Deregulated expression of insulin-like growth factor 1 in prostate epithelium leads to neoplasia in transgenic mice

Decoding the Influence of Obesity on Prostate Cancer and Its Transgenerational Impact

In recent decades, the escalating prevalence of metabolic disorders, notably obesity and being overweight, has emerged as a pressing concern in public health. Projections for the future indicate a continual upward trajectory in obesity rates, primarily attributable to unhealthy dietary patterns and sedentary lifestyles. The ramifications of obesity extend beyond its visible manifestations, intricately weaving a web of hormonal dysregulation, chronic inflammation, and oxidative stress. This nexus of factors holds particular significance in the context of carcinogenesis, notably in the case of prostate cancer (PCa), which is a pervasive malignancy and a leading cause of mortality among men. A compelling hypothesis arises from the perspective of transgenerational inheritance, wherein genetic and epigenetic imprints associated with obesity may wield influence over the development of PCa. This review proposes a comprehensive exploration of the nuanced mechanisms through which obesity disrupts prostate homeostasis and serves as a catalyst for PCa initiation. Additionally, it delves into the intriguing interplay between the transgenerational transmission of both obesity-related traits and the predisposition to PCa. Drawing insights from a spectrum of sources, ranging from in vitro and animal model research to human studies, this review endeavors to discuss the intricate connections between obesity and PCa. However, the landscape remains partially obscured as the current state of knowledge unveils only fragments of the complex mechanisms linking these phenomena. As research advances, unraveling the associated factors and underlying mechanisms promises to unveil novel avenues for understanding and potentially mitigating the nexus between obesity and the development of PCa.

Modelling the distinct roles of epithelial and stromal androgen receptor in the regulation of prostate epithelial dynamics

The prostate is an androgen-responsive organ, but the complex cellular and molecular interactions that mediate these responses remain incompletely defined. Here, I synthesise the existing literature to derive a simple conceptual framework describing the androgen-dependent regulation of prostate epithelial dynamics. In this framework, epithelial androgen receptor (AR) cell-autonomously controls luminal cell height, whereas stromal AR regulates the synthesis of growth factors that promote luminal cell survival and proliferation. With the additional aid of a reanalysis of single-cell RNA-seq data, I also propose that insulin-like growth factor 1 (IGF1) functions as a key androgen-dependent growth factor coordinating stromal-to-epithelial paracrine communication. A novel mathematical model based on this framework was able to quantitatively fit experimental data describing prostate regression and regeneration. Model analysis demonstrates how the luminal cell population can maintain a stable equilibrium size via competition for and degradation of stroma-derived IGF1 and how this population size can be controlled by androgen levels, without a requirement for distinct luminal cell subsets. Moreover, model simulations were able to qualitatively recapitulate experimental observations in inflammatory and cancerous states, thereby providing insights into potential disease mechanisms. This simple model could therefore serve as a foundation for more comprehensive modelling of both the healthy and diseased prostate.

Obesity-induced thymic involution and cancer risk

Declining thymic functions associated either with old age (i.e., age-related thymic involution), or with acute involution as a result of stress, infectious disease, or cytoreductive therapies (e.g., chemotherapy/radiotherapy), have been associated with cancer development. A key mechanism underlying such increased cancer risk is the thymus-dependent debilitation of adaptive immunity, which is responsible for orchestrating immunoediting mechanisms and tumor immune surveillance. In the past few years, a blooming set of evidence has intriguingly linked obesity with cancer development and progression. The majority of such studies has focused on obesity-driven chronic inflammation, steroid/sex hormone and adipokine production, and hyperinsulinemia, as principal factors affecting the tumor microenvironment and driving the development of primary malignancy. However, experimental observations about the negative impact of obesity on T cell development and maturation have existed for more than half a century. Here, we critically discuss the molecular and cellular mechanisms of obesity-driven thymic involution as a previously underrepresented intermediary pathology leading to cancer development and progression. This knowledge could be especially relevant in the context of childhood obesity, because impaired thymic function in young individuals leads to immune system abnormalities, and predisposes to various pediatric cancers. A thorough understanding behind the molecular and cellular circuitries governing obesity-induced thymic involution could therefore help towards the rationalized development of targeted thymic regeneration strategies for obese individuals at high risk of cancer development.

Stromal androgen signaling acts as tumor niches to drive prostatic basal epithelial progenitor-initiated oncogenesis

The androgen receptor (AR)-signaling pathways are essential for prostate tumorigenesis. Although significant effort has been devoted to directly targeting AR-expressing tumor cells, these therapies failed in most prostate cancer patients. Here, we demonstrate that loss of AR in stromal sonic-hedgehog Gli1-lineage cells diminishes prostate epithelial oncogenesis and tumor development using in vivo assays and mouse models. Single-cell RNA sequencing and other analyses identified a robust increase of insulin-like growth factor (IGF) binding protein 3 expression in AR-deficient stroma through attenuation of AR suppression on Sp1-regulated transcription, which further inhibits IGF1-induced Wnt/β-catenin activation in adjacent basal epithelial cells and represses their oncogenic growth and tumor development. Epithelial organoids from stromal AR-deficient mice can regain IGF1-induced oncogenic growth. Loss of human prostate tumor basal cell signatures reveals in basal cells of stromal AR-deficient mice. These data demonstrate a distinct mechanism for prostate tumorigenesis and implicate co-targeting stromal and epithelial AR-signaling for prostate cancer.

Aberrant androgen action in prostatic progenitor cells induces oncogenesis and tumor development through IGF1 and Wnt axes

Androgen/androgen receptor (AR) signaling pathways are essential for prostate tumorigenesis. However, the fundamental mechanisms underlying the AR functioning as a tumor promoter in inducing prostatic oncogenesis still remain elusive. Here, we demonstrate that a subpopulation of prostatic Osr1 (odd skipped-related 1)-lineage cells functions as tumor progenitors in prostate tumorigenesis. Single cell transcriptomic analyses reveal that aberrant AR activation in these cells elevates insulin-like growth factor 1 (IGF1) signaling pathways and initiates oncogenic transformation. Elevating IGF1 signaling further cumulates Wnt/β-catenin pathways in transformed cells to promote prostate tumor development. Correlations between altered androgen, IGF1, and Wnt/β-catenin signaling are also identified in human prostate cancer samples, uncovering a dynamic regulatory loop initiated by the AR through prostate cancer development. Co-inhibition of androgen and Wnt-signaling pathways significantly represses the growth of AR-positive tumor cells in both ex-vivo and in-vivo, implicating co-targeting therapeutic strategies for these pathways to treat advanced prostate cancer.

