Expression of IGF-1 receptor in KIT/PDGF receptor-α wild-type gastrointestinal stromal tumors with succinate dehydrogenase complex dysfunction

Exploring Perforated Jejunal GIST: A Rare Case Report and Review of Molecular and Clinical Literature

This case report details a rare instance of a perforated jejunal gastrointestinal stromal tumor (GIST) in a 76-year-old female patient. The patient presented with acute abdominal pain and distension without any changes in bowel habits or episodes of nausea and vomiting. Initial diagnostics, including abdominal plain radiography and ultrasonography, were inconclusive; however, a computed tomography (CT) scan revealed pneumoperitoneum and an irregular fluid collection suggestive of small intestine perforations. Surgical intervention uncovered a 35 mm jejunal GIST with a 10 mm perforation. Histopathological examination confirmed a mixed cell type GIST with high malignancy potential, further substantiated by immunohistochemistry markers CD117, DOG1, and vimentin. Molecular analysis illuminated the role of key oncogenes, primarily KIT and PDGFRA mutations, emphasizing the importance of molecular diagnostics in GIST management. Despite the severity of the presentation, the patient's postoperative recovery was favorable, highlighting the effectiveness of prompt surgical and multidisciplinary approaches in managing complex GIST cases.

Microvessel density in patients with gastrointestinal stromal tumors: A systematic review and meta-analysis

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are considered the most common mesenchymal tumors of the gastrointestinal tract. Microvessel density (MVD) constitutes a direct method of vascularity quantification and has been associated with survival rates in multiple malignancies.

AIM

To appraise the effect of MVD on the survival of patients with GIST.

METHODS

This study adhered to Systematic reviews and Meta-Analyses guidelines and the Cochrane Handbook for Systematic Reviews of Interventions. Electronic scholar databases and grey literature repositories were systematically screened. The Fixed Effects or Random Effects models were used according to the Cochran Q test.

RESULTS

In total, 6 eligible studies were identified. The pooled hazard ratio (HR) for disease free survival (DFS) was 8.52 (95%CI: 1.69-42.84, P = 0.009). The odds ratios of disease-free survival between high and low MVD groups at 12 and 60 mo did not reach statistical significance. Significant superiority of the low MVD group in terms of DFS was documented at 36 and 120 mo (OR: 8.46, P < 0.0001 and OR: 22.71, P = 0.0003, respectively) as well as at metastases rate (OR: 0.11, P = 0.0003).

CONCLUSION

MVD significantly correlates with the HR of DFS and overall survival rates at 36 and 120 mo. Further prospective studies of higher methodological quality are required.

Molecular Mechanisms of Gastrointestinal Stromal Tumors and Their Impact on Systemic Therapy Decision

Gastrointestinal stromal tumors (GISTs) are soft tissue sarcomas that mostly derive from Cajal cell precursors. They are by far the most common soft tissue sarcomas. Clinically, they present as gastrointestinal malignancies, most often with bleeding, pain, or intestinal obstruction. They are identified using characteristic immunohistochemical staining for CD117 and DOG1. Improved understanding of the molecular biology of these tumors and identification of oncogenic drivers have altered the systemic treatment of primarily disseminated disease, which is becoming increasingly complex. Gain-of-function mutations in KIT or PDGFRA genes represent the driving mutations in more than 90% of all GISTs. These patients exhibit good responses to targeted therapy with tyrosine kinase inhibitors (TKIs). Gastrointestinal stromal tumors lacking the KIT/PDGFRA mutations, however, represent distinct clinico-pathological entities with diverse molecular mechanisms of oncogenesis. In these patients, therapy with TKIs is hardly ever as effective as for KIT/PDGFRA-mutated GISTs. This review provides an outline of current diagnostics aimed at identifying clinically relevant driver alterations and a comprehensive summary of current treatments with targeted therapies for patients with GISTs in both adjuvant and metastatic settings. The role of molecular testing and the selection of the optimal targeted therapy according to the identified oncogenic driver are reviewed and some future directions are proposed.

