrate, both on phantoms and in vivo, the performance of a fast-gated digital silicon photomultiplier (SiPM) that features an overall active area of 8.6mm², overcoming the photon collection capability of established time-gated single-pixel detectors by orders of magnitude, enabling deep investigations within scattering media and high signal-to-noise ratios at late photon arrival times.

SDHA Germline Variants in Adult Patients With SDHA-Mutant Gastrointestinal Stromal Tumor

BACKGROUND

SDH-deficient gastrointestinal stromal tumors (GIST) account for 20-40% of all KIT/PDGFRA-negative GIST and are due to mutations in one of the four SDH-complex subunits, with SDHA mutations as the most frequent. Here we sought to evaluate the presence and prevalence of SDHA variants in the germline lineage in a population of SDHA-deficient GIST.

METHODS

Germline SDHA status was assessed by Sanger sequencing on a series of 14 patients with gastric SDHA-deficient GIST.

RESULTS

All patients carried a germline SDHA pathogenic variant, ranging from truncating, missense, or splicing variants. The second hit was the loss of the wild-type allele or an additional somatic mutation. One-third of the patients were over 50 years old. GIST was the only disease presentation in all cases except one, with no personal or familial cancer history. Seven metastatic cases received a multimodal treatment integrating surgery, loco-regional and medical therapy. The mean follow-up time was of 10 years, confirming the indolent clinical course of the disease.

CONCLUSION

SDHA germline variants are highly frequent in SDHA-deficient GIST, and the disease may occur also in older adulthood. Genetic testing and surveillance of SDHA-mutation carriers and relatives should be performed.

Identification of SDHA germline mutations in sporadic SDHA mutant gastrointestinal stromal tumors (GIST): The need of a genetic counselling

11537

Background: SDH- deficient GIST, as defined by the loss of expression of SDHB, account up to about 10% of all gastric GIST and generally affect younger population. Germline mutations in SDHB, SDHC, and SDHD occur in about 20–30% of SDH- deficient, that may be referred to a hereditary condition known as hereditary GIST-paraganglioma syndrome (Carney-Stratakis Syndrome), whereas germline SDHA mutations have been rarely described in apparently sporadic cases. Currently, even germline testing is recommended for SDH- deficient GIST, there are no clear guidelines for genetic counselling and follow-up of SDH x mutation carriers and relatives, especially for SDHA mutant GIST not yet linked to well-defined hereditary syndrome. The aim of this work was to study the SDHA gene in the normal DNA of patients with SDHA mutant GIST. Methods: Thirteen patients carrying SDHA-mutant GIST were studied (8F/5M). Median age of diagnosis was 45,9 years (range 25-74). All GIST were located in the stomach and 3 patients out 13 presented a metastatic disease. In all cases except one, the GIST was the only cancer presentation and no personal or familial history of cancer was revealed. All cases were negative for SDHB immunohistochemistry. Germline mutations were identified through Sanger sequencing of SDHA in the normal counterpart. Results: Germline mutations were identified in all patients for which normal counterpart was available: 4 cases harboured truncating mutations (S384X, R31X and W119X); 5 cases carried pathogenic missense mutations (G233V, R171H, R589Q, G257A and R600Q) and 2 cases had splice site alterations (c.457-3_457-1 delCAG and c.456+9 C > T). In 8 cases the tumor DNA showed the loss of the corresponding wild-type allele, while in the other 3 cases compound heterozygosity for an additional somatic mutation was detected (R589W, R451C,and R171C). In 2 patients, unfortunately, normal DNA was not available, however both tumours carried two mutational hits on SDHA (one with heterozygous G419R and E564K, and one with homozygous R585Q). Of note, 5 patients presented un-usaul SDHA related clinical characteristics as were not young adult ( > 50 years-old) or no multifocal GIST. Conclusions: We demonstrated that germline SDHA mutations are highly frequent in SDHA- deficient GIST. Therefore, although a clear syndrome has not been defined, genetic counselling and follow-up of SDHA mutation carriers and relatives should be clarified.

Rechallenge for Patients With RAS and BRAF Wild-Type Metastatic Colorectal Cancer With Acquired Resistance to First-line Cetuximab and Irinotecan: A Phase 2 Single-Arm Clinical Trial

Importance

Based on a small retrospective study, rechallenge with cetuximab-based therapy for patients with KRAS wild-type metastatic colorectal cancer (mCRC) who were previously treated with the same anti-epidermal growth factor receptor-based regimen might be efficacious. Recent data suggest the role of liquid biopsy as a tool to track molecular events in circulating tumor DNA (ctDNA).

Objective

To prospectively assess the activity of cetuximab plus irinotecan as third-line treatment for patients with RAS and BRAF wild-type mCRC who were initially sensitive to and then resistant to first-line irinotecan- and cetuximab-based therapy.

