Expression Of Platelet-derived Growth Factor Receptor-beta Research Articles

#2660 WWP2-induced pericytes to myofibroblast transition contributes to the progression of fibrosis in CKD in diabetes

Abstract Background and Aims CKD in diabetes can be characterized by different clinical and histological phenotypes, associated to different molecular pathways specifically involved in the progression of kidney disease. CKD in diabetes includes different phenotypes, commonly classified according to Mazzucco et al (PMID:11920336) as diabetic Nephropathy (DN), non-diabetic renal disease (NDRD) and mixed forms (DN+NDRD). Among these, DN represents the primary cause of end stage renal disease (ESRD) and our group demonstrated that renal damage in DN is characterized by a specific molecular feature, represented by the activation of lysine63 (K63)-ubiquitination (Ub) pathway. In particular, we demonstrated that accumulation of K63-Ub proteins is involved in the progression of renal fibrosis (PMID: 27881486). WWP2 is an E3 ubiquitin-protein ligase that modulates myofibroblast pro-fibrotic activation in cardiac fibrosis (PMID: 31399586), however its specific role in kidney fibrosis in diabetes and its subsequent involvement in K63-Ub pathway has not been described so far. Thus aim of this study was to evaluate the involvement of WWP2 in the progression of kidney fibrosis in diabetes and its involvement in K63-Ub pathway. Method WWP2, K-63Ub, alpha-sma and PDGFbeta-receptor expression were evaluated in: i) 22 kidney biopsies from patients with a biopsy proven diagnosis of DN (n = 11), NDRD (n = 6) and CKD without diabetes (n = 5), by immunohistochemistry and immunofluorescence; ii) streptozotocin (STZ)-treated DBA/2J mice, a model of human DN, in the presence or absence of a specific inhibitor of K63Ub (NSC697923) by immunohistochemistry (n = 3 for each group); iii) in HK2 tubular cells, EAHY926 endothelial cells and in human-derived pericytes under hyperglycemic conditions by western blotting and qPCR. Results Immunohistochemistry showed that WWP2 was expressed both in CKD and in DN patients’ biopsies when compared to patients with NDRD (p < 0.05 and p < 0.01 respectively), both at tubular, glomerular and in the vascular compartment. Immunofluorescence confirmed that WWP2 increased expression in DN patients compared to NDRD, was associated to accumulation of K63Ub proteins in the tubular compartment as well as in the vascular compartment in particular in pericytes, cells that envelop the surface of vessels and have been described as the major source of scar-forming myofibroblasts in CKD (PMID: 19008372). The involvement of WWP2 in the K63-Ub pathway was confirmed in vivo in DBA2J diabetic mice in which the specific inhibition by NSC697923 of the K63Ub pathway, significantly reduced WWP2 expression in kidney tissues from diabetic mice (p < 0.05). These results were confirmed in vitro where specific inhibition of K63Ub pathway by NSC697923 significantly reduced hyperglycaemia-induced WWP2 expression in HK2 cells by western blotting and qPCR (p < 0.01). Hyperglycaemic conditions did not influence WWP2 expression in EAHY926 endothelial cells (p = n.s.). Conversely, using qPCR, in pericytes we observed an hyperglycemia-induced expression of both WWP2 levels (RR>2) and alpha-sma levels (RR>3) at different time points. Moreover, western blotting showed that hyperglycemia also induced a decrease of PDGF-beta-receptor marker of pericytes, thus suggesting their transition to myofibroblasts. Conclusion These findings demonstrate the influence of WWP2 on the k63-Ub pathway thus driving fibrogenesis in DN patients, in particular through pericyte to myofibroblast transition. WWP2 could represent a potential novel target for therapeutic intervention in the treatment of chronic kidney disease in diabetes.

Co-expression patterns of cancer associated fibroblast markers reveal distinct subgroups related to patient survival in oropharyngeal squamous cell carcinoma.

Background: The incidence of oropharyngeal squamous cell carcinoma (OPSCC) is rapidly increasing in high income countries due to its association with persistent high-risk human papilloma virus (HPV) infection. Recent scientific advances have highlighted the importance of the tumor microenvironment in OPSCC. In this study, including 216 OPSCC patients, we analyze the composition of four established markers of cancer associated fibroblasts (CAFs) in the context of intratumoral CD8 T-cell infiltration. Methods: Immunohistochemical staining for fibroblast activation protein (FAP), platelet-derived growth factor receptor beta (PDGFRb), periostin, alpha smooth muscle actin (α-SMA) and CD8 were analyzed digitally and their association with survival, tumor- and patient characteristics was assessed. Results: Co-expression of CAF markers was frequent but not associated with HPV status. FAPhigh and PDGFRbhigh expression were associated with increased CD8 T-cell infiltration. Low expression of PDGFRb improved patient survival in female patients but not in male patients. We identified PDGFRblow periostinlow α-SMAlow status as an independent predictor of improved survival (hazard ratio 0.377, p = 0.006). Conclusion: These findings elucidate the co-expression of four established CAF markers in OPSCC and underscore their association with T-cell infiltration and patient survival. Future analyses of CAF subgroups in OPSCC may enable the development of individualized therapies.

α-SMA positive vascular mural cells suppress cyst formation in hemangioblastoma.

