Treatment of Gastrointestinal Stromal Tumors with Imatinib Mesylate:A Major Breakthrough in the Understanding of Tumor-specific Molecular Characteristics

Clinicopathological and immunohistochemical characterization of gastrointestinal stromal tumour at four tertiary health centers in Nigeria using CD117, DOG1, and human epidermal growth factor receptor-2 biomarkers

Aims

Gastrointestinal stromal tumors (GISTs) are neoplastic lesions that primarily affect the digestive tract and develop from interstitial cells of Cajal. These lesions require histopathological and immunohistochemical characterization due to their malignant potential and personalized treatment. In this investigation, the sex, age, lesional sites of origin, histopathological types, the prevalence of human epidermal growth factor receptors (HER-2) expression, prognostic indices (based on tumor size and mitotic figures), expression of CD117 and DOG1, and characteristics of patients with GIST were all characterized.

Materials and Methods

This was a retrospective cross-sectional analysis of GIST cases seen at four tertiary health-care centers in Nigeria over a 10-year period (2008-2017) and investigated utilizing histopathological and immunohistochemical (CD117, DOG1, and HER-2) methods.

Results

In this investigation, there were twenty GIST cases. Notably, the majority (40%) of the cases had tumors with sizes between 7.0 and 8.0 cm; the stomach was the most frequent site (70%) and the spindle cell type of GIST was the most prevalent (80%) histopathological type. In addition, the stomach was significantly associated with GIST as an origin site (with a P = 0.001), and 100% and 50% of these tumors were immunoreactive with CD117 and DOG1, respectively.

Conclusions

In our study, GISTs most frequently develop in the stomach, and CD117 and DOG1 are essential for correctly diagnosing these tumors. However, HER-2 immunoreactivity is a predictive marker of survival for personalized care.

Justification of direct Sanger sequencing application for detection of KIT and PDGFRα gene mutations in formalin-fixed, paraffin-embedded samples from gastrointestinal stromal tumours

AIMS

The knowledge concerning genetic background of gastrointestinal stromal tumours (GISTs) is well recognised, and the accurate detection of KIT and PDGFRα mutations is of great importance for the process of disease diagnosis and patient's treatment. In this study, we compare the usefulness of real-time PCR-based techniques and Sanger sequencing to detect mutations of both genes in 41 formalin-fixed, paraffin-embedded GIST samples.

METHODS

The analysis encompassed most frequently mutated coding regions of KIT (exons 9, 11, 13 and 17) and PDGFRα (exons 12, 14 and 18) genes. The GIST Mutation Detection Kit (EntroGen), direct Sanger sequencing and high-resolution melting (HRM) analysis were applied to conduct the study.

RESULTS

With the application of EntroGen kit, we found alterations in 22/38 samples, with Sanger sequencing variants were found in 36/41 samples. The concordant results for both methods were observed in 19/38 samples. With subsequently applied HRM analysis, we have confirmed that all samples, except one, harboured alterations in the regions indicated by Sanger sequencing.

CONCLUSIONS

Our results show that in GIST samples, carrying a broad spectrum of deletions, Sanger sequencing is a better, more sensitive method for mutational analysis of KIT and PDGFRα genes.

Bone marrow necrosis secondary to imatinib usage, mimicking spinal metastasis on magnetic resonance imaging and FDG-PET/CT

Imatinib mesylate has become the treatment of choice for gastrointestinal stromal tumors (GISTs) and has made a revolutionary impact on survival rates. Bone marrow necrosis is a very rare adverse event in malignant GIST. Bone metastases are also rarely encountered in the setting of this disease. The authors report on a patient with malignant GIST who developed a bone lesion, mimicking spinal metastasis on both MR imaging and FDG-PET/CT. Corpectomy and anterior fusion was performed, but the pathology report was consistent with bone marrow necrosis. Radiological and clinical similarities made the distinction between metastasis and bone marrow necrosis challenging for the treating physicians. Instead of radical surgical excision, more conservative methods such as percutaneous or endoscopic bone biopsies may be more useful for pathological confirmation, even though investigations such as MR imaging and FDG-PET/CT indicate metastatic disease.