Design, Setting, and Participants

Multicenter phase 2 single-arm trial conducted from January 7, 2015, to June 19, 2017. Liquid biopsies for analysis of ctDNA were collected at baseline. Main eligibility criteria included RAS and BRAF wild-type status on tissue samples; prior first-line irinotecan- and cetuximab-based regimen with at least partial response, progression-free survival of at least 6 months with first-line therapy, and progression within 4 weeks after last dose of cetuximab; and prior second-line oxaliplatin- and bevacizumab-based treatment.

Interventions

Biweekly cetuximab, 500 mg/m2, plus irinotecan, 180 mg/m2.

Main Outcomes and Measures

Overall response rate according to the Response Evaluation Criteria in Solid Tumors, version 1.1. Secondary end points included progression-free survival and overall survival and, as an exploratory analysis, RAS mutations in ctDNA.

Results

Twenty-eight patients (9 women and 19 men; median age, 69 years [range, 45-79 years]) were enrolled. Six partial responses (4 confirmed) and 9 disease stabilizations were reported (response rate, 21%; 95% CI, 10%-40%; disease control rate, 54%; 95% CI, 36%-70%). Primary end point was met because lower limit of 95% CI of response rate was higher than 5%. RAS mutations were found in ctDNA collected at rechallenge baseline in 12 of 25 evaluable patients (48%). No RAS mutations were detected in samples from patients who achieved confirmed partial response. Patients with RAS wild-type ctDNA had significantly longer progression-free survival than those with RAS mutated ctDNA (median progression-free survival, 4.0 vs 1.9 months; hazard ratio, 0.44; 95% CI, 0.18-0.98; P = .03).

Conclusions and Relevance

This is the first prospective demonstration that a rechallenge strategy with cetuximab and irinotecan may be active in patients with RAS and BRAF wild-type mCRC with acquired resistance to first-line irinotecan- and cetuximab-based therapy. The evaluation of RAS mutational status on ctDNA might be helpful in selecting candidate patients.

Trial Registration

ClinicalTrials.gov Identifier: NCT02296203.

Molecular Signatures for Combined Targeted Treatments in Diffuse Malignant Peritoneal Mesothelioma

Background—There are currently no effective therapies for diffuse malignant peritoneal mesothelioma (DMPM) patients with disease recurrence. In this study, we investigated the biology of DMPM by analyzing the EGFR family, Axl, and MET, in order to assess the presence of cross-talk between these receptors, suggesting the effectiveness of combined targeted treatments in DMPM. Method—We analyzed a series of 22 naïve epithelioid DMPM samples from a single institute, two of which showed higher-grade malignancy (“progressed”). EGFR, HER2, HER3, Axl, and MET activation and expression were investigated by biochemical analysis, real-time PCR immunofluorescence, immunohistochemistry, next-generation sequencing, miRNA, and mRNA in situ hybridization. Results—In most DMPMs, a strong EGFR activation was associated with HER2, HER3, Axl, and MET co-activation, mediated mainly by receptor heterodimerization and autocrine-paracrine loops induced by the expression of their cognate ligands. Axl expression was downregulated by miRNA34a. Mutations in MET Sema domain were exclusively found in two “progressed” DMPMs, and the combined Axl and MET inhibition reduced cellular motility in a DMPM cell line obtained from a “progressed” DMPM. Conclusion—The results indicate that the coordinated activity of multiple cross-talks between RTKs is directly involved in the biology of DMPM, suggesting the combined inhibition of PIK3 and mTOR as an effective strategy that may be easily implemented in clinical practice, and indicating that the combined inhibition of EGFR/HER2 and HER3 and of Axl and MET deserves further investigation.

Benefit from anti-EGFRs in RAS and BRAF wild-type metastatic transverse colon cancer: a clinical and molecular proof of concept study

Objective

Primary tumour location is regarded as a reliable surrogate of colorectal cancer biology. Sensitivity to anti-EGFRs (Epidermal Growth Factor Receptor) of metastatic transverse colon cancers (mTCCs) has usually been assumed similar to right-sided tumours; however, evidence about the clinical behaviour of mTCC is limited. Thus, to verify sensitivity of mTCC to anti-EGFRs we conducted the present study.

Methods

Patients with RAS/BRAF wild-type microsatellite stable (MSS) mTCC receiving anti-EGFR monotherapy, or in combination with irinotecan if clearly irinotecan-refractory, were included. Hypothesising an overall response rate (ORR) of 35%, 11 patients, of whom at least 3 were responders, were necessary to be able to reject the null hypothesis of an ORR of 5%, with α and β errors of 0.05 and 0.20. PRESSING panel and consensus molecular subtypes (CMS) were assessed on tumour samples, whereas in-silico data were obtained from TCGA dataset.

