PDGFRA Mutations Research Articles

Genomic analysis for potential targetable mutations in relapsed and refractory germ cell tumors.

407 Background: A large number of metastatic germ cell tumors (GCTs) are cured with platinum-based chemotherapy. Patients that have relapsed or refractory disease can be cured with salvage therapy including salvage surgery, standard dose or high-dose chemotherapy with stem-cell transplant. However, 15-20% of patients with metastatic GCT are incurable with current therapeutic options. We sought to perform a genetic analysis on a cohort of these incurable patients to determine the presence of therapeutically targetable genetic mutations. Methods: After obtaining IRB approval, patients treated at Indiana University for refractory or relapsed GCT from 2016-2019 were analyzed with a next-generation sequencing (NGS) platform. Clinically relevant genomic alterations were reviewed to determine the potential for targeted therapies. Results: 10 patients with testicular (9) or ovarian (1) GCT underwent an analysis of tissue (7), blood (1), or both (2) with a mean 2.9 potential targetable mutations per patient. Four patients had NGS from preserved gonadal tissue removed prior to chemotherapy while 6/10 sample specimens were obtained post standard (1) or high-dose (5) chemotherapy. Potential known therapeutic targets were found in 80% (8/10). Of the platforms that tested biomarkers, high microsatellite instability (MSI) (1/5), intermediate tumor mutational burden (1/4), and high PD-L1 expression of 90% (1/3) was appreciated. The MSI-high patient did not respond to pembrolizumab. A patient with a KIT only mutation did not achieve a response to imatinib. One patient with KRAS, KIT, RAF1, CCND2, MET, AR, CDK6, PDGFRA, EGFR, and BRAF mutations was treated with brentuximab and was progression free for 2.5 months. Common mutations were CCND2 (4/10), RAF1 (2/10), KIT (2/10), and KRAS (2/10). Other mutations actionable in non-GCT tumors included ERCC1, TUBB3, RRMI, PIK3CA, TOPO1 and TP53. Conclusions: NGS identifies potential clinically relevant genomic alterations. Genetic mutations may enable future effective therapies as our understanding of platinum-resistant disease evolves. To our knowledge, this is among the first reports utilizing next-generation sequencing in GCT to direct potential therapeutic agents.

Calcifying fibrous tumor: a clinicopathological analysis of 32 cases

Objective: To investigate the clinicopathological characteristics, histogenesis, immunophenotypes, molecular genetic characteristics, diagnosis and differential diagnosis of calcifying fibrous tumors (CFT). Methods: A total of 32 cases of CFT (22 cases from Henan Provincial People's Hospital and 10 cases from PLA Army Medical Center) diagnosed between June 2009 and February 2019 were reviewed. The clinical and pathologic data were analyzed. Results: There were 12 male and 20 female patients, aged from 15 to 63 years (mean 40.8 years). Eleven cases occurred in stomach, four cases in retroperitoneum, four cases in ovary, two cases in scrotum, two cases in mediastinum, two cases in head and neck, one case each in thoracic cavity, lung, adrenal gland, kidney, sigmoid colon, epididymis and mesosalpinx. All the tumors were solid masses with clear boundaries. The maximal dimension of the tumors ranged from 0.6 to 10.0 cm. Microscopically, there was hypocellular stromal sclerosis and wavy storiform coarse collagen with superimposed scattered or patchy lymphocytes and plasma cells; calcification or gravel formation were also detected. Immunohistochemistry showed that spindle cells were positive for vimentin and some were positive for CD34; and they were negative for calponin, SMA, desmin, S-100 protein, SOX10, STAT6, β-catenin, ALK, CD117, DOG1, CKpan, and EMA. No ALK rearrangement was detected by FISH in all cases. No C-KIT and PDGFRA mutation was detected in all the tested 11 cases of stomach, four cases of retroperitoneal and one case of sigmoid colon CFT. MDM2 was not amplified by FISH in all four tested cases of retroperitoneal CFT. Conclusions: CFT is a rare benign tumor of fibroblastic cell origin. The diagnosis mainly depends on histomorphologic analysis and immunophenotyping. CFT should be differentiated from other benign and malignant spindle cell mesenchymal tumors.

Circulating Tumor Cells as a Biomarker to Assist Molecular Diagnosis for Early Stage Non-Small Cell Lung Cancer.