Correlation of treatment outcome in sanger/RT‑qPCR KIT/PDGFRA wild‑type metastatic gastrointestinal stromal tumors with next‑generation sequencing results: A single‑center report

In patients with gastrointestinal stromal tumors (GIST), it has become mandatory to determine the driver mutation in order to predict the response to standard treatment with tyrosine kinase inhibitors (TKI). A total of 10–15% of all GIST lack activating mutations in KIT proto-oncogene, receptor tyrosine kinase (KIT)/platelet-derived growth factor receptor alpha (PDGFRA) and have been classified as KIT/PDGFRA wild-type (WT) GIST. They are characterized by poor response to TKI. From a group of 119 metastatic GIST patients, 17 patients with KIT/PDGFRA/BRAF WT GIST as determined by reverse transcription-quantitative (RT-q) PCR and Sanger sequencing were profiled by a targeted next-generation sequencing (NGS) approach and their treatment outcome was assessed. In the present study, 41.2% of patients as KIT/PDGFRA/BRAF WT GIST examined with RT-qPCR and Sanger sequencing were confirmed to be carriers of pathogenic KIT/PDGFRA mutations by NGS and were responsive to TKI. The percentage of genuinely KIT/PDGFRA WT GIST in the present study thereby dropped from the initial 14.3% detected with the RT-qPCR and Sanger sequencing to 7.6% after NGS. Their outcome was universally poor. The reliability of RT-qPCR and direct Sanger sequencing results in this setting is therefore insufficient and it is recommended that NGS becomes a requirement for treatment decision at least in KIT/PDGFRA/BRAF WT GIST as determined by RT-qPCR and Sanger sequencing.

Targeted therapy in SDH-deficient GIST

The medical management of advanced gastrointestinal stromal tumors (GIST) has improved with the development of tyrosine kinase inhibitors (TKIs) targeting KIT and PDGFRA mutations. However, approximately 5-10% of GIST lack KIT and PDGFRA mutations, and about a half are deficient in succinate dehydrogenase (SDH) that promotes carcinogenesis by the cytoplasmic accumulation of succinate. This rare group of GIST primarily occurs in the younger patients than other subtypes, and is frequently associated with hereditary syndromes. The role of TKIs in patients with SDH-deficient GIST is controversial, with conflicting results; thus, there is an urgent need to uncover the disease mechanisms, treatment patterns, and responses to systemic therapy among these patients. Here, based on an extensive literature search, we have provided a rigorous overview of the current evidence on the medical treatment of SDH-deficient GIST.

Prognostic Indicators for Gastrointestinal Stromal Tumors: A Review

Gastrointestinal stromal tumors (GISTs) are potentially malignancies that can occur anywhere in the digestive tract. Tyrosine kinase inhibitors (TKIs) such as imatinib have proven effective since the discovery of KIT and PDGFRA. The current version of NCNN, ESMO and EURACAN guidelines recognized that the three main prognostic factors are the mitotic rate, tumor size and tumor site. In addition, tumor rupture is also recognized as an independent risk factor. However, recent evidence shows that various types of gene mutations are associated with prognosis, and influencing factors such as gastrointestinal bleeding and high Ki67 index have been associated with poor prognosis. It shows that the current risk classification is still insufficient and controversial. With the emergence of more and more lack mutation in KIT/PDGFRA GISTs (KIT/PDGFRA wild-type GISTs) or drug resistance genes, primary and secondary drug resistance problems are caused, which makes the treatment of late or metastatic GIST face challenges. Therefore, this article will review the clinicopathological characteristics of GIST, the special molecular subtypes and other factors that may affect prognosis. We will also explore reliable prognostic markers for better postoperative management and improve the prognosis of patients with GIST.

Activated tyrosine kinases in gastrointestinal stromal tumor with loss of KIT oncoprotein expression

Oncogenic KIT or PDGFRA receptor tyrosine kinase (TK) mutations are compelling therapeutic targets in gastrointestinal stromal tumors (GISTs), and the KIT/PDGFRA kinase inhibitor, imatinib, is the standard of care for patients with metastatic GIST. However, approximately 10% of KIT-positive GIST metastases lose KIT expression at the time of clinical progression during imatinib therapy. In the present report, we performed TK-activation screens, using phosphotyrosine-TK double immunoaffinity purification and mass spectrometry, in GIST in vitro models lacking KIT expression. These studies demonstrated tyrosine-phosphorylated EGFR, AXL, and EPHA2 in four of six KIT-negative GIST lines (GIST62, GIST522, GIST54, GIST226, GIST48B, and GIST430B), and tyrosine-phosphorylated focal adhesion kinase (FAK) in each of the six KIT-negative lines. AXL expression was strong in KIT-negative or -weak clinical GIST samples that were obtained from progressing metastases during imatinib therapy. AXL knockdown inhibited viability in three KIT-negative GIST cell lines (GIST62, GIST54, and GIST522), but not in an AXL-negative, KIT-positive GIST control cell line (GIST430). AXL inhibition by R428, a specific AXL kinase inhibitor, reduced viability in AXL-activated GIST54. AXL knockdown in GIST62, GIST522, and GIST54 was accompanied by an increase in p21, p27, and p53 expression. By contrast, gefitinib-mediated EGFR inhibition, PF562271-mediated FAK inactivation, and shRNA-mediated knockdowns of EPHA2 and FAK had no effect on viability or colony formation of the KIT-negative GISTs. These findings highlight the potential relevance of AXL/p53 signaling as a therapeutic target in a subset of GISTs that have lost KIT oncoprotein expression.