Role of prostate stem cells and treatment strategies in benign prostate hyperplasia

Benign prostate hyperplasia (BPH) is a progressive disease with a direct correlation between incidence and age. Since the treatment and management of BPH involve harmful side effects and decreased quality of life for the patient, the primary focus of research should be to find better and longer-lasting therapeutic options. The mechanisms regulating prostate stem cells in development can be exploited to decrease prostate growth. BPH is defined as the overgrowth of the prostate, and BPH is often diagnosed when lower urinary tract symptoms (LUTS) of urine storage or voiding symptoms cause patients to seek treatment. While multiple factors are involved in the hyperplastic growth of the stromal and epithelial compartments of the prostate, the clonal proliferation of stem cells is considered one of the main reasons for BPH initiation and regrowth of the prostate after therapies for BPH fail. Several theories explain possible reasons for the involvement of stem cells in the development, progression, and pathogenesis of BPH. The aim of the current review is to discuss current literature on the fundamentals of prostate development and the role of stem cells in BPH. This review examines the rationale for the hypothesis that unregulated stem cell properties can lead to BPH and therapeutic targeting of stem cells may reduce treatment-related side effects and prevent the regrowth of the prostate.

Investigating the effects of two novel 4-MMPB analogs as potent lipoxygenase inhibitors for prostate cancer treatment

Background

Lipoxygenases are one of the critical signaling mediators which can be targeted for human prostate cancer (PC) therapy. In this study, 4-methyl-2-(4-methylpiperazinyl)pyrimido[4,5-b]benzothiazine (4-MMPB) and its two analogs, 4-propyl-2-(4-methylpiperazinyl)pyrimido[4,5-b]benzothiazine (4-PMPB) and 4-ethyl-2-(4-methylpiperazinyl)pyrimido[4,5-b]benzothiazine (4-EMPB), were proposed to have anti-tumor properties in prostate cancer.

Methods

After synthesizing the compounds, cytotoxic effects of 4-MMPB and its two analogs against PC-3 cancerous and HDF normal cells were investigated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and then mechanism of cell death was assessed by flow cytometry. Finally, the anti-tumor effects of the mentioned compounds were investigated in an immunocompromised C57BL/6 mouse model.

Results

4-PMPB and 4-EMPB had similar anti-cancer effects on PC-3 cells as compared with 4-MMPB, while they were not effective on normal cells. Moreover, apoptosis and ferroptosis were the main mechanisms of induced cell death in these cancerous cells. Furthermore, in vivo results indicated that both analogs had similar anti-cancer effects as 4-MMPB, leading to delayed tumor growth without any noticeable side effects in weight loss and histological investigations.

Conclusion

Thus, our results suggest that specific targeting of lipoxygenases via 4-MMPB analogs can be considered as a treatment of choice for PC therapy, although it requires further investigations.

Overweight and obesity in men with prostate cancer do not constitute risk factors for biochemical recurrence

AIM

To investigate if overweight and obesity were associated with a higher degree of biochemical recurrence (BCR) after radical prostatectomy, in Mexican men with prostate cancer (PCa).

METHODS

We included 180 men with PCa, who underwent radical prostatectomy (RP). Body mass index (BMI) was determined and the degree of PCa aggressiveness was established according to the D'Amico classification. Postoperative follow-up of all patients was performed with PSA quantification every/6 weeks after surgery and then at 3-month intervals for 1 year, followed every/6 months for 5 years. Postoperative BCR was defined as two consecutive increases in PSA levels ≥0.4 ng/mL, after RP.

RESULTS

Sixty eight percent of the patients presented overweight or obesity. We found that only intermediate/high risk patients presented an increased risk factor for BCR-free survival (HR = 4.39; 95% CI = 1.74-11.24; p = 0.002). The median follow-up of all men has been 7.9 years and no significant differences in BCR-free survival time has been observed between the BMI groups.

CONCLUSIONS

The overweight and obesity do not represent a risk factor to present BCR after RP for PCa. However, an intermediate/high risk, according to the D'Amico's classification, constitutes a risk factor to present BCR after radical prostatectomy, which is not related to the BMI.

Hormone-related diseases and prostate cancer: An English national record linkage study

Insulin-like growth factor-I (IGF-I) and testosterone may be related to prostate cancer risk. Acromegaly is associated with clinically high IGF-I concentrations. Klinefelter's syndrome, testicular hypofunction and hypopituitarism are associated with clinically low testosterone concentrations. We aimed to investigate whether diagnosis with these conditions was associated with subsequent prostate cancer diagnosis and mortality. We used linked English national Hospital Episode Statistics and mortality data from 1999 to 2017 to construct and follow-up cohorts of men aged ≥35 years diagnosed with (i) acromegaly (n = 2,495) and (ii) hypogonadal-associated diseases (n = 18,763): Klinefelter's syndrome (n = 1,992), testicular hypofunction (n = 8,086) and hypopituitarism (n = 10,331). We estimated adjusted hazard ratios (HRs) and confidence intervals (CIs) for prostate cancer diagnosis and death using Cox regression in comparison with an unexposed reference cohort of 4.3 million men, who were admitted to hospital for a range of minor surgeries and conditions (n observed cases = 130,000, n prostate cancer deaths = 30,000). For men diagnosed with acromegaly, HR for prostate cancer diagnosis was 1.33 (95% CI 1.09-1.63; p = 0.005; n observed cases = 96), HR for prostate cancer death was 1.44 (95% CI 0.92-2.26; p = 0.11; n deaths = 19). Diagnosis with Klinefelter's syndrome was associated with a lower prostate cancer risk (HR = 0.58, 95% CI 0.37-0.91; p = 0.02; n observed cases = 19) and hypopituitarism was associated with a reduction in prostate cancer death (HR = 0.53, 95% CI 0.35-0.79; p = 0.002; n deaths = 23). These results support the hypothesised roles of IGF-I and testosterone in prostate cancer development and/or progression. These findings are important because they provide insight into prostate cancer aetiology.

Targeting the IGF-Axis for Cancer Therapy: Development and Validation of an IGF-Trap as a Potential Drug

The insulin-like growth factor (IGF)-axis was implicated in cancer progression and identified as a clinically important therapeutic target. Several IGF-I receptor (IGF-IR) targeting drugs including humanized monoclonal antibodies have advanced to phase II/III clinical trials, but to date, have not progressed to clinical use, due, at least in part, to interference with insulin receptor signaling and compensatory signaling by the insulin receptor (IR) isoform A that can bind IGF-II and initiate mitogenic signaling. Here we briefly review the current state of IGF-targeting biologicals, discuss some factors that may be responsible for their poor performance in the clinic and outline the stepwise bioengineering and validation of an IGF-Trap—a novel anti-cancer therapeutic that could bypass these limitations. The IGF-Trap is a heterotetramer, consisting of the entire extracellular domain of the IGF-IR fused to the Fc portion of human IgG₁. It binds human IGF-I and IGF-II with a three-log higher affinity than insulin and could inhibit IGF-IR driven cellular functions such as survival, proliferation and invasion in multiple carcinoma cell models in vitro. In vivo, the IGF-Trap has favorable pharmacokinetic properties and could markedly reduce metastatic outgrowth of colon and lung carcinoma cells in the liver, outperforming IGF-IR and ligand-binding monoclonal antibodies. Moreover, IGF-Trap dose-response profiles correlate with their bio-availability profiles, as measured by the IGF kinase receptor-activation (KIRA) assay, providing a novel, surrogate biomarker for drug efficacy. Our studies identify the IGF-Trap as a potent, safe, anti-cancer therapeutic that could overcome some of the obstacles encountered by IGF-targeting biologicals that have already been evaluated in clinical settings.