Background and ObjectiveCompared with tissue biopsy, liquid biopsy is the most preferable non-invasive promising method in personalized medicine, although it has many limitations in isolating circulating tumor cells (CTC). Lung cancer associated mortality is drastically increased due to a shortfall of early-stage detection, which remains a challenge. Herein, we aimed to detect lung cancer at an early-stage using CellCollector device.Methods39,627 volunteers underwent low-dose computed tomography; 2508 cases with pulmonary nodules and 7080 with no pulmonary nodules were chosen. After follow-up, 24 patients were diagnosed with early-stage non-small cell lung cancer (NSCLC), and subjected to CTC detection using CellCollector, along with 72 healthy volunteers. Immunofluorescence staining for EpCAM/CKs and CD45 were performed for CTC validation.ResultsFifteen out of twenty-four (stage I, n = 18; stage II, n = 6) early-stage lung cancer patients were found to be CTC-positive, whereas no CTC was found in the control group. Genetic mutation of TP53, ERBB2, PDGFRA, CFS1R and FGFR1 in the CTC revealed 71.6% of the mutation sites similar to the tumor tissues of 13 patients. Molecular characterization revealed higher expression of protein PD-LI in CTC (40%) as compared to tumor tissue (26.7%). Moreover, CTC clusters were detected in 40% of patients.ConclusionCTC detection using the CellCollector in early-stage NSCLC had a relative high capture rate. Moreover, CTC analysis is a prospective setting for molecular diagnostic in cases when tumor tissue biopsy is not desirable.

Clinical activity of avapritinib in ≥ fourth-line (4L+) and PDGFRA Exon 18 gastrointestinal stromal tumors (GIST).

826 Background: Targeting oncogenic KIT and PDGFRA mutations revolutionized treatment of patients (pts) with advanced GIST; however, nearly all pts succumb to resistant disease. Avapritinib is a potent and selective kinase inhibitor with broad activity against oncogenic KIT/PDGFRA mutants, including PDGFRA D842V and other primary or secondary resistance mutations. Results from the phase 1 NAVIGATOR (NCT02508532) study of avapritinib in pts with advanced GIST are presented. Methods: Adult pts with unresectable PDGFRA D842V or other mutant GIST who progressed on imatinib and ≥1 other tyrosine kinase inhibitor (TKI) were treated with oral, daily, continuous avapritinib. Adverse events (AE) and response by mRECIST 1.1 per central radiology were assessed. Overall population safety (30-600 mg starting doses) and efficacy in the response-evaluable 4L+ and PDGFRA Exon 18 (Ex 18) populations treated at the MTD (400 mg)/RP2D (300 mg) were analyzed. Results: As of 16 Nov 2018, 237 pts [172 KIT, 62 PDGFRA Ex 18 [56 D842V, 6 non-D842V), 2 PDGFRA N659K, 1 missing] were enrolled including 111 in the 4L+ population (primarily KIT, median 4 prior TKI) and 43 in the Ex 18 population (median 1 prior TKI). The 4L+ ORR was 22% [1 CR, 23 PR (1 pending)], and 52 SD with mDOR of 10.2 months (95% CI: 7.2–NE). The Ex 18 ORR was 86% [3 CR, 34 PR (1 pending)] and 5 SD; mDOR was not reached (95% CI: 11.3–NE). Most AEs were grade 1–2, most commonly nausea (63%), fatigue (58%), anemia (49%), periorbital edema (42%), diarrhea (40%), vomiting (40%), decreased appetite (38%), increased lacrimation (33%), peripheral edema (33%) and memory impairment (most common cognitive AE, 29%). 10% of pts discontinued due to a related AE. Grade 3–4 related AE ≥ 2% were anemia, fatigue, hypophosphatemia, hyperbilirubinemia, neutropenia, and diarrhea. Conclusions: Avapritinib has important clinical activity in pts with advanced GIST who have no effective therapies. The ORR and DOR of avapritinib in 4L+ exceeds that of approved 2nd and 3rd line therapies and shows impressive activity in D842V and other Ex 18 mutant PDGFRA GIST. Results suggest avapritinib has the potential to change the treatment paradigm of pts with advanced GIST. Clinical trial information: NCT02508532.

ALK expressed in a gastrointestinal stromal tumor harboring PDGFRA p. D842V mutation:a case report

BackgroundGastrointestinal stromal tumors (GISTs) are the most common type of adult mesenchymal neoplasms. The events that drive GIST oncogenesis are primarily KIT or PDGFRA mutations, which lead to the susceptibility of these tumors to small-molecule tyrosine kinase inhibitors such as imatinib and sunitinib. However, previous studies have shown that patients with a PDGFRA D842V mutation in GISTs have a very low rate of response to imatinib treatment. Therefore, novel tyrosine kinase inhibitors (TKIs) are currently being evaluated in clinical trials to treat GISTs harboring a PDGFRA D842V mutation. Anaplastic lymphoma kinase (ALK) overexpression was not expected to be present in the GIST, and it has been used as a biomarker to distinguish GISTs from other types of mesenchymal tumors.Case presentationHere, we report a 37-year-old male patient who presented with a large mass in the right upper abdomen and was subsequently diagnosed with a GIST harboring a PDGFRA D842V mutation. We unexpectedly found that the GIST in this patient exhibited simultaneous ALK expression.ConclusionsThis is the first case reported of a GIST with ALK expression. This rare phenomenon suggests that the diagnosis of a GIST cannot be excluded absolutely if a tumor exhibits ALK expression. In addition, ALK may be a potential therapeutic target for patients with imatinib-resistant stromal tumors.

