?(Fig.4C,D)4C,D) to identify DCN ISH positivity localized to areas of microvascular proliferation. during resection. Surgical specimens were used to evaluate for DCN RNA and protein expression by ADC value. The IVY Glioblastoma Atlas Project Database was used to evaluate DCN localization and relationship with VEGF pathway via in situ hybridization maps and RNA sequencing data. In a cohort of 35 patients with pre-operative ADC imaging and surgical specimens, DCN RNA expression levels were significantly larger in high ADCL tumors (41.6 vs. 1.5; P?=?0.0081). In a cohort of 17 patients with prospectively targeted biopsies there was a positive linear correlation between ADCL levels and DCN protein expression between tumors (Pearson R2?=?0.3977; P?=?0.0066) and when evaluating different targets within the same tumor (Pearson R2?=?0.3068; P?=?0.0139). In situ hybridization data localized DCN expression to areas of Flumatinib microvascular proliferation and immunohistochemical studies localized DCN protein expression to the tunica adventitia of blood vessels within the tumor. DCN expression positively correlated with VEGFR1 & 2 expression and localized to similar areas of tumor. Increased ADCL on diffusion MR imaging is associated with high DCN expression as well as increased survival with anti-VEGF therapy in glioblastoma. DCN may play an important role linking the imaging features on diffusion MR and anti-VEGF treatment efficacy. DCN may serve as a target for further investigation and modulation of anti-angiogenic therapy in GBM. for survival benefit on anti-VEGF treatment in the recurrent setting in both single-center16C18 and multicenter studies19C21 suggesting a potential mechanistic link between water Flumatinib mobility within the tumor and anti-VEGF treatment efficacy. Despite these observations, only a few, rather simplistic biologic associations based on changes in cell structure and density have been identified and associated with changes in measured ADC in GCN5 the central nervous system. For example, increased ADC in the brain and spinal cord has been associated with decreased axon22 or dendrite density and myelin sheath thickness23,24, as these represent relatively impermeable barriers and restrictions to water diffusion. Similarly, a decreased ADC in brain tumors had been associated with increased cell density25C30 and mitotic index31. However, these strictly structural associations do not explain the many discrepancies reported in the post-therapeutic setting or why diffusion MR phenotypes would be particularly predictive in anti-VEGF treatment. Thus, the mechanism or rationale for how pre-treatment ADC measurements predict response to anti-VEGF therapy in glioblastoma remains unclear. A differential gene expression study from our laboratory identified overexpression of decorin (DCN) as a possible mechanism for altered water diffusivity32 and anti-VEGF efficacy. Specifically, DCN may increase water diffusivity through direct modulation (softening) of the Flumatinib extracellular matrix (ECM) along with decreased tumor cell proliferation. DCN acts to modulate the rigidity and stiffness of the ECM by binding with various ECM macromolecules and activating specific matrix metalloproteinases (MMPs)33. DCN injections soften fibrotic connective and scar tissues within body tissues34C41 and the central Flumatinib nervous system (i.e. gliotic scaring)42C44, suggesting DCN may increase fluid mobility within the extracellular environment through remodeling of the ECM. This is further evidenced by studies showing that DCN expressing viral vectors that transfect tumor tissues can improve diffusion and penetration of macromolecules including chemotherapies45C47. The protein core of DCN binds with a variety of collagen molecules, fibrils, and other macromolecules, acting to significantly increase inter-fibrillary spacing48. Since ADC is inversely correlated with fluid viscosity49,50 and tortuosity of the ECM51C55, it is conceivable.