Imatinib treatment of human DLBCL tumors was associated with pericytic dropout and disruption of microvasculature. (A1-A4) Analysis of α-SMA⁺ pericytes and CD31⁺ vessels in (A1,A3) Karpas422 and (A2,A4) OCI-Ly7 xenografts. (B1-B4) Analysis of NG2⁺ pericytes and CD31⁺ vessels in (B1,B3) Karpas422 and (B2,B4) OCI-Ly7 xenografts. (C) Confocal analysis of pericytes (red) in relation to intraluminal blood flow (isolectin, blue) in OCI-Ly7 tumors. (C1-C2) Two z-stack images focused at different depths within the same tissue; white arrows indicate disrupted microvessels with scanty PDGFRβ⁺ staining and abundant cleaved-caspase 3⁺, apoptotic nuclei; white asterisks (*) indicate microvessels with relatively intact blood flow and perivascular PDGFRβ⁺ staining. (C3-C4) White arrows indicate apoptotic α-SMA⁺ pericytes surrounding regions of functional blood flow. (D) Pericyte coverage was quantified as α-SMA⁺ area (red) and normalized to the PBS control. (E) Pericyte coverage was quantified as NG2⁺ area (green) and normalized to the PBS control. (F) Microvessel density was quantified as CD31⁺ staining area (blue) and normalized to the PBS control. *P < .05 compared with control. Scale bar, 50 μm.