Apoptotic effect of imatinib on human colon adenocarcinoma cells: influence on actin cytoskeleton organization and cell migration

Imatinib mesylate (STI571) is the first member of a new class of agents that act by inhibiting specific tyrosine kinases, rather than killing all rapidly dividing cells. This drug is usually used in the treatment of chronic myelogenous leukemia and gastrointestinal stromal tumors. It was recognized to inhibit activity of kinases such as Bcr/Abl, platelet-derived growth factor receptor, and c-kit. These proteins play important roles in cell growth, motility, and survival. Therefore, studies on the biological effects of imatinib on different cellular models are very important. Human colon adenocarcinoma LS180 cell line was used in the studies presented. Cells were exposed to 0.1-100 μM imatinib for 24 and 48 h. Dose-dependent decreases in cell viability and morphological changes were observed. Moreover, the apoptotic effect of imatinib (10 μM, 50 μM) after 24 h of exposure was demonstrated as evaluated by translocation of phosphatidylserine to external membrane leaflet and by increased activity of caspase-3. Special attention was focused on imatinib influence on actin cytoskeleton organization and migration ability of LS180 cells. Distinct alterations in actin cytoskeleton architecture occurred in response to drug treatment, accompanied by appearance of filamentous actin aggregates and decrease in actin polymerization state. These changes were correlated with remarkable decrease in cell migration capacity. In summary, our data clearly demonstrate that imatinib induces apoptosis and inhibits human colon adenocarcinoma cell migration. Therefore, this drug may have potential in colon cancer therapy in the future.

Expression of platelet-derived growth factor-alpha receptor in human osteosarcoma is not a predictor of outcome

AIMS

The aims of this study were to examine the prognostic relevance of platelet-derived growth factor-α receptor (PDGFRA) expression in human osteosarcomas and to evaluate the mutation status of exon 12 and exon 18 of the PDGFRA gene.

METHODS

PDGFRA expression was examined in 100 human osteosarcomas by immunohistochemistry using paraffin embedded tumour tissues, and capillary sequencing of genomic DNA was performed to search for mutations in exons 12 and 18 of the PDGFRA gene.

RESULTS

Ninety-six osteosarcomas showed PDGFRA expression ranging from 4% to 90% (mean 40%, median 37.5%, SD 27.11%). Furthermore, DNA sequence of exon 12 and exon 18 of the PDGFRA gene were not altered in 40 tumours with high PDGFRA expression. Overall and disease-free survival analysis did not reveal any differences between osteosarcoma patients with high PDGFRA expression and patients with low PDGFRA expression.

CONCLUSIONS

The protein expression is not linked to mutations in exon 12 or exon 18 of PDGFRA gene. Therefore, treatment modalities based on the suppression of PDGFRA tyrosine kinase activity may need further investigation. PDGFRA expression is not a prognostic marker for osteosarcoma patients.

Follow-up of hepatic and peritoneal metastases of gastrointestinal tumors (GIST) under Imatinib therapy requires different criteria of radiological evaluation (size is not everything!!!)

PURPOSE

To define computed tomography (CT) criteria for evaluating the response of patients with gastrointestinal stromal tumors (GIST) who are receiving Imatinib (tyrosine-kinase inhibitor therapy).

MATERIALS AND METHODS

This prospective CT study evaluated 107 consecutive patients with advanced metastatic GIST treated with Imatinib.

RESULTS

Seventy patients had total or partial cystic-like transformation of hepatic and/or peritoneal metastases. These pseudocysts remained unchanged in size or stable in size on successive CT examinations (stable disease according to RECIST criteria). Forty-six patients developed metastases, 17 patients showed increasing parietal thickness and 29 patients with peripheral enhancing nodules. These CT changes represented local recurrence consistent with GIST resistance to Imatinib treatment. WHO or RECIST criteria did not provide a reliable evaluation of disease evolution or recurrence. Development of new enhancement of lesions (parietal thickness or nodule) was the only reliable criterion.

CONCLUSION

The development of peripheral thickening or enhancing nodules within cystic-like metastatic lesions, even without any change in size, represented progressive GIST under Imatinib, growing in a short time and should alert the clinician for the possible need for a change in therapy.

Expression of platelet-derived growth factor-AA and platelet-derived growth factor-alpha receptor in ameloblastomas

BACKGROUND

Platelet-derived growth factor (PDGF)-AA isoform and its receptor, PDGF-alpha receptor (PDGFRA) regulate tooth development and growth. We investigated the expression of both proteins in ameloblastomas, to contribute the understanding of the potential role of the PDGF/PDGFR system in this odontogenic neoplasm.

METHOD

Twenty-nine specimens of ameloblastoma were analyzed for PDGF-AA and PDGFRA expression using immunohistochemistry. The proliferation activity was investigated with the MIB-1 antibody. Additionally, capillary sequencing of genomic DNA was performed to search for mutations in therapeutically relevant exons 12 and 18 of the PDGFRA gene.

