PDGFRA Research Articles

Clinicopathological and molecular genetic characteristics of adult IDH wild-type diffuse gliomas

Objective: To analyze the clinicopathological and molecular features and prognostic implications of adult isocitrate dehydrogenase wild type (IDH-wt) diffuse gliomas. Methods: A total of 87 cases of adult IDH-wt diffuse gliomas from 2016 to 2020 in Xuanwu Hospital of Capital Medical University were retrospectively collected. The clinicopathological characteristics and prognosis were analyzed. Molecular characteristics were also analyzed using Sanger sequencing and next generation sequencing. Results: There were 53 males and 34 females, aged from 19 to 78 years (mean 53 years). Histopathologically, there were 63 (72.4%) glioblastomas, 16 (18.4%) anaplastic astrocytomas, six (6.9%) diffuse astrocytomas, and one (1.1%) each of anaplastic oligodendrocytoma, and anaplastic oligodendroglioma. Common molecular genetic changes in IDH-wt gliomas included TERT promoter mutation which was found in 60 cases (69.0%); MGMT promoter methylation in 43 cases (49.4%); EGFR mutation in 38 cases (43.7%); PTEN mutation in 35 cases (40.2%) and TP53 mutation in 32 cases (36.8%). In addition, PDGFRA mutation was detected in 17 cases (19.5%), CDK4 amplification in 15 cases (17.2%) and MDM2 amplification in 11 cases (12.6%). In IDH-wt diffuse gliomas, there was no significant difference in the overall survival between TERT promoter, EGFR, PTEN, TP53, PDGFRA, CDK4, MDM2 mutations and the wild-type, since these gene mutations could co-occur in any case (P>0.05). Also there was no significant difference in the overall survival between the WHO grade Ⅱ/Ⅲ gliomas and glioblastoma patients with these gene mutations (P>0.05). Conclusions: TERT promoter, EGFR, PTEN, TP53, PDGFRA, CDK4 and MDM2 gene mutations are common molecular genetic changes in adult IDH-wt gliomas, and are associated with poor prognosis. It is suggested that these genes are potentially useful for predicting the prognosis and should be tested in adult IDH-wt gliomas.

P-135 Pembrolizumab/quavonlimab coformulation in combination with lenvatinib in advanced hepatocellular carcinoma: Phase 2 trial in progress

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death worldwide. Although advances in immunotherapy have improved clinical outcomes, the rate of death and disease is high, and there is an unmet need for new treatment approaches. PD-1/PD-L1 and CTLA-4 inhibitors alone or in combination have shown antitumor activity in advanced HCC. Additionally, lenvatinib, an inhibitor of vascular endothelial growth factor receptors 1-3, fibroblast growth factor receptors 1-4, platelet-derived growth factor receptor alpha, KIT, and RET, is a first-line treatment option in advanced HCC and has shown promising antitumor activity in combination with pembrolizumab in an early-stage study.

Abstract 113: Lyve-1 expressing macrophages direct the expansion of pericytes within the perivascular niche to support angiogenesis in cancer