The Continuing Evolution of Insulin-like Growth Factor Signaling

The insulin-like growth factors (IGFs; IGF1/IGF2), known for their regulation of cell and organismal growth and development, are evolutionarily conserved ligands with equivalent peptides present in flies ( D. melanogaster), worms ( C. elegans) among others. Two receptor tyrosine kinases, the IGF1 receptor and the insulin receptor mediate the actions of these ligands with a family of IGF binding proteins serving as selective inhibitors of IGF1/2. This treatise reviews recent findings on IGF signaling in cancer biology and central nervous system function. This includes overexpression of IGF1 receptors in enhancing tumorigenesis, acquired resistance and contributions to metastasis in multiple cancer types. There is accumulating evidence that insulin resistance, a hallmark of type 2 diabetes, occurs in the central nervous system, independent of systemic insulin resistance and characterized by reduced insulin and IGF1 receptor signaling, and may contribute to dementias including Alzheimer’s Disease and cognitive impairment. Controversy over the role(s) of IGF signaling in cancer and whether its inhibition would be of benefit, still persist and extend to IGF1’s role in longevity and central nervous system function.

Systemic Complications of Acromegaly and the Impact of the Current Treatment Landscape: An Update

Acromegaly is a chronic systemic disease with many complications and is associated with increased mortality when not adequately treated. Substantial advances in acromegaly treatment, as well as in the treatment of many of its complications, mainly diabetes mellitus, heart failure, and arterial hypertension, were achieved in the last decades. These developments allowed change in both prevalence and severity of some acromegaly complications and furthermore resulted in a reduction of mortality. Currently, mortality seems to be similar to the general population in adequately treated patients with acromegaly. In this review, we update the knowledge in complications of acromegaly and detail the effects of different acromegaly treatment options on these complications. Incidence of mortality, its correlation with GH (cumulative exposure vs last value), and IGF-I levels and the shift in the main cause of mortality in patients with acromegaly are also addressed.

IRS-2 deubiquitination by USP9X maintains anchorage-independent cell growth via Erk1/2 activation in prostate carcinoma cell line

Insulin-like growth factors (IGFs) have been shown to induce proliferation of many types of cells. Insulin receptor substrates (IRSs) are major targets of IGF-I receptor (IGF-IR) tyrosine kinase activated by IGFs, and are known to play important roles in the activation of downstream signaling pathways, such as the Erk1/2 pathway. Dysregulation of IGF signaling represents a central tumor promoting principle in human carcinogenesis. Prostate carcinoma is highly dependent on the IGF/IGF-IR/IRS axis. Here we identified the deubiquitinase, ubiquitin specific peptidase 9X (USP9X) as a novel binding partner of IRS-2. In a human prostate carcinoma cell line, small interfering RNA (siRNA)-mediated knockdown of USP9X reduced IGF-IR as well as IRS-2 protein levels and increased their ubiquitination. Knockdown of USP9X suppressed basal activation of the Erk1/2 pathway, which was significantly restored by exogenous expression of IRS-2 but not by IGF-IR, suggesting that the stabilization of IRS-2 by USP9X is critical for basal Erk1/2 activation. Finally, we measured anchorage-independent cell growth, a characteristic cancer feature, by soft-agar colony formation assay. Knockdown of USP9X significantly reduced anchorage-independent cell growth of prostate carcinoma cell line. Taken all together, our findings indicate that USP9X is required for the promotion of prostate cancer growth by maintaining the activation of the Erk1/2 pathway through IRS-2 stabilization.

The MDA-9/Syntenin/IGF1R/STAT3 Axis Directs Prostate Cancer Invasion

Although prostate cancer is clinically manageable during several stages of progression, survival is severely compromised once cells invade and metastasize to distant organs. Comprehending the pathobiology of invasion is required for developing efficacious targeted therapies against metastasis. Based on bioinformatics data, we predicted an association of melanoma differentiation-associated gene-9 [syntenin, or syndecan binding protein (SDCBP)] in prostate cancer progression. Using tissue samples from various Gleason stage prostate cancer patients with adjacent normal tissue, a series of normal prostate and prostate cancer cell lines (with differing tumorigenic/metastatic properties), mda-9/syntenin-manipulated variants (including loss-of-function and gain-of-function cell lines), and CRISPR/Cas9 stable MDA-9/Syntenin knockout cells, we now confirm the relevance of and dependence on MDA-9/syntenin in prostate cancer invasion. MDA-9/Syntenin physically interacted with insulin-like growth factor-1 receptor following treatment with insulin-like growth factor binding protein-2 (IGFBP2), regulating downstream signaling processes that enabled STAT3 phosphorylation. This activation enhanced expression of MMP2 and MMP9, two established enzymes that positively regulate invasion. In addition, MDA-9/syntenin-mediated upregulation of proangiogenic factors including IGFBP2, IL6, IL8, and VEGFA also facilitated migration of prostate cancer cells. Collectively, our results draw attention to MDA-9/Syntenin as a positive regulator of prostate cancer metastasis, and the potential application of targeting this molecule to inhibit invasion and metastasis in prostate cancer and potentially other cancers.Significance: This study provides new mechanistic insight into the proinvasive role of MDA-9/Syntenin in prostate cancer and has potential for therapeutic application to prevent prostate cancer metastasis. Cancer Res; 78(11); 2852-63. ©2018 AACR.

Type I insulin-like growth factor receptor signaling in hematological malignancies

The insulin-like growth factor (IGF) signaling system plays key roles in the establishment and progression of different types of cancer. In agreement with this idea, substantial evidence has shown that the type I IGF receptor (IGF-IR) and its primary ligand IGF-I are important for maintaining the survival of malignant cells of hematopoietic origin. In this review, we discuss current understanding of the role of IGF-IR signaling in cancer with a focus on the hematological neoplasms. We also address the emergence of IGF-IR as a potential therapeutic target for the treatment of different types of cancer including plasma cell myeloma, leukemia, and lymphoma.

Does milk intake promote prostate cancer initiation or progression via effects on insulin-like growth factors (IGFs)? A systematic review and meta-analysis

PURPOSE

To establish whether the association between milk intake and prostate cancer operates via the insulin-like growth factor (IGF) pathway (including IGF-I, IGF-II, IGFBP-1, IGFBP-2, and IGFBP-3).

METHODS

Systematic review, collating data from all relevant studies examining associations of milk with IGF, and those examining associations of IGF with prostate cancer risk and progression. Data were extracted from experimental and observational studies conducted in either humans or animals, and analyzed using meta-analysis where possible, with summary data presented otherwise.