Tumor-associated tertiary lymphoid structure predicts postoperative outcomes in patients with primary gastrointestinal stromal tumors

ABSTRACT Tumor-infiltrating tertiary lymphoid structures (TLS) are thought to have anti-tumor activity and are believed to indicate a favorable prognosis in cancer patients. However, the prognostic value of TLS in gastrointestinal stromal tumors (GIST) is unknown. We evaluated the prognostic value of TLS using two independent GIST cohorts. Pathological examinations identified TLS in 44.9% of patients in our discovery cohort (DC). TLS was significantly associated with smaller tumor size (P = .011), relatively well morphological classification (P < .001), lower NIH classification (P < .001), lower recurrence (P = .005), longer survival time (P < .001) and lower imatinib resistance (P = .006). Kaplan-Meier curves showed that TLS was remarkably associated with favorable survival (P = .0002) and recurrence (P = .0015) time. In addition, the presence of KIT mutations and the absence of TLS suggested worst prognosis both in terms of overall survival (OS) (P = .0029) and time to recurrence (TTR) (P = .0150), while the presence of PDGFRA mutations and TLS suggested optimal prognosis for OS and TTR. Multivariate analyzes demonstrated that TLS was an independent prognostic factor for OS (HR:0.180, P = .002) and TTR (HR:0.412, P = .023). These results were confirmed using our validation cohort. Multiplexed immunohistochemistry staining was used to determine the composition of TLS. Therapies designed to target TLS may be a novel therapeutic strategy for GIST patients with imatinib resistance.

MPC-15 FEASIBILITY OF GLIOMA SPECIFIC ONCOPANEL IN THE DIAGNOSIS OF GLIOMA

AIMMolecular classification of glioma is a mandatory in the diagnosis of glioma according to the WHO 2016 classification of tumors of the central nervous system. However, WHO does not indicate the molecular methodology to be integrated, and the versatility and cost-effectiveness of molecular diagnosis is a concern. In this study, we evaluate the feasibility of a glioma specific tailored NGS panel where driver gene mutation and 1p/19q codeletion can be analyzed in a single platform.MATERIALS AND METHODSWe developed a glioma specific tailored NGS panel consisting of 48 key driver genes including IDH1/2, TP53, PTEN, EGFR, PDGFR, NF1, RB1, CDKN2A, and the TERT promoter. DNA was extracted from FFPE tumor tissues histologically identified by a pathologist, and from patient derived blood to serve as a control. In this system, gene mutations and copy number alterations can be precisely characterized, thus 1p/19q co-deletion can also be evaluated. We have analyzed 106 glioma patients (Grade II: 19 cases, Grade III: 23 cases, Grade IV: 64 cases) using this system.RESULTSFrom these 106 cases, IDH1 and TERT promoter mutations were detected in 33 cases (28%) and 55 cases (52%), respectively. 1p/19q co-deletion was detected in 19 cases (18%), with IDH1 mutations in all cases. In 57 Grade IV cases, TP53, PTEN, RB1, NF1, PDGFRA mutations were detected in 25 cases (43%), 24 cases (41%), 10 cases (17%), 8 cases (14%) and 6 cases (10%). Although EGFR mutation frequency was low (3%), amplification was detected in 14 cases (24%). As for deletion, PTEN and CDKN2A loci were deleted in 36 cases (62%) and 30 cases (52%), respectively. To note, MET alterations were detected in 2 cases. The cases in which histopathological diagnosis is difficult to make have a tendency to show atypical genetic alterations.CONCLUSIONDiagnosis of glioma patients with this glioma-specific tailored NGS panel is feasible.

Pediatric gastrointestinal stromal tumor: Report of two novel patients harboring germline variants in SDHB and SDHC genes

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract and rarely occur in pediatric patients. 85% of pediatric GISTs and 15% of adult GISTs lack of KIT or PDGFRA mutations. 40% of these “wild-type” GISTs present loss of function mutations in genes encoding for the subunits of the succinate dehydrogenase (SDH) complex. Germline mutations in SDH complex genes have been described in patients with the Carney–Stratakis syndrome (CSS), a rare inherited condition that predisposes to GIST and paraganglioma. We report two pediatric patients with multifocal GIST, harboring respectively a novel and a previously reported loss-of-function germline variant, in SDHC and SDHB genes.