Abstract Despite the many pro-tumoral functions that have been described for the various stromal populations in cancer, it is becoming apparent that these cells are not working alone, but instead in concert with one another as part of a wider network of cross-communication to facilitate disease progression. Identifying non-redundant signaling pathways within the stromal network is desirable, as therapeutically targeting these signals could result in an unraveling of the stromal support network upon which the tumor cells rely. Tumor associated macrophages (TAMs) have been implicated in a variety of pro-tumoral processes and are polarized by signals in the tumor microenvironment (TME) to adopt a range of functionally distinct subsets to perform these tasks. Single-cell RNA-sequencing of the F4/80+ TAMs from the MMTV-PyMT murine model of mammary adenocarcinoma identified one subset selectively expressing Lyve-1 and adopting a CD206hiMHCIIlo phenotype. This population was identified to spatially reside in the niche proximal to blood vasculature within the tumor. We demonstrate that selective depletion of the Lyve-1+ TAM population using liposome-based approaches controlled tumor growth and was associated with a loss of perivascular alpha smooth muscle actin (αSMA)-expressing stromal cells. The αSMA+ stromal cells were characterized ex vivo and expressed a surface phenotype associated with pericytes (CD90+CD34-NG2+), highlighting a possible role for Lyve-1+ TAMs in maintaining the population. To exclude a role of Lyve-1+ TAMs in recruiting a pericyte-progenitor cell to the tumor, we selectively photo-labelled the TME using MMTV-PyMT mice ubiquitously expressing the photo-convertible green/red Kaede protein. Labelling the TME Kaede-red through exposure to ultraviolet light, demonstrated that pericytes and CD90+ mesenchymal cells more broadly, were not recruited from a peripheral site but instead suggested these populations must rely on local proliferation to maintain their prevalence in the TME. Indeed, we demonstrate through Edu incorporation, that loss of Lyve-1+ TAMs from the perivascular niche renders pericytes senescent. Using computational approaches, we characterized the signaling cross-talk in the perivascular niche between Lyve-1+ TAMs, pericytes and endothelial cells and identified a specific interaction involving platelet derived growth factor-CC (PDGF-CC) expression by Lyve-1+ TAMs and PDGF-receptor alpha (PDGFRα) on the pericytes. Using blocking antibodies to PDGF-CC in tumor bearing mice we demonstrate that blocking this axis of stromal crosstalk can render pericytes senescent. These data highlight that local expansion of pericytes in cancer is not an autonomous event, nor regulated by the endothelium alone, but tightly regulated by the perivascular Lyve-1+ TAM population, which dictates the success of angiogenesis in cancer. Citation Format: James W. Opzoomer, Joanne E. Anstee, Isaac Dean, Emily J. Hill, Ihssane Bouybayoune, Jonathan Caron, Tamara Muliaditan, Peter Gordon, Rosamond Nuamah, Sarah E. Pinder, Tony Ng, Francesco Dazzi, Shahram Kordasti, David R. Withers, Toby Lawrence, James N. Arnold. Lyve-1 expressing macrophages direct the expansion of pericytes within the perivascular niche to support angiogenesis in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 113.

A Case Presentation of Gastrointestinal Stromal Tumor of Duodenum

A gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. It is caused by the mutation in KIT and PDGFRα genes. It constitutes <1% of all gastrointestinal tumors. Duodenal GISTs constitute 4.5% of all GISTs. We report a 61-year-old lady, presented with generalized abdominal pain, vomiting, abdominal distension, and nausea for the last 3 years. Physical exam-ination showed a pallor and on abdominal examination, a large palpable mass was extending from the pelvis to the right upper quadrant of the abdomen. The CT scan showed a large heterogeneously echogenic mass in the abdomen and pelvis with no lymphadenopathy and distant metastasis in this region. Laparotomy showed a large globular mass extending from the pelvis to the right upper quadrant of the abdomen adherent to the wall of a third part of the duodenum. Complete surgical resection of tumor done with an intact capsule. Microscopic examination showed neoplastic spindle cells with tumor necrosis. An immunohistochemical study confirmed GIST.

High PDGFRA Expression Does Not Serve As Effective Therapeutic Target in ERG-Deleted B-Cell Precursor Acute Lymphoblastic Leukemia