RESULTS

One hundred and seventy-two studies met the inclusion criteria: 31 examining the milk-IGF relationship; 132 examining the IGF-prostate cancer relationship in humans; and 10 animal studies examining the IGF-prostate cancer relationship. There was moderate evidence that circulating IGF-I and IGFBP-3 increase with milk (and dairy protein) intake (an estimated standardized effect size of 0.10 SD increase in IGF-I and 0.05 SD in IGFBP-3 per 1 SD increase in milk intake). There was moderate evidence that prostate cancer risk increased with IGF-I (Random effects meta-analysis OR per SD increase in IGF-I 1.09; 95% CI 1.03, 1.16; n = 51 studies) and decreased with IGFBP-3 (OR 0.90; 0.83, 0.98; n = 39 studies), but not with other growth factors. The IGFBP-3 -202A/C single nucleotide polymorphism was positively associated with prostate cancer (pooled OR for A/C vs. AA = 1.22; 95% CI 0.84, 1.79; OR for C/C vs. AA = 1.51; 1.03, 2.21, n = 8 studies). No strong associations were observed for IGF-II, IGFBP-1 or IGFBP-2 with either milk intake or prostate cancer risk. There was little consistency within the data extracted from the small number of animal studies. There was additional evidence to suggest that the suppression of IGF-II can reduce tumor size, and contradictory evidence with regards to the effect of IGFBP-3 suppression on tumor progression.

CONCLUSION

IGF-I is a potential mechanism underlying the observed associations between milk intake and prostate cancer risk.

Dietary glycemic index, glycemic load and cancer: An overview of the literature

AIMS

The aim of this paper is to provide an overview of the current evidence for associations between dietary glycemic index (GI) and dietary glycemic load (GL), and the risk of various types of cancer, and to summarize mechanisms proposed to explain the associations found.

DATA SYNTHESIS

Medline was searched for cohort studies, case-control studies, and meta-analyses, published up to February 2016, that examined associations between dietary GI/GL and cancer. Findings from the main meta-analyses showed a weak-to-moderate association of high dietary GI/GL with increased risk of some cancers. High dietary GI but not GL was significantly and consistently associated with increased colorectal cancer risk in both cohort and case-control studies. Dietary GL was directly associated with breast and endometrial cancer risk in cohort studies. Positive associations between dietary GI or GL and cancer risk were found more frequently in case-control studies than cohort studies. The main mechanism for these associations is thought to be chronic hyperinsulinemia. Insulin is itself a mitogen and also increases the bioactivity of insulin-like growth factors which can promote cancer by inhibiting apoptosis and stimulating cell proliferation.

CONCLUSIONS

The review has uncovered consistent evidence that high dietary GI is associated with increased risk of colorectal cancer, and that high dietary GL is associated with increased risk of breast and endometrial cancer. However the risk increases are small or moderate.

Glycemic Index, Glycemic Load, and Lung Cancer Risk in Non-Hispanic Whites

BACKGROUND

Postprandial glucose (PPG) and insulin responses play a role in carcinogenesis. We evaluated the association between dietary glycemic index (GI) and glycemic load (GL), markers of carbohydrate intake and PPG, and lung cancer risk in non-Hispanic whites.

METHODS

GL and GI were assessed among 1,905 newly diagnosed lung cancer cases recruited from the University of Texas MD Anderson Cancer Center (Houston, TX) and 2,413 healthy controls recruited at Kelsey-Seybold Clinics (Houston, TX). We assessed associations between quintiles of GI/GL and lung cancer risk and effect modification by various risk factors. ORs and 95% confidence intervals (CI) were estimated using multivariable logistic regression.

RESULTS

We observed a significant association between GI [5th vs. 1st quintile (Q) OR = 1.49; 95% CI, 1.21-1.83; P(trend) <0.001] and lung cancer risk and GI(ac) (5th vs. 1st Q OR = 1.48; 95% CI, 1.20-1.81; P(trend) = 0.001) and lung cancer risk. We observed a more pronounced association between GI and lung cancer risk among never smokers (5th vs. 1st Q OR = 2.25; 95% CI, 1.42-3.57), squamous cell carcinomas (SCC; 5th vs. 1st Q OR = 1.92; 95% CI, 1.30-2.83), and those with less than 12 years of education (5th vs. 1st Q OR = 1.75; 95% CI, 1.19-2.58, P(interaction) = 0.02).

CONCLUSION

This study suggests that dietary GI and other lung cancer risk factors may jointly and independently influence lung cancer etiology.

IMPACT

Understanding the role of GI in lung cancer could inform prevention strategies and elucidate biologic pathways related to lung cancer risk.

TMPRSS2-ERG fusion protein regulates insulin-like growth factor-1 receptor (IGF1R) gene expression in prostate cancer: involvement of transcription factor Sp1

Prostate cancer is a major health issue in the Western world. The most common gene rearrangement in prostate cancer is the TMPRSS2-ERG fusion, which results in aberrant expression of the transcription factor ERG. The insulin-like growth factor-1 receptor (IGF1R) plays a key role in cell growth and tumorigenesis, and is overexpressed in most malignancies, including prostate cancer. In this study we show that TMPRSS2-ERG mediates its tumorigenic effects through regulation of IGF1R gene expression. Silencing of T-ERG in VCaP cells resulted in downregulation of both IGF1R and Sp1, a critical IGF1R regulator. Co-immunoprecipitation assays revealed a physical interaction between transcription factors ERG and Sp1, with potential relevance in IGF1R gene regulation. In addition, transactivation of the IGF1R gene by ERG was mediated at the level of transcription, as indicated by results of promoter assays. To identify new co-activators of the TMPRSS2-ERG fusion protein we performed mass spectrometry-based proteomic analyses. Among other interactors, we identified AP-2 complex subunit mu (AP2M1) and caveolin-1 (CAV1) in association with ERG in cell nuclei. These proteins play a mechanistic role in IGF1R internalization. Our analyses are consistent with a potential novel function of TMPRSS2-ERG as a major regulator of IGF1R gene expression. Results may impinge upon ongoing efforts to target the IGF1R in the clinics.

Mouse Models in Prostate Cancer Translational Research: From Xenograft to PDX

Despite the advancement of clinical and preclinical research on PCa, which resulted in the last five years in a decrement of disease incidence by 3-4%, it remains the most frequent cancer in men and the second for mortality rate. Based on this evidence we present a brief dissertation on numerous preclinical models, comparing their advantages and disadvantages; among this we report the PDX mouse models that show greater fidelity to the disease, in terms of histopathologic features of implanted tumor, gene and miRNA expression, and metastatic pattern, well describing all tumor progression stages; this characteristic encourages the translation of preclinical results. These models become particularly useful in meeting the need of new treatments identification that eradicate PCa bone metastases growing, clarifying pathway of angiogenesis, identifying castration-resistant stem-like cells, and studying the antiandrogen therapies. Also of considerable interest are the studies of 3D cell cultures derived from PDX, which have the ability to maintain PDX cell viability with continued native androgen receptor expression, also showing a differential sensitivity to drugs. 3D PDX PCa may represent a diagnostic platform for the rapid assessment of drugs and push personalized medicine. Today the development of preclinical models in vitro and in vivo is necessary in order to obtain increasingly reliable answers before reaching phase III of the drug discovery.