Approximately 60% of hemangioblastomas (HBs) have peritumoral cysts adjacent to the tumor, which can cause neurological deficits due to the mass effect, and the management of cyst formation is a clinical challenge. Vascular mural cells surrounding endothelial cells consist of vascular smooth muscle cells (vSMCs) and pericytes, which are essential elements that support blood vessels and regulate permeability. This study investigated the involvement of mural cells in cyst formation. We analyzed the expression of α-smooth muscle actin (α-SMA), platelet-derived growth factor receptor-beta (PDGFRB), and CD31 in 39 consecutive human cerebellar HBs, 20 of cystic and 19 of solid type. Solid type HBs showed stronger diffuse expression of α-SMA in precapillary arterioles and capillaries within the tumor than cystic type HBs (p = 0.001), whereas there was no difference in PDGFRB and CD31 expression. Detailed observation with immunofluorescence demonstrated that α-SMA was expressed in vascular mural cells surrounding capillaries in the solid rather than in the cystic type. Multivariate analysis including various clinical and pathological factors showed that lower α-SMA expression was significantly correlated with cyst formation (p < 0.001). Our data suggested that vascular mural cells from precapillary arterioles to capillaries expressing α-SMA may be pericytes and play a crucial role in HB cystogenesis.

Detection of Experimental Colorectal Peritoneal Metastases by a Novel PDGFRβ-Targeting Nanobody.

Simple SummaryColorectal cancer can metastasize to multiple distant sites. Metastases growing within the peritoneal cavity cause a high degree of morbidity and are associated with very poor survival. Moreover, peritoneal metastases are difficult to detect using conventional imaging methods. Consequently, peritoneal metastases are generally under-diagnosed and their response to therapy is difficult to assess. An extensive molecular and cellular analysis of colorectal peritoneal metastases revealed that these lesions express very high levels of specific markers that could serve as targets for imaging-based diagnosis and treatment. In the present report, we explore the potential value of one such marker, PDGFRB, to serve as a target for peritoneal metastasis detection by molecular imaging. Therefore, we generated a PDGFRB-binding llama nanobody and demonstrate its utility in detecting peritoneal metastases in mice. The clinical development of PDGFRB-targeting tracers may help to improve the diagnosis of peritoneal metastases and the clinical management of this highly aggressive disease entity.Peritoneal metastases in colorectal cancer (CRC) belong to Consensus Molecular Subtype 4 (CMS4) and are associated with poor prognosis. Conventional imaging modalities, such as Computed Tomography (CT) and Fluorodeoxyglucose-Positron Emission Tomography (FDG-PET), perform very poorly in the detection of peritoneal metastases. However, the stroma-rich nature of these lesions provides a basis for developing molecular imaging strategies. In this study, conducted from 2019 to 2021, we aimed to generate a Platelet-Derived Growth Factor Receptor beta (PDGFRB)-binding molecular imaging tracer for the detection of CMS4 CRC, including peritoneal metastases. The expression of PDGFRB mRNA discriminated CMS4 from CMS1-3 (AUROC = 0.86 (95% CI 0.85–0.88)) and was associated with poor relapse-free survival. PDGFRB mRNA and protein levels were very high in all human peritoneal metastases examined (n = 66). Therefore, we generated a PDGFRB-targeting llama nanobody (VHH1E12). Biotin-labelled VHH1E12 bound to immobilized human and mouse PDGFRB with high affinity (EC50 human PDGFRB = 7 nM; EC50 murine PDGFRB = 0.8 nM), and to PDGFRB-expressing HEK293 cells grown in vitro. A pharmacokinetic analysis of IRDye-800CW-conjugated VHH1E12 in mice showed that the plasma half-life was 6 min. IRDye-800CW-conjugated VHH1E12 specifically accumulated in experimentally induced colorectal cancer peritoneal metastases in mice. A tissue analysis subsequently demonstrated co-localization of the nanobody with PDGFRB expression in the tumour stroma. Our results demonstrate the potential value of PDGFRB-targeted molecular imaging as a novel strategy for the non-invasive detection of CMS4 CRC, in particular, peritoneal metastases.

100 Somatic Mosaicism of a PDGFRB Activating Variants in Intracranial, Coronary, Aortic and Radial Vascular Beds

INTRODUCTION: Activating variants in platelet-derived growth factor receptor beta (PDGFRB) are associated with aneurysms. Our group previously described a patient with multiple fusiform intracranial aneurysms who was found to have a somatic mosaic variant in PDGFRB. The relationship between the mosaic effects of PDGFRB variants and the vascular phenotypes is not well understood. METHODS: Following death due to subarachnoid hemorrhage, samples from the index patient’s intracranial, coronary, aortic, and radial arteries were biopsied and preserved. DNA was extracted and alternate allele fractions (AAF) of PDGFRB variants were determined using digital droplet PCR. Histopathological analysis was performed by a board-certified neuropathologist. RESULTS: A total of 80 biopsies were obtained. The AAFs of variant PDGFRB in the vertebral artery, basilar artery, and P1 segment aneurysms were 28.7%, 16.4%, and 17.8%, respectively. The AAF of the coronary and radial artery aneurysms were 22.3% and 20.6%, respectively. AAFs of normal vascular biopsies of the intracranial circulation, coronary arteries, and aorta ranged from 0 to 4.3%, 0 to 0.3%, and 0 to 35%, respectively. The PDGFRB variant was absent from lymphocyte DNA and normal tissue, confirming it to be a non-germline somatic variant. Expression of PDGFRB within the radial artery aneurysmal tissue was localized to CD31 negative, non-endothelial cell origin. CONCLUSION: Somatic mosaic expression of PDGFRB within CD31 negative cells is associated with development of fusiform aneurysms. The role of targeted therapy with tyrosine kinase inhibitors to locally alter the biology of aneurysm development in fusiform aneurysms with PDGFRB mutations should be further studied.