RESULTS

PDGF-AA and PDGFRA expression were detectable in all cases with the exception of one tumor. However, protein expression levels did neither correlate with each other nor with MIB-1 expression. Unicystic ameloblastomas did not differ from solid tumors with regard to PDGF-AA, PDGFRA, and MIB-1 expression. One tumor revealed a somatic mutation of exon 12 of the PDGFRA gene.

CONCLUSION

PDGF-AA and PDGFRA proteins are regularly expressed in variable levels in ameloblastomas, and somatic mutations of exon 12 and exon 18 of the PDGFRA gene are rare findings.

Imatimid-induced bone marrow necrosis detected on MRI examination and mimicking bone metastases

Imatinib has revolutionized the treatment and prognosis of patients with gastrointestinal stromal tumors (GIST). In contrast to liver and/or abdominal involvement, bone metastases are an uncommon event in GIST. We report here two patients with metastatic GIST who developed pelvic bone marrow focal lesions visible on MRI examinations, while Imatinib dramatically improved other tumor sites. A biopsy in one patient diagnosed bone marrow necrosis. The other patient had a favorable follow-up over several years, without bone metastases. Focal bone marrow abnormalities, detected on MRI examinations and mimicking bone metastases in patients who were otherwise responding, should be considered as probable bone marrow necrosis.

High-resolution melting amplicon analysis as a method to detect c-kit and platelet-derived growth factor receptor alpha activating mutations in gastrointestinal stromal tumors

High-resolution melting amplicon analysis (HRMAA) was used to detect c-kit and platelet-derived growth factor receptor alpha (PDGFRA) activating mutations in 96 gastrointestinal stromal tumors (GISTs). HRMAA detected mutations in 87 GISTs (91%). Of the 87 cases, 69 (79%) contained c-kit mutations and 18 (21%), PDGFRA mutations. One c-kit mutation-positive case contained an exon 9 mutation, ins FY at codon 503, that has not been previously described. One PDGFRA mutation-positive case contained mutation D842V del 843, also not previously described. Of 18 PDGFRA mutation-positive cases, 3 (17%) were strongly positive for kit expression as measured by CD117 immunohistochemical analysis. Of 69 c-kit mutation-positive cases, 66 (96%) showed strong kit immunohistochemical expression, but 3 (4%) showed negative to weak CD117 expression. Of 96 cases, 9 (9%) were wild type for c-kit and PDGFRA. Of the wild-type cases, 8 still showed strong immunohistochemical kit expression, whereas 1 showed weak kit expression. GISTs with PDGFRA mutations were found in the stomach, omentum, and peritoneum but not the small intestine. GISTs with c-kit exon 9 mutations were found primarily in the small intestine. HRMAA is a sensitive technique that can be used to rapidly identify c-kit and PDGFRA activating mutations in GISTs.

Massive intraperitoneal stromal tumour: two-year follow-up

BACKGROUND

Gastrointestinal stromal tumours (GISTs) are rare. Few cases of such tumours are reported in the literature. Until recently, they were only treated surgically but, nowadays, for high grade tumours, we can consider wide excision, not only as a palliative measure, but also to enable subsequent treatment with Imatinib mesylate.

METHODS

We describe the case of a patient with a high-grade GIST, who, two years after undergoing surgery and medical treatment, is still in remission. Computerised axial tomography (CT) of the abdomen detected the presence of multiple heterogeneous solid masses of various sizes but no localised retroperitoneal adenopathies.

MAIN FINDINGS

Median laparotomy was performed and revealed multiple intraperitoneal tumours. The larger masses were excised and the smaller residual implants are currently being treated with Imatinib mesylate. The patient had visceral, parietal and peritoneal dissemination. One of them, located in the supramesocolic area, had a maximal diameter of 20cm. Another one, at the level of the retro-gastric space, had a diameter of 22cm. The other tumours were smaller and spread over the parietal and visceral peritoneum, mainly between the loops of the small intestine and pelvis. Two years after cytoreduction surgery, the patient is well and free of obvious disease and has shown a good tolerance to pharmacological treatment.

CONCLUSIONS

Imatinib mesylate has revolutionised the treatment of GIST and offers good palliation and prolongation of overall survival.