Background and aimsSeveral oncogenic aberrations of receptor tyrosine kinases occur in B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Here, we describe a subgroup of pediatric patients lacking common chromosomal aberrations but with high gene expression of platelet-derived growth factor receptor alpha (PDGFRA). Oncogenic fusions involving the tyrosine kinase domain of PDGFRA are recurrent in eosinophilic leukemia and are responsive to kinase inhibitors (Cools et al. N Engl J Med 2003). One case with a FIP1L1-PDGFRA fusion was reported in adult BCP-ALL (Roberts et al. J Clin Oncol 2016). Therefore, we tested for genomic aberrations underlying the overexpression of PDGFRA and evaluated the inhibition of PDGFRα as treatment option in pediatric BCP-ALL.MethodsExpression profiling was performed using Affymetrix U133 plus 2.0 arrays. BCR-ABL1 -like cases were identified using the 110 probe set expression signature (Den Boer et al. Lancet Oncol 2009). High PDGFRA was defined as log2 expression of probe set 203131_at >5.9. FISH was performed using Cytocell FIP1L1/CHIC2/PDGFRA probes. Targeted locus amplification (de Vree et al. Nat Biotechnol 2014) was performed using custom-designed primers. Cells were treated for 10 minutes with 10 ng/mL PDGF-BB with or without 10 µM imatinib or 1 µM CP673451 and analyzed by western blot. Cell viability after 4 day exposure to imatinib (0.2µM - 1.6µM - 12.5µM) or CP673451 (0.02µM - 0.16µM - 1.25µM) was assessed by flow cytometry.ResultsGene expression analysis of 654 pediatric ALL cases identified high expression of PDGFRA in 26 of 574 BCP-ALL cases (4.5%). High PDGFRA expression was exclusively found in cases belonging to the B-other (n=22) or BCR-ABL1 -like (n=4) subtypes, and not present in ETV6-RUNX1, high hyperdiploid, TCF3-PBX1, BCR-ABL1 and KMT2A -rearranged BCP-ALL subtypes or T-ALL. PDGFRA expression was confirmed by RT-qPCR, and also found in the BCP-ALL cell line Nalm6. Using RT-PCR we did not detect any of the six reported PDGFRA fusions, which involve FIP1L1, STRN, BCR, CDK5RAP2, ETV6, and KIF5B, nor did we detect novel structural aberrations affecting PDGFRA by FISH. We studied the PDGFRA locus at high resolution by targeted locus amplification. Following DNA cross-linking, digestion, and proximity-based re-ligation, targeted amplification was performed from viewpoints in intron 2 and exon 15 of PDGFRA. In the eosinophilic cell line EOL1 we confirmed an interstitial deletion on chromosome 4 which rearranges FIP1L1 intron 12 to PDGFRA exon 12. The results obtained from Nalm6 and primary BCP-ALL samples with high PDGFRA expression did not indicate genomic aberrations of PDGFRA.ERG deletions were present in 10 of 16 PDGFRA -high cases (63%), compared with 0% in PDGFRA -low BCP-ALL cases (n=71; p<0.001). Vice versa, all ERG-deleted cases expressed high levels of PDGFRA . Recently, a novel BCP-ALL subtype was described with rearrangements of the transcription factor DUX4 and deletion of ERG (Lilljebjörn et al. Nat Commun 2016; Yasuda et al. Nat Genet 2016; Zhang et al. Nat Genet 2016). Furthermore, the high PDGFRA-expressing cell line Nalm6 carries a DUX4 rearrangement (Yasuda et al. Nat Genet 2016) and PDGFRA is highly expressed in DUX4 BCP-ALL and its transcription start site directly bound by DUX4 (Zhang et al. Nat Genet 2016). Therefore, we regard it as highly likely that the PDGFRA-high cases represent this novel DUX4- rearranged subtype.Because transcription factors are difficult to target with small molecule inhibitors, PDGFRα inhibition could represent a treatment option. Exposure to the PDGFR inhibitors imatinib and CP673451 reduced phosphorylation of PDGFRα in Nalm6 and primary BCP-ALL cells. However, ex vivo drug exposure revealed no cytotoxic effect of the PDGFR inhibitors on PDGFRA-high BCP-ALL cells, either in the presence or absence of the ligand PDGF-BB. Interestingly, we found a marked ex vivo sensitivity towards prednisolone in PDGFRA-high cases, in line with the good prognosis reported for ERG -deleted/DUX4-rearranged BCP-ALL.ConclusionsWe found high PDGFRA expression, in the absence of genomic aberrations of the PDGFRA locus, in a subgroup of BCP-ALL patients with frequent ERG deletions. PDGFR inhibition caused abrogation of PDGFRα phosphorylation but was not cytotoxic in PDGFRA-high expressing BCP-ALL cells. Therefore, high PDGFRA expression does not serve as effective therapeutic target in ERG -deleted BCP-ALL. DisclosuresNo relevant conflicts of interest to declare.

Altered Expression of Pdgfrα and Its Downstream Signalling Components May be Causal in the Development of Imatinib Induced Thrombocytopenia in CML Patients Receiving Imatinib Treatment