Gastrointestinal Stromal Tumors: The GIST of Precision Medicine

The discovery of activated KIT mutations in gastrointestinal (GI) stromal tumors (GISTs) in 1998 triggered a sea change in our understanding of these tumors and has ushered in a new paradigm for the use of molecular genetic diagnostics to guide targeted therapies. KIT and PDGFRA mutations account for 85-90% of GISTs; subsequent genetic studies have led to the identification of mutation/epimutation of additional genes, including the succinate dehydrogenase (SDH) subunit A, B, C, and D genes. This review focuses on integrating findings from clinicopathologic, genetic, and epigenetic studies, which classify GISTs into two distinct clusters: an SDH-competent group and an SDH-deficient group. This development is important since it revolutionizes our current management of affected patients and their relatives, fundamentally, based on the GIST genotype.

Intratumoral KIT mutational heterogeneity and recurrent KIT/ PDGFRA mutations in KIT/PDGFRA wild-type gastrointestinal stromal tumors

Objective

Gastrointestinal stromal tumors (GISTs) with no mutations in exons 9, 11, 13, and 17 of the KIT gene and exons 12, and 18 of the PDGFRA gene were defined as KIT/PDGFRA wild-type and they accounted for ~15–20% of GISTs. However, some KIT/PDGFRA wild-type GISTs with KIT mutations in other exons were occasionally reported. We therefore assessed GISTs to understand the whole genomic genotypes of KIT or PDGFRA genes in KIT/PDGFRA wild-type GISTs.

Methods

A cohort of 185 KIT/PDGFRA wild-type GISTs from 1,080 cases was retrospectively assessed. Thirty-nine patients were excluded due to insufficiency of genomic DNA data or failure of library preparation, and 146 patients were analyzed by targeted next-generation sequencing (NGS) followed by validation.

Results

For hot spots in KIT and PDGFRA genes, 23 out of 146 KIT/PDGFRA wild-type cases carried mutations according to NGS; there were 19 KIT mutations and 4 PDGFRA mutations, and these were exclusive. Intratumoral KIT mutational heterogeneity was observed in 4 of 19 samples which potentially triggered mechanisms of polyclonal evolution and metastasis and drug sensitivity. Eleven patients treated with imatinib were evaluable for clinical response, and 2 of 3 patients with KIT mutations achieved partial response (PR), while only 1 of 8 patients without KIT mutations reached PR.

Conclusion

NGS had the potential property to identify partial mutant tumors from a subset of GISTs regarded as KIT/PDGFRA wild-type tumors using Sanger sequencing, and provided a better understanding of KIT/PDGFRA genotypes as well as identified patients eligible for imatinib therapy.

The progressive fragmentation of the KIT/PDGFRA wild-type (WT) gastrointestinal stromal tumors (GIST)

Recent advances in molecular biology have revolutionized the concept of KIT/PDGFRA wild type (WT) gastrointestinal stromal tumors (GIST) than the past. Indeed, from being defined as GIST without KIT or PDGFRA mutations, we are now faced with the opposite scenario, where KIT/PDGFRA WT GIST are "positively" defined according to their specific molecular alterations. In particular, if until recently KIT/PDGFRA GIST without abnormalities of KIT, PDGFRA, SDH, and the RAS signaling pathway were referred as quadruple WT GIST, today also this small subset of GIST is emerging out as a group of heterogeneous distinct entities with multiple different molecular alterations. Therefore, given this still growing and rapidly evolving scenario, the progressive molecular fragmentation may inevitably lead over the time to the disappearance of KIT/PDGFRA WT GIST, destined to be singularly defined by their molecular fingerprint.

