Molecular profiling of pediatric and young adult colorectal cancer reveals a distinct genomic landscapes and potential therapeutic avenues.

Colorectal cancer (CRC) is a global health concern, and the incidence of early onset (EO) CRC, has an upward trend. This study delves into the genomic landscape of EO-CRC, specifically focusing on pediatric (PED) and young adult (YA) patients, comparing them with adult (AD) CRC. In this retrospective monocentric investigation, we performed targeted next-generation sequencing to compare the mutational profile of 38 EO-CRCs patients (eight PED and 30 YA) to those of a 'control group' consisting of 56 AD-CRCs. Our findings reveal distinct molecular profiles in EO-CRC, notably in the WNT and PI3K-AKT pathways. In pediatrics, we observed a significantly higher frequency of RNF43 mutations, whereas APC mutations were more prevalent in adult cases. These observations suggest age-related differences in the activation of the WNT pathway. Pathway and copy number variation analysis reveal that AD-CRC and YA-CRC have more similarities than the pediatric patients. PED shows a peculiar profile with CDK6 amplification and the enrichment of lysine degradation pathway. These findings may open doors for personalized therapies, such as PI3K-AKT pathway inhibitors or CDK6 inhibitors for pediatric patients. Additionally, the distinct molecular signatures of EO-CRC underscore the need for age-specific treatment strategies and precision medicine. This study emphasizes the importance of comprehensive molecular investigations in EO-CRCs, which can potentially improve diagnostic accuracy, prognosis, and therapeutic decisions for these patients. Collaboration between the pediatric and adult oncology community is fundamental to improve oncological outcomes for this rare and challenging pediatric tumor.

Harmonization of criteria and terminology in fetal rat skeletal evaluations.

BACKGROUND: A survey of laboratories in North American and Europe that routinely conduct fetal skeletal examinations was performed with the purpose of (1) understanding current terminology used for classifying skeletal findings in developmental toxicity (DT) studies and (2) understanding the criteria used to identify relatively common findings that sufficiently deviate from normal. The goal was to promote terminology harmonization and improve interlaboratory consistency in the criteria used to identify developmental anomalies. METHODS: The survey, designed based on terminology for developmental anomalies recommended by an international collaboration (Makris et al., Congenital Anomalies, 2009;49(3):123-246), was conducted by a subgroup (authors of this publication) of the Royal Society of Biology's International Register of Fetal Morphologists (IRFM). RESULTS: Individual and summarized anonymized responses are provided here. The authors, who are expert fetal morphologists with experience performing fetal examinations, reviewed the responses and generated recommendations on preferred terminology and criteria for determining when morphological variations deviate from normal and warrant recording of the findings for skeletal observations in Sprague Dawley (SD) fetal rats. The objective of these recommendations is to complement Makris et al. (Congenital Anomalies, 2009;49(3):123-246). CONCLUSION: The broad application will improve interlaboratory harmonization of recording fetal skeleton findings in developmental toxicity studies intended for regulatory submissions, including SEND (Standard for Exchange of Nonclinical Data).

Mechanism of Resistance in Gastrointestinal Stromal Tumors.

Imatinib has revolutionized the treatment of GIST since this drug is able to inhibit tumoral growth by blocking the activity of receptor tyrosine kinases, KIT or PDGFRA, that in these tumors are constitutively activated because of the presence of mutations that alters their catalytic activity. However, despite this enormous improvement in the RFS and OS and in the quality of life of GIST patients, imatinib is not able to eradicate the disease: recurrences occur and acquired resistance is a common event which develops during targeted treatments. Several mechanisms have been demonstrated to be responsible for tumoral growth reactivation which is due to the reactivation of the altered KIT/PDGFRA receptors, no more blocked by the drug. Secondary point mutations are generally observed in the regrowing tumors, and it has been demonstrated that they alter the architectural structure of the site in which the interaction between the drug and the receptor happens. Other mechanisms causing drug resistance have been investigated, indicating that many aspects need to be still explicated and fully understood in order to define a strategy able to fight definitively GIST growth.

Negative hyper-selection of metastatic colorectal cancer patients for anti-EGFR monoclonal antibodies: the PRESSING case-control study.