Background:The main regulators of most of the cellular signalling pathways are protein kinases. Among these the receptor tyrosine kinases (RTKs) play important roles in cellular growth and proliferation by transmitting extracellular messages to intracellular signalling circuits. An important component of the intracellular circuits is the (PDGFR/PI3K/Akt/mTOR) pathway. Aberrant functioning of this pathway is known to occur in a number of diseases through various mechanisms. We report here that expression of PDGFRα gene and its downstream signalling components viz. PI3K and AKT is down regulated after imatinib treatment in some CML patients on imatinib therapy and may be a causal in the development of imatinib induced thrombocytopenia in these patients.Methods:A cohort of 100 chronic phase CML patients admitted to the Lok Nayak Hospital, New Delhi, India were included in this study. After initiation of imatinib treatment, haematological response of CML patients was monitored regularly for two years, in which development of thrombocytopenia was the primary end point.Total RNA, from blood samples of CML patients, was extracted using Trizol method. RNA concentration was determined by measuring absorbance at 260 nm. A cDNA synthesis kit (ThermoFisher Scientific, USA) was used for cDNA synthesis according to the manufacturer's instructions. The mRNA expression of all the genes was evaluated by quantitative SYBR Green based real time polymerase chain reaction (qRT-PCR) and results were expressed as fold change (2-∆∆ct). Results:Expression of PDGFRα, PI3K and AKT1 genes was significantly downregulated after imatinib treatment with a fold change (Mean + SD) of (2.12 + 0.41, 2.38 + 0.53 and 4.78 + 0.38 respectively) in CML patients receiving imatinib therapy (p < 0.0001). Further, we analysed the expression of PDGFRα, PI3K and AKT1 genes in two groups of CML patients- one that developed thrombocytopenia after imatinib treatment and the other that did not. We observed that there was a differential expression of PDGFRα and AKT1genes in thrombocytopenic and nonthrombocytopenic CML patients. Thrombocytopenic CML patients had a lower expression of PDGFRα and AKT1 genes in comparison to non-thrombocytopenic CML patients and this difference reached a statistical significance with a p-value of 0.02 and 0.04 respectively. Moreover, the expression of PI3K gene was also slightly downregulated in thrombocytopenic CML patients (fold change = 2.21+ 0.47 ) compared to nonthrombocytopenic ones (fold change = -2.55 + 0.57) but this difference did not reach a statistical significance (p=0.14). DisclosuresNo relevant conflicts of interest to declare.

Selection of Human Cytomegalovirus Mutants with Resistance against PDGFRα-Derived Entry Inhibitors.

The human cytomegalovirus (HCMV) infects fibroblasts via an interaction of its envelope glycoprotein gO with the cellular platelet-derived growth factor receptor alpha (PDGFRα), and soluble derivatives of this receptor can inhibit viral entry. We aimed to select mutants with resistance against PDGFRα-Fc and the PDGFRα-derived peptides GT40 and IK40 to gain insight into the underlying mechanisms and determine the genetic barrier to resistance. An error-prone variant of strain AD169 was propagated in the presence of inhibitors, cell cultures were monitored weekly for signs of increased viral growth, and selected viruses were tested regarding their sensitivity to the inhibitor. Resistant virus was analyzed by DNA sequencing, candidate mutations were transferred into AD169 clone pHB5 by seamless mutagenesis, and reconstituted virus was again tested for loss of sensitivity by dose-response analyses. An S48Y mutation in gO was identified that conferred a three-fold loss of sensitivity against PDGFRα-Fc, a combination of mutations in gO, gH, gB and gN reduced sensitivity to GT40 by factor 4, and no loss of sensitivity occurred with IK40. The resistance-conferring mutations support the notion that PDGFRα-Fc and GT40 perturb the interaction of gO with its receptor, but the relatively weak effect indicates a high genetic barrier to resistance.

The genomics and epigenetics of olfactory neuroblastoma: A systematic review.

BackgroundOlfactory neuroblastoma (ONB) or esthesioneuroblastoma (ENB) is a rare malignancy of the nasal cavity believed to arise from the olfactory epithelium. The goal of this study was to systematically review the genomics, epigenetics, and cytogenetics of ONB and to understand the potential clinical implications of these studies.MethodsA systematic literature review was performed for articles published before May 2020 using Cochrane, Embase, Pubmed, and Scopus databases. Inclusion criteria included genomics, cytogenetics, and epigenetics studies on ONB. Exclusion criteria included studies not in English or systematic reviews. Articles and abstracts were reviewed by two independent reviewers to reduce bias during article selection and synthesis of results. Of the 36 studies included in this review, 24 were research articles and 12 were abstracts.ResultsAlthough recurrent mutations among ONB tumors are uncommon, alterations in TP53, DMD, PIK3CA, NF1, CDKN2A, CDKN2C, CTNNB1, EGFR, APC, cKIT, cMET, PDGFRA, CDH1, FH, SMAD4, FGFR3 and IDH2 genes have been reported in several recent studies. In addition, cytogenetic studies revealed that the landscape of chromosomal aberrations varies widely amongst ONB tumors.ConclusionsThe rare character of ONB has limited the sample size available for cytogenetic, genomic, and epigenetic studies and contributes to the limitations of this systematic review. Comprehensive genomic and epigenomic studies with larger cohorts are warranted to validate the initial reports summarized in this review and to identify potential therapeutic targets for ONB.

