Insulin-like growth factor (IGF)-binding protein-2 (IGFBP-2) has been shown to inhibit IGF-dependent cell proliferation in a number of in vitro studies. However, no in vivo model of IGFBP-2 overexpression has been established so far. Therefore, we have generated transgenic mice, in which expression of a mouse IGFBP-2 complementary DNA is controlled by the cytomegalovirus (CMV) promoter. In two independent transgenic strains, transgene expression was highest in pancreas and stomach, followed by skeletal muscle, heart, colon, spleen, adipose tissue, brain, and kidney. Within the pancreas, IGFBP-2 expression was found in the islets but not in the exocrine part. Serum IGFBP-2 levels of CMV-IGFBP-2 transgenic mice were about 3-fold (P < 0.05) increased, compared with controls, whereas serum levels of IGF-I and IGF-II were unaffected by IGFBP-2 overexpression. Fasted serum glucose and fasted insulin levels were slightly reduced in transgenic mice, compared with controls. Postprandial serum glucose insulin levels were not affected by the genotype. At days later than 23, body weights of transgenic mice were significantly (P < 0.05) reduced in both sexes, compared with nontransgenic littermates. This reduction in body weight was mainly attributable to significantly (P < 0.05) lower carcass weights of CMV-IGFBP-2 transgenic vs. control mice. In contrast, absolute organ weights were not (or only as a tendency) reduced, except for the weight of the spleen, which was significantly (P < 0.05) lower in male transgenic than in control mice. Our data suggest that IGFBP-2 represents a negative regulator of postnatal growth in mice, potentially by reducing the bioavailability of IGF-I.

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Pediatric patients with relapsed metastatic tumors have a poor prognosis and new treatment strategies are warranted. We present preliminary results of a pilot study, evaluating the feasibility and toxicity of transplantation of haploidentical T and B cell depleted grafts with high numbers of NK cells. 6 patients with relapsed metastatic neuroblastomas (n = 4), rhabdomyosarcoma (n = 1) or Ewing's sarcoma (n = 1) after previous autologous transplantation received CD3/CD19 depleted grafts from mismatched family donors with a median number of 16 x 10 (6)/kg stem cells, 167 x 10 (6)/kg Natural Killer cells and only 5.4 x 10 (4)/kg residual T cells. A melphalan-based, reduced intensity conditioning was used. Despite pretransplant chemotherapy, patients entered transplantation with significant tumor burden. Primary engraftment occurred in 6/6 patients. One patient had secondary graft failure. Hematopoietic recovery was rapid (ANC > 0.5 x 10 (9)/L: 11 days (9-12); independence from platelet substitution: 8 days (7-11)). Four patients had acute GvHD grade II, limited chronic GvHD was observed in 2 patients. No transplant-related mortality and only low toxicity occurred. Four patients died from progression, two patients are alive. Overall median survival time is 6 months (2-11) to date. Analysis of posttransplant NK cell function revealed stable cytotoxic activity against K562 targets, whereas activity against neuroblastoma targets was low. Stimulation with cytokines and use of appropriate antibodies clearly enhanced specific lysis in vitro. In summary, these preliminary results indicate the feasibility and low toxicity even in intensively pre-treated patients with neuroblastomas/sarcomas. This approach may form the basis for posttransplant immunomodulation and other therapeutic strategies. Further experience is warranted to evaluate the method.

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Insulin-like growth factor-II