Recombinant human insulin-like growth factor-binding protein 3 inhibits tumor growth and targets the Akt pathway in lung and colon cancer models.

OBJECTIVE: Insulin-like growth factor-binding protein 3 (IGFBP-3) can induce antiproliferative and proapoptotic effects in human cancer cells, by IGF-I independent mechanisms. The antitumor efficacy of recombinant human IGFBP-3 (rhIGFBP-3) and its interaction with chemotherapy in lung and colon cancers, in vitro and in vivo was evaluated. The effects of the different treatments on IGF-IR signaling pathways were also examined. DESIGN: Antiproliferative in vitro assay using rhIGFBP-3, as single agent or in combination with carboplatin or irinotecan against the murine Lewis Lung (M-3LL) and LoVo cell lines, respectively was performed. In the M-3LL model in vivo model, mice were treated with rhIGFBP-3 (3 or 10 mg/kg), carboplatin (25 or 50 mg/kg) alone or in combined treatments. In the LoVo xenograft model, mice were treated with rhIGFBP-3 (3, 10 or 30 mg/kg), irinotecan (10 or 20 mg/kg), as monotherapies or in combinations. RESULTS: rhIGFBP-3 elicited a dose-dependent tumor growth inhibition on the M-3LL model and produced a significant tumor growth inhibition at the highest dose tested. However, it failed to improve the antitumor response to carboplatin. In the LoVo colorectal xenograft model, rhIGFBP-3 caused significant single-agent inhibitory effect and enhanced the antitumor activity of irinotecan at their lowest doses tested. Western blot analysis suggests that the observed tumor growth inhibition by rhIGFBP-3 correlates with decreased Akt phosphorylation in both M-3LL and LoVo cell lines in vitro. CONCLUSIONS: Our novel findings provide evidence for in vivo activity of rhIGFBP-3 against lung and colon tumor models and reveal new insight into its interaction with chemotherapeutic drugs. The antitumor effects of rhIGFBP-3 are associated with a downregulation of AKT signaling.

Preclinical characterization of AEG35156/GEM 640, a second-generation antisense oligonucleotide targeting X-linked inhibitor of apoptosis.

PURPOSE: Cancer cells can use X-linked inhibitor of apoptosis (XIAP) to evade apoptotic cues, including chemotherapy. The antitumor potential of AEG35156, a novel second-generation antisense oligonucleotide directed toward XIAP, was assessed in human cancer models when given as a single agent and in combination with clinically relevant chemotherapeutics. EXPERIMENTAL DESIGN: AEG35156 was characterized for its ability to cause dose-dependent reductions of XIAP mRNA and protein in vitro and in vivo, to sensitize cancer cell lines to death stimuli, and to exhibit antitumor activity in multiple human cancer xenograft models as a single agent or in combination with chemotherapy. RESULTS: AEG35156 reduced XIAP mRNA levels with an EC50 of 8 to 32 nmol/L and decreased XIAP protein levels by >80%. Loss of XIAP protein correlated with increased sensitization to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis in Panc-1 pancreatic carcinoma cells. AEG35156 exhibited potent antitumor activity relative to control oligonucleotides in three human cancer xenograft models (prostate, colon, and lung) and was capable of inducing complete tumor regression when combined with taxanes. Antitumor effects of AEG35156 correlated with suppression of tumor XIAP levels. CONCLUSIONS: AEG35156 reduces XIAP levels and sensitizes tumors to chemotherapy. AEG35156 is presently under clinical assessment in multiple phase I trials in cancer patients as a single agent and in combination with docetaxel in solid tumors or cytarabine/idarubicin in leukemia.

Recombinant human insulin-like growth factor binding protein 3 inhibits growth of human epidermal growth factor receptor-2-overexpressing breast tumors and potentiates herceptin activity in vivo.

