Hereditary gastrointestinal stromal tumors sharing the KIT Exon 17 germline mutation p.Asp820Tyr develop through different cytogenetic progression pathways

Pimitespib is effective on cecal GIST in a mouse model of familial GISTs with KIT-Asp820Tyr mutation through KIT signaling inhibition

Three families with multiple gastrointestinal stromal tumors (GISTs) caused by a germline Asp820Tyr mutation at exon 17 of the c-kit gene (KIT-Asp820Tyr) have been reported. We previously generated a knock-in mouse model of the family, and the mice with KIT-Asp818Tyr corresponding to human KIT-Asp820Tyr showed a cecal tumor equivalent to human GIST. In the model mice, we reported that tyrosine kinase inhibitor, imatinib, could stabilize but not decrease the cecal tumor volume. In this report, we examined whether a heat shock protein 90 inhibitor, pimitespib (TAS-116), has an inhibitory effect on phosphorylation of KIT-Asp818Tyr and can decrease the cecal tumor volume in the model mice. First, we showed that pimitespib inhibited KIT phosphorylation both dose- and time-dependently in KIT-Asp818Tyr transfected murine Ba/F3 cells. Then, four 1-week courses of pimitespib were orally administered to heterozygous (KIT-Asp818Tyr/+) model mice. Each course consisted of once-daily administration for consecutive 5 days followed by 2 days-off. Cecal tumors were dissected, and tumor volume was histologically analyzed, Ki-67 labeling index was immunohistochemically examined, and apoptotic figures were counted. Compared to the vehicle treated mice, pimitespib administered mice showed statistically significantly smaller cecal tumor volume, lower Ki-67 labeling index, and higher number of apoptotic figures in 10 high power fields (P = 0.0344, P = 0.0019 and P = 0.0269, respectively). Western blotting revealed that activation of KIT signaling molecules was strongly inhibited in the tumor tissues of pimitespib-administered mice compared to control mice. Thus, pimitespib seemed to inhibit in vivo tumor progression effectively in the model mice. These results suggest that the progression of multiple GISTs in patients with germline KIT-Asp820Tyr might be controllable by pimitespib.

Significance of Primary Malignant Tumors on the Outcome of Patients With Resected Gastrointestinal Stromal Tumors

AIM

This study aimed to clarify the significance of primary malignant tumors for the outcome of resected gastrointestinal stromal tumors (GISTs).

PATIENTS AND METHODS

The medical history, pathological findings and prognosis of 66 patients with GISTs resected at our institute between January 2003 and December 2018 were investigated retrospectively and compared statistically.

RESULTS

Among 66 patients with GISTs, 24 (36%) had concomitant malignant tumors. In an average study period of 57 months, one patient died from GIST, seven from other malignant tumors, and one from another disease. Only coexistence of GIST and other malignant tumors was recognized as a prognostic factor. Increasing age was significantly correlated with other malignant tumor in combination with GIST. When comparing patients with GIST alone and GIST with other malignant tumors, the latter showed significantly poorer prognosis.

CONCLUSION

Coexistence of other malignant tumors was commonly observed in patients with GIST, and was associated with poorer prognosis. This association should be carefully considered and monitored in patients with GISTs.

A Novel Kindred with Familial Gastrointestinal Stromal Tumors Caused by a Rare KIT Germline Mutation (N655K): Clinico-Pathological Presentation and TKI Sensitivity

Gastrointestinal stromal tumors (GISTs), the most common mesenchymal tumors of the gastrointestinal tract, are characterized by activating mutations in KIT or PDGFRA genes. The vast majority of GISTs are sporadic, but rare hereditary forms have been reported, often featuring multifocality and younger age of onset. We here report the identification of a novel kindred affected by familial GIST caused by a KIT germline mutation in exon 13 (N655K). No family affected by hereditary GIST due to this KIT variant has been reported in literature so far. We were able to track the mutation in three members of the family (proband, mother, and second-degree cousin), all affected by multiple GISTs. Due to its rarity, the N655K variant is poorly characterized. We conducted in vitro drug sensitivity assays that indicated that most tyrosine kinase inhibitors (TKIs) currently included in the therapeutic armamentarium for GISTs have a limited inhibitory activity toward this mutation. However, when compared to a classical imatinib-resistant KIT mutation (T670I), N655K was slightly more sensitive to imatinib, and encouraging responses were observed with last-generation TKIs.

