title: Regression of progestin-accelerated 7,12-dimethylbenz[a]anthracene-induced mammary tumors in Sprague-Dawley rats by p53 reactivation and induction of massive apoptosis: a pilot study.
abstract: p53 Reactivation and induction of massive apoptosis (PRIMA-1) is a small-molecule compound that reactivates mutant p53, restoring its normal tumor suppressor function. PRIMA-1 effectively suppresses the growth of homogeneous p53-deficient tumor xenografts in immunosuppressed mice; however, the ability of PRIMA-1 to suppress the growth of mammary tumors in rodents and other species is not well characterized. Here, we examined the ability of PRIMA-1 to suppress the growth of 7,12-dimethylbenz[a]anthracene (DMBA)-induced and progestin-accelerated DMBA-induced mammary tumors in Sprague-Dawley rats. Mammary tumors were induced in female rats with DMBA or DMBA plus progestin treatment. After tumors had reached 5-25 mm(2) in size, PRIMA-1 was administered twice a day for 3 days via tail vein injection (20 or 50 mg/kg). Tumor size was monitored every day following PRIMA-1 for at least 15 days prior to killing. PRIMA-1 caused regression of approximately 40% of progestin-accelerated DMBA-induced mammary tumors, but did not induce regression of native non-progestin-accelerated DMBA-induced tumors. Importantly, PRIMA-1 also suppressed the emergence of any new progestin-accelerated tumors in this model. Immunological studies with an antibody that selectively reacts with mutant p53 suggested that none of the native DMBA-induced tumors expressed mutant p53. By contrast, six out of eight progestin-accelerated DMBA-induced tumors stained for mutant p53 protein. In PRIMA-1-treated tumor-bearing rats, tumor regression correlated with conversion of mutant to wild-type p53 conformation, reduced expression of vascular endothelial growth factor and estrogen receptor, lack of blood vessel perfusion, increased expression of p21, and massively increased expression of anti-angiogenic protein, secreted protein acidic and rich in cysteine. These pre-clinical results suggest that PRIMA-1, as a single agent or in combination with other anti-cancer compounds, has potential as a novel chemotherapeutic treatment for progestin-accelerated human breast cancer.
authors.affiliation: Department of Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri 65211, USA.
authors.forename: Indira
authors.initials: I
authors.lastname: Benakanakere
authors.forename: Cynthia
authors.initials: C
authors.lastname: Besch-Williford
authors.forename: Mark R
authors.initials: MR
authors.lastname: Ellersieck
authors.forename: Salman M
authors.initials: SM
authors.lastname: Hyder
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001372:Aza Compounds / Q000494:pharmacology*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology*; D002273:Carcinogens / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D005260:Female; D015674:Mammary Neoplasms, Animal / Q000139:chemically induced / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D017258:Medroxyprogesterone Acetate / Q000494:pharmacology*; D009154:Mutation; D009389:Neovascularization, Pathologic / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D015676:Osteonectin / Q000378:metabolism; D010865:Pilot Projects; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D018931:Antineoplastic Agents, Hormonal; D001372:Aza Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002273:Carcinogens; D015676:Osteonectin; D011960:Receptors, Estrogen; D016159:Tumor Suppressor Protein p53; D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat; D015127:9,10-Dimethyl-1,2-benzanthracene; D017258:Medroxyprogesterone Acetate; C451219:2,2-bis(hydroxymethyl)-1-azabicyclo(2,2,2,)octan-3-one