BACKGROUND: Refining the selection of metastatic colorectal cancer patients candidates for anti-epidermal growth factor receptor (EGFR) monoclonal antibodies beyond RAS and BRAF testing is a challenge of precision oncology. Several uncommon genomic mechanisms of primary resistance, leading to activation of tyrosine kinase receptors other than EGFR or downstream signalling pathways, have been suggested by preclinical and retrospective studies. PATIENTS AND METHODS: We conducted this multicentre, prospective, case-control study to demonstrate the negative predictive impact of a panel of rare genomic alterations [PRESSING (PRimary rESiStance IN RAS and BRAF wild-type metastatic colorectal cancer patients treated with anti-eGfr monoclonal antibodies) panel], including HER2/MET amplifications, ALK/ROS1/NTRK1-3/RET fusions and PIK3CA mutations. Hypothesizing a prevalence of candidate alterations of 15% and 0% in resistant and sensitive RAS and BRAF wild-type patients, respectively, with two-sided α and ß errors of 0.05 and 0.20, 47 patients per group were needed. RESULTS: Forty-seven patients per group were included. PRESSING panel alterations were significantly more frequent in resistant (24 out of 47, 51.1%) than in sensitive (1 out of 47, 2.1%) patients (P < 0.001) and in right- (12 out of 29, 41.4%) than left-sided (13 out of 65, 20.0%) tumours (P = 0.03). The predictive accuracy of PRESSING panel and sidedness was 75.3% and 70.2%, respectively. Among hyper-selected patients, right-sidedness was still associated with resistance (P = 0.002). The predictive accuracy of the combined evaluation of PRESSING panel and sidedness was 80.4%. As a secondary analysis, 8 (17.0%) resistant and 0 sensitive patients showed microsatellite instability (P < 0.001). CONCLUSION: The investigated panel of genomic alterations allows refining the selection of RAS and BRAF wild-type metastatic colorectal cancer patients candidates for anti-EGFRs, partially explaining and further corroborating the predictive ability of primary tumour sidedness.

Toward the molecular dissection of peritoneal pseudomyxoma.

BACKGROUND: Outcome of pseudomyxoma peritonei (PMP) after cytoreductive surgery (CRS) and hypertermic intraperitoneal chemotherapy (HIPEC) is heterogeneous even after adjusting for clinico-pathological prognostic variables. The identification of additional prognostic or even predictive biomarkers is an unmet clinical need. PATIENTS AND METHODS: Forty patients with mucinous appendiceal tumors and PMP were clinically eligible and had evaluable tumor samples obtained after CRS and HIPEC. We carried out next-generations sequencing (NGS) of 50 gene's hotspot regions contained in the Hotspot Cancer Panel v2 using the Ion Torrent Personal Genome Machine platform (Life Technologies). RESULTS: KRAS and GNAS mutations were found in 72% and 52%, and their allelic frequency was below 10% in 55% and 43% of samples, respectively. KRAS and GNAS mutations were associated with worse progression-free survival (PFS) at univariate analysis (P = 0.006 and 0.011, respectively). At multivariate analysis, only KRAS mutations were independently associated with PFS (P = 0.012); GNAS mutations were not-being significantly associated with other poor prognostic features such as incomplete cytoreduction or KRAS mutations. Validation of results was carried out in an independent bi-institutional cohort of 25 patients and the prognostic effect of KRAS mutations was again confirmed in the multivariate model (P = 0.029). NGS approach allowed the discovery of other potentially druggable mutations such as those in PI3K, AKT, LKB1, FGFR3 and PDGFRA. CONCLUSIONS: Given the homogeneity of this series and the sensitivity of NGS in this low-cellularity tumor, we demonstrated for the first time a poor prognostic role of KRAS mutations.

BRAF codons 594 and 596 mutations identify a new molecular subtype of metastatic colorectal cancer at favorable prognosis.

