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Sub-lethal radiation enhances anti-tumor immunotherapy in a transgenic mouse model of pancreatic cancer.

Cao ZA, Daniel D, Hanahan D - BMC Cancer (2002)

Bottom Line: In either intervention or regression, the transfer of Tag-specific T cells alone did not result in significant lymphocyte infiltration into solid tumors, not did it affect tumor growth or host survival.In contrast, the combination therapy resulted in significant reduction in tumor burden, increase in lymphocyte infiltration into solid tumors, and extension of survival.Our data suggest that such resistance can be disrupted by sub-lethal radiation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biochemistry, Diabetes and Comprehensive Cancer Centers, University of California at San Francisco, San Francisco, CA 94143-0534, USA. alex_cao001@hotmail.com

ABSTRACT

Background: It is not uncommon to observe circulating tumor antigen-specific T lymphocytes in cancer patients despite a lack of significant infiltration and destruction of their tumors. Thus, an important goal for tumor immunotherapy is to identify ways to modulate in vivo anti-tumor immunity to achieve clinical efficacy. We investigate this proposition in a spontaneous mouse tumor model, Rip1-Tag2.

Methods: Experimental therapies were carried out in two distinctive trial designs, intended to either intervene in the explosive growth of small tumors, or regress bulky end-stage tumors. Rip1-Tag2 mice received a single transfer of splenocytes from Tag-specific, CD4+ T cell receptor transgenic mice, a single sub-lethal radiation, or a combination therapy in which the lymphocyte transfer was preceded by the sub-lethal radiation. Tumor burden, the extent of lymphocyte infiltration into solid tumors and host survival were used to assess the efficacy of these therapeutic approaches.

Results: In either intervention or regression, the transfer of Tag-specific T cells alone did not result in significant lymphocyte infiltration into solid tumors, not did it affect tumor growth or host survival. In contrast, the combination therapy resulted in significant reduction in tumor burden, increase in lymphocyte infiltration into solid tumors, and extension of survival.

Conclusions: The results indicate that certain types of solid tumors may be intrinsically resistant to infiltration and destruction by tumor-specific T lymphocytes. Our data suggest that such resistance can be disrupted by sub-lethal radiation. The combinatorial approach presented here merits consideration in the design of clinical trials aimed to achieve T cell-mediated anti-tumor immunity.

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Adoptive transfer of Tag-specific TCR splenocytes following sub-lethal irradiation results in T cell infiltration of solid tumors. Representative frozen sections of tumors from 16 week old Rip1-Tag2 pancreas were analyzed by immunohistochemistry for CD4, CD8 and CD11c. The transgenic mice were treated as follows: (A-C) untreated, (D-F) TCR splenocytes, (G-I) 600R, and (J-L) 600R + TCR splenocytes. Extensive CD4+ T cell infiltration (A, D, G, J) is observed only in mice receiving both sub-lethal irradiation and adoptively transferred TCR splenocytes (J). When analyzed for infiltration by CD8+ T cells (B, E, H, K), again only tumors from mice treated with the combination therapy showed significant infiltration (K). Dendritic cells, as detected by the antibody to CD11c (C, F, I, L), were observed in all tumors, but mice receiving both 600R (I) and the combination therapy have a greater degree of CD11c+ cell infiltrate (L).
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Figure 3: Adoptive transfer of Tag-specific TCR splenocytes following sub-lethal irradiation results in T cell infiltration of solid tumors. Representative frozen sections of tumors from 16 week old Rip1-Tag2 pancreas were analyzed by immunohistochemistry for CD4, CD8 and CD11c. The transgenic mice were treated as follows: (A-C) untreated, (D-F) TCR splenocytes, (G-I) 600R, and (J-L) 600R + TCR splenocytes. Extensive CD4+ T cell infiltration (A, D, G, J) is observed only in mice receiving both sub-lethal irradiation and adoptively transferred TCR splenocytes (J). When analyzed for infiltration by CD8+ T cells (B, E, H, K), again only tumors from mice treated with the combination therapy showed significant infiltration (K). Dendritic cells, as detected by the antibody to CD11c (C, F, I, L), were observed in all tumors, but mice receiving both 600R (I) and the combination therapy have a greater degree of CD11c+ cell infiltrate (L).