Results

Among nine eligible patients, four and three achieved response and disease stabilisation (ORR 44%). At a median follow-up of 23.1 months, median progression-free survival and overall survival were 7.3 (95% CI 3.9 to NA) and 15.0 months (95% CI 10.0 to NA), respectively. A MET amplification and an ERBB4 S303F substitution were detected in patients with rapid disease progression, while others had PRESSING panel-negative tumours with CMS2 or CMS4 subtypes.

Conclusions

RAS/BRAF wild-type MSS mTCCs may be sensitive to anti-EGFRs, as confirmed by molecular analyses.

Epithelioid peritoneal mesothelioma: a hybrid phenotype within a mesenchymal-epithelial/epithelial-mesenchymal transition framework

The aim of this study was to reconsider the biological characteristics of epithelioid malignant peritoneal mesothelioma (E-MpM) in the light of new concepts about epithelial mesenchymal transition and mesenchymal epithelial reverse transition (EMT/MErT) and the role of epigenetic reprogramming in this context. To this end we profiled surgical specimens and derived cells cultures by a number of complementary approaches i.e. immunohistochemistry, immunofluorescence, in situ hybridization, biochemistry, pluripotent stem cell arrays, treatments with cytokines, growth factors and specific inhibitors.The analyses of the surgical specimens showed that i) EZH2 is expressed throughout the spectrum of MpM, ii) that E-MpM (including the high-grade undifferentiated form) are characterised by c-MYC and miRNA 17-5p expression, and iii) that progression to sarcomatoid MpM is dictated by EMT regulators. They also showed that E-MpM expressed c-MET and are enriched in E- and P-cadherins- and VEGFR2-expressing CSCs, thus strongly supporting a role for MErT reprogramming in endowing E-MpM tumour cells with stemness and plasticity, and hence with a drug resistant phenotype. The cell culture-based experiments confirmed the stemness traits and plasticity of E-MpM, and support the view that EZH2 is a druggable target in this tumor.

Sunitinib-induced morpho-functional changes and drug effectiveness in malignant solitary fibrous tumours

Sunitinib improves the outcomes of patients with solitary fibrous tumours (SFTs). The aim of this study was to investigate and contextualise sunitinib-induced morpho-functional changes in order to gain insights into the drug's mechanism of action.To this end, four surgical specimens obtained from two sunitinib-responsive patients with malignant SFT, and one primary cell culture obtained from fresh tumoral tissue and its stabilised cell line, were studied by means of immunohistochemistry, bright field in situ hybridisation, immunofluorescence/confocal microscopy, and biochemistry.The post-sunitinib surgical samples were characterised by two biologically relevant morpho-functional changes: clear areas and necrotic foci. The first were associated with the attenuation/loss of PDGFRB expression and decreased mTOR signalling, and corresponded to a pathological response. The second were associated with the over-expression of PDGFRB and VEGFA, strong mTOR signalling activation, and the appearance of HIF1α expression, hallmarks of pathological progression. The analysis clearly showed that sunitinib reduces the vascular supply network and inhibits tumoral cells. It also either induces autophagy, thus favouring drug response, or impairs autophagy as a result of lysosome sequestration, thus favouring disease progression. These distinct autophagic events were associated with different myeloid immune contextures. Finally, we also found that PDGFRB is one of the components of a complex that includes Beclin 1 and VPS34.The results of these tissue-based analyses provide new insights into sunitinib's mechanism of action in SFT patients.

Dynamics of inorganic components in lake waters from Terra Nova Bay, Antarctica

Water and Suspended Particulate Material (SPM) samples analysed in this work were collected in the austral summer 2011/12 from six shallow Antarctic lakes (Carezza, Edmonson Point 14 and 15a, Gondwana, Inexpressible Island 10b and Tarn Flat 20) of Terra Nova Bay (Northern Victoria Land, Antarctica). The total concentrations of a large suite of inorganic analytes were determined, in order to gain insight into the natural processes regulating species distribution, define natural background values and detect possible present or future local and/or global anthropogenic contamination. Lake water composition was found to be influenced by marine spray, lake geographical position and meltwater input. Seasonal variability was also evaluated for each analyte, and explained considering the natural transport processes involving each species. Multivariate chemometric techniques were used in order to identify groups of samples with similar characteristics and find out similarities and correlations among variables. The variability observed within the water samples is closely connected to the marine aerosol input; hence, it is primarily a consequence of geographical and meteorological factors, such as distance from the ocean and period of year. Higher element concentrations have been found in SPM than in water, suggesting that weathering plays an important role on the chemistry of these lakes or that adsorption processes take place. SPM samples were also examined with a Scanning Electron Microscope (SEM), and many diatoms belonging to different species were detected. No clear evidence of a relevant metal contamination was found in the investigated area.