Somatic Mosaicism of a PDGFRB Activating Variant in Aneurysms of the Intracranial, Coronary, Aortic, and Radial Artery Vascular Beds.

BackgroundActivating variants in platelet‐derived growth factor receptor beta (PDGFRB), including a variant we have previously described (p.Tyr562Cys [g.149505130T>C [GRCh37/hg19]; c.1685A>G]), are associated with development of multiorgan pathology, including aneurysm formation. To investigate the association between the allele fraction genotype and histopathologic phenotype, we performed an expanded evaluation of post‐mortem normal and aneurysmal tissue specimens from the previously published index patient.Methods and ResultsFollowing death due to diffuse subarachnoid hemorrhage in a patient with mosaic expression of the above PDGFRB variant, specimens from the intracranial, coronary, radial and aortic arteries were harvested. DNA was extracted and alternate allele fractions (AAF) of PDGFRB were determined using digital droplet PCR. Radiographic and histopathologic findings, together with genotype expression of PDGFRB were then correlated in aneurysmal tissue and compared to non‐aneurysmal tissue. The PDGFRB variant was identified in the vertebral artery, basilar artery, and P1 segment aneurysms (AAF: 28.7%, 16.4%, and 17.8%, respectively). It was also identified in the coronary and radial artery aneurysms (AAF: 22.3% and 20.6%, respectively). In phenotypically normal intracranial and coronary artery tissues, the PDGFRB variant was not present. The PDGFRB variant was absent from lymphocyte DNA and normal tissue, confirming it to be a non‐germline somatic variant. Primary cell cultures from a radial artery aneurysm localized the PDGFRB variant to CD31‐, non‐endothelial cells.ConclusionsConstitutive expression of PDGFRB within the arterial wall is associated with the development of human fusiform aneurysms. The role of targeted therapy with tyrosine kinase inhibitors in fusiform aneurysms with PDGFRB mutations should be further studied.

High tumor cell platelet-derived growth factor receptor beta expression is associated with shorter survival in malignant pleural epithelioid mesothelioma.

Malignant pleural mesothelioma (MPM) has a rich stromal component containing mesenchymal fibroblasts. However, the properties and interplay of MPM tumor cells and their surrounding stromal fibroblasts are poorly characterized. Our objective was to spatially profile known mesenchymal markers in both tumor cells and associated fibroblasts and correlate their expression with patient survival. The primary study cohort consisted of 74 MPM patients, including 16 patients who survived at least 60 months. We analyzed location‐specific tissue expression of seven fibroblast markers in clinical samples using multiplexed fluorescence immunohistochemistry (mfIHC) and digital image analysis. Effect on survival was assessed using Cox regression analyses. The outcome measurement was all‐cause mortality. Univariate analysis revealed that high expression of secreted protein acidic and cysteine rich (SPARC) and fibroblast activation protein in stromal cells was associated with shorter survival. Importantly, high expression of platelet‐derived growth factor receptor beta (PDGFRB) in tumor cells, but not in stromal cells, was associated with shorter survival (hazard ratio [HR] = 1.02, p < 0.001). A multivariable survival analysis adjusted for clinical parameters and stromal mfIHC markers revealed that tumor cell PDGFRB and stromal SPARC remained independently associated with survival (HR = 1.01, 95% confidence interval [CI] = 1.00–1.03 and HR = 1.05, 95% CI = 1.00–1.11, respectively). The prognostic effect of PDGFRB was validated with an artificial intelligence‐based analysis method and further externally validated in another cohort of 117 MPM patients. In external validation, high tumor cell PDGFRB expression associated with shorter survival, especially in the epithelioid subtype. Our findings suggest PDGFRB and SPARC as potential markers for risk stratification and as targets for therapy.

High PDGFRb Expression Predicts Resistance to Radiotherapy in DCIS within the SweDCIS Randomized Trial.

This study analyzes the potential of stromal platelet-derived growth factor receptor-beta (PDGFRb) expression as biomarker for radiotherapy (RT) benefit on ipsilateral breast events (IBE) in ductal carcinoma in situ (DCIS). Improved identification of DCIS patients refractory to adjuvant whole-breast RT is needed. Predictive biomarker studies in DCIS have focused on tumor cell features rather than the tumor-associated stroma, despite growing evidence of its influence on therapy efficiency. Samples from the Swedish randomized radiotherapy DCIS trial (SweDCIS) were subjected to IHC analysis for stromal PDGFRb expression. IBE incidence at 10 years after breast-conserving surgery was the primary endpoint. Interactions between marker and treatment were analyzed. PDGFRb score was predictive for RT benefit with regard to IBE (P interaction = 0.002 and P interaction = 0.008 adjusted multivariably). Patients of the PDGFRblow group had a strong benefit from RT regarding IBE risk [HR, 0.23; 95% confidence interval (CI), 0.12-0.45; P < 0.001] with an absolute risk reduction of 21% (cumulative risk 7% vs. 28%) at 10 years. No significant risk reduction by RT was observed for patients of the PDGFRbhigh group (HR, 0.83; 0.51-1.34; P = 0.444; cumulative risk 22% vs. 25%). The RT response-predictive effect of stromal PDGFRb was equally strong in analyses for in situ and invasive IBE when analyzed separately (in situ IBE: P = 0.029; invasive IBE: P = 0.044). Results suggest high stromal PDGFRb expression as a novel biomarker identifying DCIS patients who are refractory to standard whole-breast adjuvant RT. The data imply previously unrecognized fibroblast-mediated modulation of radiosensitivity of DCIS, which should be further explored from mechanistic and targeting perspectives.