Mentions: Because the combination of sub-lethal radiation and TCR splenocyte transfer lead to significant reduction in tumor burden in both intervention and regression trials, we asked whether the radiation had increased the number of tumor-infiltrating lymphocytes. Tissue samples were collected three weeks after treatment in the regression trial. Immunohistochemistry was used to detect CD4+, CD8+ and CD11c+ cell infiltration into the tumors. Because Rip1-Tag2 mice are inherently tolerant to Tag, little infiltration by either T lymphocytes or dendritic cells was observed in the untreated control group (Figure 3). In agreement with previous observations, little infiltration was detected in Rip1-Tag2 mice receiving TCR splenocyte transfer (Figure 3). Nor did radiation alone elicit T cell infiltration, although a modest increase in CD11c+ dendritic cell infiltration was observed. However, in both intervention and regression trials, significant CD4+ T cell and CD8+ T cell infiltration into hyperplastic/dysplastic islets and tumors was noted in Rip1-Tag2 mice that had received the combination of sub-lethal radiation and adoptive transfer of TCR splenocytes. A modest increase in CD11c+ dendritic cell infiltration was observed in the mice receiving the combination therapy. One should recall that the TCR mice express a CD4-restricted TCR, and thus produce increased numbers of anti-Tag CD4 T cells, and thus we anticipated a bias in numbers toward this T cell type. Indeed, one week after treatment, little CD8+ T infiltration of premalignant or malignant lesions was detected in Rip1-Tag2 mice receiving the combinatorial treatment (data not shown). However, three weeks after combinatorial treatment in the regression trial, significant CD8+ T cell infiltration was observed in solid tumors, suggesting a broadening of the T cell response from that contained in the adoptive transfer.


Sub-lethal radiation enhances anti-tumor immunotherapy in a transgenic mouse model of pancreatic cancer.

Cao ZA, Daniel D, Hanahan D - BMC Cancer (2002)

Adoptive transfer of Tag-specific TCR splenocytes following sub-lethal irradiation results in T cell infiltration of solid tumors. Representative frozen sections of tumors from 16 week old Rip1-Tag2 pancreas were analyzed by immunohistochemistry for CD4, CD8 and CD11c. The transgenic mice were treated as follows: (A-C) untreated, (D-F) TCR splenocytes, (G-I) 600R, and (J-L) 600R + TCR splenocytes. Extensive CD4+ T cell infiltration (A, D, G, J) is observed only in mice receiving both sub-lethal irradiation and adoptively transferred TCR splenocytes (J). When analyzed for infiltration by CD8+ T cells (B, E, H, K), again only tumors from mice treated with the combination therapy showed significant infiltration (K). Dendritic cells, as detected by the antibody to CD11c (C, F, I, L), were observed in all tumors, but mice receiving both 600R (I) and the combination therapy have a greater degree of CD11c+ cell infiltrate (L).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC113758&req=5

