Limits...
Rapamycin Promotes Mouse 4T1 Tumor Metastasis that Can Be Reversed by a Dendritic Cell-Based Vaccine.

Lin TJ, Liang WM, Hsiao PW, M S P, Wei WC, Lin HT, Yin SY, Yang NS - PLoS ONE (2015)

Bottom Line: Suppression of tumor metastasis is a key strategy for successful cancer interventions.However, rapamycin also exhibits immunosuppressant effects and is hence used clinically as an organ transplantation drug.We hypothesized that the immunosuppressive activities of rapamycin might also negatively mediate host immunity, resulting in promotion of tumor metastasis.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Injury Prevention and Control, Taipei Medical University, Taipei, Taiwan, ROC; Department of Neurosurgery, Taipei Medical University-Wan Fang Hospital, Taipei, Taiwan, ROC; Agricultural Biotechnology Research Center, Academia Sinica, Taipei, Taiwan, ROC; Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, Taiwan, ROC; Taiwan International Graduate Program (TIGP), Molecular and Biological Agricultural Sciences Program, Academia Sinica, Taipei, Taiwan, ROC.

ABSTRACT
Suppression of tumor metastasis is a key strategy for successful cancer interventions. Previous studies indicated that rapamycin (sirolimus) may promote tumor regression activity or enhance immune response against tumor targets. However, rapamycin also exhibits immunosuppressant effects and is hence used clinically as an organ transplantation drug. We hypothesized that the immunosuppressive activities of rapamycin might also negatively mediate host immunity, resulting in promotion of tumor metastasis. In this study, the effects of rapamycin and phytochemical shikonin were investigated in vitro and in vivo in a 4T1 mouse mammary tumor model through quantitative assessment of immunogenic cell death (ICD), autophagy, tumor growth and metastasis. Tumor-bearing mice were immunized with test vaccines to monitor their effect on tumor metastasis. We found that intraperitoneal (ip) administration of rapamycin after a tumor-resection surgery drastically increased the metastatic activity of 4T1 tumors. Possible correlation of this finding to human cancers was suggested by epidemiological analysis of data from Taiwan's National Health Insurance Research Database (NHIRD). Since our previous studies showed that modified tumor cell lysate (TCL)-pulsed, dendritic cell (DC)-based cancer vaccines can effectively suppress metastasis in mouse tumor models, we assessed whether such vaccines may help offset this rapamycin-promoted metastasis. We observed that shikonin efficiently induced ICD of 4T1 cells in culture, and DC vaccines pulsed with shikonin-treated TCL (SK-TCL-DC) significantly suppressed rapamycin-enhanced metastasis and Treg cell expansion in test mice. In conclusion, rapamycin treatment in mice (and perhaps in humans) promotes metastasis and the effect may be offset by treatment with a DC-based cancer vaccine.

No MeSH data available.


Related in: MedlinePlus

SK-TCL-activated DCs can suppress rapamycin-enhanced MDSC and Treg cell expansion in vivo.(A), Effect of various DC vaccines on population change of monocytic and granulocytic MDSCs in blood of test mice, quantified using flow cytometry. The monocytic and granulocytic subpopulations of MDSCs were analyzed using a FACS system and DIVA software as gated on CD11b++Ly6C++ and CD11b++Ly6G++ cells, respectively. (B), Suppression of Treg cells in rapamycin-treated mice which were subsequently immunized with or without test DC vaccines. Six days post the last vaccination, test cells were isolated from the blood of normal and various rapamycin-treated mice. The populations of Treg cells were quantified using FACS DIVA analysis and gated on CD4+CD25+ (pan-phenotype of Treg cells) and Foxp3+CD25+ (phenotype of a specific Treg population with immunosuppressive functions) cells. Normal* denotes mice that were not inoculated with 4T1 tumor cells and hence were not tumor-bearing mice.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4591294&req=5

pone.0138335.g005: SK-TCL-activated DCs can suppress rapamycin-enhanced MDSC and Treg cell expansion in vivo.(A), Effect of various DC vaccines on population change of monocytic and granulocytic MDSCs in blood of test mice, quantified using flow cytometry. The monocytic and granulocytic subpopulations of MDSCs were analyzed using a FACS system and DIVA software as gated on CD11b++Ly6C++ and CD11b++Ly6G++ cells, respectively. (B), Suppression of Treg cells in rapamycin-treated mice which were subsequently immunized with or without test DC vaccines. Six days post the last vaccination, test cells were isolated from the blood of normal and various rapamycin-treated mice. The populations of Treg cells were quantified using FACS DIVA analysis and gated on CD4+CD25+ (pan-phenotype of Treg cells) and Foxp3+CD25+ (phenotype of a specific Treg population with immunosuppressive functions) cells. Normal* denotes mice that were not inoculated with 4T1 tumor cells and hence were not tumor-bearing mice.

