Reversal of oncogene transformation and suppression of tumor growth by the novel IGF1R kinase inhibitor A-928605

BACKGROUND: The insulin-like growth factor (IGF) axis is an important signaling pathway in the growth and survival of many cell and tissue types. This pathway has also been implicated in many aspects of cancer progression from tumorigenesis to metastasis. The multiple roles of IGF signaling in cancer suggest that inhibition of the pathway might yield clinically effective therapeutics. METHODS: We describe A-928605, a novel pyrazolo [3,4-d]pyrimidine small molecule inhibitor of the receptor tyrosine kinases (IGF1R and IR) responsible for IGF signal transduction. This compound was first tested for its activity and selectivity via conventional in vitro kinome profiling and cellular IGF1R autophosphorylation. Additionally, cellular selectivity and efficacy of A-928605 were analyzed in an IGF1R oncogene-addicted cell line by proliferation, signaling and microarray studies. Finally, in vivo efficacy of A-928605 was assessed in the oncogene-addicted cell line and in a neuroblastoma model as a single agent as well as in combination with clinically approved therapeutics targeting EGFR in models of pancreatic and non-small cell lung cancers. RESULTS: A-928605 is a selective IGF1R inhibitor that is able to abrogate activation of the pathway both in vitro and in vivo. This novel compound dosed as a single agent is able to produce significant growth inhibition of neuroblastoma xenografts in vivo. A-928605 is also able to provide additive effects when used in combination with clinically approved agents directed against EGFR in non-small cell lung and human pancreatic tumor models. CONCLUSION: These results suggest that a selective IGF1R inhibitor such as A-928605 may provide a useful clinical therapeutic for IGF pathway affected tumors and warrants further investigation

The Transcription Factor PU.1 Regulates γδ T Cell Homeostasis

T cell development results in the generation of both mature αβ and γδ T cells. While αβ T cells predominate in secondary lymphoid organs, γδ T cells are more abundant in mucosal tissues. PU.1, an Ets family transcription factor, also identified as the spleen focus forming virus proviral integration site-1 (Sfpi1) is essential for early stages of T cell development, but is down regulated during the DN T-cell stage.In this study, we show that in mice specifically lacking PU.1 in T cells using an lck-Cre transgene with a conditional Sfpi1 allele (Sfpi1(lck-/-)) there are increased numbers of γδ T cells in spleen, thymus and in the intestine when compared to wild-type mice. The increase in γδ T cell numbers in PU.1-deficient mice is consistent in γδ T cell subsets identified by TCR variable regions. PU.1-deficient γδ T cells demonstrate greater proliferation in vivo and in vitro.The increase of γδ T cell numbers in Lck-Cre deleter strains, where deletion occurs after PU.1 expression is diminished, as well as the observation that PU.1-deficient γδ T cells have greater proliferative responses than wild type cells, suggests that PU.1 effects are not developmental but rather at the level of homeostasis. Thus, our data shows that PU.1 has a negative influence on γδ T cell expansion

Targeting insulin-like growth factor pathways

Some cancer cells depend on the function of specific molecules for their growth, survival, and metastatic potential. Targeting of these critical molecules has arguably been the best therapy for cancer as demonstrated by the success of tamoxifen and trastuzumab in breast cancer. This review will evaluate the type I IGF receptor (IGF-IR) as a potential target for cancer therapy. As new drugs come forward targeting this receptor system, several issues will need to be addressed in the early clinical trials using these agents

Mammary tumors that become independent of the type I insulin-like growth factor receptor express elevated levels of platelet-derived growth factor receptors

