The relationship of histamine H2 receptor-bearing suppressor cells with the growth and metastasis of FANFT-induced bladder cancer

Cimetidine down-regulates stability of Foxp3 protein via Stub1 in Treg cells

Foxp3-expressing Treg cells have been well documented to provide immune regulation by promoting immune tolerance and suppressing immune over-reaction. Cimetidine (CIM), used to inhibit stomach acid secretion, has been reported to promote immune responses and suppress Treg cell function in several studies. However, the underlying mechanism is unknown. To investigate CIM effects on the suppressive function of Treg and Foxp3, here we used CIM to stimulate human CD4⁺CD25⁺ Treg cells and Jurkat T cells and evaluated changes of Foxp3 expression and stability. Our data showed that CIM leads to a reduction of Foxp3 via E3 ligase Stub1-mediated proteosomal degradation, which is dependent on an activated PI3K-AKT-mTOR pathway. Thus, CIM affects the suppressive function of Treg cells by destabilizing their Foxp3 expression.

Novel enhanced lung-colonizing variant of murine MBT-2 bladder cancer cells

OBJECTIVES

To develop an enhanced lung-colonizing variant of murine bladder cancer that will allow the mechanism of metastasis to be studied more readily.

METHODS

We implanted murine bladder tumor cells (MBT-2) into the leg muscles of C3H mice. We developed variant cells from a lung metastasis nodule. We compared the MBT-2 cells and variant cells (MBT-2V) in vivo by evaluating lung nodule formation, survival, in vitro adhesion, and migration-invasion assays. Zymography and semiquantitative reverse transcriptase-polymerase chain reaction analyses were also performed to characterize the metastatic ability of both cells.

RESULTS

MBT-2 and MBT-2V cells were tumorigenic when injected intramuscularly into C3H mice, but MBT-2 cells had little potential to metastasize compared with MBT-2V cells. Metastases were observed in the lungs of mice injected in the tail vein with MBT-2 and MBT-2V cells. Mice receiving MBT-2V cells had significantly shorter survival (P <0.01) and more lung nodules (245 versus 106, P <0.0001) than those receiving MBT-2 cells. In vitro study revealed that MBT-2V cells exhibited more adhesion, greater migration, and more invasiveness than did MBT-2 cells. Pathologic examination revealed the tumors from MBT-2V cells to be more aggressive than those from MBT-2 cells. MBT-2V also showed significantly greater matrix metalloproteinase-9 expression.

CONCLUSIONS

We generated an enhanced lung-colonizing variant of MBT-2 cells. Our MBT-2V cells showed more aggressive and invasive metastatic ability than that of the MBT-2 cells. Zymography and reverse transcriptase-polymerase chain reaction analyses indicated that matrix metalloproteinase-9 might be associated with the metastatic ability of MBT-2V cells.

Influence of transplantation site on metastatic ability of mouse bladder carcinoma sublines

The influence of the primary implantation site on the metastatic behavior of a murine transitional cell carcinoma line (MBT-2) and three metastatic sublines (L3F1, L3F2, and L3F3) was studied. The parent MBT-2 cell line produced a low incidence of lung metastasis after intravenous injection and no metastases from the primary tumor when injected either subcutaneously in the right hind flank or in the footpad. Intramuscular implantation of the MBT-2 cells in the right hind flank resulted in a significant increase over the subcutaneous, footpad, and intravenous sites in the incidence and number of lung metastases. Three in vivo/in vitro selected metastatic sublines (L3F1, L3F2, and L3F3) were highly metastatic when injected subcutaneously, intramuscularly, and intravenously. A low number of pulmonary metastases was observed after footpad implantation of the three sublines. This study demonstrated a definite implantation site-influence on the metastatic ability of the parent MBT-2 line and the three selected sublines. Intramuscular implantation was the most permissive implantation site for the development of spontaneous metastasis for the MBT-2 line and the L3F1, L3F2, and L3F3 sublines.

Isolation and characterization of metastatic sublines from a murine transitional cell bladder carcinoma

Four sublines of a murine N-[4-(5-nitro-2-furyl)-2-thiazolyl]-foramide (FANFT)-induced transitional cell carcinoma (MBT-2) possessing spontaneous metastatic ability were isolated via in vivo/in vitro serial selection of metastatic lung lesions. Subcutaneous inoculation of the parent cell line (MBT-2) produced primary tumors when injected into C3H mice. These primary tumors rarely metastasize. A subline designated L3F1 was established from 1 MBT-2 pulmonary metastatic tumor. Further in vivo/in vitro selections established three additional sublines designated L3F2, L3F3 and L3F4. Serial selection resulted in MBT-2 sublines of greater metastatic potential in terms of both incidence of metastasis and the number of metastatic tumors per lung. The parent line differed from the four sublines in metastatic potential, in vitro cell morphology, and in vitro growth parameters. The L3F2 subline was examined for the time of onset of metastasis by removal of the primary tumor. Metastasis of the subcutaneously transplanted tumor occurred between 14 and 21 days after injection of the L3F2 subline. The L3F2 primary tumors and lung metastases were morphologically characterized by light and electron microscopy.