EPCT-05. A PHASE 1/2 STUDY OF AVAPRITINIB FOR KIT- OR PDGFRA-MUTANT PEDIATRIC RELAPSED/REFRACTORY SOLID TUMORS

Prognosis for pediatric patients with advanced relapsed/refractory (R/R) solid (including central nervous system [CNS]) tumors is poor; targeted therapies achieve response rates of only ~15%. Germ cell tumors and high-grade glioma (HGG) are the most common with KIT mutations; sarcoma and HGG are the most common tumors with platelet-derived growth factor receptor alpha (PDGFRA) mutations. Two-year overall survival is <10% for pediatric patients with diffuse intrinsic pontine glioma, often driven by PDGFRA mutations. No KIT/PDGFRA targeted therapies are currently approved for pediatric patients with R/R solid tumors. The selective KIT and PDGFRA inhibitor, avapritinib, demonstrated potent activity against KIT activation-loop (exon 17), juxtamembrane (exon 11), and extracellular-domain (exon 9) mutants (IC50 <2 nM), and PDGFRA activation-loop (D842V) mutants (IC50=0.24 nM). CNS penetration in preclinical models (brain-to-plasma ratios at steady-state ranging from 0.74–1.00) demonstrated potential for activity against CNS tumors. Avapritinib is approved for the treatment of adults with unresectable/metastatic gastrointestinal stromal tumors (GIST) harboring PDGFRA exon 18 mutations (including D842V) in the USA based on an overall response rate ³84% with 59% response durations >6 months, and in the EU for adults with unresectable/metastatic GIST harboring a PDGFRA D842V mutation. The objectives of this 2-part phase 1/2 multicenter, open-label study, anticipated to enroll 31 patients from Q3 2021, are to assess avapritinib safety, preliminary efficacy, and pharmacokinetics in pediatric patients with KIT/PDGFRA-mutant solid R/R tumors. Eligible patients are aged 2 to <18 years with no alternative treatment options. Part 1 will enroll ≥6 patients; primary endpoint is confirmed age and body surface area physiologically-based pharmacokinetic modeling dose to provide equivalent exposure to the 300 mg adult avapritinib dose. Part 2 will enroll ≥25 patients at the recommended modeled avapritinib dose from Part 1; primary endpoint is overall response rate. Avapritinib once-daily will be administered in continuous 28-day cycles.

Mutations of the c-Kit and PDGFRA gene in gastrointestinal stromal tumors among hakka population of Southern China.

The aim of the present study was to investigate mutation status of the cKit and PDGFRA genes in patients with a gastrointestinal stromal tumor (GIST). In total, 96 patients with a GIST were included in the study, in which polymerase chain reaction amplification and gene sequencing were used to detect the sequences of exons 9, 11, 12, 13, 14, 17, and 18 in KIT and exons 12, 14, and 18 in PDGFRA. KIT mutations were detected in 65 cases (67.71%), of which 81.54% (53/65) were located on exon 11, 12.31% (8/65) were located on exon 9, 4.61% (3/65) were located on exon 17, which included a concomitant mutation of exon 9 and 11, and 4.08% (2/65) were located on exon 13, which included a concomitant mutation on exon 11. The most common mutation in exon 11 was deletion, which accounted for 77.36% (41/53) of the cases, followed by a point mutation observed in 22.64% (12/53) of the cases. Among the 31 GIST cases without a KIT mutation, a mutation in PDGFRA was detected in 5 cases (5.21%, 5/96; 16.13%, 5/31). With respect to gender, age, tumor max diameter, tumor position, and mitotic index, there were no significant differences between KIT/PDGFRA mutations and non-mutations. GIST mainly occurs in the stomach, and the cytological morphology is mainly spindle cells, and the mutations mainly occur in KIT genes. We need a large sample size to analyze the regularity of GIST gene mutations in Hakka population and understand the independent prognostic correlation of all KIT/PDGFRA genotypes.

Platelet-Derived Growth Factor Receptor-α Subunit Targeting Suppresses Metastasis in Advanced Thyroid Cancer In Vitro and In Vivo.

