Translating Metabolic Interventions into Breast Cancer Therapy: A Comprehensive Review

Dysregulation of the IGF (insulin-like growth factor) signaling pathway plays a key role in cancer development. It is still unclear whether germline variation in genes in the IGF pathway may affect risk of breast cancer. We conducted a gene-based analysis of 184 genes in the IGF signaling pathway to identify genes carrying genetic variation affecting risk of breast cancer and the specific estrogen receptor (ER) subtypes. Tagging single nucleotide polymorphisms (SNPs) for each gene were selected and genotyped on a customized Illumina Exome Array. Imputation was carried out using 1000 Genomes haplotypes. The analysis included 91,627 SNPs in 3,663 breast cancer cases (including 1,983 ER positive,1,098 ER-negative) and 4,687 controls from the African American Breast Cancer Epidemiology and Risk (AMBER) consortium, a collaborative project of four large studies of breast cancer in African American women (Carolina Breast Cancer Study, Black Women's Health Study, Women's Circle of Health Study, and Multiethnic Cohort). We used a multi-locus adaptive joint (AdaJoint) test to determine the association of each gene in the IGF signaling pathway with overall breast cancer and ER subtypes. None of the 184 tested genes, including IGF, IGF binding protein (IGFBP), and IGF receptor (IGFR) genes were associated with disease after adjustment for multiple testing. At the nominal level of P≤0.01, BAIAP2 (P = 0.003), and CALM2 (P = 0.009) genes were associated with overall breast cancer; BAIAP2 (P = 0.001), and CSNK2A1 (P = 0.01) with ER+ breast cancer; and BRAF (P = 0.003), BAD (P = 0.005), and MAPK3 (P = 0.009) with ER- breast cancer. The intronic rs9913477 SNP in the BAIPA2 gene was significantly associated with overall (P = 3.2×10−7) and ER+ (P = 4.4×10−7) breast cancer at the pathway-wide level after adjusting for the total number of tested SNPs. Odds ratios and 95% confidence intervals of the risk G-allele were 1.44 (1.25, 1.66), and 1.53 (1.30, 1.81) for overall and ER+ breast cancer, respectively. BAIAP2 codes an adaptor protein, IRSp53, which functions as a substrate of the insulin receptor and IGF-1 receptor tyrosine kinases and links Rho-family small GTPases such as Rac. In vitro studies have shown that activation of Rac promotes metastatic behavior of breast cancer cells. In conclusion, we identified a SNP in BAIAP2 associated with overall and ER+ breast cancer. These results highlight the importance of the IGF signaling pathway in the pathogenesis of breast cancer. Citation Format: Edward A. Ruiz-Narvaez, Kathryn L. Lunetta, Chi-Chen Hong, Stephen A. Haddad, Song Yao, Ting-Yuan D. Cheng, Jeannette T. Bensen, Elisa V. Bandera, Christopher A. Haiman, Andrew F. Olshan, Christine B. Ambrosone, Lynn Rosenberg, Julie R. Palmer. Gene-based analysis of the IGF signaling pathway and risk of breast cancer in African American women: The AMBER consortium. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 814.

Loss-of-function mutations of the GPC3 gene are the cause of the human Simpson-Golabi-Behmel syndrome. Based on the overgrowth phenotype of the Simpson-Golabi-Behmel syndrome patients and the key role played by the insulin-like growth factor (IGF) signaling system in regulating embryonic growth, it was speculated that GPC3 regulates IGF signaling. In order to test the validity of this hypothesis, we mated GPC3 knockout mice with insulin receptor substrate-1 (IRS-1) nullizygous mice. We found that GPC3 regulates organism growth independent of IRS-1, suggesting that GPC3 does not modulate IGF signaling. Instead, we found that GPC3 knockout mice exhibit alterations in the Wnt signaling pathway, which is also associated with the regulation of cell proliferation. In particular, the loss of GPC3 led to the inhibition of the non-canonical Wnt/JNK signaling pathway, while concomitantly causing the activation of canonical Wnt/beta-catenin signaling. These in vivo findings were confirmed in vitro upon the ectopic overexpression of GPC3 in mesothelioma cells. In these cells, the GPC3-induced increase in JNK activity was associated with an enhanced response to Wnt5a. Most interestingly, the heparan sulfate chains of GPC3 were not required for its stimulatory activity on Wnt5a signaling and for the formation of GPC3-Wnt5a complexes. We propose that at least in some cell types GPC3 serves as a selective regulator of Wnt signaling, by potentiating non-canonical Wnt signaling, while inhibiting the canonical Wnt signaling pathway.