Insulin activates EGFR by stimulating its interaction with IGF-1R in low-EGFR-expressing TNBC cells

The expression of epidermal growth factor receptor (EGFR) is an important diagnostic marker for triple-negative breast cancer (TNBC) cells, which lack three hormonal receptors: estrogen and progesterone receptors as well as epidermal growth factor receptor 2. EGFR transactivation can cause drug resistance in many cancers including TNBC, but the mechanism underlying this phenomenon is poorly defined. Here, we demonstrate that insulin treatment induces EGFR activation by stimulating the interaction of EGFR with insulin-like growth factor receptor 1 (IGF-1R) in the MDA-MB-436 TNBC cell line. These cells express low levels of EGFR, while exhibiting high levels of IGF-1R expression and phosphorylation. Low-EGFRexpressing MDA-MB-436 cells show high sensitivity to insulinstimulated cell growth. Therefore, unexpectedly, insulin stimulation induced EGFR transactivation by regulating its interaction with IGF-1R in low-EGFR-expressing TNBC cells.

The insulin-like growth factor (IGF) axis as an anticancer target in prostate cancer

Prostate cancer (PCa) is the most common cancer and the second leading cause of cancer death in males. In recent years, several new targeting agents have been introduced for the treatment of advanced stages of the disease. However, development of resistance limits the efficacy of new drugs and there is a further need to develop additional novel treatment approaches. One of the most investigated targets in cancer research is the insulin-like growth factor (IGF) axis, whose receptors are overexpressed in several cancer entities including PCa. In preclinical studies in PCa, targeting of the IGF axis receptors showed promising anti-tumor effects. Currently available data on clinical studies do not meet the expectations for this new treatment approach. In this review we provide a summary of preclinical and clinical studies on the IGF axis in PCa including treatment with monoclonal antibodies and tyrosine kinase inhibitors. Moreover, we summarize preliminary results from ongoing studies and discuss limitations and side effects of the substances used. We also address the role of the IGF axis in the biomarkers setting including IGF-binding proteins and genetic variants.

Drug discovery in prostate cancer mouse models

INTRODUCTION

The mouse is an important, though imperfect, organism with which to model human disease and to discover and test novel drugs in a preclinical setting. Many experimental strategies have been used to discover new biological and molecular targets in the mouse, with the hopes of translating these discoveries into novel drugs to treat prostate cancer in humans. Modeling prostate cancer in the mouse, however, has been challenging, and often drugs that work in mice have failed in human trials.

AREAS COVERED

The authors discuss the similarities and differences between mice and men; the types of mouse models that exist to model prostate cancer; practical questions one must ask when using a mouse as a model; and potential reasons that drugs do not often translate to humans. They also discuss the current value in using mouse models for drug discovery to treat prostate cancer and what needs are still unmet in field.

EXPERT OPINION

With proper planning and following practical guidelines by the researcher, the mouse is a powerful experimental tool. The field lacks genetically engineered metastatic models, and xenograft models do not allow for the study of the immune system during the metastatic process. There remain several important limitations to discovering and testing novel drugs in mice for eventual human use, but these can often be overcome. Overall, mouse modeling is an essential part of prostate cancer research and drug discovery. Emerging technologies and better and ever-increasing forms of communication are moving the field in a hopeful direction.

Insulin-like growth factor receptor-1 (IGF-IR) as a target for prostate cancer therapy

Prostate cancer is the most commonly diagnosed cancer in men and is the second leading cause of cancer-related deaths in men each year. Androgen deprivation therapy is and has been the gold standard of care for advanced or metastatic prostate cancer for decades. While this treatment strategy initially shows benefit, eventually tumors recur as castration-resistant prostate cancer for which there are limited treatment options with only modest survival benefit. Upregulation of the insulin-like growth factor receptor type I (IGF-IR) signaling axis has been shown to drive the survival of prostate cancer cells in many studies. As many IGF-IR blockades have been developed, few have been tested preclinically and even fewer have entered clinical trials for prostate cancer therapy. In this review, we will update the most recent preclinical and clinical studies of IGF-IR therapy for prostate cancer. We will also discuss the challenges for IGF-IR targeted therapies to achieve clinical benefit for prostate cancer.

Insulin-like growth factor system in cancer: novel targeted therapies

Insulin-like growth factors (IGFs) are essential for growth and survival that suppress apoptosis and promote cell cycle progression, angiogenesis, and metastatic activities in various cancers. The IGFs actions are mediated through the IGF-1 receptor that is involved in cell transformation induced by tumour. These effects depend on the bioavailability of IGFs, which is regulated by IGF binding proteins (IGFBPs). We describe here the role of the IGF system in cancer, proposing new strategies targeting this system. We have attempted to expand the general viewpoint on IGF-1R, its inhibitors, potential limitations of IGF-1R, antibodies and tyrosine kinase inhibitors, and IGFBP actions. This review discusses the emerging view that blocking IGF via IGFBP is a better option than blocking IGF receptors. This can lead to the development of novel cancer therapies.

Insulin/Insulin-like growth factors in cancer: new roles for the aryl hydrocarbon receptor, tumor resistance mechanisms, and new blocking strategies

The insulin-like growth factor 1 receptor (IGF1R) and the insulin receptor (IR) are receptor tyrosine kinases that are expressed in cancer cells. The results of different studies indicate that tumor proliferation and survival is dependent on the IGF1R and IR, and that their inhibition leads to reductions in proliferation and increases in cell death. Molecular targeting therapies that have been used in solid tumors include anti-IGF1R antibodies, anti-IGF1/IGF2 antibodies, and small molecule inhibitors that suppress IGF1R and IR kinase activity. New advances in the molecular basis of anti-IGF1R blocking antibodies reveal they are biased agonists and promote the binding of IGF1 to integrin β3 receptors in some cancer cells. Our recent reports indicate that pharmacological aryl hydrocarbon receptor (AHR) ligands inhibit breast cancer cell responses to IGFs, suggesting that targeting AHR may have benefit in cancers whose proliferation and survival are dependent on insulin/IGF signaling. Novel aspects of IGF1R/IR in cancer, such as biased agonism, integrin β3 signaling, AHR, and new therapeutic targeting strategies will be discussed.

Ectopic expression of AP-2α transcription factor suppresses glioma progression

The transcriptional factor AP-2α is a tumor suppressor gene and is downregulated in various neoplasms including glioma. Although the level of AP-2α is negatively associated with the grade of human glioma, the specific functions of AP-2α in glioma are still unknown. In this study, we experimentally showed that artificial overexpression of AP-2α in glioma T98G and U251 cells significantly downregulated the mRNA levels of Bcl-xl, Bcl-2, c-IAP2 and survivin, together with upregulation of the Hrk mRNA levels. Reintroduction of AP-2α also induced downregulation of the protein levels of survivin and VEGF in glioma cells. In biological assays with T98G and U251 cells, AP-2α reduced tumor cell growth, increased cell death, attenuated cell migration and endothelial tube formation. The AP-2α transcription factor may play an important role in suppressing glioma progression.

Genetic and dietary determinants of insulin-like growth factor (IGF)-1 and IGF binding protein (BP)-3 levels among Chinese women

Background

Higher insulin-like growth factor (IGF)-1 and lower IGF binding protein (BP)-3 levels have been associated with higher commoncancer risk, including breast cancer. Dietary factors, genetic polymorphisms, and the combination of both may influence circulating IGF-1 and IGFBP-3 serum concentrations.

