Antisense-mediated reduction in thrombospondin reverses the malignant phenotype of a human squamous carcinoma.
Thrombospondin (TSP) is a trimeric glycoprotein which is synthesized and incorporated into the extracellular matrix by a wide variety of cells. TSP is involved in a number of cellular processes which govern tumor cell behavior including mitogenesis, attachment, migration, and differentiation. To directly assess the role of TSP in tumor cell growth and spread, a human squamous carcinoma cell line, with high TSP production and an invasive phenotype, was transfected with a TSP cDNA antisense expression vector. Five unique transfected clones were obtained with reduced TSP production. Expression of the transfected antisense sequence in these clones was verified by a ribonuclease protection assay. These clones demonstrated reduced growth rates in vitro when compared with a vector transfected control. After subcutaneous inoculation into athymic mice, the antisense clones formed either no tumors or tumors that were slow growing and highly differentiated. This contrasted with the vector-transfected clone which produced poorly differentiated, rapidly growing, invasive tumors. Our results argue in favor of a direct role for TSP in determining the malignant phenotype of certain human tumors.
Castle
V
V
Department of Pediatrics, University of Michigan, Ann Arbor 48109.
Varani
J
J
Fligiel
S
S
Prochownik
E V
EV
Dixit
V
V
D000818:Animals; D015139:Blotting, Southern; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000473:pathology*; D002454:Cell Differentiation; D002455:Cell Division; D015870:Gene Expression; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D010980:Platelet Membrane Glycoproteins / Q000502:physiology*; D011233:Precipitin Tests; D016372:RNA, Antisense; D019699:Thrombospondins; D014162:Transfection
D010980:Platelet Membrane Glycoproteins; D016372:RNA, Antisense; D019699:Thrombospondins