Genetic alteration profile of EGFR-mutant resected IIB-IIIA stage NSCLC and correlation to clinical outcomes.

Genetic alteration profile of epidermal growth factor receptor (EGFR) mutant resected non-small cell lung cancer (NSCLC) and its relationship with clinical outcomes remains to be illustrated and genetic biomarkers that can predict recurrence need to be figured out. Clinicopathological and follow-up information were collected for 99 EGFR-mutant resected NSCLC. Tumor sections were collected for genetic alteration detection. Targeted next-generation sequencing (NGS) was performed to detect somatic mutations within each sample using a 285-gene panel on the Ion Torrent platform. Concurrent driver gene mutations were detected in 86 participants. Adjuvant therapy was a positive factor in disease-free survival (DFS) period, and patients receiving tyrosine kinase inhibitors (TKIs) gained the longest DFS. A total of 34 concurrent mutant driver genes were found. The median number of mutated driver genes for each sample was 2 (range, 0-12). TP53 and NOTCH1 were the most frequent concurrent mutant driver genes with rates of 53.54% and 25.25% respectively. The number of concurrent mutant genes did not have a significant effect on recurrence. Multivariable analysis found that mutations of ATM (P=0.021), KIT (P=0.002), FGFR2 (P<0.001), MET (P=0.015), PDGFRA (P=0.042), RB1 (P=0.006), and wildtype NOTCH1 (P=0.032), ERBB4 (P=0.012), FGFR3 (P=0.035) were independent risk factors for the recurrence of resected EGFR mutant NSCLC. TP53 and NOTCH1 was the most common concurrent mutant driver gene. Mutations of ATM, KIT, FGFR2, MET, PDGFRA, RB1, and wildtype NOTCH1, ERBB4, FGFR3 were independent risk factors for the recurrence of resected EGFR mutant NSCLC.

Abstract C077: Updated results of phase 1 study of ripretinib (DCC-2618), a broad-spectrum KIT and PDGFRA inhibitor, in patients with gastrointestinal stromal tumor (GIST) by line of therapy (NCT02571036)

Abstract Objective: Ripretinib (DCC-2618) is a kinase switch control inhibitor designed to broadly inhibit KIT and PDGFRA mutations. Based on clinical activity observed in heavily pretreated patients (pts) with GIST in a Phase 1 study (NCT02571036), ripretinib is under evaluation in two Phase 3 studies: INVICTUS (NCT03353753) in ≥4th-line pts and INTRIGUE (NCT03673501) in 2nd-line pts, each at the recommended dose of 150 mg once daily (QD). This abstract reports updated results from the escalation and expansion phases of the Phase 1 study for pts treated with ≥100 mg daily dose. Methods: The Phase 1 study includes a dose-escalation phase that tested oral ripretinib QD or twice daily (BID) in 28-day cycles, followed by an expansion phase with the recommended Phase 2 dose (RP2D) of 150 mg QD in 6 cohorts, including cohorts for pts with GIST based on prior regimens (2nd/ 3rd, 4th, and &amp;gt;4th-line). Local Response Evaluation Criteria in Solid Tumors (RECIST) response assessments were performed every 2 cycles and pts who progressed per RECIST in the expansion cohorts were allowed to dose escalate to 150 mg BID. Results: At a cut-off date of March 01, 2019, 179 pts with GIST in the escalation and expansion phases (median follow-up of 10.4 months; range, 0.1–32.3) were enrolled at dose levels of ≥100 mg daily with KIT-driven (169 pts), PDGFRA-driven (9 pts), or wild-type-driven GIST (1 pt). Of 178 pts with GIST treated at the ≥100 mg daily dose (1 pt was not included in the intent-to-treat population as the pt only participated in the food effect portion of the study), there were 37 2nd-line pts, 31 3rd-line pts, 60 4th-line pts, and 50 &amp;gt;4th-line pts. The objective response rate (ORR) by best response was 30% in 2nd-line pts (n=11; includes 3 unconfirmed responses), 23% in 3rd-line pts (n=7; includes 3 unconfirmed responses), and 11% in ≥4th-line pts (n=12; includes 4 unconfirmed responses); responses ≥4th-line include 15% in 4th-line pts (n=9; includes 4 unconfirmed responses) and 6% in &amp;gt;4th-line pts (n=3; includes no unconfirmed responses). In 2nd-line pts, the disease control rate (DCR) was 31% (n=9) at 52 weeks. The median progression-free survival (mPFS) was 42 weeks in 2nd-line pts, 40 weeks in 3rd-line pts, and 24 weeks in ≥4th-line pts (includes 30 weeks in 4th-line pts and 16 weeks in &amp;gt;4th-line pts). In 2nd-line pts, the median duration of response was 80 weeks and the median duration of treatment was 44 weeks. For any line, 13% of pts (n=24) experienced treatment-emergent adverse events (TEAEs) leading to study treatment discontinuation, 17% of pts (n=31) experienced TEAEs leading to dose reduction and 49% (n=88) had TEAEs leading to study drug interruption. Grade 3 or 4 TEAEs in &amp;gt;5% of pts were lipase increased (18%; n=33), anemia (11%; n=20), hypertension (7%; n=13), and abdominal pain (6%; n=11). Conclusion: In this Phase 1 study, ripretinib demonstrated encouraging clinical benefit (as measured by mPFS, ORR [best response] and DCR) and was generally well-tolerated in pts with GIST treated in the 2nd-line or later. Preliminary data from this Phase 1 study further supports testing in the ongoing Phase 3 study in 2nd-line GIST. Citation Format: Ping Chi, Filip Janku, Michael Heinrich, Kristen Ganjoo, Hans Gelderblom, Michael Gordon, Robin Jones, Albiruni Razak, Jonathan Trent, Margaret von Mehren, Simin Hu, Ying Su, Rodrigo Ruiz-Soto, Suzanne George. Updated results of phase 1 study of ripretinib (DCC-2618), a broad-spectrum KIT and PDGFRA inhibitor, in patients with gastrointestinal stromal tumor (GIST) by line of therapy (NCT02571036) [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C077. doi:10.1158/1535-7163.TARG-19-C077