Figure 3: Adoptive transfer of Tag-specific TCR splenocytes following sub-lethal irradiation results in T cell infiltration of solid tumors. Representative frozen sections of tumors from 16 week old Rip1-Tag2 pancreas were analyzed by immunohistochemistry for CD4, CD8 and CD11c. The transgenic mice were treated as follows: (A-C) untreated, (D-F) TCR splenocytes, (G-I) 600R, and (J-L) 600R + TCR splenocytes. Extensive CD4+ T cell infiltration (A, D, G, J) is observed only in mice receiving both sub-lethal irradiation and adoptively transferred TCR splenocytes (J). When analyzed for infiltration by CD8+ T cells (B, E, H, K), again only tumors from mice treated with the combination therapy showed significant infiltration (K). Dendritic cells, as detected by the antibody to CD11c (C, F, I, L), were observed in all tumors, but mice receiving both 600R (I) and the combination therapy have a greater degree of CD11c+ cell infiltrate (L).
Mentions: Because the combination of sub-lethal radiation and TCR splenocyte transfer lead to significant reduction in tumor burden in both intervention and regression trials, we asked whether the radiation had increased the number of tumor-infiltrating lymphocytes. Tissue samples were collected three weeks after treatment in the regression trial. Immunohistochemistry was used to detect CD4+, CD8+ and CD11c+ cell infiltration into the tumors. Because Rip1-Tag2 mice are inherently tolerant to Tag, little infiltration by either T lymphocytes or dendritic cells was observed in the untreated control group (Figure 3). In agreement with previous observations, little infiltration was detected in Rip1-Tag2 mice receiving TCR splenocyte transfer (Figure 3). Nor did radiation alone elicit T cell infiltration, although a modest increase in CD11c+ dendritic cell infiltration was observed. However, in both intervention and regression trials, significant CD4+ T cell and CD8+ T cell infiltration into hyperplastic/dysplastic islets and tumors was noted in Rip1-Tag2 mice that had received the combination of sub-lethal radiation and adoptive transfer of TCR splenocytes. A modest increase in CD11c+ dendritic cell infiltration was observed in the mice receiving the combination therapy. One should recall that the TCR mice express a CD4-restricted TCR, and thus produce increased numbers of anti-Tag CD4 T cells, and thus we anticipated a bias in numbers toward this T cell type. Indeed, one week after treatment, little CD8+ T infiltration of premalignant or malignant lesions was detected in Rip1-Tag2 mice receiving the combinatorial treatment (data not shown). However, three weeks after combinatorial treatment in the regression trial, significant CD8+ T cell infiltration was observed in solid tumors, suggesting a broadening of the T cell response from that contained in the adoptive transfer.

Bottom Line: In either intervention or regression, the transfer of Tag-specific T cells alone did not result in significant lymphocyte infiltration into solid tumors, not did it affect tumor growth or host survival.In contrast, the combination therapy resulted in significant reduction in tumor burden, increase in lymphocyte infiltration into solid tumors, and extension of survival.Our data suggest that such resistance can be disrupted by sub-lethal radiation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biochemistry, Diabetes and Comprehensive Cancer Centers, University of California at San Francisco, San Francisco, CA 94143-0534, USA. alex_cao001@hotmail.com

ABSTRACT

Background: It is not uncommon to observe circulating tumor antigen-specific T lymphocytes in cancer patients despite a lack of significant infiltration and destruction of their tumors. Thus, an important goal for tumor immunotherapy is to identify ways to modulate in vivo anti-tumor immunity to achieve clinical efficacy. We investigate this proposition in a spontaneous mouse tumor model, Rip1-Tag2.

Methods: Experimental therapies were carried out in two distinctive trial designs, intended to either intervene in the explosive growth of small tumors, or regress bulky end-stage tumors. Rip1-Tag2 mice received a single transfer of splenocytes from Tag-specific, CD4+ T cell receptor transgenic mice, a single sub-lethal radiation, or a combination therapy in which the lymphocyte transfer was preceded by the sub-lethal radiation. Tumor burden, the extent of lymphocyte infiltration into solid tumors and host survival were used to assess the efficacy of these therapeutic approaches.

Results: In either intervention or regression, the transfer of Tag-specific T cells alone did not result in significant lymphocyte infiltration into solid tumors, not did it affect tumor growth or host survival. In contrast, the combination therapy resulted in significant reduction in tumor burden, increase in lymphocyte infiltration into solid tumors, and extension of survival.

Conclusions: The results indicate that certain types of solid tumors may be intrinsically resistant to infiltration and destruction by tumor-specific T lymphocytes. Our data suggest that such resistance can be disrupted by sub-lethal radiation. The combinatorial approach presented here merits consideration in the design of clinical trials aimed to achieve T cell-mediated anti-tumor immunity.

Show MeSH
Related in: MedlinePlus