Posttransplant administration of cyclophosphamide and donor lymphocyte infusion induces potent antitumor immunity to solid tumor.
OBJECTIVE
Nonmyeloablative allogeneic stem cell transplantation (SCT) has been increasingly used for the treatment of hematologic and solid malignancies, and mature donor T cells are considered to be the main effectors of the graft-versus-tumor (GVT) activity. However, the association between degree of donor chimerism and intensity of GVT effects has not been fully elucidated. We recently proposed a unique nonmyeloablative cell therapy using posttransplant cyclophosphamide and donor lymphocyte infusion, by which a significant antitumor effect against murine renal cell carcinoma, RENCA, was induced, although the level of mixed chimerism was relatively low. In this study, we attempted to clarify a role of chimerism for in vivo antitumor effects on GVT effects in radiation-associated nonmyeloablative SCT.


METHODS
We assessed antitumor effects on RENCA tumors and the degree of donor chimerism after several doses of irradiation followed by allogeneic SCT and compared the results with those of cyclophosphamide-based cell therapy.


RESULTS
Allogeneic SCT following sublethal irradiation (6 Gy) induced almost complete donor chimerism, whereas cyclophosphamide-based cell therapy produced low levels of donor chimerism. Nonetheless, GVT activity was much more potent in cyclophosphamide-based cell therapy than irradiation-conditioned SCT. Furthermore, cyclophosphamide-conditioned SCT induced more potent immune reconstitution with less severe graft-versus-host disease than irradiation-conditioned SCT.


CONCLUSIONS
Our results indicate that a high level of chimerism is not essential for the in vivo antitumor effect of nonmyeloablative allogeneic cell therapy against solid tumor and that the recovery of peripheral lymphocytes after the initial immunosuppression might be a critical event for the elicitation of in vivo antitumor effects of that treatment modality.
Eto
Masatoshi
M
Department of Urology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan. etom@uro.med.kyushu-u.ac.jp
Kamiryo
Yoriyuki
Y
Takeuchi
Ario
A
Harano
Masahiko
M
Tatsugami
Katsunori
K
Harada
Mamoru
M
Kiyoshima
Keijiro
K
Hamaguchi
Masumitsu
M
Teshima
Takanori
T
Tsuneyoshi
Masazumi
M
Yoshikai
Yasunobu
Y
Naito
Seiji
S
D000818:Animals; D002292:Carcinoma, Renal Cell / Q000139:chemically induced / Q000276:immunology* / Q000378:metabolism / Q000628:therapy; D046528:Chimerism; D003131:Combined Modality Therapy; D003520:Cyclophosphamide / Q000008:administration & dosage*; D005260:Female; D006086:Graft vs Host Disease; D020350:Graft vs Tumor Effect; D018380:Hematopoietic Stem Cell Transplantation; D007166:Immunosuppressive Agents / Q000008:administration & dosage* / Q000494:pharmacology; D007680:Kidney Neoplasms / Q000139:chemically induced / Q000276:immunology* / Q000378:metabolism / Q000628:therapy; D017710:Lymphocyte Transfusion; D051379:Mice; D008807:Mice, Inbred BALB C; D008811:Mice, Inbred DBA; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D019172:Transplantation Conditioning
D007166:Immunosuppressive Agents; D003520:Cyclophosphamide