Rapamycin delays growth of Wnt-1 tumors in spite of suppression of host immunity

<p>Abstract</p> <p>Background</p> <p>Rapamycin, an inhibitor of mammalian target of Rapamycin (mTOR), is an immunosuppressive agent that has anti-proliferative effects on some tumors. However, the role of Rapamycin-induced immune suppression on tumor progression has not been examined.</p> <p>Methods</p> <p>We developed a transplantation model for generation of mammary tumors in syngeneic recipients that can be used to address the role of the immune system on tumor progression. We examined the effect of Rapamycin on the immune system and growth of MMTV-driven Wnt-1 mammary tumors which were transplanted into irradiated and bone marrow-reconstituted, or naïve mice.</p> <p>Results</p> <p>Rapamycin induced severe immunosuppression and significantly delayed the growth of Wnt-1 tumors. T cell depletion in spleen and thymus and reduction in T cell cytokine secretion were evident within 7 days of therapy. By day 20, splenic but not thymic T cell counts, and cytokine secretion recovered. We determined whether adoptive T cell therapy enhances the anti-cancer effect using <it>ex vivo </it>generated Rapamycin-resistant T cells. However, T cell transfer during Rapamycin therapy did not improve the outcome relative to drug therapy alone. Thus, we could not confirm that suppression of T cell immunity contributes to tumor growth in this model. Consistent with suppression of the mTOR pathway, decreased 4E-BP1, p70 S6-kinase, and S6 protein phosphorylation correlated with a decrease in Wnt-1 tumor cell proliferation.</p> <p>Conclusion</p> <p>Rapamycin has a direct anti-tumor effect on Wnt-1 breast cancer <it>in vivo </it>that involves inhibition of the mTOR pathway at doses that also suppress host immune responses.</p

Rapamycin delays growth of Wnt-1 tumors in spite of suppression of host immunity-6

F Wnt-1 tumor cells were incubated for 72 hours with or without 1 μM of Rapamycin. Wnt-1 cells were incubated overnight to achieve adherent state before Rapamycin addition. Average percent of cells in G1, G2, and S phases from 3 independent experiments is shown. Significant differences (p < 0.02) are indicated by the bars.<p><b>Copyright information:</b></p><p>Taken from "Rapamycin delays growth of Wnt-1 tumors in spite of suppression of host immunity"</p><p>http://www.biomedcentral.com/1471-2407/8/176</p><p>BMC Cancer 2008;8():176-176.</p><p>Published online 21 Jun 2008</p><p>PMCID:PMC2453140.</p><p></p

Rapamycin delays growth of Wnt-1 tumors in spite of suppression of host immunity-5

Cubated with or without 1 μM Rapamycin for 24 hours, labeled with DiOCand stained with annexinV-APC. Representative contour plots for splenocytes and Wnt-1 culture are shown. Apoptotic cells are gated in a square in each panel. C. Percent of apoptotic cells (mean ± SD) is shown for 5 spleens and 6 Wnt-1 cultures. D and E. Expression of Fas on Wnt-1 cells (D) or activated splenocytes (E).<p><b>Copyright information:</b></p><p>Taken from "Rapamycin delays growth of Wnt-1 tumors in spite of suppression of host immunity"</p><p>http://www.biomedcentral.com/1471-2407/8/176</p><p>BMC Cancer 2008;8():176-176.</p><p>Published online 21 Jun 2008</p><p>PMCID:PMC2453140.</p><p></p

Rapamycin delays growth of Wnt-1 tumors in spite of suppression of host immunity-3

T-1 tumor cells. C and D. Proliferation of normal CD3/28 activated splenocytes (pooled from 5 mice) (C) or primary Wnt-1 cells from 3 different tumors (D). Cells were incubated with 1 μM of Rapamycin for 72 hours and proliferation was measured by H-thymidine incorporation.<p><b>Copyright information:</b></p><p>Taken from "Rapamycin delays growth of Wnt-1 tumors in spite of suppression of host immunity"</p><p>http://www.biomedcentral.com/1471-2407/8/176</p><p>BMC Cancer 2008;8():176-176.</p><p>Published online 21 Jun 2008</p><p>PMCID:PMC2453140.</p><p></p

Rapamycin delays growth of Wnt-1 tumors in spite of suppression of host immunity-0

Of irradiated and bone marrow reconstituted (XRT, n = 10/group) (A and B) or naïve (no XRT, n = 5/group) mice (C). D. Summary of the effect of irradiation and bone marrow reconstitution on the growth of Wnt-1 tumors implanted subcutaneously (S.C.) or into MFP. Data are presented as tumor volume at day 60 for s.c. and at day 50 for MFP after implantation. Mice were treated with 1.5 mg/kg of Rapamycin for 30 days in s.c. groups (A and D) or 20 days in MFP groups (B, C and D) starting the day after tumor implantation (arrows). Tumor size was calculated as described in Methods.<p><b>Copyright information:</b></p><p>Taken from "Rapamycin delays growth of Wnt-1 tumors in spite of suppression of host immunity"</p><p>http://www.biomedcentral.com/1471-2407/8/176</p><p>BMC Cancer 2008;8():176-176.</p><p>Published online 21 Jun 2008</p><p>PMCID:PMC2453140.</p><p></p

Rapamycin delays growth of Wnt-1 tumors in spite of suppression of host immunity-1

With Rapamycin in vivo for 7 and 20 days (n = 5/group). B and C. Spontaneous apoptosis in splenocytes from mice treated for 7 days with Rapamycin (B) or control mice (C). D. Cytokine production by CD3/CD28 stimulated splenocytes from control and Rapamycin treated mice at days 7 and 20 post treatment.<p><b>Copyright information:</b></p><p>Taken from "Rapamycin delays growth of Wnt-1 tumors in spite of suppression of host immunity"</p><p>http://www.biomedcentral.com/1471-2407/8/176</p><p>BMC Cancer 2008;8():176-176.</p><p>Published online 21 Jun 2008</p><p>PMCID:PMC2453140.</p><p></p

Rapamycin delays growth of Wnt-1 tumors in spite of suppression of host immunity-7

Of irradiated and bone marrow reconstituted (XRT, n = 10/group) (A and B) or naïve (no XRT, n = 5/group) mice (C). D. Summary of the effect of irradiation and bone marrow reconstitution on the growth of Wnt-1 tumors implanted subcutaneously (S.C.) or into MFP. Data are presented as tumor volume at day 60 for s.c. and at day 50 for MFP after implantation. Mice were treated with 1.5 mg/kg of Rapamycin for 30 days in s.c. groups (A and D) or 20 days in MFP groups (B, C and D) starting the day after tumor implantation (arrows). Tumor size was calculated as described in Methods.<p><b>Copyright information:</b></p><p>Taken from "Rapamycin delays growth of Wnt-1 tumors in spite of suppression of host immunity"</p><p>http://www.biomedcentral.com/1471-2407/8/176</p><p>BMC Cancer 2008;8():176-176.</p><p>Published online 21 Jun 2008</p><p>PMCID:PMC2453140.</p><p></p