BACKGROUND: While the negative prognostic role of BRAF V600E mutation in metastatic colorectal cancer (mCRC) is well established, the impact of BRAF codons 594 and 596 mutations, occurring in <1% of CRCs, is completely unknown. The present work aims to describe clinical, pathological and molecular features and prognosis of BRAF codons 594 and 596 mutant mCRCs, compared with BRAF V600E mutant and wild-type ones. PATIENTS AND METHODS: Patients treated for mCRC at three Italian Institutions between October 2006 and October 2014, with available KRAS and NRAS codon 12, 13, 59, 61, 117 and 146 and BRAF codon 594, 596 and 600 mutational status, as detected by means of direct sequencing or matrix assisted laser desorption ionization time-of-flight MassArray, were included. RESULTS: Ten patients bearing BRAF codons 594 or 596 mutated tumors were identified and compared with 77 and 542 patients bearing BRAF V600E mutated and BRAF wild-type tumors, respectively. While BRAF V600E mutated tumors were more frequently right-sided, mucinous and with peritoneal spread, BRAF 594 or 596 mutated were more frequently rectal, nonmucinous and with no peritoneal spread. All BRAF 594 or 596 mutated tumors were microsatellite stable. Patients with BRAF codons 594 or 596 mutated tumors had markedly longer overall survival (OS) when compared with BRAF V600E mutated [median OS: 62.0 versus 12.6 months; hazard ratio: 0.36 (95% confidence interval 0.20-0.64), P = 0.002], both at univariate and multivariate analyses. CONCLUSIONS: BRAF codon 594 or 596 mutated mCRCs are different from BRAF V600E ones in terms of molecular features, pathological characteristics and clinical outcome. This is consistent with preclinical evidences of a kinase inactivating effect of these mutations. The role of CRAF in transducing the intracellular signal downstream BRAF 594 or 596 mutated proteins opens the way to further preclinical investigation.

The status of PD-L1 and tumor-infiltrating immune cells predict resistance and poor prognosis in BRAFi-treated melanoma patients harboring mutant BRAFV600.

BACKGROUND: BRAF inhibitors (BRAFi) improve survival in metastatic melanoma patients (MMP) but the duration of clinical benefit is limited by development of drug resistance. Here, we investigated whether the expression of programmed death-ligand 1 (PD-L1) and the density of tumor-infiltrating mononuclear cells (TIMC) predict the occurrence of resistance, hence affecting the clinical outcome in BRAFi-treated MMP. METHODS: PD-L1 expression (cutoff 5%) was analyzed by immunohistochemistry with two different antibodies in BRAF(V600)-mutated formalin-fixed and paraffin-embedded samples from 80 consecutive MMP treated with BRAFi at a single institution. TIMC were evaluated by conventional hematoxylin and eosin staining. RESULTS: Forty-six and 34 patients received vemurafenib and dabrafenib, respectively. Membranous expression of PD-L1 was detected in 28/80 (35%) of patients. At multivariate analysis, absence of tumoral PD-L1 staining [odd ratio (OR) 10.8, 95% confidence interval (CI) 2.7-43.3, P < 0.001] and the presence of TIMC (OR 6.5, 95% CI 1.7-24.3, P < 0.005) were associated with a better response to treatment. Median progression-free survival (PFS) and overall survival were 10 and 15 months, respectively. By multivariate assessment, PD-L1 expression [hazard ratio (HR) 4.3, 95% CI 2.1-8.7, P < 0.0001] and absence of TIMC (HR 2.5, 95% CI 1.4-4.7, P < 0.002) correlated with shorter PFS. PD-L1 overexpression (HR 6.2, 95% CI 2.8-14.2, P < 0.0001) and absence of TIMC (HR 3.1, 95% CI 1.5-6.5, P < 0.002) were independent prognostic factors for melanoma-specific survival. CONCLUSION: Our results provide the first proof-of-principle evidence for the predictive and prognostic relevance of PD-L1 immunohistochemical expression and density of immune cell infiltration in BRAF(V600)-mutated MMP treated with BRAFi.

PD-L1 marks a subset of melanomas with a shorter overall survival and distinct genetic and morphological characteristics.