Thyroid cancer is the most common endocrine malignancy. Patients with well-differentiated thyroid cancers, such as papillary and follicular cancers, have a favorable prognosis. However, poorly differentiated thyroid cancers, such as medullary, squamous and anaplastic advanced thyroid cancers, are very aggressive and insensitive to radioiodine treatment. Thus, novel therapies that attenuate metastasis are urgently needed. We found that both PDGFC and PDGFRA are predominantly expressed in thyroid cancers and that the survival rate is significantly lower in patients with high PDGFRA expression. This finding indicates the important role of PDGF/PDGFR signaling in thyroid cancer development. Next, we established a SW579 squamous thyroid cancer cell line with 95.6% PDGFRA gene insertion and deletions (indels) through CRISPR/Cas9. Protein and invasion analysis showed a dramatic loss in EMT marker expression and metastatic ability. Furthermore, xenograft tumors derived from PDGFRA gene-edited SW579 cells exhibited a minor decrease in tumor growth. However, distant lung metastasis was completely abolished upon PDGFRA gene editing, implying that PDGFRA could be an effective target to inhibit distant metastasis in advanced thyroid cancers. To translate this finding to the clinic, we used the most relevant multikinase inhibitor, imatinib, to inhibit PDGFRA signaling. The results showed that imatinib significantly suppressed cell growth, induced cell cycle arrest and cell death in SW579 cells. Our developed noninvasive apoptosis detection sensor (NIADS) indicated that imatinib induced cell apoptosis through caspase-3 activation. In conclusion, we believe that developing a specific and selective targeted therapy for PDGFRA would effectively suppress PDGFRA-mediated cancer aggressiveness in advanced thyroid cancers.

The Impact of Fixation on the Detection of Oligodendrocyte Precursor Cell Morphology and Vascular Associations.

Oligodendrocyte precursor cells (OPCs) display numerous protrusions that extend into the surrounding parenchyma in the brain. Depending on the preparation of the tissue analyzed, these protrusions are more or less visible. We applied six different fixation methods and compared the effect of prolonged and stronger fixation on fluorescence intensity of platelet-derived growth factor receptor alpha, a surface marker of OPCs. Importantly, the fluorescence signal is mostly lost on protrusions as compared to the cell body, which has to be considered for specific analyses. Additionally, we show numerous contacts established between OPCs and the brain vasculature, which will contribute to the understanding of the interactions between these two elements.

Many roles for oligodendrocyte precursor cells in physiology and pathology

Oligodendrocyte precursor cells (OPCs) are a fourth resident glial cell population in the mammalian central nervous system. They are evenly distributed throughout the gray and white matter and continue to proliferate and generate new oligodendrocytes (OLs) throughout life. They were understudied until a few decades ago when immunolabeling for NG2 and platelet-derived growth factor receptor alpha revealed cells that are distinct from mature OLs, astrocytes, neurons, and microglia. In this review, we provide a summary of the known properties of OPCs with some historical background, followed by highlights from recent studies that suggest new roles for OPCs in certain pathological conditions.

P033 Scleroderma-like fibrotic disorder associated with a gastro-intestinal stromal tumour which responded only to imatinib

Abstract Background/Aims Gastro-intestinal stromal tumour (GIST) is recognised as the most prevalent mesenchymal tumour of the gastro-intestinal (GI) tract. The vast majority of GIST display activating mutations in receptor tyrosine kinases, such as platelet-derived growth factor receptor alpha (PDGFRA) and c-kit. This characteristic has lead to the development and approval of targeted therapies such as Imatinib for metastatic GIST. Scleroderma is an idiopathic fibrotic syndrome which involves excess collagen deposition in multiple tissues and organs. There is emerging evidence that dysfunctional fibroblasts are central to the underlying pathogenesis of this disease. An increasing awareness of the complex interplay of these fibroblasts with other cells and inflammatory mediators, such as platelet-derived growth factor (PDGF), is being recognised. This novel case serves to further develop our understanding of these pathological interactions, and to highlight a prospective role for Imatinib in disrupting them. Methods We present a case report below. Results A 54-year-old Caucasian male was referred to our rheumatology clinic due to worsening Raynaud's syndrome, arthralgia, and dry cough. He subsequently developed weight loss, pyrosis and skin thickening. This clinical picture was suggestive of a new diagnosis of systemic sclerosis. However, fibrotic skin changes did not extend to the distal finger, and anti-nuclear antibody (ANA) was negative. Symptoms were also refractory to various vasodilator and immunosuppressive therapies, including nifedipine, repeated iloprost infusions, azathioprine, mycophenolic acid, prednisolone, and sildenafil. Computed tomography (CT) imaging revealed interstitial pulmonary fibrosis and a mass within the gastric fundus. Histopathologic features and immunological staining of this mass were consistent with a GIST. Resection of the tumour did not improve fibrotic symptoms. Surveillance imaging one-year later was highly concerning for metastatic recurrence, which was later confirmed with tissue biopsy. He was subsequently initiated on Imatinib therapy, which led to a rapid improvement in fibrotic changes within weeks. Conclusion While there have been previous descriptions of para-neoplastic fibrotic syndromes, this is the first reported case of a scleroderma-mimicking disorder associated with GIST. It hints at an important potential overlap in the pathogenesis of these disease processes, and a potential role for tyrosine-kinase inhibitors in the treatment of scleroderma-like fibrotic disorders. Disclosure Z.A. Butt: None. W. Ng: None. D. Howard: None. K. Osman: None.