Efficacy and Biological Activity of Imatinib in Metastatic Dermatofibrosarcoma Protuberans (DFSP)

PURPOSE

To report on imatinib mesylate (IM) in patients with metastatic dermatofibrosarcoma protuberans (DFSP)/fibrosarcomatous (FS)-DFSP and on the impact of the treatment on tumor biology.

EXPERIMENTAL DESIGN

Ten consecutive patients treated with IM from 2007 to 2015 for a metastatic relapse from DFSP/FS-DFSP were identified. FISH analysis for COL1A1-PDGFB was performed. Two IM-treated and 4 naïve FS-DFSP were transcriptionally profiled by RNAseq on HiScanSQ platform. Differential gene expression was analyzed with edgeR (Bioconductor), followed by hierarchical clustering and Principal Component Analysis.

RESULTS

All cases featured fibrosarcomatous in the metastasis and retained the COL1A1-PDGFB. Best RECIST response was: 8 partial response, 1 stable disease, and 1 progressive disease. Median progression-free survival was 11 months. Five patients received surgery after IM and all relapsed. IM was restored in 4 patients with a new response. After IM, the most upregulated genes included those encoding for immunoglobulins and those affecting functions and differentiation of endothelial cells. Pathway enrichment analysis revealed upregulation in genes involved in antigen processing and presentation, natural killer-mediated cytotoxicity, and drug and xenobiotics metabolism. Conversely, a significant down-regulation of kinase signaling pathways was detected.

CONCLUSIONS

All metastatic cases were fibrosarcomatous. Most patients responded to IM, but PFS was shorter than reported in published series which included both DFSP and FS-DFSP. All patients operated after IM had a relapse, suggesting that IM cannot eradicate metastatic cases and that the role of surgery is limited. Transcriptional profile of naïve and posttreatment samples pointed the contribution of immune infiltrates in sustaining the response to IM.

Abstract 74: Establishment and characterization of the new sacral chordoma cell line Chor-IN-1

Chordomas are rare, slowly growing but locally invasive bone tumors, derived from notocord remnants and characterized by the expression of “Brachyury” transcription factor.

No standard medical therapy is available for this indication that is resistant to chemotherapy. Surgery associated to radiation, is the conventional treatment, but recurrence is extremely common and disease progression is severely crippling for patients.

Expression of activated tyrosine kinase receptors and downstream pathways has been observed, including PDGFRβ and EGFR. Although some clinical responses have been obtained with Imatinib, also in combination with Sirolimus, and with Erlotinib, these treatments cannot eradicate the disease, and there is a strong need for new effective therapies.

Only a handful of chordoma cell lines are available today and the paucity of in vitro models has so far limited the identification of new molecular targets and the assessment of the efficacy of small molecules inhibitors on chordoma cells proliferation.

Here we present the establishment and the characterization of the new Chor-IN-1 chordoma cell line from a recurrent sacral tumor of a patient previously treated with Imatinib and radiotherapy. The cell line has a very slow growth rate, as normally observed for this type of tumors, and displays the typical chordoma physaliferous morphology. The karyotype is indicative of a single population and the Short Tandem Repeat (STR) profile is unique and 100% identical to that of the original tumor sample. The cell line expresses the most relevant chordoma biomarkers, like the product of the “T” gene Brachyury, CD24 and Cytoketatin 19. The non synonymous rs2305089 polymorphism in the “T” gene, associated with chordoma predisposition, was identified in the Chor-IN-1, as well as in the UCH-1 and UCH-2 chordoma reference cell lines.

To further characterize the new cell line, its genetic background and transcriptional profile, with particular focus on kinases, was analysed by a Next Generation Sequencing (NGS) approach, in parallel with UCH-1 and UCH-2, to identify common and unique cancer related features.

Finally, the cell line was characterized for its sensitivity to selected kinase inhibitor drugs already approved or in clinical testing, in parallel with the control cell lines. Among the several EGFR inhibitors tested, Afatinib resulted generally the most active, suggesting that treatment with this drug may represent a valuable therapeutic approach in chordoma.

In conclusion, we report the establishment and in depth characterization of a new chordoma cell line that, retaining all the typical features of chordomas, represents a useful tool for the identification of candidate new druggable targets, or active drugs for chordoma therapy.

