Combined treatment with exogenous estradiol and progesterone increases the incidence of breast cancer in TA2 mice without ovaries

Fibroblast growth factor 3 promotes spontaneous mammary tumorigenesis in Tientsin albino 2 mice via the FGF3/FGFR1/STAT3 pathway

Introduction

Tientsin albino 2 (TA2) mice can develop spontaneous breast cancer (SBC), which is associated with multiple pregnancies and infection with the mouse mammary tumor virus (MMTV). In this study, we sought to elucidate the molecular mechanisms underlying the development of SBC in TA2 mice induced by MMTV.

Methods

The integration site of MMTV in TA2 SBC was identified using whole-genome sequencing. The expression of fibroblast growth factor 3 (FGF3) in SBCs and normal breast tissues was compared. The primary cell line, TA-1106, derived from SBC, was cultured. The proliferation, cell cycle, migration, invasion, and tumorigenicity abilities, as well as the expression of epithelial-mesenchymal transition-related proteins, phosphorylated STAT3, and phosphorylated Akt, were assessed in MA-891cell line from TA2 and TA-1106 cells after FGF3 knockdown. The binding of FGF3 to FGF receptor 1 (FGFR1) was determined by co-immunoprecipitation. Additionally, the relationship between STAT3 and Akt phosphorylation was investigated using a small molecule inhibitor and STAT3 knockdown.

Results

MMTV integrated upstream of the FGF3 gene, and the FGF3 protein was highly expressed in TA2 SBCs. FGF3 knockdown in MA-891 and TA-1106 decreased their proliferation, migration, and invasion abilities, affected the cell cycle and expression of epithelial-mesenchymal transition-related proteins, and inhibited the growth of animal xenografts. FGF3 binds to FGFR1, and either FGF3 or FGFR1 knockdown decreases STAT3 and Akt phosphorylation levels. Inhibition of phosphorylation or expression of STAT3 resulted in decreased Akt phosphorylation levels. Inhibition of Akt phosphorylation also resulted in decreased STAT3 phosphorylation levels. Furthermore, treatment of MA-891 and TA-1106 cells with Wortmannin or Stattic caused FGFR1 upregulation in addition to inhibiting Akt or STAT3 phosphorylation.

Conclusion

The results of this study demonstrate that FGF3 plays a significant role in the development of SBC through the FGF3/FGFR1/STAT3 signaling pathway. There is a reciprocal activation between STAT3 and Akt. Inhibition of STAT3 or Akt phosphorylation promoted the expression of FGFR1. Validating the conclusions obtained in this study in human breast cancer (HBC) may contribute to targeted therapy and it is worth exploring whether the homologous sequences of MMTV in HBC have a similar oncogenic effect.

Endogenous retroviruses promote homeostatic and inflammatory responses to the microbiota

The microbiota plays a fundamental role in regulating host immunity. However, the processes involved in the initiation and regulation of immunity to the microbiota remain largely unknown. Here, we show that the skin microbiota promotes the discrete expression of defined endogenous retroviruses (ERVs). Keratinocyte-intrinsic responses to ERVs depended on cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes protein (STING) signaling and promoted the induction of commensal-specific T cells. Inhibition of ERV reverse transcription significantly impacted these responses, resulting in impaired immunity to the microbiota and its associated tissue repair function. Conversely, a lipid-enriched diet primed the skin for heightened ERV- expression in response to commensal colonization, leading to increased immune responses and tissue inflammation. Together, our results support the idea that the host may have co-opted its endogenous virome as a means to communicate with the exogenous microbiota, resulting in a multi-kingdom dialog that controls both tissue homeostasis and inflammation.

FGFR2/STAT3 Signaling Pathway Involves in the Development of MMTV-Related Spontaneous Breast Cancer in TA2 Mice

The Tientsin Albino 2 (TA2) mouse has a high incidence of spontaneous breast cancer (SBC) in the absence of external inducers or carcinogens. The initiation of SBC is related to mouse mammary tumor virus (MMTV) infection and pregnancy. Pathologic analysis showed that breast cancer cells in TA2 mice are triple negative. Our previous study confirmed that fibroblast growth factor receptor 2 (FGFR2) expression increased in SBC tissue compared to that in their corresponding normal breast tissues of TA2 mice. The present study focused on the function of the FGFR2/STAT3 signaling pathway in the initiation of SBC. In this study, the expression of FGF3, FGFR2, STAT3, p-STAT3^Tyr705, and p-STAT3^Ser727 was detected in serum and normal mammary gland tissues of TA2 mice with different number of pregnancies and SBC. The proliferation, invasiveness, and migration abilities of MA-891 cells from TA2 SBC were compared before and after cryptotanshinone and Stattic treatment. Transient siRNA transfection was used to detect the invasiveness, and migration abilities to avoid the off-targets effects. Downstream protein expression of STAT3 was also detected in MA-891 cells and TA2 xenografts from MA-891 inoculation. In addition, STAT3 expression was analyzed in 139 cases of human breast cancer including 117 cases of non-triple negative breast cancer (non-TNBC) (group I) and 22 cases of triple-negative breast cancer (TNBC) (group II). Results of our study confirmed that MMTV-LTR amplification, and FGFR2, p-STAT3^Tyr705, p-STAT3^Ser727 expression increased with the number of pregnancies in the breast tissue of TA2 mice and were the highest in SBC. Serum FGF3 expression of SBC was higher than it of TA2 mice with different number of pregnancies. After STAT3 was inhibited, the abilities of proliferation, invasiveness, and migration in MA-891 decreased and the expression levels of STAT3, p-STAT3^Ser727, p-STAT3^Tyr705, Bcl2, cyclin D1, and c-myc in MA-891 and animal xenografts were also down-regulated. In human breast cancer, STAT3 expression was significantly higher in TNBC than that in non-TNBC. Our results showed that the FGFR2/STAT3 signaling pathway may be related to SBC initiation in TA2 mice. Inhibition of STAT3 can decrease proliferation, invasiveness, and migration in MA-891 cells and the growth of TA2 xenografts.