Gene mutation profiling in Chinese colorectal cancer patients and its association with clinicopathological characteristics and prognosis.

BackgroundGene mutations may play an important role in the development, response to treatment and prognosis of colorectal cancer (CRC). This retrospective study aimed to investigate the mutation profiling of Chinese patients with CRC, and its correlation with clinicopathological features and prognosis.MethodsThis study included 1190 Chinese CRC patients who were diagnosed between May 1998 and December 2018 and received clinical genetic testing. The OncoCarta Panel was used to test a total of 238 possible mutations in 19 common oncogenes.ResultsFive hundred and eighty‐two (48.9%) cases were detected with gene mutations. Of the 582 cases, there were 111 cases (19.7%) with two concurrent mutations, and six cases (1.0%) with three concurrent mutations. KRAS was the most common gene mutation that occurred in all cases (429, 36.1%), followed by PIK3CA (121, 10.2%), NRAS (47, 3.9%), BRAF (35, 2.9%), HRAS (11, 0.9%) and epidermal growth factor receptor (EGFR) (11, 0.9%). AKT1, KIT, FGFR1, FGFR3, FLT3, CDK, ERBB2, ABL1, MET, RET and PDGFRA mutations were also detected in several cases. When it came to prognosis, we found that KRAS/NRAS/PIK3CA/BRAF mutation was not associated with prognosis. But BRAF mutation was associated with poor prognosis in patients who accepted anti‐EGFR therapy.ConclusionsThe molecular testing offered the clinical data and mutation profile of Chinese CRC patients. The information of these mutated genes may help to find out the correlation between mutated genes and the development or prognosis of CRC.

Mutational Profile of Driver Genes in Brazilian Melanomas.

PURPOSEMutation testing of the key genes involved in melanoma oncogenesis is now mandatory for the application of targeted therapeutics. However, knowledge of the mutational profile of melanoma remains largely unknown in Brazil.PATIENTS AND METHODSIn this study, we assessed the mutation status of melanoma driver genes BRAF, NRAS, TERT, KIT, and PDGFRA in a cohort of 459 patients attended at Barretos Cancer Hospital between 2001 and 2012. We used polymerase chain reaction followed by Sanger sequencing to analyze the hot spot mutations of BRAF exon 15 (V600E), NRAS (codons 12/13 and 61), TERT (promoter region), KIT (exons 9, 11, 13, and 17), and PDGFRA (exons 12, 14, and 18) in tumors. The mutational profile was investigated for associations with demographic, histopathologic, and clinical features of the disease.RESULTSThe nodular subtype was most frequent (38.9%) followed by the superficial spreading subtype (34.4%). The most frequent tumor location was in the limbs (50.0%). The mutation rates were 34.3% for TERT and 34.1% for BRAF followed by NRAS (7.9%), KIT (6.2%), and PDGFRA (2.9%). The BRAF (P = .014) and TERT (P = .006) mutations were associated with younger patients and with different anatomic locations, particularly in the trunk, for the superficial spreading and nodular subtypes, respectively (P = .0001 for both). PDGFRA mutations were associated with black skin color (P = .023) and TERT promoter mutations with an absence of ulceration (P = .037) and lower levels of lactate dehydrogenase. There was no association between patient survival rates and mutational status.CONCLUSIONThe similar mutational profile we observe in melanomas in Brazil compared with other populations will help to guide precision medicine in this country.