BACKGROUND: Programmed cell death ligand 1 (PD-L1) is a cell surface molecule that plays a critical role in suppressing immune responses, mainly through binding of the PD-1 receptor on T lymphocytes. PD-L1 may be expressed by metastatic melanoma (MM). However, its clinical and biological significance remains unclear. Here, we investigated whether expression of PD-L1 in MM identifies a biologically more aggressive form of the disease, carrying prognostic relevance. PATIENTS AND METHODS: PD-L1 expression was analyzed by immunohistochemistry using two different antibodies in primary tumors and paired metastases from 81 melanoma patients treated at a single institution. Protein expression levels were correlated with PD-L1 mRNA, BRAF mutational status and clinical outcome. PD-L1(+) and PD-L1(-) subsets of the A375 cell line were stabilized in vitro and compared using gene expression profiling and functional assays. Results were confirmed using xenograft models. RESULTS: PD-L1 membrane positivity was detected in 30/81 (37%) of patients. By multivariate analysis, Breslow thickness and PD-L1 membrane positivity were independent risk factors for melanoma-specific death {PD-L1 5% cutoff [hazard ratio (HR) 3.92, confidence interval (CI) 95% 1.61-9.55 P < 0.003], PD-L1 as continuous variable (HR 1.03, 95% CI 1.02-1.04 P < 0.002)}. PD-L1 expression defined a subset of the BRAF-mutated A375 cell line characterized by a highly invasive phenotype and by enhanced ability to grow in xenograft models. CONCLUSIONS: PD-L1 is an independent prognostic marker in melanoma. If confirmed, our clinical and experimental data suggest that PD-L1(+) melanomas should be considered a disease subset with distinct genetic and morpho-phenotypic features, leading to enhanced aggressiveness and invasiveness.

Activity of temozolomide in patients with advanced chemorefractory colorectal cancer and MGMT promoter methylation.

BACKGROUND: No evidence-based treatment options are available for patients with advanced colorectal cancer (CRC) progressing after standard therapies. MGMT is involved in repair of DNA damage and MGMT promoter methylation may predict benefit from alkylating agents such as temozolomide. The aim of our study was to evaluate the activity of temozolomide in terms of response rate in patients with metastatic CRC and MGMT methylation, after failure of approved treatments. PATIENTS AND METHODS: Patients were enrolled in a monocentre, open-label, phase II study and treated with temozolomide at a dose of 150 mg/m2/day for 5 consecutive days in 4-weekly cycles. The treatment was continued for at least six cycles or until progressive disease. RESULTS: Thirty-two patients were enrolled from August 2012 to July 2013. Treatment was well tolerated with one grade 4 thrombocytopenia and no other grade≥3 toxicities. No complete response occurred. The objective response rate was 12%, reaching the pre-specified level for promising activity. Median progression-free survival and overall survival were 1.8 and 8.4 months, respectively. Patients with KRAS, BRAF and NRAS wild-type CRC showed significantly higher response when compared with those with any RAS or BRAF mutation (44% versus 0%; P=0.004). TP53 status had no influence on the primary end point. CONCLUSIONS: Temozolomide is tolerable and active in heavily pre-treated patients with advanced CRC and MGMT promoter methylation. Further studies in biomolecularly enriched populations or in a randomized setting are necessary to demonstrate the efficacy of temozolomide after failure of standard treatments.

Mode of action of trabectedin in myxoid liposarcomas.

To elucidate the mechanisms behind the high sensitivity of myxoid/round cell liposarcoma (MRCL) to trabectedin and the suggested selectivity for specific subtypes, we have developed and characterized three MRCL xenografts, namely ML017, ML015 and ML004 differing for the break point of the fusion gene FUS-CHOP, respectively of type I, II and III. FUS-CHOP binding to the promoters of some target genes such as Pentraxin 3 or Fibronectin 1, assessed by chromatin immunoprecipitation, was strongly reduced in the tumor 24 h after the first or the third weekly dose of trabectedin, indicating that the drug at therapeutic doses causes a detachment of the FUS-CHOP chimera from its target promoters as previously shown in vitro. Moreover, the higher sensitivity of MRCL types I and II appears to be related to a more prolonged block of the transactivating activity of the fusion protein. Doxorubicin did not affect the binding of FUS-CHOP to target promoters. Histologically, the response to trabectedin in ML017 and ML015 was associated with a marked depletion of non-lipogenic tumoral cells and vascular component, as well as lipidic maturation as confirmed by PPARγ2 expression in western Blot. By contrast, in ML004 no major changes either in the cellularity or in the amount of mature were found, and consistently PPARγ2 was null. In conclusion, the data support the view that the selective mechanism of action of trabectedin in MRCL is specific and related to its ability to cause a functional inactivation of the oncogenic chimera with consequent derepression of the adypocytic differentiation.