Genome-Wide Analysis Identifies MEN1 and MAX Mutations and a Neuroendocrine-Like Molecular Heterogeneity in Quadruple WT GIST

Quadruple wild-type (WT) gastrointestinal stromal tumor (GIST) is a genomic subgroup lacking KIT/PDGFRA/RAS pathway mutations, with an intact succinate dehydrogenase (SDH) complex. The aim of this work is to perform a wide comprehensive genomic study on quadruple WT GIST to improve the characterization of these patients. We selected 14 clinical cases of quadruple WT GIST, of which nine cases showed sufficient DNA quality for whole exome sequencing (WES). NF1 alterations were identified directly by WES. Gene expression from whole transcriptome sequencing (WTS) and miRNA profiling were performed using fresh-frozen, quadruple WT GIST tissue specimens and compared with SDH and KIT/PDGFRA-mutant GIST. WES identified an average of 18 somatic mutations per sample. The most relevant somatic oncogenic mutations identified were in TP53, MEN1, MAX, FGF1R, CHD4, and CTDNN2. No somatic alterations in NF1 were identified in the analyzed cohort. A total of 247 mRNA transcripts and 66 miRNAs were differentially expressed specifically in quadruple WT GIST. Overexpression of specific molecular markers (COL22A1 and CALCRL) and genes involved in neural and neuroendocrine lineage (ASCL1, Family B GPCRs) were detected and further supported by predicted miRNA target analysis. Quadruple WT GIST show a specific genetic signature that deviates significantly from that of KIT/PDGFRA-mutant and SDH-mutant GIST. Mutations in MEN1 and MAX genes, a neural-committed phenotype and upregulation of the master neuroendocrine regulator ASCL1, support a genetic similarity with neuroendocrine tumors, with whom they also share the great variability in oncogenic driver genes.Implications: This study provides novel insights into the biology of quadruple WT GIST that potentially resembles neuroendocrine tumors and should promote the development of specific therapeutic approaches. Mol Cancer Res; 15(5); 553-62. ©2017 AACR.

Gastrointestinal stromal tumors (GIST): Facing cell death between autophagy and apoptosis

Autophagy and apoptosis are 2 fundamental biological mechanisms that may cooperate or be antagonistic, although both are involved in deciding the fate of cells in physiological or pathological conditions. These 2 mechanisms coexist simultaneously in cells and share common upstream signals and stimuli. Autophagy and apoptosis play pivotal roles in cancer development. Autophagy plays a key function in maintaining tumor cell survival by providing energy during unfavorable metabolic conditions through its recycling mechanism, and supporting the high energy requirement for metabolism and growth. This review focuses on gastrointestinal stromal tumors and cell death through autophagy and apoptosis, taking into account the involvement of both of these processes in tumor development and growth and as mechanisms of drug resistance. We also focus on the crosstalk between autophagy and apoptosis as an emerging field with major implications for the development of novel therapeutic options.

SETD2 histone modifier loss in aggressive GI stromal tumours

BACKGROUND

GI stromal tumours (GISTs) are clinically heterogenous exhibiting varying degrees of disease aggressiveness in individual patients.

OBJECTIVES

We sought to identify genetic alterations associated with high-risk GIST, explore their molecular consequences, and test their utility as prognostic markers.

DESIGNS

Exome sequencing of 18 GISTs was performed (9 patients with high-risk/metastatic and 5 patients with low/intermediate-risk), corresponding to 11 primary and 7 metastatic tumours. Candidate alterations were validated by prevalence screening in an independent patient cohort (n=120). Functional consequences of SETD2 mutations were investigated in primary tissues and cell lines. Transcriptomic profiles for 8 GISTs (4 SETD2 mutated, 4 SETD2 wild type) and DNA methylation profiles for 22 GISTs (10 SETD2 mutated, 12 SETD2 wild type) were analysed. Statistical associations between molecular, clinicopathological factors, and relapse-free survival were determined.