Citation Format: Paola Magnaghi, Roberta Bosotti, Nadia Amboldi, Liviana Cozzi, Alessio Somaschini, Silvia Stacchiotti, Fabio Bozzi, Elena Tamborini, Elena Conca, Silvana Pilotti, Marco A. Pierotti, Sebastiano Di Bella, Carlo Cusi, Dario Ballinari, Arturo Galvani, Barbara Salom, Antonella Isacchi. Establishment and characterization of the new sacral chordoma cell line Chor-IN-1. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 74. doi:10.1158/1538-7445.AM2015-74

Activity of sunitinib in extraskeletal myxoid chondrosarcoma

BACKGROUND

Extraskeletal myxoid chondrosarcoma (EMC) is a rare soft tissue sarcoma, marked by NR4A3 rearrangement. Herein we report on the activity of sunitinib in a series of 10 patients, strengthening what initially observed in two cases.

PATIENTS AND METHODS

From July 2011, 10 patients with progressive metastatic translocated EMC have been consecutively treated with sunitinib 37.5mg/day, on a named-use basis. In an attempt to interpret the activity of sunitinib in EMC, genotype/phenotype correlations were carried out by fluorescence in situ hybridization (FISH) analyses. Moreover, transcriptome, immunohistochemical and biochemical analyses of a limited set of samples were performed focusing on some putative targets of sunitinib.

RESULTS

Eight of 10 patients are still on therapy. Six patients had a Response Evaluation Criteria in Solid Tumours (RECIST) partial response (PR), two were stable, two progressed. Positron emission tomography (PET) was consistent in 6/6 evaluable cases. One patient underwent surgery after sunitinib, with evidence of a pathologic response. At a median follow-up of 8.5 months (range 2-28), no secondary resistance was detected. Median progression free survival (PFS) has not been reached. Interestingly, all responsive cases turned out to express the typical EWSR1-NR4A3 fusion, while refractory cases carried the alternative TAF15-NR4A3 fusion. Among putative sunitinib targets, only RET was expressed and activated in analysed samples.

CONCLUSIONS

This report confirms the therapeutic activity of sunitinib in EMC. Genotype/phenotype analyses support a correlation between response and EWSR1-NR4A3 fusion. Involvement of RET deserves further investigation.

Development of transplantable human chordoma xenograft for preclinical assessment of novel therapeutic strategies

BACKGROUND

Chordomas are rare and indolent bone tumors that arise in the skull base and mobile spine. Distant metastases occur in >20% of cases, but morbidity and mortality are mainly related to local relapses that affect the majority of patients. Standard chemotherapy has modest activity, whereas new targeted therapies (alone or in combination) have some activity in controlling disease progression. However, the scarcity of preclinical models capable of testing in vivo responses to these therapies hampers the development of new medical strategies.

METHODS

In this study, 8 chordoma samples taken from 8 patients were implanted in nude mice. Four engrafted successfully and gave rise to tumor masses that were analyzed histologically, by means of fluorescence in situ hybridization and biochemical techniques. The data relating to each of the mouse tumors were compared with those obtained from the corresponding human tumor.

RESULTS

All 4 engraftments retained the histological, genetic and biochemical features of the human tumors they came from. In one epidermal growth factor receptor(EGFR)-positive xenograft, responsiveness to lapatinib was evaluated by comparing the pre- and post treatment findings. The treatment induced a low-level, heterogeneous switching off of EGFR and its downstream signaling effectors.

CONCLUSIONS

Overall, this model is very close to human chordoma and represents a new means of undertaking preclinical investigations and developing tailored therapies.

Development of transplantable human chordoma xenograft for preclinical assessment of novel therapeutic strategies

BACKGROUND

Chordomas are rare and indolent bone tumors that arise in the skull base and mobile spine. Distant metastases occur in >20% of cases, but morbidity and mortality are mainly related to local relapses that affect the majority of patients. Standard chemotherapy has modest activity, whereas new targeted therapies (alone or in combination) have some activity in controlling disease progression. However, the scarcity of preclinical models capable of testing in vivo responses to these therapies hampers the development of new medical strategies.

METHODS

In this study, 8 chordoma samples taken from 8 patients were implanted in nude mice. Four engrafted successfully and gave rise to tumor masses that were analyzed histologically, by means of fluorescence in situ hybridization and biochemical techniques. The data relating to each of the mouse tumors were compared with those obtained from the corresponding human tumor.

RESULTS

All 4 engraftments retained the histological, genetic and biochemical features of the human tumors they came from. In one epidermal growth factor receptor(EGFR)-positive xenograft, responsiveness to lapatinib was evaluated by comparing the pre- and post treatment findings. The treatment induced a low-level, heterogeneous switching off of EGFR and its downstream signaling effectors.

CONCLUSIONS

Overall, this model is very close to human chordoma and represents a new means of undertaking preclinical investigations and developing tailored therapies.

Phase II study on lapatinib in advanced EGFR-positive chordoma

BACKGROUND

To report on a prospective, investigator-driven, phase II study on lapatinib in epidermal growth factor receptor (EGFR)-positive advanced chordoma patients.