Mentions: The importance of Tregs and myeloid derived suppressor cells (MDSCs) in the regulation of tumor growth is well documented.[24–27] We, therefore, went on to analyze the possible effect of the test vaccines on inhibition of MDSC and Treg cells in immunized animals. There are two major subsets of MDSCs, monocytic (CD11b+Ly6C+) and granulocytic (CD11b+Ly6G+) MDSCs. The monocytic cells were previously shown to inhibit T-cell proliferation in vitro, whereas granulocytic MDSCs were reported not to inhibit such activity.[27] In our present study the populations of monocytic and granulocytic MDSCs in blood samples of various DC-vaccinated mice were analyzed and compared at 3 weeks post tumor resection. As shown in Fig 5A, compared with the PBS (vehicle)-treated mice, the CD11b+Ly6C+ and CD11b+Ly6G+ MDSC populations in rapamycin-treated mice were significantly increased, from 56.0% to 66.6% and from 53.6% to 68.1%, respectively. In contrast, DC vaccination (SK-TCL-mDCs) in combination with the in vivo administration of rapamycin subsequently reduced CD11b+Ly6C+ and CD11b+Ly6G+ MDSC populations to 44.9% and 49.7% (33% and 28% decrease), respectively. These levels were even lower than those (56.0% and 53.5% for m-MDSC and g-MDSC, respectively) detected in test mice treated with PBS only, without DC vaccine treatment. However it is important and interesting to note here that the drastic expansion of the granulocytic MDSCs (CD11b+Ly6G+) after 4T1 tumor inoculation (from 5.1% in normal mice to 53.5% in PBS treated mice) was not able to be reversed by the combined treatment of rapamycin and SK-TCL-mDCs (i.e., 49.7%), suggesting that a portion of the tumor metastasis-mediated granulocytic MDSC expansion can not be rescued by the activity of test DC vaccine. This specific portion or level of g-MDSC expansion is apparently not associated or caused by the same mechanism(s) related to the interference of immune cell activities by rapamycin. And, we hence term this activity as rapamycin-independent g-MDSC expression activity during tumor metastasis. This class of tumor-promoted g-MDSC activity is apparently refractile to our present TCL-DC based vaccine therapy. Future studies are needed to dissect the mechanistic mode of action for this class of MDSC activity. When rapamycin treatment was combined with three other DC-vaccine groups (i.e., mDCs, DMSO-TCL-mDCs and SK-AS-mDCs), much less suppressive effect was detected for the rapamycin-enhanced populations of monocytic and granulocytic MDSC cells, as compared to the combined treatment of rapamycin and SK-TCL-mDCs (Fig 5A). These results suggest that only the SK-TCL-mDC vaccination was able to substantially reverse the rapamycin-enhanced monocytic as well as granulocytic MDSC populations.


Rapamycin Promotes Mouse 4T1 Tumor Metastasis that Can Be Reversed by a Dendritic Cell-Based Vaccine.

Lin TJ, Liang WM, Hsiao PW, M S P, Wei WC, Lin HT, Yin SY, Yang NS - PLoS ONE (2015)

SK-TCL-activated DCs can suppress rapamycin-enhanced MDSC and Treg cell expansion in vivo.(A), Effect of various DC vaccines on population change of monocytic and granulocytic MDSCs in blood of test mice, quantified using flow cytometry. The monocytic and granulocytic subpopulations of MDSCs were analyzed using a FACS system and DIVA software as gated on CD11b++Ly6C++ and CD11b++Ly6G++ cells, respectively. (B), Suppression of Treg cells in rapamycin-treated mice which were subsequently immunized with or without test DC vaccines. Six days post the last vaccination, test cells were isolated from the blood of normal and various rapamycin-treated mice. The populations of Treg cells were quantified using FACS DIVA analysis and gated on CD4+CD25+ (pan-phenotype of Treg cells) and Foxp3+CD25+ (phenotype of a specific Treg population with immunosuppressive functions) cells. Normal* denotes mice that were not inoculated with 4T1 tumor cells and hence were not tumor-bearing mice.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4591294&req=5