Methods

From September 2011 to July 2012, we collected demographic, reproductive and dietary data on 143 women (≥40 years). We genotyped IGF-1 rs1520220 and IGFBP-3 rs2854744 and measured circulating IGF-1 and IGFBP-3 levels in serum. Covariance analyses were used to estimate the associations of serum levels of IGF-1 and IGFBP-3, and the molar ratio of IGF-1to IGFBP-3 with IGF-1 rs1520220 and IGFBP-3 rs2854744 genotypes. We subsequently assessed the combined influence of genetics and diet (daily intake of protein, fat and soy isoflavones) on IGF-1 and IGFBP-3 levels.

Results

Among women aged less than 50 years, circulating IGF-1 serum levels were significantly lower for those with CC genotype for IGF-1 rs1520220 than levels for those with the GC or GG genotypes (in recessive model: P = 0.007).In gene-diet analyses among these women, we found carrying CC genotype for IGF-1 rs1520220 and high soy isoflavone intake tend to be associated with lower circulating IGF-1 levels synthetically (P = 0.002). Women with GG or GC genotypes for IGF-1 rs1520220 and with low intake of soy isoflavones had the highest levels of circulating IGF-1 (geometric mean [95% CI]: 195 [37, 1021] µg/L). Comparatively, women with both the CC genotype and high soy intake had the lowest levels of circulating IGF-1 (geometric mean [95% CI]: 120 [38,378] µg/L).

Conclusions

IGF-1 serum levels are significantly lower among women with the CC genotype for IGF-1-rs1520220. High soy isoflavone intake may interact with carrying CC genotype for IGF-1-rs1520220 to lower women's serum IGF-1 levels more.

Obesity and cancer--mechanisms underlying tumour progression and recurrence

Over the past several years, the field of cancer research has directed increased interest towards subsets of obesity-associated tumours, which include mammary, renal, oesophageal, gastrointestinal and reproductive cancers in both men and women. The increased risk of breast cancer that is associated with obesity has been widely reported; this has drawn much attention and as such, warrants investigation of the key mechanisms that link the obese state with cancer aetiology. For instance, the obese setting provides a unique adipose tissue microenvironment with concomitant systemic endocrine alterations that favour both tumour initiation and progression. Major metabolic differences exist within tumours that distinguish them from non-transformed healthy tissues. Importantly, considerable metabolic differences are induced by tumour cells in the stromal vascular fraction that surrounds them. The precise mechanisms that underlie the association of obesity with cancer and the accompanying metabolic changes that occur in the surrounding microenvironment remain elusive. Nonetheless, specific therapeutic agents designed for patients with obesity who develop tumours are clearly needed. This Review discusses recent advances in understanding the contributions of obesity to cancer and their implications for tumour treatment.

Evaluation of protein biomarkers of prostate cancer aggressiveness

BACKGROUND

Prognostic multibiomarker signatures in prostate cancer (PCa) may improve patient management and provide a bridge for developing novel therapeutics and imaging methods. Our objective was to evaluate the association between expression of 33 candidate protein biomarkers and time to biochemical failure (BF) after prostatectomy.

METHODS

PCa tissue microarrays were constructed representing 160 patients for whom clinicopathologic features and follow-up data after surgery were available. Immunohistochemistry for each of 33 proteins was quantified using automated digital pathology techniques. Relationships between clinicopathologic features, staining intensity, and time to BF were assessed. Predictive modeling using multiple imputed datasets was performed to identify the top biomarker candidates.

RESULTS

In univariate analyses, lymph node positivity, surgical margin positivity, non-localized tumor, age at prostatectomy, and biomarkers CCND1, HMMR, IGF1, MKI67, SIAH2, and SMAD4 in malignant epithelium were significantly associated with time to BF. HMMR, IGF1, and SMAD4 remained significantly associated with BF after adjusting for clinicopathologic features while additional associations were observed for HOXC6 and MAP4K4 following adjustment. In multibiomarker predictive models, 3 proteins including HMMR, SIAH2, and SMAD4 were consistently represented among the top 2, 3, 4, and 5 most predictive biomarkers, and a signature comprised of these proteins best predicted BF at 3 and 5 years.

CONCLUSIONS

This study provides rationale for investigation of HMMR, HOXC6, IGF1, MAP4K4, SIAH2, and SMAD4 as biomarkers of PCa aggressiveness in larger cohorts.

Role of receptor tyrosine kinases and their ligands in glioblastoma

Glioblastoma multiforme is the most frequent, aggressive and fatal type of brain tumor. Glioblastomas are characterized by their infiltrating nature, high proliferation rate and resistance to chemotherapy and radiation. Recently, oncologic therapy experienced a rapid evolution towards “targeted therapy,” which is the employment of drugs directed against particular targets that play essential roles in proliferation, survival and invasiveness of cancer cells. A number of molecules involved in signal transduction pathways are used as molecular targets for the treatment of various tumors. In fact, inhibitors of these molecules have already entered the clinic or are undergoing clinical trials. Cellular receptors are clear examples of such targets and in the case of glioblastoma multiforme, some of these receptors and their ligands have become relevant. In this review, the importance of glioblastoma multiforme in signaling pathways initiated by extracellular tyrosine kinase receptors such as EGFR, PDGFR and IGF-1R will be discussed. We will describe their ligands, family members, structure, activation mechanism, downstream molecules, as well as the interaction among these pathways. Lastly, we will provide an up-to-date review of the current targeted therapies in cancer, in particular glioblastoma that employ inhibitors of these pathways and their benefits.

Nonalcoholic fatty liver disease is a negative risk factor for prostate cancer recurrence

Nonalcoholic fatty liver disease (NAFLD) is closely related to the metabolic syndrome, which is associated with an increased risk of various malignancies. In this study, we investigated the association between NAFLD and prostate cancer biochemical recurrence (BCR) after radical prostatectomy. Consecutive prostate cancer patients who underwent radical prostatectomy were enrolled from two hospitals in Korea and randomly assigned to the training (n=147) or validation set (n=146). The presence of NAFLD, BMI, preoperative prostate-specific antigen, and histological findings including Gleason score (GSc) were analyzed in regard to their association with BCR. NAFLD was diagnosed based on ultrasonography or unenhanced computed tomography images. BCR-free survival rates were calculated using the Kaplan-Meier method. In the training set, 32 (21.8%) patients developed BCR during a median follow-up period of 51 (inter-quartile range, 35-65) months. In the multivariate analysis, the presence of NAFLD (hazard ratio (HR), 0.36; 95% CI, 0.14-0.97; P=0.04) was an independent negative predictive factor of BCR after adjustment for pathological GSc. Applied to the validation set, the presence of NAFLD maintained its prognostic value for longer time-to-BCR (HR, 0.17; 95% CI, 0.06-0.49; P=0.001). In the subgroup analysis of patients with NAFLD, NAFLD fibrosis score was a single independent negative predictor for BCR (HR, 0.54; 95% CI, 0.30-0.98; P=0.04). Our study demonstrated that NAFLD may play a protective role against BCR after radical prostatectomy for prostate cancer. Further study is warranted to elucidate the mechanism of protective effect in patients with NAFLD.