Dacarbazine in solitary fibrous tumor: a case series analysis and preclinical evidence vis-a-vis temozolomide and antiangiogenics.

PURPOSE: To explore the value of triazines in solitary fibrous tumor (SFT). EXPERIMENTAL DESIGN: We retrospectively reviewed 8 cases of patients with SFT treated with dacarbazine (1,200 mg/m(2) every 3 weeks) as from January 2012. Then, we studied a dedifferentiated-SFT subcutaneously xenotransplanted into severe combined immunodeficient (SCID) mice. Dacarbazine, temozolomide, sunitinib, bevacizumab, and pazopanib were administered at their reported optimal doses for the mouse model when mean tumor volume (TV) was about 80 mm(3); each experimental groups included 6 mice. Drug activity was assessed as tumor volume inhibition percentage (TVI%). Dacarbazine was tested according to two different schedules of administration. One hunded twenty days after treatment interruption, mouse tumor samples were analyzed. RESULTS: Among the eight patients treated with dacarbazine, best response evaluation criteria in solid tumors responses (RECIST) were three partial responses, 4 stable disease, 1 progression. Two responsive patients had paraneoplastic hypoglycemia that disappeared after 10 days from starting dacarbazine. In the dedifferentiated-SFT xenograft model, dacarbazine and temozolomide showed the highest antitumor activity (about 95% TVI), confirmed pathologically. Sunitinib and pazopanib were only marginally active (52% and 41% TVI, respectively), whereas bevacizumab caused a 78% TVI. No tumor regrowth was observed up to 100 days from end of treatment with temozolomide and dacarbazine, whereas secondary progression followed sunitinib, pazopanib, and bevacizumab interruption. CONCLUSIONS: Dacarbazine as single agent has antitumor activity in SFT. Our preclinical results suggest a cytotoxic effect of temozolomide and dacarbazine, as compared with a cytostatic role for sunitinib, pazopanib, and bevacizumab. A phase II study on dacarbazine in advanced SFT is planned.

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.

Multiangle static and dynamic light scattering in the intermediate scattering angle range.

We describe a light scattering apparatus based on a novel optical scheme covering the scattering angle range 0.5° ≤ θ ≤ 25°, an intermediate regime at the frontier between wide angle and small angle setups that is difficult to access by existing instruments. Our apparatus uses standard, readily available optomechanical components. Thanks to the use of a charge-coupled device detector, both static and dynamic light scattering can be performed simultaneously at several scattering angles. We demonstrate the capabilities of our apparatus by measuring the scattering profile of a variety of samples and the Brownian dynamics of a dilute colloidal suspension.

Phase II clinical trial of neoadjuvant trabectedin in patients with advanced localized myxoid liposarcoma.

BACKGROUND: To evaluate neoadjuvant trabectedin (1.5 mg/m(2) 24-h i.v. infusion every 3 weeks; three to six cycles) in patients with locally advanced myoxid liposarcoma (ML) previously untreated with chemotherapy or radiation. PATIENTS AND METHODS: Primary efficacy end point was pathological complete response (pCR) or tumoral regression rate. Objective response according to RECIST (v.1.0) was a secondary end point. RESULTS: Three of 23 assessable patients had pCR [13%; 95% confidence interval (CI), 3% to 34%]. Furthermore, very good and moderate histological responses were observed in another 2 and 10 patients, respectively. Histological decrement in the cellular and vascular tumor component and maturation of tumor cells to lipoblasts were observed in both myoxid and myoxid/round cell variants. Seven patients had partial response according to RECIST (objective response rate of 24%; 95% CI, 10% to 44%). No disease progression was reported. Neoadjuvant trabectedin was usually well tolerated, with a safety profile similar to that described in patients with soft tissue sarcoma or other tumor types. CONCLUSION: Trabectedin 1.5 mg/m(2) given as a 24-h i.v. infusion every 3 weeks is a therapeutic option in the neoadjuvant setting of ML.