TMEM119 facilitates ovarian cancer cell proliferation, invasion, and migration via the PDGFRB/PI3K/AKT signaling pathway

BackgroundOvarian cancer (OV) is the deadliest gynecological cancer. Transmembrane protein 119 (TMEM119) has been reported as oncogene in several human cancers. However, the function of TMEM119 in OV is still poorly known.MethodsWestern blot and qRT-PCR were used to analyze TMEM119 levels. Transwell assays, wound healing assays, CCK-8 assays and EdU cell proliferation assays were designed to explore the function and potential mechanism of TMEM119 in malignant biological behaviors in OV.ResultsTMEM119 was observed to be overexpressed in OV tissues and associated with poor survival in OV patients. Knockdown and overexpression experiments demonstrated that TMEM119 promoted proliferation, invasion, and migration in OV cells in vitro. TMEM119 mRNA expression was related to the pathways of focal adhesion according to Gene Set Enrichment Analyses and was correlated with the mRNA expression level of platelet-derived growth factor receptor beta (PDGFRB). TMEM119 exerted oncogenic effects partially by regulating the expression of PDGFRB and by activating the PI3K/AKT signaling pathway.ConclusionsCollectively, our findings highlight the potential role of TMEM119 in the malignant biological behavior of OV, which may serve as a potential biomarker and a therapeutic candidate for OV.

Prognostic and predictive impact of stroma cells defined by PDGFRb expression in early breast cancer: results from the randomized SweBCG91RT trial

PurposePredictive biomarkers are needed to aid the individualization of radiotherapy (RT) in breast cancer. Cancer-associated fibroblasts have been implicated in tumor radioresistance and can be identified by platelet-derived growth factor receptor-beta (PDGFRb). This study aims to analyze how PDGFRb expression affects RT benefit in a large randomized RT trial.MethodsPDGFRb was assessed by immunohistochemistry on tissue microarrays from 989 tumors of the SweBCG91RT trial, which enrolled lymph node-negative, stage I/IIA breast cancer patients randomized to RT after breast-conserving surgery. Outcomes were analyzed at 10 years for ipsilateral breast tumor recurrence (IBTR) and any recurrence and 15 years for breast cancer specific death (BCSD).ResultsPDGFRb expression correlated with estrogen receptor negativity and younger age. An increased risk for any recurrence was noted in univariable analysis for the medium (HR 1.58, CI 95% 1.11–2.23, p = 0.011) or PDGFRb high group (1.49, 1.06–2.10, p = 0.021) compared to the low group. No differences in IBTR or BCSD risk were detected. RT benefit regarding IBTR risk was significant in the PDGFRb low (0.29, 0.12–0.67, p = 0.004) and medium (0.31, 0.16–0.59, p < 0.001) groups but not the PDGFRb high group (0.64, 0.36–1.11, p = 0.110) in multivariable analysis. Likewise, risk reduction for any recurrence was less pronounced in the PDGFRb high group. No significant interaction between RT and PDGFRb-score could be detected.ConclusionA higher PDGFRb-score conferred an increased risk of any recurrence, which partly can be explained by its association with estrogen receptor negativity and young age. Reduced RT benefit was noted among patients with high PDGFRb, however without significant interaction.

Abstract P3-08-08: Prognostic and predictive impact of stroma cells defined by platelet derived growth factor receptor beta in early breast cancer: Results from the randomized SweBGR91RT trial

