Increased expression of actin-like protein in human and ethylnitrosourea-induced tumors of the nervous system.

Twenty-one human intracranial tumors comprising 15 astrocytomas and 6 meningiomas and 26 ethylnitrosourea-induced rat neural tumors comprising 7 astrocytomas and 9 schwannomas were examined by indirect immunofluorescence for reactivity with a human anti-actin antibody. In cryostat sections both human and rat astrocytomas showed an increased reaction with the anti-actin antibody compared to normal astrocytes, and the reaction with astrocytomas was greater than that with meningiomas. Malignant rat schwannomas also showed prominent anti-actin staining contrasting with the negative reaction in normal Schwann cells. These in vivo observations were paralleled by concurrent studies with impression films and in vitro monolayer cultures of tumor tissue. The results, reviewed in the light pfo previous studies of anti-actin antibody reactivity with other nonneural tumors, suggest that an enhanced actin expression in vivo may be a general feature of the neoplastic state and that this increased expression may be more pronounced in malignant than in benign tumors.