PATIENTS AND METHODS

From December 2009 to January 2012, 18 advanced progressing chordoma patients entered this study (median age: 61 years; disease extent: metastatic 72% and locally advanced 28%). Epidermal growth factor receptor (EGFR) expression and activation were evaluated by immunohistochemistry and/or phospho-arrays, real-time polimerase chain reaction, fluorescence immunostaining. Fluorescence in situ hybridization analysis was also carried out. Patients received lapatinib 1500 mg/day (mean dose intensity = 1282 mg/day), until progression or toxicity. The primary study end point was response rate (RR) as per Choi criteria. Secondary end points were RR by Response Evaluation Criteria in Solid Tumor (RECIST), overall survival, progression-free survival (PFS) and clinical benefit rate (CBR; RECIST complete response + partial response (PR) + stable disease (SD) ≥ 6 months).

RESULTS

All patients were evaluable for response. Six (33.3%) patients had PR and 7 (38.9%) SD, as their best Choi responses, corresponding to RECIST SD in all cases. Median PFS by Choi was 6 [interquartile (IQ) range 3-8] months. Median PFS by RECIST was 8 (IQ range 4-12) months, with a 22% CBR.

CONCLUSIONS

This phase II study showed a modest antitumor activity of lapatinib in chordoma. The clinical exploitation of EGFR targeting in chordoma needs to be further investigated, both clinically and preclinically. Clinical trial Registration No: EU Clinical Trials Register trial no. 2009-014456-29.

Are two better than one? A novel double-mutant KIT in GIST that responds to Imatinib

Gastrointestinal stromal tumors carry in about 85% of the cases activating mutations in KIT gene. Generally only one KIT mutation is found in primary tumors and the majority of mutations affecting KIT exon 11 is sensitive to Imatinib. We report upon a GIST case harboring a double-mutant KIT gene at exon 11, which expresses a receptor bearing the known activating W557G mutation and a newly discovered missense Y578C alteration. The relative affinities for ATP and Imatinib of each single (W557G, Y578C) and double (W557G/Y578C) mutant KITs were predicted by in silico studies (computer-based molecular simulations), and compared with those obtained for known Imatinib sensitive and resistant KIT mutants. In parallel, biochemical analysis of the single and double KIT mutants expressed in mammalian cells was performed. Both the in-silico/in-vitro investigations showed constitutive activation and sensitivity to Imatinib of the yet mentioned Y578C mutation as well as of the double mutant, providing evidence that the concomitant presence of the W557G and Y578C mutations does not affect Imatinib response compare to the single mutations, in line with what observed in Imatinib treated patient.

KRAS and BRAF mutations predict primary resistance to imatinib in gastrointestinal stromal tumors

PURPOSE

Gastrointestinal stromal tumors (GIST) are characterized by gain-of-function mutations in KIT/PDGFRA genes leading to a constitutive receptor activation which is well counteracted by imatinib. However, cases in which imatinib as first-line treatment has no effects are reported (primary resistance). Our purpose is to investigate alterations in downstream effectors, not reported so far in mutated GIST, possibly explaining the primary resistance to targeted treatments.

EXPERIMENTAL DESIGN

Two independent naive GIST cohorts have been analyzed for KIT, PDGFRA, KRAS, and BRAF mutations by direct sequencing. Cell lines expressing a constitutively activated and imatinib-responding KIT, alone or in combination with activated KRAS and BRAF, were produced and treated with imatinib. KIT receptor and its downstream effectors were analyzed by direct Western blotting.

RESULTS

In naive GISTs carrying activating mutations in KIT or PDGFRA a concomitant activating mutation was detected in KRAS (5%) or BRAF (about 2%) genes. In vitro experiments showed that imatinib was able to switch off the mutated receptor KIT but not the downstream signaling triggered by RAS-RAF effectors.

CONCLUSIONS

These data suggest the activation of mitogen-activated protein kinase pathway as a possible novel mechanism of primary resistance to imatinib in GISTs and could explain the survival curves obtained from several clinical studies where 2% to 4% of patients with GIST treated with imatinib, despite carrying KIT-sensitive mutations, do not respond to the treatment.

High CD133 expression levels in gastrointestinal stromal tumors

BACKGROUND

Gastrointestinal stromal tumours (GISTs) have activating KIT or PDGFRA gene mutations. Imatinib mesylate, which targets KIT and PDGFRA, is effective in treating GISTs, but 90% of GIST patients become imatinib-resistant as a result of acquiring secondary KIT mutations. Recent findings suggest that tumour growth can be driven by mutated self-renewing progenitors known as cancer stem cells (CSCs), which are believed to be present in all neoplastic proliferations and are thought to accumulate mutations. It is therefore possible that the acquisition of secondary KIT mutations during imatinib treatment may occur in putative GIST CSCs.