Abstract Background: Although preclinical studies have indicated that stroma cells can modulate the radiosensitivity of tumor cells, non-leukocytic stroma cells have not yet been explored as potential predictive markers for radiotherapy (RT) through systematic analyses of clinical samples. Platelet-derived growth factor receptor beta (PDGFRb) is a key regulator of fibroblasts, pericytes and smooth muscle cells. A high expression of PDGFRb in tumor-associated stroma has previously been associated with worse recurrence free and breast cancer specific survival as well as reduced tamoxifen sensitivity in invasive breast cancer. Purpose: To analyze the prognostic and predictive impact of stromal PDGFRb regarding ipsilateral breast tumor recurrence (IBTR) and any recurrence in a large randomized RT trial. Methods: Stromal PDGFRb expression was assessed by immunohistochemical staining of tissue microarrays (TMAs) with 958 tumors from the SweBCG91RT trial (Swedish Breast Cancer Group 91 Radiotherapy). The trial enrolled node-negative, stage I or IIA breast cancer patients, who were randomized to postoperative RT or not after breast conserving surgery. Stained TMAs were evaluated by two independent raters for PDGFRb staining intensity (0/negative; 1/low; 2/moderate; 3/high) and positive stroma fraction (0/0%; 1/1-10%; 2/11-50; 3/51-75%; 4/76-100%). The evaluations of both raters were averaged and the product between the two scoring metrics was formed. For final analysis the data was split in tertiles, as predefined, and referred to as PDGFRb low, medium or high score group. Outcomes were analyzed at 10 years of follow-up. Results: A high PDGFRb score was correlated with ER negativity (p=0.003,), young age (p&amp;lt;0.001), large tumor size (p=0.058) and high histological grade (p=0.067) in Spearman’s Rank test. With regard to prognosis, a significantly increased risk for any recurrence was detected in univariable analysis for patients with a medium (HR 1.57, CI95% 1.11-2.23, p=0.011) or high PDGFRb score (HR 1.49, CI95% 1.06-2.10, p=0.021) compared to the PDGFRb low score group. The significance remained for the PDGFRb medium (HR 1.47, CI95% 1.03-2.11, p=0.034) but not the PDGFRb high score group (HR 1.32, CI95% 0.93-1.88, p=0.125) in a multivariable analysis including grade, age and RT. The benefit of RT regarding the risk of IBTR was significant in the PDGFRb low (HR 0.28, CI95% 0.12-0.65, p=0.003) and medium (HR 0.32, CI95% 0.16-0.61, p=0.001) score groups but not in the PDGFRb high (HR 0.61, CI95% 0.35-1.07, p=0.086) score group in a multivariable analysis including grade and age. The risk reduction from RT regarding any recurrence was also less pronounced in the PDGFRb high (HR 0.73, CI95% 0.48-1.12, p=0.149) score group compared to the PDGFRb low (HR 0.57, CI95 0.32-1.03, p=0.065) and medium (HR 0.46, CI95% 0.28-0.75, p=0.002) score groups in multivariable analysis. No significant interaction between RT and PDGFRb expression could however be detected for IBTR (p=0.14) or any recurrence (p=0.33). Conclusion: A higher PDGFRb score conferred a negative prognosis with increased risk of any recurrence in univariable analyses, which in part can be explained by its association with ER negativity, young age and grade. A predictive effect of RT benefit from PDGFRb could not be confirmed although a tendency toward less benefit was observed in the patient group with the highest PDGFRb score. Citation Format: Carina Strell, Reidunn J Edelmann, Axel Stenmark Tullberg, Per Malmström, Mårten Fernö, Arne Östman, Erik Holmberg, Per Karlsson. Prognostic and predictive impact of stroma cells defined by platelet derived growth factor receptor beta in early breast cancer: Results from the randomized SweBGR91RT trial [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-08-08.

Imatinib +/- Brentuximab Vedotin Induces Sustained Complete Remission in Chemotherapy-Resistant Anaplastic Large Cell Lymphoma Expressing PDGFR

Background. Anaplastic lymphoma kinase positive systemic anaplastic large cell lymphoma (ALK+ ALCL) represents an aggressive T-cell malignancy that primarily affects children and younger adults. Upon treatment with CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) or CHOP-like regimens its prognosis is relatively favourable compared to other aggressive T-cell lymphomas, however, the rare event of disease reoccurrence remains particularly challenging. ALCL is CD30 positive, and mono treatment with brentuximab vedotin (BrV) can achieve long term remissions in only few relapsed patients not receiving consolidating stem cell transplantation (Pro B. et al. Blood 2017). A subset of ALCL patients express platelet derived growth factor receptor (PDGFR) alpha or beta in their tumour cells which is induced by ALK via AP-1 transcription factor activation. We previously demonstrated that PDGFR blockade by the Abl/c-Kit/PDGFR kinase inhibitor imatinib is an effective treatment concept for ALK+ ALCL in experimental mouse models (Laimer D. et al. Nature Med. 2012). Here we aimed to assess the prognostic value of PDGFR expression and to probe the clinical value of its targeting by imatinib in ALK+ ALCL patients. Methods. The impact of PDGFR expression to predict clinical outcome was analyzed in samples of 98 ALK+ ALCL patients included in the studies NHL-BFM 90, 95 and ALCL99 between 1992 and 2006. Six patients (age 18-45) with chemo-refractory ALK+ ALCL were prospectively treated with imatinib plus (4) or minus (2) BrV. 33% (2/6) had previously received salvage treatment with stem cell transplantation (SCT). Three of the patients had been enrolled in a prospective single-arm study combining imatinib and BrV, a trial that was terminated due to poor patient recruitment (AGMT ALCL1 trial, EudraCT No.: 2013-003505-26, supported by Takeda®). PDGFR alpha and beta expression analyses were performed on tumour samples of treated patients. Results. ALK+ ALCL patients with high PDGFR expression on tumor cells (n=11) had a significantly lower event-free survival rate (EFS) at 5 years compared to patients with no or low expression (n=87) (27±13% versus 70±5%, respectively, p&lt;0.001, figure 1a). Four of the six patients with relapsed/ refractory ALK+ ALCL responded to imatinib +/- BrV with a rapid metabolic complete remission (CR). At a median clinical follow-up of 52 months (range 20 to108) all responding patients demonstrated an ongoing CR without SCT even after imatinib was discontinued with an average time on imatinib of 49 weeks (range 32 to 130; figure 1b). Half (2/4) of responding patients received no or only 1 infusion of BrV; both non-responding patients had received BrV. Importantly, despite the few patients that could be prospectively treated, PDGFR expression status had a significant impact on clinical course. All patients (4/4) who expressed either PDGFR alpha or beta in tumour cells and in the lymph node microenvironment responded with an ongoing metabolic CR, whereas the two patients whose lymphoma cells had negative PDGFR expression failed to respond (EFS: 4 versus 210 weeks, p = 0.018; figure 1c). Conclusions. 1) PDGFR expression is a poor risk factor in ALK+ ALCL. 2) Imatinib alone or in combination with BrV overcomes chemo-resistance conferred by PDGFR expression. 3) Imatinib treatment can be discontinued with ongoing CR. 4) These observations suggest that PDGFR expressing ALK+ ALCL patients might benefit from early treatment with imatinib. Disclosures Staber: Takeda-Millenium: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Honoraria, Speakers Bureau; MSD: Honoraria, Speakers Bureau; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Klapper:Roche, Takeda, Amgen, Regeneron: Honoraria, Research Funding. Mayerhoefer:Siemens: Research Funding, Speakers Bureau; BMS: Speakers Bureau. Greil:Gilead: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Ratiopharm: Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Eisai: Honoraria; Genentech: Honoraria, Research Funding; Janssen-Cilag: Honoraria; GSK: Research Funding; Sandoz: Honoraria; Roche: Consultancy, Honoraria, Research Funding; Daiichi Sankyo: Consultancy, Honoraria; MSD: Consultancy, Honoraria, Research Funding; Merck: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Sanofi Aventis: Honoraria; Boehringer Ingelheim: Honoraria; Mundipharma: Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding. Jaeger:Novartis, Roche, Sandoz: Consultancy; AbbVie, Celgene, Gilead, Novartis, Roche, Takeda Millennium: Research Funding; Amgen, AbbVie, Celgene, Eisai, Gilead, Janssen, Novartis, Roche, Takeda Millennium, MSD, BMS, Sanofi: Honoraria; Celgene, Roche, Janssen, Gilead, Novartis, MSD, AbbVie, Sanofi: Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: Imatinib - bcr-abl Inhibitor

