Cyclooxygenase inhibition in early onset of tumor growth and related angiogenesis evaluated in EP1 and EP3 knockout tumor-bearing mice.
It is well established that prostanoids are essential for local inflammation including cell proliferation and apoptosis. Accordingly, prostaglandin E2 (PGE(2)) is a critical factor in wound healing, tumor invasiveness and progression. Therefore, the aim of the present work was to evaluate effects by PGE(2) on tumor vascular density at early onset of tumor growth where hypoxia is limited. Wild-type mice (C57Bl, C3H/HeN) bearing either MCG-101 tumors or a malignant melanoma (K1735-M2) with either high or insignificant PGE(2) production and subsequently different in sensitivity to cyclooxygenase (COX) inhibition were used. Tumor angiogenesis was estimated by intravital microscopy and immune histochemical analysis in wild type and EP(1) or EP(3) subtype receptor knockout mice (C57Bl). Both MCG-101 and K1735-M2 tumor cells stimulated early outgrowth of tumor vessels in proportion to intrinsic growth rate of tumor cells. Indomethacin had no effects on tumor growth or tumor related vascular area in K1735-M2 bearing mice. By contrast, indomethacin decreased tumor cell proliferation and increased apoptosis in MCG-101 tumors with subsequent adaptation in tumor vascular density. Effects of indomethacin on early growth of MCG-101 tumors were not related to tumor content of bFGF protein, while our earlier studies on long-term tumor growth have shown decreased mRNA levels of bFGF during indomethacin treatment. Early onset of tumor growth was significantly promoted in EP(3)- but not in EP(1)-knockouts, although long-term tumor growth is attenuated in EP(1)-knockouts as reported elsewhere. Our results demonstrate that tumor production of PGE(2) promotes primarily net growth of tumor cells with subsequent adaptations in development of the tumor vasculature. Therefore, it is likely that angiogenesis is not a limiting step at the early onset of tumor growth.
Axelsson
Hans
H
Department of Surgery, Surgical Metabolic Research Laboratory at Lundberg Laboratory for Cancer Research, Sahlgrenska University Hospital, Göteborg, Sweden.
Lönnroth
Christina
C
Wang
Wenhua
W
Svanberg
Elisabeth
E
Lundholm
Kent
K
D000818:Animals; D045744:Cell Line, Tumor; D051545:Cyclooxygenase 1 / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D007213:Indomethacin / Q000494:pharmacology*; D008545:Melanoma / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009389:Neovascularization, Pathologic / Q000188:drug therapy* / Q000201:enzymology; D018078:Receptors, Prostaglandin E / Q000172:deficiency / Q000235:genetics*; D058306:Receptors, Prostaglandin E, EP1 Subtype; D058308:Receptors, Prostaglandin E, EP3 Subtype
D016861:Cyclooxygenase Inhibitors; D008565:Membrane Proteins; C545636:Ptger1 protein, mouse; C545648:Ptger3 protein, mouse; D018078:Receptors, Prostaglandin E; D058306:Receptors, Prostaglandin E, EP1 Subtype; D058308:Receptors, Prostaglandin E, EP3 Subtype; C077623:Ptgs2 protein, mouse; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496512:Ptgs1 protein, mouse; D007213:Indomethacin