The
calponin (basic or h1) gene, normally expressed in maturated smooth muscle cells, is aberrantly expressed in a variety of human soft tissue and bone
tumors. In this study, we show that expression of the
calponin gene in human soft tissue and bone
tumor cells is regulated at the transcriptional level by the sequence between positions -260 and -219 upstream of the translation initiation site. A novel conditionally replicating
herpes simplex virus-1 vector (d12.CALP) in which the
calponin promoter drives expression of ICP4, a major trans-activating factor for viral genes was constructed and tested as an experimental treatment for malignant human soft tissue and bone
tumors. In cell culture, d12.CALP at low multiplicity of
infection (0.001 plaque-forming unit/cell) selectively killed
calponin-positive human
synovial sarcoma,
leiomyosarcoma, and
osteosarcoma cells. For in vivo studies, 10 animals harboring SK-LMS-1 human
leiomyosarcoma cells were randomly divided and treated twice on days 0 and 9 intraneoplastically with either 1 x 10(7) plaque-forming units of d12.CALP/100 mm(3) of
tumor volume or with medium alone. The viral treatment group showed stable and significant inhibition of tumorigenicity with apparent cure in four of five mice by day 35. Replication of
viral DNA demonstrated by PCR amplification and expression of the inserted LacZ gene visualized by 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside histochemistry was associated with oncolysis of d12.CALP-treated
tumors, while sparing normal vascular smooth muscle cells. In mice harboring two SK-LMS-1
tumors, replication of d12.CALP was detected in a nontreated
tumor distant from the site of virus inoculation. These results indicate that replication-competent virus vectors controlled by the
calponin transcriptional regulatory sequence may be a new therapeutic strategy for treatment of malignant human soft tissue and bone
tumors.