Abstract 708: Platelet Derived Growth Factor-Beta Communication Axis is Critical for Mediating Pericyte-Endothelial Cell Interactions and Angiogenic Support in Combination Therapy of Human Umbilical Cord Perivascular Cells and Endothelial Progenitor Cells

Introduction: First Trimester Human Umbilical Cord Perivascular Cells (FTM HUCPVC) have higher cardiovascular regenerative potential compared to older sources of MSC. We designed a cell combination therapy with FTM HUCPVC and endothelial progenitor cells (EPC) to enhance angiogenesis after MI. However, the mechanism of PVC-EPC interaction is unclear. Hypothesis: Platelet derived growth factor beta receptor (PDGFB-R) expression of HUCPVC mediates homing and integration with endothelial networks and required for supporting neovasculature. Methods: Expression of pericyte markers PDGFB-R and CD146 of xeno-free expanded (HPL 2.5%) FTM and term HUCPVC was analyzed by flow cytometry. PDGFB-driven trans-ECM migration was assessed by Corning Biocoat Invasion assay with 1-100 ng/ml PDGFB. siRNA for PDGFB-R, CD146 and scrambled control was used with lipofectamine for 72 hours. Silencing was confirmed by qPCR and flow cytometry. 10% HPL was used for PDGFB-R desensitization. HUCPVC of all treatment groups were co-cultured with EPC and rat aortic rings on Matrigel TM . Cell migration, endothelial adhesion and network properties were quantified. Statistics: one-way ANOVA N=5 Results: PDGFB-R and CD146 expression and endothelial network augmenting function of FTM HUCPVC was significantly higher than of term HUCPVC. PDGFB dependent migration of FTM HUCPVC was disabled by both ligand (&lt;10%) and siRNA-based (&lt;5%) downregulation of PDGFB-R. Fluorescence microscopy (24 h) showed limited homing and endothelial interactions of PDGFB-R-reduced FTM HUCPVC. PDGFB-R-reduced FTM HUCPVC had significantly decreased network growth and nodes ( p &lt;0.0001) compared to control groups (day3). In EPC co-cultures, PDGFB-R-reduced FTM HUCPVC had limited endothelial interactions and coverage compared to control FTM HUCPVC. PDGFB-R-reduced FTM HUCPVC treated networks had significantly thinner ( p &lt;0.001) and shorter tubules ( p &lt;0.001) compared to control FTM HUCPVC groups. Down-regulation of C146 did not alter FTM HUCPVC pericyte properties. Conclusions: PDGFB-R is crucial for the homing and endothelial support of HUCPVC. This interaction is critical in vascular cell combination therapies and PDGFB-R expression can be a novel criterion for cardiovascular cell therapy.

PDGF Modulates BMP2-Induced Osteogenesis in Periosteal Progenitor Cells.

ABSTRACTBMPs are used in various clinical applications to promote bone formation. The limited success of the BMPs in clinical settings and supraphysiological doses required for their effects prompted us to evaluate the influence of other signaling molecules, specifically platelet‐derived growth factor (PDGF) on BMP2‐induced osteogenesis. Periosteal cells make a major contribution to fracture healing. We detected broad expression of PDGF receptor beta (PDGFRβ) within the intact periosteum and healing callus during fracture repair. In vitro, periosteum‐derived progenitor cells were highly responsive to PDGF as demonstrated by increased proliferation and decreased apoptosis. However, PDGF blocked BMP2‐induced osteogenesis by inhibiting the canonical BMP2/Smad pathway and downstream target gene expression. This effect is mediated via PDGFRβ and involves ERK1/2 MAPK and PI3K/AKT signaling pathways. Therapeutic targeting of the PDGFRβ pathway in periosteum‐mediated bone repair might have profound implications in the treatment of bone disease in the future. © 2018 The Authors JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Vascular Remodelling is Impaired in Parkinson Disease