RESULTS

High-risk GISTs harboured increased numbers of somatic mutations compared with low-risk GISTs (25.2 mutations/high-risk cases vs 6.8 mutations/low-risk cases; two sample t test p=3.1×10^-5). Somatic alterations in the SETD2 histone modifier gene occurred in 3 out of 9 high-risk/metastatic cases but no low/intermediate-risk cases. Prevalence screening identified additional SETD2 mutations in 7 out of 80 high-risk/metastatic cases but no low/intermediate-risk cases (n=29). Combined, the frequency of SETD2 mutations was 11.2% (10/89) and 0% (0/34) in high-risk and low-risk GISTs respectively. SETD2 mutant GISTs exhibited decreased H3K36me3 expression while SETD2 silencing promoted DNA damage in GIST-T1 cells. In gastric GISTs, SETD2 mutations were associated with overexpression of HOXC cluster genes and a DNA methylation signature of hypomethylated heterochromatin. Gastric GISTs with SETD2 mutations, or GISTs with hypomethylated heterochromatin, showed significantly shorter relapse-free survival on univariate analysis (log rank p=4.1×10^-5).

CONCLUSIONS

Our data suggest that SETD2 is a novel GIST tumour suppressor gene associated with disease progression. Assessing SETD2 genetic status and SETD2-associated epigenomic phenotypes may guide risk stratification and provide insights into mechanisms of GIST clinical aggressiveness.

Integrating miRNA and gene expression profiling analysis revealed regulatory networks in gastrointestinal stromal tumors

AIM

Currently, little is known about differences in miRNA expression between KIT/PDGFRA mutant and KIT/PDGFRA wild-type (WT)-SDH deficient gastrointestinal stromal tumors (GIST). This prompted us to perform an integrated multiple expression profile of miRNA and mRNA, constructing an original miRNA-mRNA regulatory network in KIT/PDGFRA WT-SDH deficient GIST patients.

PATIENTS & METHODS

Analyses were carried out on KIT/PDGFRA mutant versus KIT/PDGFRA WT-SDH deficient GIST. Genome-wide miRNA and gene-expression analysis were performed using Agilent Human miRNA microarray and Affimetrix array, respectively.

RESULTS

Three potential regulatory networks (IGF1R → miR-139-5p/miR-455/let-7b, cyclin-dependent kinase 6 (CDK6) → miR-139-5p/let-7b and CD44 → miR-330-3p) were identified.

CONCLUSION

The miR-139-5p, 455-5p and let-7b signature, in particular, may represent an important therapeutic target in KIT/PDGFRA WT-SDH deficient GIST, usually characterized by IGF1R overexpression.

Personalized Medicine in Gastrointestinal Stromal Tumor (GIST): Clinical Implications of the Somatic and Germline DNA Analysis

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. They are characterized by gain of function mutations in KIT or PDGFRA tyrosine kinase receptors, with their consequent constitutive activation. The gold standard therapy is imatinib that offers a good and stable response for approximately 18–36 months. However, resistance is very common and it is vital to identify new biomarkers. Up until now, there have been two main approaches with focus to characterize novel targets. On the one hand, the focus is on the tumor genome, as the final clinical outcome depends mainly from the cancer specific mutations/alterations patterns. However, the germline DNA is important as well, and it is inconceivable to think the patients response to the drug is not related to it. Therefore the aim of this review is to outline the state of the art of the personalized medicine in GIST taking into account both the tumor DNA (somatic) and the patient DNA (germline).

Succinate dehydrogenase-deficient gastrointestinal stromal tumors

Most gastrointestinal stromal tumors (GISTs) are characterized by KIT or platelet-derived growth factor alpha (PDGFRA) activating mutations. However, there are still 10%-15% of GISTs lacking KIT and PDGFRA mutations, called wild-type GISTs (WT GISTs). Among these so-called WT GISTs, a small subset is associated with succinate dehydrogenase (SDH) deficiency, known as SDH-deficient GISTs. In addition, GISTs that occur in Carney triad and Carney-Stratakis syndrome represent specific examples of SDH-deficient GISTs. SDH-deficient GISTs locate exclusively in the stomach, showing predilection for children and young adults with female preponderance. The tumor generally pursues an indolent course and exhibits primary resistance to imatinib therapy in most cases. Loss of succinate dehydrogenase subunit B expression and overexpression of insulin-like growth factor 1 receptor (IGF1R) are common features of SDH-deficient GISTs. In WT GISTs without succinate dehydrogenase activity, upregulation of hypoxia-inducible factor 1α may lead to increased growth signaling through IGF1R and vascular endothelial growth factor receptor (VEGFR). As a result, IGF1R and VEGFR are promising to be the novel therapeutic targets of GISTs. This review will update the current knowledge on characteristics of SDH-deficient GISTs and further discuss the possible mechanisms of tumorigenesis and clinical management of SDH-deficient GISTs.

