Immunoprotection against murine bladder carcinoma by octaarginine-modified liposomes incorporating cell wall of Mycobacterium bovis bacillus Calmette-Guérin.
OBJECTIVE
To develop a prototype of a non-live bacterial agent that consists of a cell wall (CW) preparation from heat-killed bacillus Calmette-Guérin (BCG-CW) incorporated into octaarginine-modified cationized liposomes as a vector (R8-liposome-BCG-CW), and to evaluate its immunoprotective potentiation in mice, as although BCG is an established effective immunotherapy for nonmuscle-invasive bladder cancer, more active and less toxic treatments are needed.


METHODS
The cellular interaction of R8-liposome-BCG-CW co-cultured with mouse bladder cancer cell line (MBT-2) was examined by confocal laser scanning microscopy. MBT-2 cells (7 x 10(5)) were subcutaneously inoculated with 1 mg BCG, 0.1 mg or 1 mg BCG-CW, 0.1 mg or 1 mg R8-liposome-BCG-CW in female C3H/HeN mice. The MBT-2 cells pretreated with BCG or R8-liposome-BCG-CW were re-challenged at 6 weeks. The sizes of the primary and re-challenged tumours were evaluated at 4 and 10 weeks, respectively.


RESULTS
Confocal laser scanning microscopy showed the enhanced incorporation of R8-liposome-BCG-CW into MBT-2 cells after 1 h of co-incubation. 0.1 mg R8-liposome-BCG-CW completely inhibited the growth of MBT-2 tumours while 0.1 mg BCG-CW alone did not (P = 0.002). Mice vaccinated with a mixture of MBT-2 cells and R8-liposome-BCG-CW inhibited the growth of re-challenged tumour of MBT-2 cells pretreated with BCG or R8-liposome-BCG-CW but did not inhibit that of MBT-2 cells with no pretreatment at 10 weeks, with mean (sd) tumours sizes of 54 (60) mm(2) (P < 0.001) or 69 (43) mm(2) (P = 0.003) compared with 309 (125) mm(2), respectively.


CONCLUSIONS
The immunotherapeutic potential of BCG-CW was enhanced by improving cellular association using the R8-liposomes delivery system. Development of this non-live bacterial agent may contribute to providing a more active and less toxic tool as a substitute for live BCG as immunotherapy against nonmuscle-invasive bladder cancer in the future.
Joraku
Akira
A
Graduate School of Comprehensive Human Sciences, Department of Urology, University of Tsukuba, Tsukuba, Ibaraki, Japan. ajoraku@md.tsukuba.ac.jp
Homhuan
Atthachai
A
Kawai
Koji
K
Yamamoto
Takahiro
T
Miyazaki
Jun
J
Kogure
Kentaro
K
Yano
Ikuya
I
Harashima
Hideyoshi
H
Akaza
Hideyuki
H
D000276:Adjuvants, Immunologic / Q000009:adverse effects / Q000627:therapeutic use*; D000818:Animals; D001500:BCG Vaccine / Q000009:adverse effects / Q000627:therapeutic use*; D045744:Cell Line, Tumor; D002473:Cell Wall / Q000276:immunology*; D016503:Drug Delivery Systems; D005260:Female; D008081:Liposomes; D051379:Mice; D008809:Mice, Inbred C3H; D018613:Microscopy, Confocal; D009163:Mycobacterium bovis; D009842:Oligopeptides / Q000494:pharmacology*; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy* / Q000276:immunology
D000276:Adjuvants, Immunologic; D001500:BCG Vaccine; D008081:Liposomes; D009842:Oligopeptides; C448619:octaarginine