Contribution of PDGFR\u03b1-positive cells in maintenance and injury responses in mouse large vessels

The maladaptive remodeling of vessel walls with neointima formation is a common feature of proliferative vascular diseases. It has been proposed that neointima formation is caused by the dedifferentiation of mature smooth muscle cells (SMCs). Recent evidence suggests that adventitial cells also participate in neointima formation; however, their cellular dynamics are not fully understood. In this study, we utilized a lineage tracing model of platelet-derived growth factor receptor alpha (PDGFRa) cells and examined cellular behavior during homeostasis and injury response. PDGFRa marked adventitial cells that were largely positive for Sca1 and a portion of medial SMCs, and both cell types were maintained for 2 years. Upon carotid artery ligation, PDGFRa-positive (+) cells were slowly recruited to the neointima and exhibited an immature SMC phenotype. In contrast, in a more severe wire denudation injury, PDGFRa+ cells were recruited to the neointima within 14 days and fully differentiated into SMCs. Under pressure overload induced by transverse aortic constriction, PDGFRa+ cells developed marked adventitial fibrosis. Taken together, our observations suggest that PDGFRa+ cells serve as a reservoir of adventitial cells and a subset of medial SMCs and underscore their context-dependent response to vascular injuries.

Gastrointestinal stromal tumor: a review of current and emerging therapies.

Gastrointestinal stromal tumors (GIST) are rare neoplasms arising from the interstitial cell of Cajal in the gastrointestinal tract. Two thirds of GIST in adult patients have c-Kit mutation and smaller fractions have platelet derived growth factor receptor alpha (PDGFRA) mutation. Surgery is the only curative treatment for localized disease. Imatinib improves survival when used adjuvantly and in advanced disease. Several targeted therapies have also improved survival in GIST patients after progression on imatinib including sunitinib and regorafenib. Recently, United States Federal and Drug Administration (FDA) approved two new tyrosine kinase inhibitors for the treatment of heavily pretreated advanced/unresectable GIST including avapritinib (a selective inhibitor for PDGFRA exon 18 mutation including D842V mutations) and ripretinib (a broad-spectrum kinase inhibitor of c-Kit and PDGFRA). In this article, we will provide a comprehensive review of GIST including the current standard of care treatment and exploring future paradigm shifts in therapy.

Development and validation of the quantitative determination of avapritinib in rat plasma by a bioanalytical method of UPLC-MS/MS

Avapritinib, an orally consumed, highly selective inhibitor of platelet-derived growth factor receptor alpha (PDGFRA), is approved in the USA for PDGFRA exon 18 (including D842V) mutant gastrointestinal stromal tumour (GIST). The research conducted investigates an advanced reliable and fast UPLC-MS/MS method that could verify and determine avapritinib concentration in plasma of rats. An addition of acetonitrile was incorporated along with the plasma sample in order to precipitate protein with the analyte separated from the matrix by a gradient elution procedure on a Waters Acquity UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm). The active stage in mobile phase consists of a mixture of 0.1% formic acid in water and acetonitrile with a 0.40 mL/min flow rate. UPLC-MS/MS detection was done employing a mode of multiple reaction monitoring (MRM), and the ion transitions of avapritinib and imatinib (internal standard, IS) was m/z 499.10 → 482.09, and m/z 494.30 → 394.20, respectively. This method has good linearity within 2–4000 ng/mL of avapritinib calibration range and a lower limit of quantification (LLOQ) of 2 ng/mL verified. Avapritinib precisions in both intra-day and inter-day were below 15% with the determined accuracy of −12.9% to 12.0%. The recoveries, stabilities, and matrix effect of avapritinib and IS were credible. 30 mg/kg avapritinib was administered as a single dose orally to rats. The determination of avapritinib level in pharmacokinetic studies was accomplished by efficiently applying a newly optimized UPLC-MS/MS assay.

Age-related changes in NG2-expressing telocytes of rat stomach.