Role of EGFR family receptors in proliferation of squamous carcinoma cells induced by wound healing fluids of head and neck cancer patients.

BACKGROUND: Mounting evidence suggests that recurrence of resected head and neck squamous cell carcinomas (HNSCCs) is due to the outgrowth of unrecognized residual tumor cells as well as to the premalignant and/or precursor-field epithelial cells. We studied the impact of processes triggered by HNSCC surgery in stimulating both residual tumor cells [demonstrated to overexpress epidermal growth factor receptor (EGFR)], and premalignant cells surrounding the resected lesion. PATIENTS AND METHODS: EGFR expression/activation by immunohistochemistry/biochemistry and gene status by FISH were investigated in 23 primary HNSCCs and surrounding tissues. The ability to induce cell proliferation of wound healing drainages collected from 12 relapsed and 11 not relapsed patients was evaluated by a colorimetric assay in squamous cell carcinoma cell lines A431 (carrying EGFR amplification) and CAL27 (carrying three EGFR copies) in the presence/absence of EGFR therapeutic inhibitors. RESULTS: Primary tumors showed intermediate/high EGFR expression (91%), EGFR phosphorylation and EGFR-positive FISH (35%). Normal, metaplastic and dysplastic epithelium surrounding the resected tumor displayed EGFR overexpression. EGFR activation and gene amplification were observed in normal and dysplastic epithelium, respectively. Each tested wound healing drainage induced the cells to proliferate and the proliferation was significantly higher in relapsed compared with not relapsed HNSCC patients (P = 0.02 and P = 0.03). Anti-EGFR treatments inhibited the drainage-induced proliferation, with the highest inhibitory efficiency by cetuximab on A431 cells, while CAL27 cell growth was more efficiently inhibited by tyrosine kinase inhibitors. CONCLUSIONS: Surgery could favor the proliferation of cells showing EGFR overexpression/activation/amplification such as residual tumor cells and/or precursor-field epithelial cells already present after surgery. Treatment with anti-EGFR reagents inhibits wound-induced stimulation, according to the EGFR family status.

Post-imatinib surgery in advanced/metastatic GIST: is it worthwhile in all patients?

BACKGROUND: Surgical indication for metastatic gastrointestinal stromal tumor (GIST) treated with imatinib is not yet established. MATERIALS AND METHODS: We analyzed 80 patients who underwent surgery for metastatic GIST after imatinib therapy from July 2002 to October 2007. Patients were divided into those with surgery at best clinical response (group A, n = 49) and those with surgery at focal progression (group B, n = 31). Primary end points were progression-free survival (PFS) and disease-specific survival (DSS). RESULTS: Two-year postoperative PFS was 64.4% in group A and 9.7% in group B (P < 0.01). In group A, median PFS was not reached; in group B, it was 8 months. Median DSS from the time of imatinib onset was not reached in either group. Five-year DSS was 82.9% in group A and 67.6% in group B (P < 0.01). Multivariate analysis confirmed a significantly shorter PFS and DSS in group B. Surgical morbidity occurred in 13 patients (16.3%). CONCLUSIONS: Surgery for focal progressive lesions could be considered as part of the second-line/third-line armamentarium in selected cases. Surgery of residual disease upon best clinical response seems associated with survival benefit compared with historical controls in similar patient collectives treated with imatinib alone. However, evidence from prospective randomized trials is needed to make definite recommendations.

Response to imatinib plus sirolimus in advanced chordoma.

