Differential Expression of Decorin by Human Malignant and Benign Vascular Tumors

Henriikka H. Salomäki ¹, Annele O. Sainio ¹, Mirva Söderström ¹, Sari Pakkanen ¹, Jukka Laine ¹ and Hannu T. Järveläinen ^1*

¹ Departments of Medical Biochemistry (HHS,AOS,SP,HTJ), Pathology (MS,JL), and Medicine (HTJ), University of Turku, Turku, Finland

^* To whom correspondence should be addressed. E-mail: hannu.jarvelainen{at}utu.fi.

Submitted on November 19, 2007
Accepted on 26 March 2008

	Abstract

An increasing amount of evidence is available indicating that a small extracellular chondroitin/dermatan sulphate proteoglycan decorin, is indirectly involved in angiogenesis. Given that angiogenesis is a sine qua non for tumor growth and progression, we attempted to examine whether human malignant vascular tumors differ from human benign vascular tumors in terms of their decorin expression and synthesis. CD31 immunostaining demonstrated that the human malignant vascular tumors Kaposis sarcoma and angiosarcoma were filled with capillary-like structures whereas in benign cavernous and capillary hemangiomas blood vessels were not as abundantly present. By utilising in situ hybridization and immunocytochemical assays for decorin, we showed that there was no detectable decorin mRNA expression or immunoreactivity within the tumor mass in the Kaposis sarcoma or angiosarcoma group. Instead, decorin was expressed in the connective tissue stroma lining the sarcoma tissue. In contrast to sarcomas, in hemangiomas decorin mRNA expression and immunoreactivity were observed also within the tumor mass, particularly in the connective tissue stroma surrounding the clusters of intratumoral blood vessels. Finally, distribution of type I collagen was found to be similar to that of decorin in these tumor tissues. Our findings can be explained with different states of angiogenesis in dissimilar growths. In sarcomas angiogenesis is extremely powerful whereas in hemangiomas angiogenesis has ceased. Thus, decorin is likely to possess a suppressive effect on human tumor angiogenesis in vivo, as previously described by studies using different experimental models. Decorin certainly provides a usable biomarker to distinguish between benign and malignant vascular tumors in patients.

Key Words: decorin, type I collagen, sarcoma, hemangioma, angiogenesis

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