OBJECTIVETo generate two genetically engineered mouse models of ErbB2/Neu positive-PTEN deficient breast cancer and to compare their biological properties.

METHODSThe genetically engineered mice previously developed with mouse mammary tumor virus (MMTV) promoter driven expression of activated ErbB2/Neu and recombinant Cre (FVB/N-MMTV-NIC) were interbred with Flox-PTEN mice; and FVB/N-ErbB2KI mice, harboring endogenous promoter driven activated ErbB2/Neu expression, FVB/N-MMTV-Cre mice and the flox-PTEN mice were interbred. Neu, Cre and PTEN genes were amplified by PCR for genotyping of the offsprings. ErbB2/Neu and PTEN expression in mammary tumors were detected by immunohistochemistry. Tumor formation time, tumor number, histopathology and lung metastasis were compared between two models, Ki-67 expression was detected by immunohistochemistry, and TUNEL staining of tumor tissues was performed.

RESULTSTwo genetically engineered mouse models of ErbB2/Neu positive-PTEN homozygous deficient breast cancer were generated. The models were confirmed by genotyping and immunohistochemistry. One model with exogenous MMTV promoter driven expression of activated ErbB2/Neu and Cre coupling PTEN disruption was designated as NIC/PTEN(-/-) mice, and the other with MMTV-Cre induced endogenous promoter driven expression of activated ErbB2/Neu with PTEN disruption was designated as ErbB2KI/PTEN(-/-) mice. The tumor formation time in NIC/PTEN(-/-) mice was significantly shorter than that of ErbB2KI/PTEN(-/-) mice (30 vs 368 d, P<0.01); the number of tumor and incidence of lung metastasis was also significantly higher in NIC/PTEN(-/-) mice (10 vs 1-2 and 75.0% vs 37.5%, respectively, Ps<0.01). The Two models displayed distinct histopathological morphology. NIC/PTEN(-/-) tumor showed more Ki-67 positive cells than ErbB2KI/PTEN(-/-) tumor did (86.9%±2.8% vs 37.4%±7.2%, P<0.01), while the amount of cell apoptosis in tumors was not significantly different between two models.

CONCLUSIONTwo genetically engineered mouse models of ErbB2/Neu positive-PTEN homozygous deficient breast cancer with different phenotypes have been successfully generated, which may provide useful resource for further investigation of the initiation and progression of HER2/ErbB2 breast cancer, as well as for the development of novel prevention and treatment regimens of this malignance.

Animals ; Breast Neoplasms ; genetics ; Disease Models, Animal ; Female ; Gene Deletion ; Mammary Neoplasms, Animal ; Mammary Tumor Virus, Mouse ; genetics ; Mice ; Mice, Transgenic ; PTEN Phosphohydrolase ; genetics ; Receptor, ErbB-2 ; genetics

PURPOSE: We investigated whether recombinant human granulocyte colony-stimulating factor (rhG-CSF) could promote the development of preinvasive and invasive breast cancer in mouse mammary tumor virus (MMTV-erbB2) mice with estrogen receptor-positive tumors. METHODS: MMTV-erbB2 mice were randomly divided into three experimental groups with 20 mice in each group. MMTV-erbB2 mice were treated with daily subcutaneous injections of vehicle or rhG-CSF (low-rhG-CSF group, rhG-CSF 0.125 microg; vehicle-rhG-CSF group, normal saline 0.25 microg; and high-rhG-CSF group, rhG-CSF 0.25 microg) at 3 months of age. Cellular and molecular mechanisms of G-CSF action in mammary glands were investigated via immunohistochemistry and reverse transcription polymerase chain reaction. RESULTS: Low, but not high, rhG-CSF doses significantly accelerated mammary tumorigenesis in MMTV-erbB2 mice. Short-term treatment with rhG-CSF could significantly promote the development of preinvasive mammary lesions. The cancer prevention effect was associated with reduced expression of proliferating cell nuclear antigen, cluster of differentiation 34, and signal transducers and activators of transcription 3 in mammary glands by >80%. CONCLUSION: We found that G-CSF was regulated by rhG-CSF both in vitro and in vivo. Identification of G-CSF genes helped us further understand the mechanism by which G-CSF promotes cancer. Low doses of rhG-CSF could significantly increase tumor latency and increase tumor multiplicity and burden. Moreover, rhG-CSF effectively promotes development of both malignant and premalignant mammary lesions in MMTV-erbB2 mice.
Animals ; Breast Neoplasms ; Carcinogenesis ; Cell Proliferation ; Estrogens* ; Granulocyte Colony-Stimulating Factor* ; Humans ; Immunohistochemistry ; Injections, Subcutaneous ; Mammary Glands, Human ; Mammary Tumor Virus, Mouse ; Mice* ; Polymerase Chain Reaction ; Proliferating Cell Nuclear Antigen ; Reverse Transcription ; Transducers