Elevated insulin-like growth factor binding protein-1 (IGFBP-1) in men with metastatic prostate cancer starting androgen deprivation therapy (ADT) is associated with shorter time to castration resistance and overall survival

BACKGROUND

Insulin-like growth factor (IGF) and adipokines have been implicated in prostate cancer carcinogenesis.

METHOD

Data from 122 men with serum samples drawn within 3 months of starting ADT for metastatic prostate cancer was accessed retrospectively. IGF-1, IGF binding protein (BP)-1, leptin, and adiponectin levels were measured by multiplex electrochemiluminescence assays. A multivariable Cox model assessed the association of time to castration resistant prostate cancer (CRPC) and overall survival by the protein levels, adjusted for clinical variables, age and prostate specific antigen (PSA) levels at start of ADT, race, ECOG status, extent of metastases and were reported as hazard ratio (HR) with 95% confidence interval (CI).

RESULTS

Median follow-up and overall survival were 44 and 42.2 months, respectively. ECOG performance status (≥ 1 vs. 0) was negatively associated with overall survival [H  = 2.8 (1.1-7.0), P = 0.03], and PSA nadir <0.2 was predictive of longer time to CRPC [HR = 0.3 (0.2-0.5), P < 0.0001]. The median time to CRPC by low, middle, and top IGFBP-1 tertile distribution was 20.7, 18.1, and 12.4 months, respectively, with HR for middle versus low tertile levels 3.1 (1.7-5), P = 0.0003, and for top versus low tertile levels was 2.4 (1.3-4.2), P = 0.003. The median overall survival by low, middle and top tertile IGFBP-1 level was 48.5, 46.4, and 32.8 months, respectively, with HR for top versus low tertile 2.5 (1.2-5.1), P = 0.01. There was no association with IGF-1, adiponectin and leptin.

CONCLUSION

Elevated IGFBP-1 appears to be associated with shorter time to CRPC and lower overall survival in men with metastatic prostate cancer.

Formononetin induces the mitochondrial apoptosis pathway in prostate cancer cells via downregulation of the IGF-1/IGF-1R signaling pathway

Abstract Context: Formononetin, an isoflavone, can inhibit the proliferation of cancer cells, including those of the prostate. However, its antitumor mechanism remains unclear. Aim: To investigate whether the insulin-like growth factor 1 (IGF-1)/insulin-like growth factor 1 receptor (IGF-1 R) signaling pathway mediates the formononetin antitumor effect on prostate cancer cells. Materials and methods: The viability of PC-3 cells was measured by MTT assay 48 h after formononetin treatment (25, 50 and 100 μM). Formononetin-induced cell apoptosis was measured by Hoechst 33258 staining and flow cytometry. Expression of Bax mRNA was detected by real-time PCR, and the expression levels of Bax and IGF-1 R proteins were detected by western blots. Results: At concentrations >12.5 μM, formononetin significantly inhibited the proliferation of human prostate cancer cells. Formononetin increased Bax mRNA and protein expression levels and decreased the expression levels of pIGF-1 R protein in a dose-dependent manner. Conclusion: High concentrations of formononetin-induced apoptosis in androgen-independent prostate cancer cells through inhibition of the IGF-1/IGF-1 R pathway.

Androgen receptor splice variant AR3 promotes prostate cancer via modulating expression of autocrine/paracrine factors

Deregulation of androgen receptor (AR) splice variants has been implicated to play a role in prostate cancer development and progression. To understand their functions in prostate, we established a transgenic mouse model (AR3Tg) with targeted expression of the constitutively active and androgen-independent AR splice variant AR3 (a.k.a. AR-V7) in prostate epithelium. We found that overexpression of AR3 modulates expression of a number of tumor-promoting autocrine/paracrine growth factors (including Tgfβ2 and Igf1) and expands prostatic progenitor cell population, leading to development of prostatic intraepithelial neoplasia. In addition, we showed that some epithelial-mesenchymal transition-associated genes are up-regulated in AR3Tg prostates, suggesting that AR3 may antagonize AR activity and halt the differentiation process driven by AR and androgen. This notion is supported by our observations that the number of Ck5(+)/Ck8(+) intermediate cells is increased in AR3Tg prostates after castration, and expression of AR3 transgene in these intermediate cells compromises prostate epithelium regeneration upon androgen replacement. Our results demonstrate that AR3 is a driver of prostate cancer, at least in part, through modulating multiple tumor-promoting autocrine/paracrine factors.

Multiple molecular and cellular mechanisms of action of lycopene in cancer inhibition

Epidemiological studies suggest that including fruits, vegetables, and whole grains in regular dietary intake might prevent and reverse cellular carcinogenesis, reducing the incidence of primary tumours. Bioactive components present in food can simultaneously modulate more than one carcinogenic process, including cancer metabolism, hormonal balance, transcriptional activity, cell-cycle control, apoptosis, inflammation, angiogenesis and metastasis. Some studies have shown an inverse correlation between a diet rich in fruits, vegetables, and carotenoids and a low incidence of different types of cancer. Lycopene, the predominant carotenoid found in tomatoes, exhibits a high antioxidant capacity and has been shown to prevent cancer, as evidenced by clinical trials and studies in cell culture and animal models. In vitro studies have shown that lycopene treatment can selectively arrest cell growth and induce apoptosis in cancer cells without affecting normal cells. In vivo studies have revealed that lycopene treatment inhibits tumour growth in the liver, lung, prostate, breast, and colon. Clinical studies have shown that lycopene protects against prostate cancer. One of the main challenges in cancer prevention is the integration of new molecular findings into clinical practice. Thus, the identification of molecular biomarkers associated with lycopene levels is essential for improving our understanding of the mechanisms underlying its antineoplastic activity.

Neuroendocrine-derived peptides promote prostate cancer cell survival through activation of IGF-1R signaling

BACKGROUND

Neuroendocrine (NE) cells promote the progression of prostate cancer to a castration-resistant state through the production of paracrine growth factors. We have demonstrated this principle using in vitro and in vivo proliferative endpoints; however, the contributions of NE-derived pro-survival factors and anti-apoptosis to this phenomenon have not been thoroughly investigated.

METHODS

Here, we utilized conditioned-medium (CM) from LNCaP cells, engineered to undergo NE differentiation, and examined its effects on PC3 and LNCaP cell survival.

RESULTS

Statistically significant changes in clonogenic survival, Annexin V staining, PARP cleavage and trypan blue positivity of approximately twofold were observed in the presence of NE-derived CM relative to control-CM for both LNCaP and PC3 cells. These changes were partially abrogated by antagonists of the neuropeptides neurotensin, bombesin, and PTHrP. Selective inhibitors of IGF-1R, EGFR or Src caused significant and nearly complete blockade of prostate cancer cell survival due to NE secretions. Similar increases in cell survival were observed for LNCaP or PC3 cells treated with NE-derived medium in the presence of docetaxel. Increased phosphorylation of IGF-1R, following treatment with NE-derived medium, was accompanied by decreased protein tyrosine phosphatase, receptor type F (PTPRF) mRNA, and protein levels. Overexpression of PTPRF decreased cell survival, the amplitude and duration of IGF-1R phosphorylation, and enhanced PARP cleavage in the presence of NE-derived medium.