Identifying Secondary Mutations in Chinese Patients with Imatinib-Resistant Gastrointestinal Stromal Tumors (GISTs) by Next Generation Sequencing (NGS).

The aim of this study was to characterize secondary kinase mutations in Chinese patients with imatinib-resistant gastrointestinal stromal tumors (GISTs). Mutations in receptor tyrosine kinase (KIT; exons 9, 11, 13, 14, 17, and 18) and platelet-derived growth factor-alpha (PDGFRA; exons 12, 14, and 18) were analyzed by direct sequencing. After imatinib treatment, 425 cancer-related target genes were analyzed by next generation sequencing (NGS) in imatinib-resistant patients. Correlation of sequencing results with clinicopathologic features were analyzed. We identified 320 patients with secondary acquired resistance. We determined that 65.63% (210/320) of resistant patients had secondary KIT mutations in exon 13 (n = 134), exon 14 (n = 10), or exon 17 (n = 66), and 4.38% (14/320) had additional PDGFRA mutations in exon 14 (n = 3) or exon 18 (n = 11). All secondary KIT mutations were missense mutations and were mostly located in kinase domains. Ninety-six imatinib-resistant GIST patients did not have secondary KIT or PDGFRA mutations. Common independent mutation events were found in retinoblastoma protein 1 (RB1) (18/96 cases), SWI/SNF-related matrix associated actin-dependent regulator of chromatin subfamily B member 1 (SMARCB1) (16/96 cases), and myc-associated factor X (MAX) (10/96 cases). RB1 or SMARCB1 mutations coexisted with activation of other oncogenes in 6 or 15 cases, respectively. Multiple mutations were also seen in cases with MAX mutations. These mutations are frequently associated with clinicopathological factors. Secondary mutations of KIT/PDGFRA were the most important contributors in GISTs developing resistance to imatinib treatment. Additional genetic events including RB1, SMARCB1, and MAX except secondary KIT/PDGFRA mutations are the most common for GISTs to evolve into resistant disease. Clinical assessment of the effect of these mutations may benefit existing risk assessment models and selection of adjuvant therapies in GIST patients.

Clinicopathological analysis of gastrointestinal stromal tumors with PDGFRA mutations

目的： 探讨伴有PDGFRA突变型胃肠道间质瘤（GIST）的临床病理特征、诊断及鉴别诊断。 方法： 收集2014年11月到2018年5月南京医科大学第一附属医院诊治的13例伴有PDGFRA突变型GIST的临床病理特点、免疫表型和分子特征，与60例C-KIT突变型GIST进行对比，并复习相关文献。 结果： 13例伴有PDGFRA突变型GIST中，发病年龄38至84岁，男女比例为9∶4，与C-KIT突变型GIST相比发生于胃更多见（P<0.05）。大体肿瘤呈囊实性或实性的结节，镜下肿瘤细胞呈弥漫状或束状分布，以上皮样细胞为主，部分区域混合梭形细胞。瘤细胞胞质丰富红染，有轻到中度异型性，但核分裂象相对少见，部分区可见横纹肌样细胞、多核瘤巨细胞、间质水肿或黏液变性、散在肥大细胞浸润。与C-KIT突变型相比，PDGFRA突变型组织学类型（多为上皮样或混合型）、不同程度间质水肿或黏液变性并可见多核瘤巨细胞、横纹肌样细胞、肥大细胞及肿瘤间质淋巴细胞浸润，差异有统计学意义（P<0.05）。免疫组织化学检测：PDGFRA突变型Ki-67多呈低增殖活性而结蛋白、平滑肌肌动蛋白、S-100蛋白大多阴性；CD34和CD117免疫表达较C-KIT突变型减弱（P<0.05），DOG1均呈不同程度表达。全部病例均行C-KIT和PDGFRA分子检查，C-KIT在13例中均为野生型，而PDGFRA位点存在突变（均为PDGFRA第18号外显子突变，第12号外显子为野生型）。13例中有4例失访，1例复发，其余病例均无病生存。 结论： PDGFRA突变型GIST有特殊的临床病理特征，但明确诊断还需依靠分子病理检查；患者一般预后较好，手术切除是最佳治疗方案。.