Multiple gastrointestinal stromal tumors caused by a novel germline KIT gene mutation (Asp820Gly): a case report and literature review

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract; most of them have gain-of-function mutations of the KIT gene. There have been rare cases of families with multiple GISTs, that had autosomal dominant germline KIT mutations. Here, we present a case of multiple GISTs caused by a novel germline KIT mutation. Intraoperatively, the main tumor was present in the body of the stomach, and multiple small nodules were detected mainly in the upper and middle part of the gastric wall; several nodules were also present in the small bowel wall. The main tumor and surrounding nodules were resected. DNA sequencing of the tumor tissue, adjacent normal mucosal tissue, and peripheral blood leukocytes revealed that the patient had germline Asp820Gly mutation in exon 17 of the KIT gene. This is the first case with germline Asp820Gly mutation in exon 17 of the KIT gene.

Remarkable effects of imatinib in a family with young onset gastrointestinal stromal tumors and cutaneous hyperpigmentation associated with a germline KIT-Trp557Arg mutation: case report and literature overview

Gastrointestinal stromal tumors (GISTs) occur mostly sporadically. GISTs associated with a familial syndrome are very rare and are mostly wild type for KIT and platelet-derived growth factor alpha (PDGFRA). To date 35 kindreds and 8 individuals have been described with GISTs associated with germline KIT mutations. This is the third family described with a germline p.Trp557Arg mutation in exon 11 of the KIT gene. The effect of imatinib in patients harboring a germline KIT mutation has been rarely described. Moreover, in some studies imatinib treatment was withheld considering the lack of evidence for efficacy of this treatment in GIST patients harboring a germline KIT mutation. This paper describes a 52-year old patient with a de novo germline p.Trp557Arg mutation with multiple GISTs throughout the gastrointestinal tract and cutaneous hyperpigmentation. Imatinib treatment showed long-term regression of the GISTs and evident pathological response was seen after resection. Remarkably, the hyperpigmentation of the skin also diminished during imatinib treatment. Genetic screening of the family revealed the same mutation in two daughters, both with similar cutaneous hyperpigmentation. One daughter, aged 23, was diagnosed with multiple small intestine GISTs, which were resected. She was treated with adjuvant imatinib which prompted rapid regression of the cutaneous hyperpigmentation. Imatinib treatment in GIST patients harboring a germline KIT mutation shows favorable and long-term responses in both the tumor and the phenotypical hyperpigmentation.

Imatinib response of gastrointestinal stromal tumor patients with germline mutation on KIT exon 13: A family report

Familial gastrointestinal stromal tumor (GIST) is a rare autosomal dominant disorder associated with mutations in the KIT gene in the majority of cases. Although, exon 11 appears to be the hot spot region for approximately 95% of germline mutations, pathogenic variations have also been identified in exon 8, 13 and 17. Exon 13 germline mutations are extremely rare amongst familial GISTs and seven families with a germline mutation have been reported to date. Moreover, the role of imatinib mesylate in this rare familiar settings is not completely known so far. We describe here clinical, imaging, pathological and genetic findings of a family with four affected members; grandmother, his son and two grand-sons having a germline gain-of-function mutation of KIT in exon 13 and discuss the imatinib mesylate treatment surveillance outcomes towards disease management.