The insulin-like growth factor (IGF) signalling pathway has been highly conserved in animal evolution and, in mammals and Xenopus, plays a key role in embryonic growth and development, with the IGF-1 receptor (IGF-1R) being a crucial regulator of the signalling cascade. Here we report the first functional role for the IGF pathway in zebrafish. Expression of mRNA coding for a dominant negative IGF-1R resulted in embryos that were small in size compared to controls and had disrupted head and CNS development. At its most extreme, this phenotype was characterized by a complete loss of head and eye structures, an absence of notochord and the presence of abnormal somites. In contrast, up-regulation of IGF signalling following injection of IGF-1 mRNA, resulted in a greatly expanded development of anterior structures at the expense of trunk and tail. IGF-1R knockdown caused a significant decrease in the expression of Otx2, Rx3, FGF8, Pax6.2 and Ntl, while excess IGF signalling expanded Otx2 expression in presumptive forebrain tissue and widened the Ntl expression domain in the developing notochord. The observation that IGF-1R knockdown reduced expression of two key organizer genes (chordin and goosecoid) suggests that IGF signalling plays a role in regulating zebrafish organizer activity. This is supported by the expression of IGF-1, IGF-2 and IGF-1R in shield-stage zebrafish embryos and the demonstration that IGF signalling influences expression of BMP2b, a gene that plays an important role in zebrafish pattern formation. Our data is consistent with a common pathway for integration of IGF, FGF8 and anti-BMPs in early vertebrate development.

The insulin-like growth factor 1 (IGF1) signaling pathway as an aging mechanism related to p53 in human melanogenesis remains unclear. The aim of this study was to investigate the relationship between p53 and IGF1 signaling pathway in young, senescent and H2O2-treated cells. The protein and gene expression in young, senescent and H2O2-treated cells were analyzed using western blot and reverse transcription polymerase chain reaction (RT-PCR) assays, respectively. The expression levels of (phosphoinositide 3-kinases) PI3K, v-akt murine thymoma viral oncogene homolog 1 (AKT1), mammalian target of rapamycin, β-catenin (CTNNB1), acetylated p53 (ac-p53), p53 and p-p21 proteins, related to IGF1 and p53 signaling pathways, were higher in senescent and H2O2-treated cells than those of young cells. Furthermore, AKT reduced melanogenesis through microphthalmia-associated transcription factor (MITF) inactivation by the inhibition of CTNNB1. The gene expression levels of PI3K, TP53 and catalase (CAT) in senescent and H2O2-treated cells were increased compared to young cells. p53 protein plays a key role in the aging of melanocytes via IGF1 signaling pathways.

Insulin-like growth factor 1(IGF1) and ephrin ligand (EFN)-receptor (EPH) signaling are both crucial for bone cell function and skeletal development and maintenance. IGF1 signaling is the major mediator of growth hormone-induced bone growth, but a host of different signals and factors regulate IGF1 signaling at the systemic and local levels. Disruption of the Igf1 gene results in reduced peak bone mass in both experimental animal models and humans. Additionally, EFN-EPH signaling is a complex system which, particularly through cell-cell interactions, contributes to the development and differentiation of many bone cell types. Recent evidence has demonstrated several ways in which the IGF1 and EFN-EPH signaling pathways interact with and depend upon each other to regulate bone cell function. While much remains to be elucidated, the interaction between these two signaling pathways opens a vast array of new opportunities for investigation into the mechanisms of and potential therapies for skeletal conditions such as osteoporosis and fracture repair.