KIT-Dependent and KIT-Independent Genomic Heterogeneity of Resistance in Gastrointestinal Stromal Tumors — TORC1/2 Inhibition as Salvage Strategy

Sporadic gastrointestinal stromal tumors (GIST), characterized by activating mutations of KIT or PDGFRA, favorably respond to KIT inhibitory treatment but eventually become resistant. The development of effective salvage treatments is complicated by the heterogeneity of KIT secondary resistance mutations. Recently, additional mutations that independently activate KIT-downstream signaling have been found in pretreated patients-adding further complexity to the scope of resistance. We collected genotyping data for KIT from tumor samples of pretreated GIST, providing a representative overview on the distribution and incidence of secondary KIT mutations (n = 80). Analyzing next-generation sequencing data of 109 GIST, we found that 18% carried mutations in KIT-downstream signaling intermediates (NF1/2, PTEN, RAS, PIK3CA, TSC1/2, AKT, BRAF) potentially mediating resistance to KIT inhibitors. Notably, we found no apparent other driver mutations in refractory cases that were analyzed by whole exome/genome sequencing (13/109). Using CRISPR/Cas9 methods, we generated a panel of GIST cell lines harboring mutations in KIT, PTEN, KRAS, NF1, and TSC2 We utilized this panel to evaluate sapanisertib, a novel mTOR kinase inhibitor, as a salvage strategy. Sapanisertib had potent antiproliferative effects in all cell lines, including those with KIT-downstream mutations. Combinations with KIT or MEK inhibitors completely abrogated GIST-survival signaling and displayed synergistic effects. Our isogenic cell line panel closely approximates the genetic heterogeneity of resistance observed in heavily pretreated patients with GIST. With the clinical development of novel, broad spectrum KIT inhibitors, emergence of non-KIT-related resistance may require combination treatments with inhibitors of KIT-downstream signaling such as mTOR or MEK.

Gastrointestinal stromal tumors – Summary of mutational status of the primary/secondary KIT/PDGFRA mutations, BRAF mutations and SDH defects

The most important findings revealing pathogenesis, molecular characteristics, genotyping and targeted therapy of gastrointestinal stromal tumors (GISTs) are activated oncogenic mutations in KIT and PDGFRA genes. Imatinib mesylate (IM), which inhibits both KIT and PDGFRA receptors, significantly improved treatment of advanced (metastatic, recurrent, and/or inoperable) GISTs. However, in a significant number of patients the treatment fails due to the primary or secondary resistance to targeted therapy. Most common cause of secondary resistance is a presence of secondary mutations. Approximately 15% of adult patients with GISTs are negative for mutations in KIT or PDGFRA genes. These so-called wild-type GISTs appear to be characterized by other oncogenetic drivers, including mutations in BRAF, RAS, NF1 genes, and subunits of succinate dehydrogenase (SDH) complex.In the present study we investigated 261 tumour specimens from 239 patients with GIST. Primary mutations were detected in 82 % tumor specimens. 66 of them were in KIT, and 16 % in PDGFRA genes. Remaining 18 % were KIT/PDGFRA wild-type. Secondary KIT mutations were detected in 10 from 133 (7 %) patients treated with IM. We examined secondary KIT mutations in exons 13 and 17 and secondary PDGFRA mutation in exon 18 in sixteen progressive tumors and/or metastasis (from overall 22 samples). We identified BRAF V600E point mutation in 4 % of KIT/PDGFRA wild-type GIST patients. Moreover, we analysed SDH complex mutations in 4 younger patients (15, 33, 37, and 45 years old) from 44 patients without KIT, PDGFRA, and BRAF mutations. Two patients (a 37-year old man, and a 33-year old woman) had defects of the SDH complex.Our findings of mutational status of the primary and secondary KIT/PDGFRA mutations in patients with GIST confirm mechanisms of primary and secondary resistance, and also intralesional and interlesional heterogeneity of secondary mutations within and between progressive lesions. Moreover, detection of V600E BRAF mutation and defects of SDH complex in KIT/PDGFRA wild-type GISTs confirm their activation and allow for a selection of targeted therapy.

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

AimsThe 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...

A rare simultaneous coexistence of epithelioid gastrointestinal stromal tumors and schwannoma in the stomach: a case report