Integrated genomic study of quadruple-WT GIST (KIT/PDGFRA/SDH/RAS pathway wild-type GIST)

Background

About 10-15% of adult gastrointestinal stromal tumors (GIST) and the vast majority of pediatric GIST do not harbour KIT or platelet-derived growth factor receptor alpha (PDGFRA) mutations (J Clin Oncol 22:3813–3825, 2004; Hematol Oncol Clin North Am 23:15–34, 2009). The molecular biology of these GIST, originally defined as KIT/PDGFRA wild-type (WT), is complex due to the existence of different subgroups with distinct molecular hallmarks, including defects in the succinate dehydrogenase (SDH) complex and mutations of neurofibromatosis type 1 (NF1), BRAF, or KRAS genes (RAS-pathway or RAS-P).

In this extremely heterogeneous landscape, the clinical profile and molecular abnormalities of the small subgroup of WT GIST suitably referred to as quadruple wild-type GIST (quadruple^WT or KIT^WT/PDGFRA^WT/SDH^WT/RAS-P^WT) remains undefined. The aim of this study is to investigate the genomic profile of KIT^WT/PDGFRA^WT/SDH^WT/RAS-P^WT GIST, by using a massively parallel sequencing and microarray approach, and compare it with the genomic profile of other GIST subtypes.

Methods

We performed a whole genome analysis using a massively parallel sequencing approach on a total of 16 GIST cases (2 KIT^WT/PDGFRA^WT/SDH^WT and SDHB^IHC+/SDHA^IHC+, 2 KIT^WT/PDGFRA^WT/SDHA^mut and SDHB^IHC-/SDHA^IHC- and 12 cases of KIT^mut or PDGFRA^mut GIST). To confirm and extend the results, whole-genome gene expression analysis by microarray was performed on 9 out 16 patients analyzed by RNAseq and an additional 20 GIST patients (1 KIT^WT/PDGFRA^WTSDHA^mut GIST and 19 KIT^mut or PDGFRA^mut GIST). The most impressive data were validated by quantitave PCR and Western Blot analysis.

Results

We found that both cases of quadruple^WT GIST had a genomic profile profoundly different from both either KIT/PDGFRA mutated or SDHA-mutated GIST. In particular, the quadruple^WT GIST tumors are characterized by the overexpression of molecular markers (CALCRL and COL22A1) and of specific oncogenes including tyrosine and cyclin- dependent kinases (NTRK2 and CDK6) and one member of the ETS-transcription factor family (ERG).

Conclusion

We report for the first time an integrated genomic picture of KIT^WT/PDGFRA^WT/SDH^WT/RAS-P^WT GIST, using massively parallel sequencing and gene expression analyses, and found that quadruple^WT GIST have an expression signature that is distinct from SDH-mutant GIST as well as GIST harbouring mutations in KIT or PDGFRA. Our findings suggest that quadruple^WT GIST represent another unique group within the family of gastrointestintal stromal tumors.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-685) contains supplementary material, which is available to authorized users.

Quadruple wild-type (WT) GIST: defining the subset of GIST that lacks abnormalities of KIT, PDGFRA, SDH, or RAS signaling pathways

A subset of GISTs lack mutations in the KIT/PDGFRA or RAS pathways and yet retain an intact succinate dehydrogensase (SDH) complex. We propose that these KIT/PDGFRA/SDH/RAS-P WT GIST tumors be designated as quadruple wild-type (WT) GIST. Further molecular and clinicophatological characterization of quadruple WT GIST will help to determine their prognosis as well as assist in the optimization of medical management, including clinical test of novel therapies.

Phase 1b study of safety, tolerability and efficacy of R1507, a monoclonal antibody to IGF-1R in combination with multiple standard oncology regimens in patients with advanced solid malignancies

BACKGROUND

R1507 is a human IgG1 Mab that binds to the insulin-like growth factor-1 receptor (IGF-1R) and inhibits IGF-1- or IGF-2-mediated anchorage-independent growth of malignant cells. A phase 1b study evaluated the safety, tolerability and efficacy of R1507 in combination with multiple standard oncology regimens.