Familial gastrointestinal stromal tumors, lentigines, and café-au-lait macules associated with germline c-kit mutation treated with imatinib

BACKGROUND

Familial lentiginosis syndromes are characterized by a wide array of manifestations resulting from activation of molecular pathways which control growth, proliferation, and differentiation of a broad range of tissues. Familial gastrointestinal stromal tumors (GISTs) are often accompanied by additional features like hyperpigmentation, mastocytosis, and dysphagia. They have been described with mutations in c-kit (most commonly), platelet-derived growth factor receptor A, neurofibromatosis-1, and succinate dehydrogenase genes.

MATERIALS AND METHODS

We report on molecular characterization and tumor histopathology of two siblings in whom lentigines and café-au-lait macules were present along with multifocal GIST. Immuhistochemical analysis of CD34 and CD117 was performed on GIST biopsy samples from both siblings, while c-kit mutational analysis was done by PCR and direct sequencing on DNA from peripheral blood leukocytes of all family members and from paraffin-embedded gastric biopsy specimens of affected siblings.

RESULTS

Histopathology revealed positive expression of CD117 and CD34. Mutational analysis showed the germline c.1676T>C mutation in c-kit exon 11, (p.(Val559Ala)), in the peripheral blood of both siblings and a second exon 11 mutation, c.1669T>A (p.(Trp557Arg)) in the tumor biopsy of one of them. Initiation of imatinib treatment resulted in striking resolution of their hyperpigmentation and a stable gastrointestinal disease in one of them.

CONCLUSIONS

A c-kit mutational test in familial GISTs is indicated before initiation of imatinib therapy, as it can help predict tumor response to treatment.

Germline mutations of KIT in gastrointestinal stromal tumor (GIST) and mastocytosis

Somatic mutations of KIT are frequently found in mastocytosis and gastrointestinal stromal tumor (GIST), while germline mutations of KIT are rare, and only found in few cases of familial GIST and mastocytosis. Although ligand-independent activation is the common feature of KIT mutations, the phenotypes mediated by various germline KIT mutations are different. Germline KIT mutations affect different tissues such as interstitial cells of Cajal (ICC), mast cells or melanocytes, and thereby lead to GIST, mastocytosis, or abnormal pigmentation. In this review, we summarize germline KIT mutations in familial mastocytosis and GIST and discuss the possible cellular context dependent transforming activity of KIT mutations.

Syndromic gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of gastrointestinal tract. They feature heterogeneous triggering mechanisms, implying relevant clinical differences. The vast majority of GISTs are sporadic tumors. Rarely, however, GIST-prone syndromes occur, mostly depending on heritable GIST predisposing molecular defects involving the entire organism. These conditions need to be properly identified in order to plan appropriate diagnostic, prognostic and therapeutic procedures. Clinically, GIST-prone syndromes must be thought of whenever GISTs are multiple and/or associated with accompanying signs peculiar to the background tumorigenic trigger, either in single individuals or in kindreds. Moreover, syndromic GISTs, individually considered, tend to show distinctive features depending on the underlying condition. When applicable, genotyping is usually confirmatory. In GIST-prone conditions, the prognostic features of each GIST, defined according to the criteria routinely applied to sporadic GISTs, combine with the characters proper to the background syndromes, defining peculiar clinical settings which challenge physicians to undertake complex decisions. The latter concern preventive therapy and single tumor therapy, implying possible surgical and molecularly targeted options. In the absence of specific comprehensive guidelines, this review will highlight the traits characteristic of GIST-predisposing syndromes, with particular emphasis on diagnostic, prognostic and therapeutic implications, which can help the clinical management of these rare diseases.

Gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumor of the gastrointestinal tract. Soon after GIST was recognized as a tumor driven by a KIT or platelet-derived growth factor receptor mutation, it became the first solid tumor target for tyrosine kinase inhibitor therapies. More recently, alternative molecular mechanisms for GIST pathogenesis have been discovered. These are related to deficiencies in the succinate dehydrogenase complex, NF1-gene alterations in connection with neurofibromatosis type 1 tumor syndrome, and mutational activation of the BRAF oncogene in very rare cases.