METHODS

Using flow cytometry, in vivo murine xenografts and molecular characterization, we tried to identify putative GIST CSCs by looking for the occurrence of common CSC markers such as KIT, CD133, CD90, CD44, and CD34 in 18 surgical samples obtained from nine untreated and nine imatinib-treated KIT-mutated GIST patients.

RESULTS

The results indicated the homogeneous and previously unreported expression of CD133 (18/18), CD90 (15/16), and CD44 (12/14), together with KIT (18/18) and CD34 (13/18). This profile is similar to that identified in bone marrow mesenchymal progenitors and does not seem to be significantly modified by imatinib as only marginal changes in KIT and CD133 expression (P ≤ 0.05, Mann-Whitney test) were found in the treated samples.

CONCLUSIONS

These findings suggest that GISTs are a clonal expansion of quite primitive cells that strictly depend on KIT oncogenic addiction, and have no cancer/stem cell component that can be detected by means of the antigens used in this study.

Sunitinib in advanced alveolar soft part sarcoma: evidence of a direct antitumor effect

BACKGROUND

The purpose of this study was to confirm sunitinib activity in alveolar soft part sarcoma (ASPS) and to report on new insights into the molecular bases thereof.

PATIENTS AND METHODS

From July 2007, nine patients with progressive metastatic ASPS received sunitinib 37.5 mg/day, within a named use program. Cryopreserved material was available for five naive patients, among whom three received sunitinib. Immunofluorescence (IF)/confocal microscopy, biochemical, and molecular/cytogenetic analyses were carried out, complemented by antiproliferative and activation assays in a short-term culture derived from one case.

RESULTS

All patients were eligible for response. Best RECIST response was partial response in five cases, stable disease in three, and progression in one. The median progression-free survival was 17 months. Positron emission tomography results were consistent. Two cases of interval progressions were recorded. Antiproliferative assays and biochemistry on short-term culture showed that sunitinib is able to markedly impair ASPS cells growth and switch-off PDGFRB. IF/confocal microscopy demonstrated coexpression and physical association between PDGFRB/vascular endothelial growth factor receptor 2 (VEGFR2) and RET/VEGFR2 in ASPS cells, which was validated by biochemistry. PDGFRB, RET, and MET ligand-dependent activation was confirmed.

CONCLUSIONS

We confirm the clinical efficacy of sunitinib in ASPS, mediated by PDGFRB, VEGFR2, and RET, which are all expressed in tumor cells. A direct antitumor effect was shown in a short-term cell culture.

Sunitinib malate and figitumumab in solitary fibrous tumor: patterns and molecular bases of tumor response

Antiangiogenic treatment activity has been reported in solitary fibrous tumor (SFT), a rare and little chemosensitive sarcoma. We explored the activity of sunitinib malate (SM) in SFT and studied receptor tyrosine kinase (RTK) activation profile. Eleven patients with progressive metastatic SFT resistant to chemotherapy were treated with continuous-dosing 37.5 mg/d SM on a named-use basis. One of them also received the insulin-like growth factor I receptor (IGFIR) inhibitor figitumumab after developing secondary resistance to SM. Besides, biochemical, molecular, and fluorescence in situ hybridization analyses were done in eight naïve SFTs whose cryopreserved material was available to clarify RTK upstream and downstream signaling. In two cases treated with SM and belonging to the naïve series, both pretreatment and posttreatment samples were available. Ten patients were evaluable for response to SM. The best response according to the Choi criteria was six partial response (all with Response Evaluation Criteria in Solid Tumors stable disease), one stable disease, and three progressive disease. Responses lasted >6 months in five patients. The eight naïve samples showed high expression/phosphorylation of PDGFRB, epidermal growth factor receptor, and IGFIR/IR, in the presence of their cognate ligands. Downstream pathways revealed expression/activation of Akt, extracellular signal-regulated kinase 1-2 and, closely related to SFT subtypes, of S6 and 4E-BP1. In two patients, whose pretreatment and posttreatment clinical and molecular status were available, biochemical data confirmed the activity of SM, although they also suggested a possible time-dependent shift of dominant RTK from PDGFRB to IGFIR/insulin receptor. A Response Evaluation Criteria in Solid Tumors partial response to figitumumab corroborated these findings. SM has antitumor activity in SFT, possibly through a PDGFRB-mediated mechanism, but treatments with IGFIR/insulin receptor and possibly epidermal growth factor receptor inhibitors are worth testing.