pone.0138335.g005: SK-TCL-activated DCs can suppress rapamycin-enhanced MDSC and Treg cell expansion in vivo.(A), Effect of various DC vaccines on population change of monocytic and granulocytic MDSCs in blood of test mice, quantified using flow cytometry. The monocytic and granulocytic subpopulations of MDSCs were analyzed using a FACS system and DIVA software as gated on CD11b++Ly6C++ and CD11b++Ly6G++ cells, respectively. (B), Suppression of Treg cells in rapamycin-treated mice which were subsequently immunized with or without test DC vaccines. Six days post the last vaccination, test cells were isolated from the blood of normal and various rapamycin-treated mice. The populations of Treg cells were quantified using FACS DIVA analysis and gated on CD4+CD25+ (pan-phenotype of Treg cells) and Foxp3+CD25+ (phenotype of a specific Treg population with immunosuppressive functions) cells. Normal* denotes mice that were not inoculated with 4T1 tumor cells and hence were not tumor-bearing mice.
Mentions: The importance of Tregs and myeloid derived suppressor cells (MDSCs) in the regulation of tumor growth is well documented.[24–27] We, therefore, went on to analyze the possible effect of the test vaccines on inhibition of MDSC and Treg cells in immunized animals. There are two major subsets of MDSCs, monocytic (CD11b+Ly6C+) and granulocytic (CD11b+Ly6G+) MDSCs. The monocytic cells were previously shown to inhibit T-cell proliferation in vitro, whereas granulocytic MDSCs were reported not to inhibit such activity.[27] In our present study the populations of monocytic and granulocytic MDSCs in blood samples of various DC-vaccinated mice were analyzed and compared at 3 weeks post tumor resection. As shown in Fig 5A, compared with the PBS (vehicle)-treated mice, the CD11b+Ly6C+ and CD11b+Ly6G+ MDSC populations in rapamycin-treated mice were significantly increased, from 56.0% to 66.6% and from 53.6% to 68.1%, respectively. In contrast, DC vaccination (SK-TCL-mDCs) in combination with the in vivo administration of rapamycin subsequently reduced CD11b+Ly6C+ and CD11b+Ly6G+ MDSC populations to 44.9% and 49.7% (33% and 28% decrease), respectively. These levels were even lower than those (56.0% and 53.5% for m-MDSC and g-MDSC, respectively) detected in test mice treated with PBS only, without DC vaccine treatment. However it is important and interesting to note here that the drastic expansion of the granulocytic MDSCs (CD11b+Ly6G+) after 4T1 tumor inoculation (from 5.1% in normal mice to 53.5% in PBS treated mice) was not able to be reversed by the combined treatment of rapamycin and SK-TCL-mDCs (i.e., 49.7%), suggesting that a portion of the tumor metastasis-mediated granulocytic MDSC expansion can not be rescued by the activity of test DC vaccine. This specific portion or level of g-MDSC expansion is apparently not associated or caused by the same mechanism(s) related to the interference of immune cell activities by rapamycin. And, we hence term this activity as rapamycin-independent g-MDSC expression activity during tumor metastasis. This class of tumor-promoted g-MDSC activity is apparently refractile to our present TCL-DC based vaccine therapy. Future studies are needed to dissect the mechanistic mode of action for this class of MDSC activity. When rapamycin treatment was combined with three other DC-vaccine groups (i.e., mDCs, DMSO-TCL-mDCs and SK-AS-mDCs), much less suppressive effect was detected for the rapamycin-enhanced populations of monocytic and granulocytic MDSC cells, as compared to the combined treatment of rapamycin and SK-TCL-mDCs (Fig 5A). These results suggest that only the SK-TCL-mDC vaccination was able to substantially reverse the rapamycin-enhanced monocytic as well as granulocytic MDSC populations.

Bottom Line: Suppression of tumor metastasis is a key strategy for successful cancer interventions.However, rapamycin also exhibits immunosuppressant effects and is hence used clinically as an organ transplantation drug.We hypothesized that the immunosuppressive activities of rapamycin might also negatively mediate host immunity, resulting in promotion of tumor metastasis.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Injury Prevention and Control, Taipei Medical University, Taipei, Taiwan, ROC; Department of Neurosurgery, Taipei Medical University-Wan Fang Hospital, Taipei, Taiwan, ROC; Agricultural Biotechnology Research Center, Academia Sinica, Taipei, Taiwan, ROC; Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, Taiwan, ROC; Taiwan International Graduate Program (TIGP), Molecular and Biological Agricultural Sciences Program, Academia Sinica, Taipei, Taiwan, ROC.

ABSTRACT
Suppression of tumor metastasis is a key strategy for successful cancer interventions. Previous studies indicated that rapamycin (sirolimus) may promote tumor regression activity or enhance immune response against tumor targets. However, rapamycin also exhibits immunosuppressant effects and is hence used clinically as an organ transplantation drug. We hypothesized that the immunosuppressive activities of rapamycin might also negatively mediate host immunity, resulting in promotion of tumor metastasis. In this study, the effects of rapamycin and phytochemical shikonin were investigated in vitro and in vivo in a 4T1 mouse mammary tumor model through quantitative assessment of immunogenic cell death (ICD), autophagy, tumor growth and metastasis. Tumor-bearing mice were immunized with test vaccines to monitor their effect on tumor metastasis. We found that intraperitoneal (ip) administration of rapamycin after a tumor-resection surgery drastically increased the metastatic activity of 4T1 tumors. Possible correlation of this finding to human cancers was suggested by epidemiological analysis of data from Taiwan's National Health Insurance Research Database (NHIRD). Since our previous studies showed that modified tumor cell lysate (TCL)-pulsed, dendritic cell (DC)-based cancer vaccines can effectively suppress metastasis in mouse tumor models, we assessed whether such vaccines may help offset this rapamycin-promoted metastasis. We observed that shikonin efficiently induced ICD of 4T1 cells in culture, and DC vaccines pulsed with shikonin-treated TCL (SK-TCL-DC) significantly suppressed rapamycin-enhanced metastasis and Treg cell expansion in test mice. In conclusion, rapamycin treatment in mice (and perhaps in humans) promotes metastasis and the effect may be offset by treatment with a DC-based cancer vaccine.

No MeSH data available.


Related in: MedlinePlus