Clinical studies indicate that Herceptin (trastuzumab), a recombinant humanized monoclonal antibody directed against the human epidermal growth factor receptor-2 (HER-2) tyrosine kinase growth factor receptor, provides a significant but transient survival advantage to a subset of patients with HER-2-overexpressing metastatic breast cancer when given as a first-line agent. Increased insulin-like growth factor (IGF)-I receptor (IGF-IR) signaling has recently been identified as a potential factor adversely influencing the response to Herceptin. We examined the effect of recombinant human IGF binding protein 3 (rhIGFBP-3), an antagonist of IGF-IR signaling, in Herceptin-resistant breast cells in vitro and in tumors in vivo. Consistent with results obtained using HER-2- or IGF-IR-transfected cells (MCF-7/HER2-18 and SKBR3/IGF-IR, respectively), we found that rhIGFBP-3 significantly reduced IGF-I-induced IGF-IR phosphorylation and displayed a synergistic interaction with Herceptin against cultured HER-2-overexpressing breast cancer cells in vitro. We show, for the first time, the antitumor activity of rhIGFBP-3 against advanced-stage MCF-7/HER2-18-transfected human breast cancer xenografts and its potentiation of Herceptin activity. We also provide evidence that IGF-IR activation counters the early suppressive effect of Herceptin on HER-2 signaling via Akt and p44/p42 mitogen-activated protein kinase (MAPK), and that inhibition of HER-2-overexpressing human breast tumor growth by rhIGFBP-3 is associated with restored down-regulation of Akt and p44/p42 MAPK phosphorylation in vitro and in vivo. These results emphasize the merit of evaluating simultaneous blockade of the HER-2 and IGF-IR pathways using combination therapy with rhIGFBP-3 plus Herceptin in human clinical trials of patients with HER-2-positive breast cancer.

Anti-insulin-like growth factor strategies in breast cancer.

The insulin-like growth factors (IGF-I and -II) are potent mitogens and survival factors for both normal and malignant breast cells. These effects are mediated primarily through the IGF-I receptor (IGF-IR), which is significantly overexpressed and highly activated in breast tumors. The IGF-binding proteins are competitive inhibitors of IGF/IGF-IR interaction, limiting cellular proliferation and survival. Higher serum IGF-I levels or an increased ratio of IGF-I to IGF binding protein-3 is associated with an increased risk of developing breast cancer. Hence, interest in the IGF system as a potential target for the development of novel antineoplastic therapies has ensued. Several strategies to interrupt IGF-IR signaling are currently being evaluated for the treatment of breast cancer, including suppression of IGF production, reduction of functional IGF-IR levels, neutralization of IGF action, and inhibition of IGF-IR activation.

Overexpression of the myeloid leukemia-associated Hoxa9 gene in bone marrow cells induces stem cell expansion.

Cytogenetic, genetic, and functional studies have demonstrated a direct link between deregulated Hoxa9 expression and acute myeloid leukemia (AML). Hoxa9 overexpression in mouse bone marrow cells invariably leads to AML within 3 to 10 months, suggesting the requirement for additional genetic events prior to AML. To gain further insight into how Hoxa9 affects hematopoietic development at the preleukemic stage, we have engineered its overexpression (1) in hematopoietic stem cells using retrovirus-mediated gene transfer and generated bone marrow transplantation chimeras and (2) in lymphoid cells using transgenic mice. Compared with controls, recipients of Hoxa9-transduced cells had an about 15-fold increase in transplantable lymphomyeloid long-term repopulating cells, indicating the capacity for this oncogene to confer a growth advantage to hematopoietic stem cells. In addition, overexpression of Hoxa9 in more mature cells enhanced granulopoiesis and partially blocked B lymphopoiesis at the pre-B-cell stage but had no detectable effect on T lymphoid development. Interestingly, despite specifically directing high expression of Hoxa9 in T and B lymphoid lineages, none of the Hoxa9 transgenic mice developed lymphoid malignancies for the observation period of more than 18 months.