[Hereditary and non-hereditary syndromic gastointestinal stromal tumours]

The majority of gastrointestinal stromal tumours (GISTs) present as solitary gastrointestinal masses in adults aged 50-70 years. A small subset of GISTs (≤5%) occurs in the setting of familial or idiopathic multitumour syndrome. In decreasing order of frequency, neurofibromatosis Recklinghausen (NF-1), Carney triad (gastric GIST, pulmonary chondroma and extra-adrenal paraganglioma), familial GIST syndromes resulting from germline mutations in c-Kit/PDGFRA and the Carney-Stratakis syndrome (hereditary GIST paraganglioma syndrome caused by germline mutations in the mitochondrial tumour suppressor gene pathway involving the succinate dehydrogenase subunits SDHD, SDHC and SDHB) represent the four most important GIST syndromes characterized to date. Since affected patients and their family members require special treatment and/or counseling and follow-up, early diagnosis and precise classification of this likely still underdiagnosed diseases is of the utmost importance. This review summarizes the pertinent clinicopathological and molecular features of the main GIST syndromes to facilitate their diagnosis and distinction from their non-syndromic mimics.

Diagnostic criteria, specific mutations, and genetic predisposition in gastrointestinal stromal tumors

In 1998, gastrointestinal stromal tumor (GIST) emerged as a distinct oncogenetic entity and subsequently became a paradigm of targeted therapies in solid tumors. Diagnosis of GIST relies on both histology and immunohistochemistry. Ninety-five percent of GISTs express either KIT or DOG-1. Approximately 80%-90% of GISTs harbor gain-of-function mutations of either KIT or platelet-derived growth factor receptor alpha polypeptide (PDGFRA) receptor tyrosine kinase (RTK). More than 100 different mutations have been described, some of which are associated with specific clinical and/or histological characteristics. Detection of KIT or PDGFRA mutations is recommended in advanced GISTs because they are highly predictive of tumor response to RTK inhibitors, as well as in KIT-negative cases to confirm diagnosis. In most cases, GISTs are sporadic, but in rare cases, they are related with genetic predisposition, such as neurofibromatosis type 1, Carney triad, Carney-Stratakis syndrome, and inherited KIT or PDGFRA germline mutations.

Chromosome copy number changes carry prognostic information independent of KIT/PDGFRA point mutations in gastrointestinal stromal tumors

BACKGROUND

Oncogenic point mutations in KIT or PDGFRA are recognized as the primary events responsible for the pathogenesis of most gastrointestinal stromal tumors (GIST), but additional genomic alterations are frequent and presumably required for tumor progression. The relative contribution of such alterations for the biology and clinical behavior of GIST, however, remains elusive.

METHODS

In the present study, somatic mutations in KIT and PDGFRA were evaluated by direct sequencing analysis in a consecutive series of 80 GIST patients. For a subset of 29 tumors, comparative genomic hybridization was additionally used to screen for chromosome copy number aberrations. Genotype and genomic findings were cross-tabulated and compared with available clinical and follow-up data.

RESULTS

We report an overall mutation frequency of 87.5%, with 76.25% of the tumors showing alterations in KIT and 11.25% in PDGFRA. Secondary KIT mutations were additionally found in two of four samples obtained after imatinib treatment. Chromosomal imbalances were detected in 25 out of 29 tumors (86%), namely losses at 14q (88% of abnormal cases), 22q (44%), 1p (44%), and 15q (36%), and gains at 1q (16%) and 12q (20%). In addition to clinico-pathological high-risk groups, patients with KIT mutations, genomic complexity, genomic gains and deletions at either 1p or 22q showed a significantly shorter disease-free survival. Furthermore, genomic complexity was the best predictor of disease progression in multivariate analysis.

CONCLUSIONS

In addition to KIT/PDGFRA mutational status, our findings indicate that secondary chromosomal changes contribute significantly to tumor development and progression of GIST and that genomic complexity carries independent prognostic value that complements clinico-pathological and genotype information.