In vitro, tumor-selective Hsp70 plasma membrane localization correlates with increased sensitivity to lysis mediated by a subpopulation of human natural killer (NK) cells that adhere to plastic following cytokine stimulation. In the present study, we analyzed the capacity of adoptively transferred human NK cells in SCID/beige mice for local tumor control and prevention of metastatic dissemination of Hsp70-expressing CX(+) and non-expressing CX(-) tumors following orthotopic (o.t.) injection. Both tumor sublines were derived by cell sorting of the original cell line, CX2, and thus exhibit an identical MHC and adhesion molecule expression pattern but differ with respect to Hsp70 plasma membrane expression. Viability of adherent, human NK cells in SCID/beige mice up to 18 days and the capacity to migrate have been demonstrated. Growth of Hsp70-expressing and non-expressing CX(+) and CX(-) tumor cells was completely suppressed when 10 x 10(6) NK cells were injected into the i.p. cavity on day 4 after inoculation of 2.5 x 10(6) tumor cells. Although a single injection of 5 or 2.5 x 10(6) NK cells was not sufficient to suppress tumor growth completely in all mice, the reduction in size of CX(+) tumors was significantly greater than that of CX(-) tumors. To mimic the clinical situation, ex vivo stimulated NK cells were injected i.v. on day 4 after o.t. injection of tumor cells. Under these conditions, growth of Hsp70-expressing primary tumors and metastases was suppressed. If CX(-) tumor cells were injected, 3 of 9 mice developed Hsp70-negative primary tumors. However, none of these mice developed distant metastases. In summary, our data indicate that Hsp70 acts as a recognition structure for adherent NK cells in a SCID/beige mouse model.

BACKGROUND

The conserved cytokine-induced apoptosis inhibitor-1 (CIAPIN1) gene has been implicated in several processes, such as apoptosis, cell division, angiogenesis and Fe/S protein biogenesis. In this study, we identified the Drosophila CIAPIN1 homologue (D-CIAPIN1) and studied its role in ovarian development.

RESULTS

We found that D-CIAPIN1 is conserved as it can complement the nonviability of the yeast CIAPIN1-deletion strain. Several D-CIAPIN1 alleles were identified, including one allele in which that codon encoding the highly conserved twin cysteine CX2 C motif is mutated, demonstrating for the first time the importance of this motif to protein function. We demonstrated D-CIAPIN1 is an essential gene required for ovarian development. We found that D-CIAPIN1 female mutants are sterile, containing rudimentary ovaries. We noted a decrease in follicle cell numbers in D-CIAPIN1 mutant egg chambers. We further demonstrated that the decrease in follicle cell numbers in D-CIAPIN1 mutants is due to a reduced mitotic index and enhanced cell death.

CONCLUSIONS

Our study reveals that D-CIAPIN1 is essential for egg chamber development and is required for follicle cell proliferation and survival.