Non-radiolabeled in situ hybridization and immunohistochemistry of .ALPHA.-smooth muscle actin in myoepithelial cells.

Background: Concerted alterations between stromal fibroblasts and neoplastic cells underline the carcinogenic process. Activation of alpha-smooth muscle actin (SMA) expression, a cytoskeleton protein normally expressed only in myoepithelial cells, is considered a landmark for the activation of stromal fibroblasts with little however being known regarding the mechanism governing the expression of SMA in the stroma.Methods: We have evaluated by immunohistochemistry the expression of SMA in the stroma of oral malignant and pre-malignant lesions, in association with the expression of p53 and p21 tumor suppressors that were shown previously to be deregulated and/or mutated in stromal fibroblasts of various cancers. The effects of p21 knockdown in SMA expression and cell migration and the mRNA levels of endogenous p21 in fibroblasts co-cultured with cancer cells were also assessed.Results: We found that both p21 and SMA expression was elevated in the stroma, but not the epithelium, of malignant as compared to pre-malignant lesions. We also noted that the expression of both was positively correlated, implying that SMA expression may be regulated by p21. Consistently with this notion we found that siRNA-mediated p21 suppression resulted in the reduction of SMA levels and also inhibited cell migration.Conclusion: Our results show that p21 deregulation is associated with the activation of stromal fibroblasts of oral cancers by a mechanism that involves the stimulation of SMA expression.

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Specific demonstration of myoepithelial cells by anti-alpha smooth muscle actin antibody.

Journal of Histochemistry & Cytochemistry ◽

10.1177/36.6.3367051 ◽

1988 ◽

Vol 36 (6) ◽

pp. 659-663 ◽

Cited By ~ 89

Author(s):

P Gugliotta ◽

A Sapino ◽

L Macrí ◽

O Skalli ◽

G Gabbiani ◽

...

Keyword(s):

Smooth Muscle ◽

Epithelial Cells ◽

Salivary Glands ◽

Smooth Muscle Actin ◽

Practical Interest ◽

Myoepithelial Cells ◽

Basal Cells ◽

Muscle Actin ◽

Alpha Smooth Muscle Actin ◽

Microfilament Bundles

The myoepithelial cells of the sweat, mammary, tracheobronchial, and salivary glands are specifically identified by monoclonal antibody alpha-SM-1, which recognizes alpha smooth muscle actin and not the other actin isoforms. Basal or "reserve" cells in the stratified epithelia and excretory ducts of the salivary glands are negative, as well as all other epithelial cells in various organs. The reaction can be performed in routinely fixed and embedded tissues and is of practical interest in diagnostic histopathology. In immunoelectron cytochemistry, alpha-SM-1 antibody binds to the microfilament bundles in myoepithelial cells of the breast, but does not stain luminal cells and occasional basally located epithelial cells. These basal cells are morphologically and immunocytochemically distinct from the myoepithelial cells, and their nature and significance remain to be clarified.

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