Vinblastine and hyperthermia target the neovasculature in BT(4)AN rat gliomas: therapeutic implications of the vascular phenotype.
OBJECTIVE
The antivascular and antitumor activity of vinblastine and hyperthermia at different tumor volumes were examined in the subcutaneous (s.c.) BT(4)An rat glioma model.


METHODS
The influence of vinblastine (3 mg/kg) and hyperthermia (44 degrees C/60 min) on tumor growth was assessed in small (100 mm(3)) and large (200 mm(3)) BT(4)An tumors. To disclose how vinblastine and hyperthermia interacted in the neoplasms, tumor blood flow and the extent of vascular damage, hypoxia, cell proliferation, and apoptosis were assessed after treatment. The content of smooth muscle cells/pericytes in the tumor vasculature was examined in small and large tumors to assess how the vascular phenotype changed during tumor growth.


RESULTS
In the large tumors, vinblastine reduced the blood flow, but the tumor growth was not affected. The combination of drug and local heating yielded massive vascular damage and a significant tumor response. The small neoplasms had a higher content of smooth muscle cells/pericytes in the vessel walls (host vasculature), and the tumor vasculature displayed a higher resistance to vascular damage than the large neoplasms. Yet, vinblastine alone exhibited a potent antiproliferative activity and induced massive apoptosis in the small tumors, and the drug significantly inhibited tumor growth. The addition of hyperthermia yielded no additional growth delay in the small tumors.


CONCLUSIONS
The antivascular properties of vinblastine and hyperthermia can be exploited to facilitate vascular damage in BT(4)An solid tumors with a low content of host vasculature.
Eikesdal
H P
HP
Department of Oncology, Institute of Medicine, University of Bergen, Haukeland Hospital, Bergen, Norway. hans_eikesdal@hotmail.com
Bjerkvig
R
R
Dahl
O
O
D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use*; D017209:Apoptosis; D001932:Brain Neoplasms / Q000098:blood supply / Q000628:therapy*; D002455:Cell Division; D015687:Cell Hypoxia; D003131:Combined Modality Therapy; D005260:Female; D005910:Glioma / Q000098:blood supply / Q000628:therapy*; D006979:Hyperthermia, Induced; D020287:In Situ Nick-End Labeling; D008297:Male; D009389:Neovascularization, Pathologic / Q000628:therapy*; D010641:Phenotype; D051381:Rats; D014747:Vinblastine / Q000627:therapeutic use*
D000972:Antineoplastic Agents, Phytogenic; D014747:Vinblastine