NG2 immunoreactive cells (NG2 cells) are found in the brain and peripheral tissues including the skin, intestinal tracts, and bladder. In a previous study, we observed the presence of NG2 cells in the stomach using bioluminescence imaging techniques in NG2-firefly luciferase (fLuc) transgenic (Tg) rats. Here, we aimed to identify and characterize NG2 cells in the adult rat stomach. Immunohistochemical studies showed that NG2 cells were mainly present in the lamina propria and most of the cells were gastric telocytes, co-expressing CD34, and platelet-derived growth factor receptor alpha (PDGFRα), with a small oval-shaped cell body and extremely long and thin cellular prolongations. In the rat stomach, NG2-expressing telocytes comprised two subpopulations: NG2+/CD34+/PDGFRα+ and NG2+/CD34+/PDGFRα-. Furthermore, we showed that the expression of NG2 gene in the aged rat stomach decreased relative to that of the young rat stomach and the decline of NG2 expression in aged rats was mainly observed in NG2+/CD34+/PDGFRα+ telocytes. These findings suggested age-related alterations in NG2+/CD34+/PDGFRα+ telocytes of rat stomach.

Presyncope Leading to the Diagnosis of Gastrointestinal Stromal Tumor in a Pediatric Patient.

A 16-year-old African American girl presented after a presyncopal event. Initial evaluation revealed anemia (hemoglobin 5.2 mmol/L) and positive stool hemoccult. Esophagogastroduodenoscopy revealed an ulcerated, bleeding, submucosal mass (Fig. 1). Bleeding was controlled with argon plasma coagulation. Abdominal computed tomography showed a heterogenous 6.8 cm mass at the serosal surface of the lesser curvature. Neck and thorax computed tomography did not show metastases. Endoscopic ultrasound with fine needle biopsy (Fig. 2) revealed histology consistent with a gastrointestinal stromal tumor (GIST). Laparotomy was performed with complete resection of the mass. Pediatric GISTs are rare and they account for about 1% of all GISTs (1). When suspected, endoscopic biopsy, either core needle or forceps biopsy, is the preferred method to prevent tumor spillage which is highly associated with GIST recurrence (2). Pediatric GISTs usually lack KIT or PDGFRA gene mutations, making them wild-type GISTs (3). In this case, genetic testing revealed associations with hereditary paraganglioma-pheochromocytoma syndromes (4). Prognosis is based on the mitotic rate, tumor size, and tumor site; gastric site being the most favorable (5). MRI after surgery showed no residual tumor. The patient will continue close monitoring via annual MRI, which is the preferred modality for surveillance (6).FIGURE 1: Endoscopic photograph showing a bleeding submucosal mass.FIGURE 2: Endoscopic ultrasound of the mass while obtaining fine needle biopsy.

Targeted Hot Spot Sequencing of Uzbek Lung Cancer Patients

Objectives: Carcinoma of lung is a widespread multifactorial disease with a poor prognosis. Uzbek lung cancer patients screening for prevalent mutations, associated with cancer development by targeted next generation sequencing was the main objective of current research. Materials and methods: Preparation of sequencing libraries was conducted using the Illumina Cancer Hot spot Panel v2 covering mutational hot spot regions of 50 cancer genes, from DNA extracted from formalin-fixed paraffin-embedded tumor samples of 10 patients. Sequencing was performed with the Mi Seq Next Generation Sequencing machine(NGS). Results: Hot spot mutations data analysis revealed clinically benign mutations in allstudied samples, with 70% having 3 or more mutations stored in the COSMIC database.According to ClinVarFGFR3 gene was associated with Crouzon syndrome with acanthosis nigricans, PDGFRA, EGFR and TP53 gene mutations were corellated with Idiopathic hypereosinophilic syndrome, Lung cancer and Glioma susceptibility respectively.KIT and KDR gene mutations were, respectively, associated with Gastrointestinal stromal tumor and Hemangioma, capillary infantile. Synonymous variants in RET and HRAS genes, were associated congenital central hypoventilation and epidermal nevus syndrome respectively. EGFR gene mutations occurred exclusively in patients with adenocarcinoma G2. where as MET and BRAF mutations were identified in bronchioalveolar cancer samples. Conclusion. In conclusion, particular polymorphisms and mutations affect treatment response and the toxicity level among patients with lung cancer, undergoing chemotherapy. Variety of SNPs were reported to have impact on disease outcomes of those patients, therefore they should be validated in an independent population, prior to being adopted for pre-personalised therapy screening.