Stromal immunoglobulin κC expression is associated with initiation of breast cancer in TA2 mice and human breast cancer

The initiation of spontaneous breast cancer (SBC) in Tientsin Albino 2 (TA2) mice is related to mouse mammary tumor virus (MMTV) infection, and MMTV amplification is hormonally regulated. To explore the insertion site of MMTVLTR in TA2 mouse genome, reverse PCR and nested PCR were used to amplify the unknown sequence on both sides of the MMTV‐LTRSAG gene in SBC and normal breast tissue of TA2 mice. Furthermore, the clinicopathological significance of the insertion site was evaluated in 43 samples of normal breast tissue, 46 samples of breast cystic hyperplasia, 54 samples of ductal carcinoma in situ, 142 samples of primary breast cancer and 47 samples of lymph node metastatic breast cancer by RNA in situ hybridization. We confirmed that the insertion site of the MMTV‐LTRSAG gene was located between Igκv2‐112 and Igκv14‐111 in chromosome 6 of TA2 mouse. IGκC was localized in the stromal cells of TA2 mouse with SBC and in human breast cancer tissues. Tumor cells were negative for IGκC in RNA in situ hybridization. The positive staining index of IGκC in stromal cells was the highest in lymph node metastatic breast cancer, followed by primary breast cancer, ductal carcinoma in situ, and breast cystic hyperplasia. Furthermore, the positive staining index of IGκC was related to the expression of ER, PR, HER2 and Ki‐67. Our findings showed that stromal IGκC expression was associated with the initiation of SBC in TA2 mice. IGκC may be a high‐risk factor for the initiation and progression of human breast cancer.

The role of β-catenin in the initiation and metastasis of TA2 mice spontaneous breast cancer

Purpose: Tientsin Albino 2 (TA2) mice have a high incidence of spontaneous breast cancer. Tumor initiation is related to mouse mammary tumor virus (MMTV) infection. MMTV is hormonally regulated and may promote tumor formation via Wnt/β-catenin signaling pathway. This study attempts to clarify the relationship between β-catenin expression and the initiation and metastasis of spontaneous breast cancer in TA2 mice.

Materials and Methods: Pathological samples illustrating the development of spontaneous breast cancer in TA2 mice were collected and the presence of virus particles was verified in the cancer tissue by electron microscope. Expression of Wnt/β-catenin signaling-pathway-related proteins including β-catenin, Wnt 5a, GSK-3β, and cyclin D1 were detected. MA-891 cell line derived from TA2 spontaneous breast cancer was cultured and siRNA was used to inhibit the expression of β-catenin in the primary culture cell line. Cell cycle analyses and comparisons of the invasiveness and migration capability of tumor cells were performed before and after β-catenin inhibition. Downstream protein expression of β-catenin was studied by western blot, co-immunoprecipitation assay. Tumorigenesis and metastasis were compared with that of negative control, siRNA control, and siRNA β-catenin-1512. Furthermore, proteins related to the proliferation and invasion of tumor were detected by western blot.

Results: β-catenin expression was found to be located in the membrane and cytoplasm in normal mammary tissue and precancerous lesions, respectively. However, in the breast cancer tissue, β-catenin expression was located in the nuclei. After transfection with siRNA-1512, the cells showed decreased proliferation, invasiveness and migration capability, tumorigenicity, and metastasis, and the expression of the proteins related to tumor proliferation and metastasis such as c-myc, Cyclin D1, MMP-9, and VEGF were down-regulated.

Conclusion: These results confirmed that the expression and location of β-catenin were associated with the initiation and metastasis of spontaneous breast cancer in TA2 mice.

Combined treatment of glibenclamide and CoCl2 decreases MMP9 expression and inhibits growth in highly metastatic breast cancer

Background

To observe the influence of combination treatment with glibenclamide and CoCl₂ on the growth and invasiveness of TA2 breast cancer, and to detect the protein and mRNA expression of MMP9.

Methods

50 adult female TA2 mice were randomly divided into 5 groups including DMSO control, CoCl_2, glibenclamide, CoCl₂ + glibenclamide and paclitaxel. All of these mice were inoculated with TA2 spontaneous breast cancer cells in the left groin. Nine days after inoculation the tumor could be palpated. Different treatments for each group were then subcutaneously administered near the tumors on the 9th and 14th days after injection. Tumor size was measured to determine the growth curve. All mice were sacrificed on the 18th day after initial inoculation and tumor tissues were collected. Some fresh tissues without necrosis were stored at −80°C for mRNA detection and the other tumor tissue was fixed with 10% formalin for H&E and immunohistochemical staining.

Results

The growth rate of tumor cells in the CoCl₂ + glibenclamide group was lower than that seen in the other groups. On the 14th day, the average volume of tumor in the CoCl₂ + glibenclamide group was the lowest and the difference has statistical significance (P < 0.05), while the differences among the CoCl₂, glibenclamide and paclitaxel had no statistical significance. The mean percentage of cells expressing MMP9 and PCNA was the lowest in the CoCl₂ + glibenclamide group (P < 0.05). MMP9 mRNA expression paralleled MMP9 protein expression in these groups (P < 0.05).

Conclusions

Combined treatment with glibenclamide and CoCl₂ inhibits TA2 spontaneous breast cancer growth and invasiveness with effects similar to paclitaxel.