Chronic prenatal ethanol exposure alters expression of central and peripheral insulin signaling molecules in adult guinea pig offspring

Although clinical outcomes of some cancer have been greatly improved by advancements made in surgery, chemo or radiotherapy and development of novel strategies such as molecular targeted therapy, Traditional Chinese Medicine (TCM) is particularly appreciated for cancer therapy in China based on its 5,000-year-old history, well established theoretical system and numerous exciting case reports. However, due to lack of quality assurance, laboratory evidences and well-designed clinical trials, TCM always encounters much skepticism and pessimism by the West. The study aims to identify the bioactive compounds in a Chinese herb Spatholobus suberectus (SS, 雞血藤) by targeting on lactate dehydrogenase A (LDH-A) in breast cancer.\n\n\n\nGlycolysis inhibition has been considered as important strategy to block cancer energy metabolism and therefore suppressing cancer growth. LDH-A has been demonstrated to be up-regulated in various cancer cells. In our study, 46 breast cancer specimens were collected to study the relation between LDH-A expression and clinicopathological characteristics including menopause, tumor size, node involvement, differentiation and pathological subtypes classified by estrogen receptor (ER), progesterone receptor (PR) and Her-2. LDH-A expression was found to be correlated significantly with breast cancer size and independent with other clinicopathological factors. LDH-A silencing in breast cancer cell lines MDA-MB-231 and MCF-7 resulted in an inhibited breast cancer cell proliferation, elevated intracellular oxidative stress, induction of mitochondiral pathway apoptosis and limited tumorigenic ability, indicating that LDH-A inhibition might offer a promising therapeutic strategy for breast cancer.\n\n\n\nSS is historically recommended to invigorate blood circulation and has been prescribed to treat diseases relating to blood stasis syndromes including menstrual abnormalities, anemia, numbness of the limbs, arthritis and cancer, etc. Our following study revealed that SS aqueous extracts could significantly inhibited breast cancer LDH-A expression and activity in both in vitro and in vivo models built by MDA-MB-231 and MCF-7 cell lines. Bioactivity guided fractionation based on LDH-A activity, apoptosis and LDH-A expression further identified epigallocatechin (EGC) as the key compound responsible for the inhibited LDH-A expression.\n\n\n\nMechanistic studies found that the inhibitory effect of EGC on LDH-A expression was mainly through promoting Hypoxia inducible factor-1α (HIF-1α) proteasome degradation rather than inhibiting transcription activity, which might be correlated with decreased binding between HIF-1α and Hsp90. Consistent with in vitro findings, EGC was also demonstrated effecitve in suppressing breast cancer growth in vivo correlating to down-regulation of LDH-A, HIF-1α and triggerment of apoptosis.\n\n\n\nThis study provides preliminary laboratory evidences for applying SS in breast cancer therapy. However, further research is needed to evaluate its metabolism, the synergistic effects with chemotherapeutic agents and clinical efficiency.

Tumor hypoxia is an obstacle to radiotherapy. Radiosensitivity under hypoxic conditions is determined by molecular oxygen levels, as well as by various biological cellular responses. The insulin-like growth factor (IGF) signaling pathway is a widely recognized survival signal that confers radioresistance. However, under hypoxic conditions the role of IGF signaling in radiosensitivity is still poorly understood. Here, we demonstrate that IGF-II stimulation decreases clonogenic survival under hypoxic conditions in the pancreatic cancer cell lines AsPC-1 and Panc-1, and in the human breast cancer cell line MCF-7. IGF treatment under hypoxic conditions suppressed increased radiation sensitivity in these cell lines by pharmacologically inhibiting the phosphoinositide 3-kinase-mammalian target of rapamycin pathway, a major IGF signal-transduction pathway. Meanwhile, IGF-II induced the endoplasmic reticulum stress response under hypoxia, including increased protein levels of CHOP and ATF4, mRNA levels of CHOP, GADD34, and BiP, as well as splicing levels of XBP-1. The response was suppressed by inhibiting phosphoinositide 3-kinase and mammalian target of rapamycin activity. Overexpression of CHOP in AsPC-1 cells increased radiation sensitivity by IGF-II simulation under hypoxic conditions, whereas suppression of CHOP expression levels with small hairpin RNA or a dominant negative form of a proline-rich extensin-like receptor protein kinase in hypoxia decreased IGF-induced radiosensitivity. IGF-induced endoplasmic reticulum stress contributed to radiosensitization independent of cell cycle status. Taken together, IGF stimulation increased radiosensitivity through the endoplasmic reticulum stress response under hypoxic conditions.