<p>Abstract</p> <p>Background</p> <p>Targeted therapies are becoming an essential part of breast cancer treatment and agents targeting the type I insulin-like growth factor receptor (IGF-IR) are currently being investigated in clinical trials. One of the limitations of targeted therapies is the development of resistant variants and these variants typically present with unique gene expression patterns and characteristics compared to the original tumor.</p> <p>Results</p> <p>MTB-IGFIR transgenic mice, with inducible overexpression of the IGF-IR were used to model mammary tumors that develop resistance to IGF-IR targeting agents. IGF-IR independent mammary tumors, previously shown to possess characteristics associated with EMT, were found to express elevated levels of PDGFRα and PDGFRβ. Furthermore, these receptors were shown to be inversely expressed with the IGF-IR in this model. Using cell lines derived from IGF-IR-independent mammary tumors (from MTB-IGFIR mice), it was demonstrated that PDGFRα and to a lesser extent PDGFRβ was important for cell migration and invasion as RNAi knockdown of PDGFRα alone or PDGFRα and PDGFRβ in combination, significantly decreased tumor cell migration in Boyden chamber assays and suppressed cell migration in scratch wound assays. Somewhat surprisingly, concomitant knockdown of PDGFRα and PDGFRβ resulted in a modest increase in cell proliferation and a decrease in apoptosis.</p> <p>Conclusion</p> <p>During IGF-IR independence, PDGFRs are upregulated and function to enhance tumor cell motility. These results demonstrate a novel interaction between the IGF-IR and PDGFRs and highlight an important, therapeutically relevant pathway, for tumor cell migration and invasion.</p

Heterodimerization of Glycosylated Insulin-Like Growth Factor-1 Receptors and Insulin Receptors in Cancer Cells Sensitive to Anti-IGF1R Antibody

Identification of predictive biomarkers is essential for the successful development of targeted therapy. Insulin-like growth factor 1 receptor (IGF1R) has been examined as a potential therapeutic target for various cancers. However, recent clinical trials showed that anti-IGF1R antibody and chemotherapy are not effective for treating lung cancer.In order to define biomarkers for predicting successful IGF1R targeted therapy, we evaluated the anti-proliferation effect of figitumumab (CP-751,871), a humanized anti-IGF1R antibody, against nine gastric and eight hepatocellular cancer cell lines. Out of 17 cancer cell lines, figitumumab effectively inhibited the growth of three cell lines (SNU719, HepG2, and SNU368), decreased p-AKT and p-STAT3 levels, and induced G 1 arrest in a dose-dependent manner. Interestingly, these cells showed co-overexpression and altered mobility of the IGF1R and insulin receptor (IR). Immunoprecipitaion (IP) assays and ELISA confirmed the presence of IGF1R/IR heterodimeric receptors in figitumumab-sensitive cells. Treatment with figitumumab led to the dissociation of IGF1-dependent heterodimeric receptors and inhibited tumor growth with decreased levels of heterodimeric receptors in a mouse xenograft model. We next found that both IGF1R and IR were N-linked glyosylated in figitumumab-sensitive cells. In particular, mass spectrometry showed that IGF1R had N-linked glycans at N913 in three figitumumab-sensitive cell lines. We observed that an absence of N-linked glycosylation at N913 led to a lack of membranous localization of IGF1R and figitumumab insensitivity.The data suggest that the level of N-linked glycosylated IGF1R/IR heterodimeric receptor is highly associated with sensitivity to anti-IGF1R antibody in cancer cells

Inhibition of IGF-1 Signalling Enhances the Apoptotic Effect of AS602868, an IKK2 Inhibitor, in Multiple Myeloma Cell Lines

Multiple myeloma (MM) is a B cell neoplasm characterized by bone marrow infiltration with malignant plasma cells. IGF-1 signalling has been explored as a therapeutic target in this disease. We analyzed the effect of the IKK2 inhibitor AS602868, in combination with a monoclonal antibody targeting IGF-1 receptor (anti-IGF-1R) in human MM cell lines. We found that anti-IGF-1R potentiated the apoptotic effect of AS602868 in LP1 and RPMI8226 MM cell lines which express high levels of IGF-1R. Anti-IGF-1R enhanced the inhibitory effect of AS602868 on NF-κB pathway signalling and potentiated the disruption of mitochondrial membrane potential caused by AS602868. These results support the role of IGF-1 signalling in MM and suggest that inhibition of this pathway could sensitize MM cells to NF-κB inhibitors