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.

Inhibitory effects of nordihydroguaiaretic acid (NDGA) on the IGF-1 receptor and androgen dependent growth of LAPC-4 prostate cancer cells.

BACKGROUND: Nordihydroguaiaretic acid (NDGA) is an inhibitor of the IGF-1 receptor (IGF-1R) in breast and other cancers, and concomitantly inhibits tumor growth both in cultured cells and animals. The current study evaluates the effect of NDGA on the androgen-stimulated growth of human prostate cancer cells. METHODS: LAPC-4 prostate cancer cells in tissue culture were androgen starved for 3 days, 1 nM dihydrotestosterone (DHT) and other androgens were then added for up to 7 days, and cell proliferation measured. IGF-1R protein expression was measured by Western blot, and IGF-1R mRNA expression by quantitative PCR. IGF-1R receptor kinase activation was measured by ELISA. RESULTS: After 7 days, LAPC-4 growth was doubled by 1 nM DHT. NDGA had a rapid effect to inhibit IGF-1R autophosphorylation induced by IGF-1. DHT increased the expression of IGF-1R protein and mRNA levels. Maximal IGF-1R protein levels were observed 3 days after the addition of androgen. In addition, NDGA, at 10 microM or less, inhibited DHT-induced proliferation in both cells grown in plates and cells grown in soft agar. Androgen receptor (AR) studies by FRET revealed that NDGA had no conformational effects on the AR in response to ligand. CONCLUSIONS: NDGA blocks the DHT-induced growth of LAPC-4 prostate cancer cells by several mechanisms including rapid inhibition of the IGF-1R kinase, and a dose-dependent inhibition of androgen stimulation of IGF-1R expression. Clinical studies of this agent will determine its efficacy in the setting of androgen-dependent prostate cancer.

Nordihydroguaiaretic acid (NDGA), an inhibitor of the HER2 and IGF-1 receptor tyrosine kinases, blocks the growth of HER2-overexpressing human breast cancer cells.

We have reported that nordihydroguaiaretic acid (NDGA) inhibits the tyrosine kinase activities of the IGF-1 receptor (IGF-1R) and the HER2 receptor in breast cancer cells. Herein, we studied the effects of NDGA on the growth of estrogen receptor (ER) positive MCF-7 cells engineered to overexpress HER2 (MCF-7/HER2-18). These cells are an in vitro model of HER2-driven, ER positive, tamoxifen resistant breast cancer. NDGA was equally effective at inhibiting the growth of both parental MCF-7 and MCF-7/HER2-18 cells. Half maximal effects for both cell lines were in the 10-15 microM range. The growth inhibitory effects of NDGA were associated with an S phase arrest in the cell cycle and the induction of apoptosis. NDGA inhibited both IGF-1R and HER2 kinase activities in these breast cancer cells. In contrast, Gefitinib, an epidermal growth factor receptor inhibitor but not an IGF-1R inhibitor, was more effective in MCF-7/HER2-18 cells than in the parental MCF-7 cells and IGF binding protein-3 (IGFBP-3) was more effective against MCF-7 cells compared to MCF-7/HER2-18. MCF-7/HER2-18 cells are known to be resistant to the effects of the estrogen receptor inhibitor, tamoxifen. Interestingly, NDGA not only inhibited the growth of MCF-7/HER2-18 on its own, but it also demonstrated additive growth inhibitory effects when combined with tamoxifen. These studies suggest that NDGA may have therapeutic benefits in HER2-positive, tamoxifen resistant, breast cancers in humans.

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.

D-chiro-Inositol enhances effects of hypothalamic toxin gold-thioglucose.

D-chiro-Inositol (DCI) enhances reproductive function in insulin-resistant women with polycystic ovarian disease and enhances the effects of insulin in the periphery, suggesting that this compound may act in part by sensitizing the hypothalamus to effects of insulin. Effects of gold-thioglucose (GTG) to produce hypothalamic lesions and subsequent obesity are insulin-dependent, suggesting that responses to GTG may be a marker of hypothalamic sensitivity to insulin. To assess these hypotheses, the present study assessed if DCI would enhance the ability of a subthreshhold dose of GTG to produce hypothalamic lesions and subsequent obesity. At the subthreshhold dose used (0.4 mg/kg i.p.), injection of GTG produced no subsequent effect on body weight compared to saline; similarly, at the dose of DCI used (10 mg/kg/day in drinking water), DCI produced no effect on body weight. In contrast, when given to mice exposed to DCI, this dose of GTG produced significant increase in body weight and evidence of an enhanced medial arcuate hypothalamic lesion.

Ontogeny of enhanced decorin levels and distribution within myocardium of failing hearts.

The proteoglycan, decorin, is a regulator of collagen fibril organization and its resulting functional properties. The temporal and spatial expression of decorin during the progression to heart failure is not well understood and may play a significant role in extracellular matrix remodeling. Decorin and types I and III collagen levels were measured in male Spontaneously Hypertensive Heart Failure (SHHF) and control Wistar-Furth rats at 2 and 8 mo, and at congestive heart failure (CHF). Decorin levels increased in the SHHF rats relative to the control rats in CHF. Type I collagen levels increased while type III levels decreased in the SHHF rats in CHF relative to the age matched controls. The SHHF rats have 48 and 45 KDa isoforms of the decorin core protein expressed at all ages while control Wistar-Furths produced only a 45 KDa form. Decorin was localized in the outer ventricle wall but during CHF, decorin was expressed throughout the ventricular myocardium. Immunogold localization of decorin demonstrated an increased distribution of decorin along the myocardium collagen fibrils at CHF. The enhanced expression and greater distribution of decorin may be linked to extracellular matrix remodeling which occurs with the development of heart failure.

Gender modulates activation of renin-angiotensin and endothelin systems in hypertension and heart failure.

Sexual dimorphism may occur during the development of hypertension and congestive heart failure (CHF). Male and female spontaneous hypertension heart failure (SHHF) rats with established hypertension, but before CHF (age 5-8 mo) and during cardiac decompensation leading to CHF (age 18-20 mo in male rats and 22-24 mo in female rats), were studied. At 5-8 mo, male SHHF rats showed early activation of the renin-angiotensin system (RAS), as indicated by increased plasma renin activity (PRA) and higher serum angiotensin-converting enzyme activity compared with female rats. The increase in PRA in female rats was delayed compared with males rats, but it reached comparable levels just before CHF. Urinary endothelin excretion was significantly greater in 5- to 8-mo-old female rats compared with age-matched male rats. Urinary endothelin excretion increased in both male and female rats as CHF developed. Plasma atrial natriuretic peptide (ANP) was comparable at both time points, and both genders showed similar, marked increases as CHF developed. In conclusion, male rats show early activation of the RAS, whereas female rats show early activation of the endothelin vasopressor system. During cardiac decompensation, generalized activation of the RAS, endothelin, and ANP systems occurs and is similar in male and female SHHF rats.