BACKGROUND: Imatinib (IM) is active in advanced chordoma. The evidence of upstream and/or downstream mammalian target of rapamycin (mTOR) pathway activation prompted us to combine an mTOR inhibitor, sirolimus, to IM in IM-resistant advanced chordoma. PATIENTS AND METHODS: Since July 2007, 10 progressive advanced chordoma patients with secondary resistance to IM, and biochemical and/or immunohistochemical evidence of upstream and/or downstream mTOR effector activation, started IM (400 mg/day) plus sirolimus (2 mg/day) on a named basis. RESULTS: The mean treatment duration was 9 months. Of nine patients assessable for response, at 3 months, we had one RECIST partial response (PR), seven stable disease (SD) and one progressive disease (PD). According to Choi criteria applied even to magnetic resonance imaging, we had seven PR (> or =10% decrease in size in four cases), one SD and one PD. Seven patients had a positron emission tomography response. The clinical benefit [RECIST complete response + PR + SD > or =6 months] was 89%. Pretreatment mTOR effectors analysis carried out in nine cases was positive in all patients (AKT activation in six patients, S6Sp6 expression/activation in seven). Post-treatment biopsy in one responsive patient confirmed S6 switch off. CONCLUSION: In addition to PDGFRB, mTOR pathway can be activated in chordomas and the combination of IM plus rapalogs may be effective in IM-resistant chordomas.

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.

Preoperative imatinib mesylate for unresectable or locally advanced primary gastrointestinal stromal tumors (GIST).

AIM: To explore the effect of preoperative imatinib mesylate (IM) in patients with unresectable or locally advanced primary gastrointestinal stromal tumor (GIST). METHODS: From January 2003 to January 2008, all patients affected by bulky localized GIST who presented at our institution were considered for preoperative IM with cytoreductive intent. Clinical, pathological and molecular characteristics were assessed and the rate of response recorded. Progression-free survival (PFS) was calculated according to Kaplan-Meier analysis. RESULTS: Fifteen patients (1 esophageal, 7 gastric, 3 duodenal, 4 rectal GISTs) received preoperative IM for a median of 9 months. All patients had tumor shrinkage, with a median size reduction of 34%. One patient had radiological complete response. In all cases an improvement of the originally planned surgical procedure was obtained: 3 patients initially considered unresectable underwent complete surgery; 7 patients with initial indication for extensive surgery were more conservatively operated on; 4 patients initially deemed at high perioperative risk underwent safe surgery. Due to the small sample size, no association between tumor shrinkage and tumor site, size, IM duration, mutational status and pathological response could be formally explored. PFS at 3 years from IM onset was 77%. CONCLUSIONS: In unresectable or locally advanced GISTs, preoperative IM is a useful tool both to improve resectability and reduce surgical morbidity. It should be therefore always be considered before embarking on a major surgical procedure. The long-term impact of IM on PFS and survival is presently under investigation in multicenter prospective randomized trials.

Analysis of potential receptor tyrosine kinase targets in intimal and mural sarcomas.

Primary sarcomas of the great vessels are very rare neoplasms and only a few cases have been reported. They are divided into the two broad categories of intimal or luminal and mural sarcomas. We analysed eight advanced high-grade sarcomas originating from major vessels (seven intimal and one mural sarcoma) by means of immunohistochemistry and FISH analysis for PDGFRA, PDGFRB, EGFR and KIT receptor tyrosine kinases (RTKs), together with immunoprecipitation/western blotting, sequencing of the corresponding genes, and the search for cognate ligands. The intimal sarcomas showed a wide spectrum of morphologies and immunophenotypes, whereas the mural sarcoma had common leiomyosarcomatous features. Regardless of their category, all of the cases had a PDGFRA-deregulated cytogenetic profile mainly consisting of an amplification cluster; five were also polysomic for PDGFRB, whereas three showed disomy. Six cases had a deregulated EGFR gene, and c-Kit gene status was similar to that of PDGFRA. In one case, biochemical analysis revealed the presence of activated and highly expressed PDGFRA, PDGFRB and EGFR, whereas KIT was expressed at reference level. Sequencing of the corresponding genes revealed no activating mutations in any of the analysed receptors. The cognate ligands were detected in all cases. In predictive terms, the evidence of gene amplification/high polysomy of several RTKs, together with PDGFRA, PDGFRB and EGFR expression and phosphorylation, suggests that these tumours may be sensitive to RTK-inhibiting treatments.