Comparative Analysis of Smooth Muscle Isoactin Gene Expression in Normal and Neoplastic Tissues

Abstract

Monoclonal antibodies derived from the actin multigene family are routinely used as an adjunct to morphologic diagnoses of smooth muscle tumors. Northern blot analysis was performed on 60 surgical resections utilizing isoactin-specific cDNAs. A comparison of this analysis to immunohistochemical studies demonstrated that actin-specific monoclonal antibodies represent reliable markers of the smooth muscle lineage. Smooth muscle neoplasms showed a unique pattern of γ-smooth muscle isoactin gene expression, providing a potentially valuable molecular adjunct to the morphologic diagnosis of uterine smooth muscle tumors.

Differential Binding of an SRF/NK-2/MEF2 Transcription Factor Complex in Normal Versus Neoplastic Smooth Muscle Tissues

“…B, representative EMSA analysis of the 36-bp ACH promoter fragment incubated with 10 g of cytoplasmic proteins isolated from smooth muscle myoblasts (lanes 1-3), immature smooth muscle myocytes (lanes 4 -6), neonatal mature smooth muscle myocytes (lanes 7-9), adult mature smooth muscle myocytes (lanes 10 and 11), normal myometrium (lanes 12-14), uterine leiomyomas (lanes [15][16][17], and uterine leiomyosarcomas (lanes 18 -20). Lanes 1,4,7,10,12,15, and 18, NE ϩ labeled ACH; lanes 2,5,8,11,13,16, and 19, NE ϩ labeled ACH ϩ SRF antibody; and lanes 3,6,9,14,17, and 20, NE ϩ labeled ACH ϩ TN domain antibody. Primary bands are identified alphabetically in series with reference to previous figures.…”

“…In addition to a role in smooth muscle development, ␥-smooth muscle isoactin represents a reliable marker for the malignant potential of smooth muscle tumors, with ␥-smooth muscle isoactin expression being significantly reduced in leiomyomas and completely absent in leiomyosarcomas (7)(8)(9). Over 95% of all smooth muscle tumors arise in the female genital tract, with the few remaining lesions variably arising in the gastrointestinal tract, vasculature, skin, and bladder (1,(53)(54).…”

“…Representative EMSA analysis of the 36-bp ACH ␥-smooth muscle isoactin promoter fragment using antibodies specific for SRF (Santa Cruz Biotechnology, Inc.), MEF2A (11), MEF2B (12), MEF2D (12), and the TN domain of NK-2 proteins. Labeled ACH was incubated with 10 g of rat nuclear proteins isolated from smooth muscle myoblasts (lanes 1-6), immature smooth muscle myocytes (lanes [7][8][9][10][11][12], and neonatal (lanes [13][14][15][16][17][18] and adult mature smooth muscle myocytes (lanes 19 -24 6,12,18, and 24, NE ϩ labeled ACH ϩ TN domain antibody. Primary bands are identified alphabetically in series with reference to previous figures (i.e.…”

“…(7)(8)(9). With the knowledge that SRF and an NK-2 factor cooperatively bind to the ␥-smooth muscle isoactin promoter in a differentiation-specific manner, we decided to examine whether there were alterations in the binding of these proteins in nuclear extracts from normal uterine myometrium, uterine leiomyomas, and uterine leiomyosarcomas.…”

“…One marker of differentiation, ␥-smooth muscle isoactin, is expressed in differentiated smooth muscle cells from early embryonic development into adulthood (5,6). Additionally, the absence of ␥-smooth muscle isoactin expression correlates strongly with the malignant potential of smooth muscle tumors (7)(8)(9). Therefore, ␥-smooth muscle isoactin represents an excellent model for understanding the events leading to smooth muscle-specific gene expression in both normal and neoplastic tissues.…”