Point mutations of protein kinases and individualised cancer therapy

The treatment of cancer is rapidly changing, with an increasing focus on converting our improved understanding of the molecular basis of disease into clinical benefit for patients. Protein kinases that are mutated in cancer represent attractive targets, as they may result in cellular dependency on the mutant kinase or its associated pathway for survival, a condition known as 'oncogene addiction'. Early clinical experiences have demonstrated dramatic clinical benefit of targeting oncogenic mutations in diseases that have been largely resistant to traditional cytotoxic chemotherapy. Further, mutational activation of kinases can indicate which patients are likely to respond to targeted therapeutics. However, these experiences have also illuminated a number of critical challenges that will have to be addressed in the development of effective drugs across different cancers, to fully realise the potential of individualised molecular therapy. This review utilises examples of genetic activation of kinases to illustrate many of the lessons learned, as well as those yet to be implemented.

Imatinib mesylate therapy in advanced gastrointestinal stromal tumors: experience from a single institute

Gastrointestinal stromal tumors (GIST) are rare soft tissue sarcomas arising primarily from mesenchymal tissue in the gastrointestinal tract and abdomen. Since there is no effective treatment in the advanced stages, the outcome is poor in such patients. Recently, imatinib mesylate, a selective tyrosine kinase inhibitor, has shown a promising effect in GIST. Hence, we report our experience on the management of advanced GIST with imatinib therapy. A total of 14 patients were enrolled in this study, including 10 males and four females (median age, 51 years). The results showed that the small intestine was the most frequent site of primary lesion, while the liver was the most frequently metastasized organ. Most of the patients experienced tolerable side effects with imatinib therapy, including edema of periorbital area and/or legs and abdominal pain. Only two mortalities were noted during follow-up. The patients clinically benefited from imatinib therapy, with one patient having a complete response, three having a partial response, and seven having stable disease. The results demonstrate promising effects of imatinib in advanced GIST.

Expression of c-kit in human osteosarcoma and its relevance as a prognostic marker

AIMS

To examine the prognostic relevance of c-kit expression in human osteosarcomas and to evaluate the mutation status in exon 9 and exon 11 of the c-kit gene.

METHODS

c-kit expression was examined in 100 human osteosarcomas by immunohistochemistry using paraffin embedded tumour tissues, and capillary sequencing of genomic DNA was performed to search for mutations in exons 9 and 11 of the c-kit gene.

RESULTS

20 osteosarcomas showed c-kit expression ranging from 5% to 90% (mean 5.9%; SD 16.74%). Furthermore, DNA sequences of exon 9 and exon 11 of the c-kit gene were not altered in these tumours. Overall and disease free survival analysis did not reveal any differences between patients with osteosarcoma with c-kit expression and those with c-kit negative tumours.

CONCLUSIONS

C-kit expression is not a prognostic marker in patients with osteosarcoma. The protein expression is not linked to mutations in exon 9 or exon 11 of the c-kit gene. Therefore, these exons may not function as targets for treatment modalities based on the suppression of c-kit tyrosine kinase activity.

Phase II trial of imatinib mesylate in patients with recurrent platinum- and taxane-resistant epithelial ovarian and primary peritoneal cancers

OBJECTIVES

To evaluate the efficacy and tolerability of imatinib mesylate (Gleevec; Novartis Pharmaceuticals, Basel, Switzerland) in patients with recurrent ovarian and primary peritoneal cancer.

METHODS

This was an open-label, single-institution phase II trial. Patients were eligible if they had measurable platinum/taxane-resistant disease, received 2-4 prior treatment regimens, and over-expressed at least one imatinib target (c-Kit, PDGFR-beta, or c-Abl) by immunohistochemistry. Imatinib was administered orally at 600 mg daily for 6 weeks (one course) and was repeated in the absence of measurable progression.

RESULTS

Sixteen enrolled patients were evaluable for toxicity and 12 for response. The median number of prior treatments was 4. A total of 29 courses were initiated. No complete or partial responses were documented during a median follow-up of 6.6 months. However, 4 (33%) of the 12 evaluable patients had stable disease lasting 3.8, 6.4, 7.5, and 8+ months. Expression of PDGFR-beta and c-Abl was seen in 15 (94%) and c-Kit in 8 (50%) patients' tumors. There was no relationship between best response (stable disease) and target expression. Adverse events were uncommon, with fatigue and nausea/vomiting being reported in 34% and 31% of cycles, respectively. Two patients underwent dose reduction for rash and edema (n = 1) and grade 3 neutropenia (n = 1). No grade 4 toxicity was observed.

CONCLUSION

Imatinib mesylate was well tolerated but did not produce clinical responses in patients with previously treated metastatic ovarian and primary peritoneal carcinoma.