Objective: We have previously reported vascular degeneration of human Parkinson disease (PD). In which we described degenerative pathology of endothelial cells and its association with increased string vessels in the grey matter of middle frontal gyrus (MFG). Growth factors, for example platelet-derived growth factor (PDGF), insulin-like growth factor-1 (IGF-1) and vascular endothelial growth factor (VEGF), involve in vascular remodelling by promoting cell proliferations and angiogenesis through capillary pericytes. Thus current study examined the hypothesis whether vascular degeneration in human PD is associated with impairment of vascular remodelling. Methods: Using tissue microarray method we conducted immuno histochemical staining in the grey matter of MFG of human PD (n=17) and age-matched control cases (n=17). The expression of PDGF receptor-beta, proliferating cell nuclear antigen and phosphorylation of IGF-1 receptor in capillaries, IGF binding protein-2 and VEGF were evaluated using automated image analysis software. Results: PDGF receptor-beta was specifically expressed in the pericytes which formed capillary morphology. Compared to the age-matched control cases, there were significant decrease in PDGF receptor-beta positive capillaries (p<0.05; p<0.01), proliferating vascular cells (p<0.05) and VEGF (p<0.05) in the PD cases. There no difference in phosphorylation of IGF-1 receptors, expressed in the capillaries between the groups. We found a significant increase in IGF binding protein-2, expressed in the astrocytes of PD when compared to the control cases (p<0.05). Interestingly the levels of phosphorylated IGF receptors in the capillaries were significantly correlated with the numbers of pericytes and proliferating cells in capillaries (p=0.001). Conclusion: Impaired PDGF function in the pericytes, reduced cell proliferation and VEGF suggested that the ability of vascular remodelling is impaired in PD. The maintained IGF-1 function appeared to be ineffective to retain vascular remodelling process in PD. The up-regulation of IGF binding protein-2 may suggest a role for autocrine/ paracrine of IGF-1 in PD.

Thrombin Stimulated Platelet-Derived Exosomes Inhibit Platelet-Derived Growth Factor Receptor-Beta Expression in Vascular Smooth Muscle Cells

Background/Aims: It is difficult to predict acute thrombotic cardiovascular events in the clinic. Few studies have reported the presence of plasma exosomes containing microRNAs (miRNAs) in cardiovascular events. Therefore, we aimed to investigate the levels of miR-223, miR-339 and miR-21 in plasma exosomes before thrombosis in mouse models of carotid tandem stenosis, as well as the mechanisms underlying the origin and function of these exosomal miRNAs. Methods: Plasma samples were collected from the carotid tandem stenosis and sham control groups of our successfully developed atherothrombosis mouse models before thrombosis. Platelets from healthy volunteers and mice were purified to obtain thrombin stimulated platelet-derived exosomes. Exosomes were isolated via differential ultracentrifugation, and western blotting and transmission electron microscopy were used for their identification. The total RNA was extracted, and quantitative real-time PCR was performed to determine the expression levels of miR-223, miR-339 and miR-21. DAVID Tools were used to analyze the pathways that were enriched among the miRNA target genes. Immuno-fluorescence staining was performed to identify the protein expression levels of platelet-derived exosome target genes in vascular smooth muscle cells (SMCs) in vitro and in vivo. Results: The levels of miR-223, miR-339 and miR-21, which are associated with platelet activation, were elevated in pooled mouse plasma exosomes before thrombosis and enriched in thrombin-stimulated platelet-derived exosomes in vitro. Platelet-derived growth factor receptor-beta (PDGFRβ) was a target of these miRNAs, and PDGFRβ expression in vascular smooth muscle cells (SMCs) was inhibited following incubation with platelet-derived exosomes. Platelet-derived exosomes could also inhibit PDGF-stimulated SMC proliferation. Furthermore, a decrease in PDGFRβ expression was observed in vascular SMCs around thrombotic areas in vivo. Conclusions: Our data indicate that activated platelet-derived exosomes containing miR-223, miR-339 and miR-21 could be transferred into SMCs and inhibit PDGFRβ expression; these exosomal miRNAs may be a biomarker for predicting atherothrombosis.

ALK gene aberrations and the JUN/JUNB/PDGFR axis in metastatic NSCLC.

Anaplastic lymphoma kinase (ALK) gene aberrations are found in several tumor types including anaplastic large cell lymphoma (ALCL) and non-small cell lung cancer (NSCLC). Crizotinib, an inhibitor of ALK-fusion proteins, has shown clinical activity, but resistance mechanisms limit long-lasting disease control. It has been shown that ALK-NPM fusion upregulates platelet-derived growth factor receptor beta (PDGFRB) via JUN and transcription factor Jun B (JUNB) in ALCL. PDGFRB inhibition has been identified as therapy option for ALK-positive ALCL. Here, we investigated the ALK/JUN/JUNB/transcription factor Jun C (JUNC)/PDGFR axis in metastatic NSCLC with regard to ALK aberrations. We performed immunohistochemical analysis of platelet-derived growth factor receptor alpha (PDGFRA), PDGFRB, JUNB and JUNC expression in formalin-fixed, paraffin-embedded specimens of 15 NSCLC brain metastases (5 ALK translocations, 3 of them involving EML4, 5 ALK amplifications, 5 without ALK aberrations). We did not find a statistically significant difference in expression of PDGFRA, PDGFRB, JUNB or JUNC in tumor samples with normal ALK status, ALK amplification or ALK translocations (Kruskal-Wallis test p>0.05). Interestingly, PDGFRB was not expressed in tumor cells (but in vascular and stromal cells) in any of our cases. Our data argue against PDGFRB activation in association with ALK gene aberrations in metastatic NSCLC and thus seem to imply differential pathobiological roles of ALK alterations in lung cancer and lymphoma, possibly depending on different fusion partner genes. These results may be relevant for targeted therapies, as they indicate that inhibition of PDGFRB in ALK translocated NSCLC seems to be no therapeutic opportunity.