Fluorescence in situ hybridization analysis and immunophenotyping of c-Kit/PDGFRA and Bcl-2 expression in gastrointestinal stromal tumors

OBJECTIVE

To investigate c-Kit/PDGFRA genomic alterations, KIT-PDGFRA coexpression in gastrointestinal stromal tumors (GISTs) and the role of Bcl-2.

STUDY DESIGN

We analyzed 70 primary tumors, 6 recurrences, 4 metastases and 1 recurrence plus metastasis, all molecularly characterized. Alterations in gene copy number were detected by fluorescence in situ hybridization (FISH) and expression of KIT, PDGFRA and Bcl-2 by immunohistochemistry.

RESULTS

c-Kit/PDGFRA gene alterations affected 38% of all cases and 39% of primary tumors, with major changes accounting for 15% in both all the cases and primary tumors. Cytoplasmic KIT/PDGFRA coexpression was present in 96.5% of the c-Kit-mutated cases, 100% of the wt c-Kit/PDGFRA cases and 66.6% of the PDGFRA-mutated cases. Bcl-2 immunoreactivity was present in 70% of cases, with expression levels of +++ in 29%, ++ in 38% and + in 33%.

CONCLUSION

FISH confirmed cytogenetic alterations in about 40% of primary GISTs at the onset. The high rate of c-Kit/PDGFRA coexpression suggests that both receptors are involved in oncogenicity and may affect imatinib efficacy. The assumption that Bcl-2 expression is supported by the KIT pathway and that its imatinib-mediated down-regulation contributes to autophagic cell death, although attractive, needs to be further confirmed.

Analysis of receptor tyrosine kinases (RTKs) and downstream pathways in chordomas

We have previously demonstrated that chordomas express activated platelet-derived growth factor receptor (PDGFRB) and that treatment with imatinib, which is capable of switching off the activation of various receptor tyrosine kinases (RTKs) including PDGFRB, benefits a number of patients. The aim of this study was to identify the possible presence of other activated RTKs and their downstream signaling effectors. Cryopreserved material from 22 naïve sporadic chordomas was investigated for the presence of activated RTKs and their cognate ligands and downstream signaling effectors by means of human phospho-RTK antibody arrays, Western blotting, and molecular analysis; immunohistochemistry and fluorescence in situ hybridization were used to analyze the corresponding formalin-fixed and paraffin-embedded samples. We detected activated PDGFRB, FLT3, and colony stimulating factor 1 receptor (CSF1R) of the PDGFR family and highly phosphorylated EGFR, HER2/neu, and (to a lesser extent) HER4 of the EGFR family. The detection of PDGFRB/PDGFB confirmed our previous data. The presence of activated EGFR was paralleled by the finding of high levels of epidermal growth factor (EGF) and transforming growth factor alpha (TGFalpha) and PDGFB co-expression and PDGFRB co-immunoprecipitation. Of the downstream effectors, the PI3K/AKT and RAS/MAPK pathways were both activated, thus leading to the phosphorylation of mammalian target of rapamycin (mTOR) and 4E-BP1 among the regulators involved in translational control. Taken together, our results (i) provide a rationale for tailored treatments targeting upstream activated receptors, including the PDGFR and EGFR families; (ii) support the idea that a combination of upstream antagonists and mTOR inhibitors enhances the control of tumor growth; and (iii) indicate that the 4E-BP1/eIF4E pathway is a major regulator of protein synthesis in chordoma.

Oncogenic and ligand-dependent activation of KIT/PDGFRA in surgical samples of imatinib-treated gastrointestinal stromal tumours (GISTs)

As the range of receptor tyrosine kinase (RTK) inhibitors widens, a detailed understanding of the activating mechanisms of KIT/platelet-derived growth factor receptor (PDGFR)A and the related downstream pathways involved in the development and maintenance of GISTs is becoming increasingly important. We analysed areas with different histological response ratios in surgical specimens taken from imatinib-treated and untreated GIST patients in order to investigate KIT and PDGFRA expression/activation, the presence of their cognate ligands and the activation of downstream signalling, by means of biochemistry, immunohistochemistry and flow cytometry. All of the cases showed KIT and PDGFRA co-expression. In addition to the oncogenic activation of mutated receptors, activation of wild-type KIT and wild-type PDGFRA, sustained by heterodimerization and an autocrine-paracrine loop, was demonstrated by the presence of their specific ligands, stem cell factor (SCF) and PDGFA. To confirm RTK activation further, all of the samples (including those with the highest regression ratios) were investigated for downstream effectors, and all proved to have activated downstream signalling. The results show that after the mutated receptors are switched off, heterologous wild-type receptors become important in imatinib-treated GISTs as a means of maintaining signalling activation. Taken together, our findings suggest that drugs targeting wild-type receptors should be tested in imatinib-treated GIST patients.