METHODS

R1507 (3, 5, 9, 10 and 16 mg/kg IV, Q2 W or Q3 W) was added to six treatment regimens: gemcitabine + erlotinib (GE); paclitaxel + bevacizumab (PB); carboplatin + etoposide (CE); mFOLFOX6 + bevacizumab (FB); capecitabine + trastuzumab (CT); and sorafenib (S). If tolerable, R1507 dose was escalated utilizing a 3 + 3 + 6 and a 3 + 9 design.

RESULTS

A total of 104 patients enrolled into regimens 1-6: 93 % were non-recent diagnoses. Eighteen withdrew for safety [one death, 17 adverse events (AEs)]. A total of 1,337 AEs any grade, across regimens and doses were nausea, vomiting and diarrhea. A total of 123 had grade ≥3 AEs (n = 28 dose level 1; n = 95 dose level 1) and in 60 patients were myelosuppression, fatigue and mucosal inflammation. ORR (PR plus SD) of evaluable patients across six regimens was 36 % with five PRs: regimens PB (non-small cell lung cancer, nasopharyngeal cancer), CE (melanoma), FB (colon cancer) and S (GIST). The GIST pt (>4 prior therapies) had a PR for 3 years. Three patients (breast cancer, melanoma and adenoid cystic carcinoma) were on study for >1 year; 76 % of patients had SD or better for 4 months.

CONCLUSIONS

R1507 added to six standard oncology regimens was well tolerated with an ORR of 36 %.

Gastrointestinal stromal tumors: what do we know now?

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the GI tract, arising from the interstitial cells of Cajal, primarily in the stomach and small intestine. They manifest a wide range of morphologies, from spindle cell to epithelioid, but are immunopositive for KIT (CD117) and/or DOG1 in essentially all cases. Although most tumors are localized at presentation, up to half will recur in the abdomen or spread to the liver. The growth of most GISTs is driven by oncogenic mutations in either of two receptor tyrosine kinases: KIT (75% of cases) or PDGFRA (10%). Treatment with tyrosine kinase inhibitors (TKIs) such as imatinib, sunitinib, and regorafenib is effective in controlling unresectable disease; however, drug resistance caused by secondary KIT or PDGFRA mutations eventually develops in 90% of cases. Adjuvant therapy with imatinib is commonly used to reduce the likelihood of disease recurrence after primary surgery, and for this reason assessing the prognosis of newly resected tumors is one of the most important roles for pathologists. Approximately 15% of GISTs are negative for mutations in KIT and PDGFRA. Recent studies of these so-called wild-type GISTs have uncovered a number of other oncogenic drivers, including mutations in neurofibromatosis type I, RAS genes, BRAF, and subunits of the succinate dehydrogenase complex. Routine genotyping is strongly recommended for optimal management of GISTs, as the type and dose of TKI used for treatment is dependent on the mutation identified.

Analysis of all subunits, SDHA, SDHB, SDHC, SDHD, of the succinate dehydrogenase complex in KIT/PDGFRA wild-type GIST

Mutations of genes encoding the subunits of the succinate dehydrogenase (SDH) complex were described in KIT/PDGFRA wild-type GIST separately in different reports. In this study, we simultaneously sequenced the genome of all subunits, SDHA, SDHB, SDHC, and SDHD in a larger series of KIT/PDGFRA wild-type GIST in order to evaluate the frequency of the mutations and explore their biological role. SDHA, SDHB, SDHC, and SDHD were sequenced on the available samples obtained from 34 KIT/PDGFRA wild-type GISTs. Of these, in 10 cases, both tumor and peripheral blood (PB) were available, in 19 cases only tumor, and in 5 cases only PB. Overall, 9 of the 34 patients with KIT/PDGFRA wild-type GIST carried mutations in one of the four subunits of the SDH complex (six patients in SDHA, two in SDHB, one in SDHC). WB and immunohistochemistry analysis showed that patients with KIT/PDGFRA wild-type GIST who harbored SDHA mutations exhibited a significant downregulation of both SDHA and SDHB protein expression, with respect to the other GIST lacking SDH mutations and to KIT/PDGFRA-mutated GIST. Clinically, four out of six patients with SDHA mutations presented with metastatic disease at diagnosis with a very slow, indolent course. Patients with KIT/PDGFRA wild-type GIST may harbor germline and/or de novo mutations of SDH complex with prevalence for mutations within SDHA, which is associated with a downregulation of SDHA and SDHB protein expression. The presence of germline mutations may suggest that these patients should be followed up for the risk of development of other cancers.