Effects of radiotherapy and of differences in the extent of surgery for early breast cancer on local recurrence and 15-year survival: an overview of the randomised trials

Instability of IGF–IGFBP complex as a cause of the different performance of serum and EDTA-plasma after storage: EDTA-plasma is preferable for evaluating bioactive IGF especially in the mouse

Simple SummaryMyeloid-derived suppressive cells (MDSCs) are important for the progression of human tumors and represent potential targets for novel therapeutic strategies in breast and other cancers. To develop such strategies, pre-clinical models mimicking patient tumors are needed. In this study, we demonstrate that tumor models established by transplanting breast cancer patient tumor biopsies into the mammary tissues of mice represent excellent tools for studying and targeting MDSCs. Using molecular and genetic analyses, we show that these patient-derived xenograft (PDX) tumors produce signaling proteins that actively recruit MDSCs to the tumors, with differences between models that reflect those seen in breast cancer patients. Furthermore, MDSCs were associated with the spread of cancer cells to distant sites in the mice, similar to what is observed in patients. In conclusion, the use of breast cancer PDX models may greatly facilitate the development of novel therapeutic strategies for breast cancer and other cancer types.The pivotal role of myeloid-derived suppressive cells (MDSCs) in cancer has become increasingly apparent over the past few years. However, to fully understand how MDSCs can promote human tumor progression and to develop strategies to target this cell type, relevant models that closely resemble the clinical complexity of human tumors are needed. Here, we show that mouse MDSCs of both the monocytic (M-MDCS) and the granulocytic (PMN-MDSC) lineages are recruited to human breast cancer patient-derived xenograft (PDX) tumors in mice. Transcriptomic analysis of FACS-sorted MDSC-subpopulations from the PDX tumors demonstrated the expression of several MDSC genes associated with both their mobilization and immunosuppressive function, including S100A8/9, Ptgs2, Stat3, and Cxcr2, confirming the functional identity of these cells. By combining FACS analysis, RNA sequencing, and immune florescence, we show that the extent and type of MDSC infiltration depend on PDX model intrinsic factors such as the expression of chemokines involved in mobilizing and recruiting tumor-promoting MDSCs. Interestingly, MDSCs have been shown to play a prominent role in breast cancer metastasis, and in this context, we demonstrate increased recruitment of MDSCs in spontaneous PDX lung metastases compared to the corresponding primary PDX tumors. We also demonstrate that T cell-induced inflammation enhances the recruitment of MDSC in experimental breast cancer metastases. In conclusion, breast cancer PDX models represent a versatile tool for studying molecular mechanisms that drive myeloid cell recruitment to primary and metastatic tumors and facilitate the development of innovative therapeutic strategies targeting these cells.