Association of tumor perivascular desmin expression with survival in patients with sunitinib-treated renal carcinoma.

11097 Background: The introduction of tyrosine kinase inhibitors has markedly improved the outcome for patients with metastatic renal carcinoma (mRCC), but lack of reliable response-predictive markers makes it difficult to individualize treatment. Pericytes surround endothelial cells of capillaries and regulate vessel function. Associations between pericyte marker expression and response to sunitinib have not been well characterized. Methods: A tissue micro array with samples from 67 mRCC patients ( 34 males, 33 females, age 42 – 84) treated at Dept. of Oncology, Karolinska University Hospital where constructed from primary tumors. All patients included had received at least one course with the tyrosine kinase receptor inhibitor sunitinib. Data of treatment, progression free survival and overall survival was collected in a clinical registry. Tissues were double-stained with the endothelial cell marker CD 34 and either of three pericyte markers desmin, PDGF beta receptor and alpha smoth muscle actin (ASMA). By semi-quantitative visual scoring, the perivascular staining of these markers was evaluated and cases dichotomized into negative/low- or positive/high-expressing groups. Results: For patients with desmin positive/high vessels ( n = 12), median PFS where 5.0 months (2.9 – 7.1, 95% CI) vs 7.0 months for patients with desmin negative/low vessels (n = 55, 3.8 – 10.2, 95% CI, Mantel Cox log rank test p&lt;0.02). The median OS in the desmin-positive/high group was 24 months ( 7 – 41, 95% CI) vs 46 months in the negative/low group ( 34 – 58, 95 % CI, Mantel Cox log rank test p&lt;0.014). No significant associations were seen between PFS or OS and the expression of perivascular PDGF beta receptor or ASMA. Conclusions: Metastatic RCC displays a clinically relevant variation in perivascular desmin expression which is associated with survival in sunitinib-treated patients. Future studies are warranted which further explores the prognostic and/or response-predicative capacity of this novel candidate renal cell cancer biomarker.

Changes in pericytic expression of NG2 and PDGFRB and vascular permeability in the sensory circumventricular organs of adult mouse by osmotic stimulation

The blood-brain barrier (BBB) is a barrier that prevents free access of blood-derived substances to the brain through the tight junctions and maintains a specialized brain environment. Circumventricular organs (CVOs) lack the typical BBB. The fenestrated vasculature of the sensory CVOs, including the organum vasculosum of the lamina terminalis (OVLT), subfornical organ (SFO) and area postrema (AP), allows parenchyma cells to sense a variety of blood-derived information, including osmotic ones. In the present study, we utilized immunohistochemistry to examine changes in the expression of NG2 and platelet-derived growth factor receptor beta (PDGFRB) in the OVLT, SFO and AP of adult mice during chronic osmotic stimulation. The expression of NG2 and PDGFRB was remarkably prominent in pericytes, although these angiogenesis-associated proteins are highly expressed at pericytes of developing immature vasculature. The chronic salt loading prominently increased the expression of NG2 in the OVLT and SFO and that of PDGFRB in the OVLT, SFO and AP. The vascular permeability of low-molecular-mass tracer fluorescein isothiocyanate was increased significantly by chronic salt loading in the OVLT and SFO but not AP. In conclusion, the present study demonstrates changes in pericyte expression of NG2 and PDGFRB and vascular permeability in the sensory CVOs by chronic osmotic stimulation, indicating active participation of the vascular system in osmotic homeostasis.

Loss of SOX10 function contributes to the phenotype of human Merlin-null schwannoma cells

Loss of the Merlin tumour suppressor causes abnormal de-differentiation and proliferation of Schwann cells and formation of schwannoma tumours in patients with neurofibromatosis type 2. Within the mature peripheral nerve the normal development, differentiation and maintenance of myelinating and non-myelinating Schwann cells is regulated by a network of transcription factors that include SOX10, OCT6 (now known as POU3F1), NFATC4 and KROX20 (also known as Egr2). We have examined for the first time how their regulation of Schwann cell development is disrupted in primary human schwannoma cells. We find that induction of both KROX20 and OCT6 is impaired, whereas enforced expression of KROX20 drives both myelin gene expression and cell cycle arrest in Merlin-null cells. Importantly, we show that human schwannoma cells have reduced expression of SOX10 protein and messenger RNA. Analysis of mouse SOX10-null Schwann cells shows they display many of the characteristics of human schwannoma cells, including increased expression of platelet derived growth factor receptor beta (PDGFRB) messenger RNA and protein, enhanced proliferation, increased focal adhesions and schwannoma-like morphology. Correspondingly, reintroduction of SOX10 into human Merlin-null cells restores the ability of these cells to induce KROX20 and myelin protein zero (MPZ), localizes NFATC4 to the nucleus, reduces cell proliferation and suppresses PDGFRB expression. Thus, we propose that loss of the SOX10 protein, which is vital for normal Schwann cell development, is also key to the pathology of Merlin-null schwannoma tumours.