BackgroundGastrointestinal stromal tumors (GISTs), a type of mesenchymal tumor in the gastrointestinal tract, are believed to be closely associated with PDGFRA and C-KIT mutations. Schwannoma in the stomach, which is an unusual location, is a rare disorder. The simultaneous occurrence of the two diseases is rarer than metachronous occurrences, and its pathological characteristics have not been reported to date. We present a case report on a patient with simultaneous coexistence of gastric schwannoma and GISTs.Case presentationA 39-year-old female visited our hospital complaining of intermittent abdominal pain for the previous 3 months. CT revealed a 3.4 cm slight homogeneous enhancement in the lesser curvature of the stomach; the mass was nodular soft tissue, which was removed by radical surgery. Two solid tumors with different volumes were located in the stomach. Histologically and immunohistochemically different, the larger tumor consisted of spindle cells surrounded by a peripheral lymphoid cuff, and was positive for S-100. The larger tumor was therefore classified as a gastric schwannoma. The smaller tumor was composed of medium-sized round, oval cells with amphiphilic granular cytoplasm; vacuolization was also observed. The tumor cells were positive for DOG1 and sporadically positive for CD34 and CD117. Hence, the smaller tumor was diagnosed as epithelioid GISTs. Sanger sequencing revealed that the GIST tumor cells contained a deletion mutation (c.2527_2538 del12,843–846del4), which was located in exon 18 of PDGFRA.ConclusionGISTs combined with gastric schwannoma are a considerably rare subgroup of gastric tumors. Related clinical research is comparatively weak, and the mechanism remains unknown. We reviewed related articles to provide knowledge to improve the correct identification, diagnosis and management of patients with gastric cancer. All pathologists involved in the diagnosis and clinicians involved in the treatment should be aware of this new kind of disease pattern to improve their understanding of the disease.

Steroid Receptor Coactivator-1 Expression in Pheochromocytoma: Clinicopathologic Correlation and Potential Diagnostic Pitfall.

Pheochromocytoma is a relatively uncommon tumor, and the histomorphologic and biochemical features that may portend malignant behavior have poor overall consensus across various proposed classification systems. Steroid receptor coactivator-1 (SRC-1) is a nuclear protein that mediates transcriptional activity. Current diagnostic applications of SRC-1 are limited, and include distinguishing adrenocortical carcinoma (ACC) from renal cell carcinoma, and other mimickers. SRC-1 expression in pheochromocytoma has not been previously studied. Pheochromocytoma cases were retrieved from our Urological Pathology database and expert consultation files of the senior author, from 2015 to 2019. Clinicopathological data were obtained. SRC-1 expression was scored systematically. Thirty-eight cases were included, with a female predominance, and a mean age of 52 years (range, 16 to 75 y). Seven patients had heritable mutations including RET (n=3), VHL (2), SDHB (1), and ATM and PDGFRA (1). Two patients developed clinical metastasis, who individually had ATM and PDGFRA mutations, and SDHB p.V140F mutation. All heritable tumors were positive for SRC-1, including diffuse/strong staining and intensity in the VHL cases, and diffuse staining with variable intensity in RET cases. Diffuse positivity was seen in most of our heritable cases, providing evidence for a putative link between RET and downstream SRC-1 signaling. An inverse relationship was observed between SRC-1 expression and Pheochromocytoma of the Adrenal Gland Scaled Score/tumor size, suggesting that SRC-1 phenotype may become muted in pheochromocytomas that have malignant potential. SRC-1 expression in aggressive pheochromocytomas, may also be a potential diagnostic pitfall in view of the fact that these tumors may be misinterpreted as ACC in the primary or metastatic setting.

Driver gene alterations and activated signaling pathways toward malignant progression of gastrointestinal stromal tumors.

Mutually exclusive KIT and PDGFRA mutations are considered to be the earliest events in gastrointestinal stromal tumors (GIST), but insufficient for their malignant progression. Herein, we aimed to identify driver genes and signaling pathways relevant to GIST progression. We investigated genetic profiles of 707 driver genes, including mutations, gene fusions, copy number gain or loss, and gene expression for 65 clinical specimens of surgically dissected GIST, consisting of six metastatic tumors and 59 primary tumors from stomach, small intestine, rectum, and esophagus. Genetic alterations included oncogenic mutations and amplification‐dependent expression enhancement for oncogenes (OG), and loss of heterozygosity (LOH) and expression reduction for tumor suppressor genes (TSG). We assigned activated OG and inactivated TSG to 27 signaling pathways, the activation of which was compared between malignant GIST (metastasis and high‐risk GIST) and less malignant GIST (low‐ and very low‐risk GIST). Integrative molecular profiling indicated that a greater incidence of genetic alterations of driver genes was detected in malignant GIST (96%, 22 of 23) than in less malignant GIST (73%, 24 of 33). Malignant GIST samples groups showed mutations, LOH, and aberrant expression dominantly in driver genes associated with signaling pathways of PI3K (PIK3CA, AKT1, and PTEN) and the cell cycle (RB1, CDK4, and CDKN1B). Additionally, we identified potential PI3K‐related genes, the expression of which was upregulated (SNAI1 and TPX2) or downregulated (BANK1) in malignant GIST. Based on our observations, we propose that inhibition of PI3K pathway signals might potentially be an effective therapeutic strategy against malignant progression of GIST.