It has been proposed that ligand occupancy of integrin alphavbeta3 with extracellular matrix ligands (e.g. vitronectin) plays a critical role in insulin-like growth factor-1 (IGF-1) signaling. We found that expression of alphavbeta3 enhanced IGF-1-induced proliferation of Chinese hamster ovary cells in serum-free conditions (in the absence of vitronectin). We hypothesized that the direct integrin binding to IGF-1 may play a role in IGF-1 signaling. We demonstrated that alphavbeta3 specifically and directly bound to IGF-1 in cell adhesion, enzyme-linked immunosorbent assay-type binding, and surface plasmon resonance studies. We localized the amino acid residues of IGF-1 that are critical for integrin binding by docking simulation and mutagenesis. We found that mutating two Arg residues at positions 36 and 37 in the C-domain of IGF-1 to Glu (the R36E/R37E mutation) effectively reduced integrin binding. Interestingly, although the mutant still bound to IGF1R, it was defective in inducing IGF1R phosphorylation, AKT and ERK1/2 activation, and cell proliferation. Furthermore wild type IGF-1 mediated co-precipitation of alphavbeta3 and IGF1R, whereas the R36E/R37E mutant did not, suggesting that IGF-1 mediates the interaction between alphavbeta3 and IGF1R. These results suggest that the direct binding to IGF-1 to integrin alphavbeta3 plays a role in IGF-1 signaling through ternary complex formation (alphavbeta3-IGF-IGF1R), and integrin-IGF-1 interaction is a novel target for drug discovery.

735 THE IMPACT OF INSULIN AND ITS RECEPTORS ON IGF TARGETING THERAPIES IN PROSTATE CANCER

Targeting of estrogen receptor is commonly used as a first-line treatment for hormone-positive breast cancer patients, and is considered as a keystone of systemic cancer therapy. Likewise, HER2-targeted therapy significantly improved the survival of HER2-positive breast cancer patients, indicating that targeted therapy is a powerful therapeutic strategy for breast cancer. However, for triple-negative breast cancer (TNBC), an aggressive breast cancer subtype, there are no clinically approved targeted therapies, and thus, an urgent need to identify potent, highly effective therapeutic targets. In this mini-review, we describe general strategies to inhibit tumor growth by targeted therapies and briefly discuss emerging resistance mechanisms. Particularly, we focus on therapeutic targets for TNBC and discuss combination therapies targeting the epidermal growth factor receptor (EGFR) and associated resistance mechanisms.

Purpose: Insulin-like growth factor 1 (IGF1) signaling regulates breast cancer initiation and progression and associated cancer phenotypes. We previously identified E-cadherin (CDH1) as a repressor of IGF1 signaling and in this study examined how loss of E-cadherin affects IGF1R signaling and response to anti-IGF1R/insulin receptor (InsR) therapies in breast cancer.Experimental Design: Breast cancer cell lines were used to assess how altered E-cadherin levels regulate IGF1R signaling and response to two anti-IGF1R/InsR therapies. In situ proximity ligation assay (PLA) was used to define interaction between IGF1R and E-cadherin. TCGA RNA-seq and RPPA data were used to compare IGF1R/InsR activation in estrogen receptor-positive (ER+) invasive lobular carcinoma (ILC) and invasive ductal carcinoma (IDC) tumors. ER+ ILC cell lines and xenograft tumor explant cultures were used to evaluate efficacy to IGF1R pathway inhibition in combination with endocrine therapy.Results: Diminished functional E-cadherin increased both activation of IGF1R signaling and efficacy to anti-IGF1R/InsR therapies. PLA demonstrated a direct endogenous interaction between IGF1R and E-cadherin at points of cell-cell contact. Increased expression of IGF1 ligand and levels of IGF1R/InsR phosphorylation were observed in E-cadherin-deficient ER+ ILC compared with IDC tumors. IGF1R pathway inhibitors were effective in inhibiting growth in ER+ ILC cell lines and synergized with endocrine therapy and similarly IGF1R/InsR inhibition reduced proliferation in ILC tumor explant culture.Conclusions: We provide evidence that loss of E-cadherin hyperactivates the IGF1R pathway and increases sensitivity to IGF1R/InsR targeted therapy, thus identifying the IGF1R pathway as a potential novel target in E-cadherin-deficient breast cancers. Clin Cancer Res; 24(20); 5165-77. ©2018 AACR.