Matricellular protein SPARCL1 regulates tumor microenvironment–dependent endothelial cell heterogeneity in colorectal carcinoma
Elisabeth Naschberger, … , Werner Hohenberger, Michael Stürzl
Elisabeth Naschberger, … , Werner Hohenberger, Michael Stürzl
Published October 10, 2016
Citation Information: J Clin Invest. 2016;126(11):4187-4204. https://doi.org/10.1172/JCI78260.
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Matricellular protein SPARCL1 regulates tumor microenvironment–dependent endothelial cell heterogeneity in colorectal carcinoma

Abstract

Different tumor microenvironments (TMEs) induce stromal cell plasticity that affects tumorigenesis. The impact of TME-dependent heterogeneity of tumor endothelial cells (TECs) on tumorigenesis is unclear. Here, we isolated pure TECs from human colorectal carcinomas (CRCs) that exhibited TMEs with either improved (Th1-TME CRCs) or worse clinical prognosis (control-TME CRCs). Transcriptome analyses identified markedly different gene clusters that reflected the tumorigenic and angiogenic activities of the respective TMEs. The gene encoding the matricellular protein SPARCL1 was most strongly upregulated in Th1-TME TECs. It was also highly expressed in ECs in healthy colon tissues and Th1-TME CRCs but low in control-TME CRCs. In vitro, SPARCL1 expression was induced in confluent, quiescent ECs and functionally contributed to EC quiescence by inhibiting proliferation, migration, and sprouting, whereas siRNA-mediated knockdown increased sprouting. In human CRC tissues and mouse models, vessels with SPARCL1 expression were larger and more densely covered by mural cells. SPARCL1 secretion from quiescent ECs inhibited mural cell migration, which likely led to stabilized mural cell coverage of mature vessels. Together, these findings demonstrate TME-dependent intertumoral TEC heterogeneity in CRC. They further indicate that TEC heterogeneity is regulated by SPARCL1, which promotes the cell quiescence and vessel homeostasis contributing to the favorable prognoses associated with Th1-TME CRCs.

Authors

Elisabeth Naschberger, Andrea Liebl, Vera S. Schellerer, Manuela Schütz, Nathalie Britzen-Laurent, Patrick Kölbel, Ute Schaal, Lisa Haep, Daniela Regensburger, Thomas Wittmann, Ludger Klein-Hitpass, Tilman T. Rau, Barbara Dietel, Valérie S. Méniel, Alan R. Clarke, Susanne Merkel, Roland S. Croner, Werner Hohenberger, Michael Stürzl

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Figure 9

SPARCL1 regulates vessel maturation.

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SPARCL1 regulates vessel maturation. (A) Primary human SMCs were treated...
(A) Primary human SMCs were treated with recombinant human SPARCL1 (1.5 μg/ml) and migration (scratch and transmigration assays) as well as proliferation were analyzed. Human recombinant PDGF (PDGF-AA and PDGF-BB, 10 ng/ml each) was used as a positive control to activate SMC migration and proliferation. Human recombinant IFN-γ (100 U/ml) served as a negative control. PDGF-induced closure of the wound was significantly inhibited by SPARCL1 (left); PDGF-induced transmigration was significantly inhibited by SPARCL1 (middle); and PDGF-induced proliferation of SMCs was not inhibited by SPARCL1 (right). Representative experiments of 2 (right and left) and 3 (middle) independent experiments are depicted. Lines indicate SD. (B) Colon tissue of WT (n = 11) and Sc1–/– mice (n = 10) was immunostained for SC1 (green), CD31 (red), and α-SMA (blue). Vessels are indicated by arrows. α-SMA–positive mural cell coverage was categorized as negative/weak, moderate, or high for 210 vessels, and the relative number of vessels for each category is shown for WT and Sc1–/– vessels (left). Vessel perimeters and areas (n = 210) were quantitatively determined and are depicted by dot plots (red bars represent the mean values and SD). Scale bar: 25 μm. *P < 0.05 and ***P < 0.001, by ANOVA, with Levene and Bonferroni’s (equal variance) or Games-Howell (unequal variance) test (A), χ2 test B, bar graph), or Student’s t test (B, dot plots).