CONCLUSIONS

These data support the hypothesis that NE-derived factors act upon prostate cancer cells to stimulate pro-survival signaling and describe a novel mechanism of cross-talk between NE-derived factors and IGF-1R, mediated in part by PTPRF.

The influence of growth hormone/insulin-like growth factor deficiency on prostatic dysplasia in pbARR2-Cre, PTEN knockout mice

BACKGROUND

Elevated insulin-like growth factor-I (IGF-I) serum levels and phosphatase and tensin homolog (PTEN) loss are prostate cancer (PCa) risk factors that enhance androgen-responsive and castration-resistant PCa xenografts growth.

METHODS

The impact of suppressed growth hormone (GH)/IGF-I levels on neoplastic initiation of PTEN-deficient prostate epithelia was assessed histologically and by epithelial-to-mesenchymal marker expression in Ghrhr D60G homozygous (lit/lit) and heterozygous (lit/+) pbARR2-Cre, PTEN(fl/fl) (PTEN-/-) mice. How suppressed GH/IGF-I levels impacted growth of PTEN-/- mouse-derived prostate cells (MPPK) was examined by growth and survival signaling of cells cultured in lit/+ or lit/lit serum.

RESULTS

Body weight, prostate weight and serum GH and IGF-I levels were reduced in lit/lit relative to lit/+ PTEN-/- littermates. While the anterior lobes of lit/+ PTEN-/- prostates consistently presented swollen, indicative of ductal blockage, the degree of prostatic dysplasia in 15- and 20-week-old lit/lit and lit/+ PTEN-/- mice was indistinguishable as measured by normalized prostatic weight, tissue histology, or probasin, PSP94, E-cadherin, N-cadherin and vimentin expression. However, growth and AKT activation of MPPK cells was decreased when cultured in lit/lit serum as compared with lit/+ serum and restored in lit/lit serum supplemented with IGF-I and, to a lesser extent, GH.

CONCLUSIONS

These results suggest that initiation of prostate carcinogenesis by loss of PTEN is not influenced by germline variation of genes encoding signaling molecules in the GH/IGF-I axis, but suggests that these factors may affect the progression of dysplastic phenotype and supports previous studies, indicating that the GH/IGF milieu does impact the growth of PTEN-deficient dysplastic prostatic cells once transformed.

Critical role of a survivin/TGF-β/mTORC1 axis in IGF-I-mediated growth of prostate epithelial cells

Survivin is a unique member of the inhibitor of apoptosis (IAP) proteins that is overexpressed in numerous cancers through poorly defined mechanisms. One such mechanism may be through constitutive activation of the insulin-like growth factor-I (IGF-I) signaling pathway, implicated in the development and progression of prostate cancer. Using the pre-neoplastic NRP-152 rat prostate cell line as a model, we showed that IGF-I induces Survivin expression, and that silencing Survivin by lentiviral-mediated small hairpin RNA (shRNA) represses IGF-I-stimulated cell growth, implicating Survivin as a mediator of this growth response. Moreover, our data support that the induction of Survivin by IGF-I occurs through a transcriptional mechanism that is mediated in part by the PI3K/Akt/mTORC1 pathway. Use of various Survivin promoter-luciferase constructs revealed that the CDE and CHR response elements in the proximal region of the Survivin promoter are involved in this IGF-I response. Transforming growth factor (TGF-β) signaling antagonists similarly activated the Surivin promoter and rendered cells refractory to further promoter activation by IGF-I. IGF-I suppressed levels of phospho-Smads 2 and 3 with kinetics similar to that of Survivin induction. Suppression of TGF-β signaling, either by TGF-β receptor kinase inhibitors or by silencing Smads 2 and 3, induced Survivin expression and promoted cell growth similar to that induced by IGF-I. TGF-β receptor antagonists also rescued cells from down-regulation of Survivin expression and growth suppression by pharmacological inhibitors of PI3K, Akt, MEK and mTOR. Sh-RNA gene silencing studies suggest that mTORC1 induces while mTORC2 represses the expression of Survivin by IGF-I. Taken together, these results suggest that IGF-I signaling through a PI3K/Akt/mTORC1 mechanism elevates expression of Survivin and promotes growth of prostate epithelial cells by suppressing Smad-dependent autocrine TGF-β signaling.

Mechanisms linking obesity and cancer

The incidence of obesity in US adults has been steadily increasing over the past few decades. Many comorbidities associated with obesity have been well-established such as type 2 diabetes and cardiovascular diseases. However, more recently an epidemiological relationship between obesity and the prevalence of a variety of cancers has also been uncovered. The shift of the paradigm surrounding white adipose tissue function from purely an energy storage tissue, to one that has both endocrine and metabolic relevance, has led to several mechanisms implicated in how obesity drives cancer prevalence and cancer deaths. Currently, there are four categories into which these mechanisms fall - increased lipids and lipid signaling, inflammatory responses, insulin resistance, and adipokines. In this review, we examine each of these categories and the mechanisms through which they drive cancer pathogenesis. Understanding the relationship(s) between obesity and cancer and especially the nodal points of control in these cascades will be essential in developing effective therapeutics or interventions for combating this deadly combination. This article is part of a Special Issue entitled Lipid Metabolism in Cancer.

Genetically engineered mouse models of prostate cancer

Despite major improvement in treatment of early stage localised prostate cancer, the distinction between indolent tumors and those that will become aggressive, as well as the lack of efficient therapies of advanced prostate cancer, remain major health problems. Genetically engineered mice (GEM) have been extensively used to investigate the molecular and cellular mechanisms underlying prostate tumor initiation and progression, and to evaluate new therapies. Moreover, the recent development of conditional somatic mutagenesis in the mouse prostate offers the possibility to generate new models that more faithfully reproduce the human disease, and thus should contribute to improve diagnosis and treatments. The strengths and weaknesses of various models will be discussed, as well as future opportunities.

Consumption of dairy and meat in relation to breast cancer risk in the Black Women's Health Study

PURPOSE

Dairy and meat consumption may impact breast cancer risk through modification of hormones (e.g., estrogen), through specific nutrients (e.g., vitamin D), or through products formed in processing/cooking (e.g., heterocyclic amines). Results relating meat and dairy intake to breast cancer risk have been conflicting. Thus, we examined the risk of breast cancer in relation to intake of dairy and meat in a large prospective cohort study.

METHODS

In the Black Women's Health Study, 1,268 incident breast cancer cases were identified among 52,062 women during 12 years of follow-up. Multivariable (MV) relative risks (RRs) and 95 % confidence intervals (CIs) were calculated using Cox proportional hazards models.

RESULTS

Null associations were observed for total milk (MV RR = 1.05, 95 % CI 0.74-1.46 comparing ≥1,000-0 g/week) and total meat (MV RR = 1.04, 95 % CI 0.85-1.28 comparing ≥1,000 < 400 g/week) intake and risk of breast cancer. Associations with intakes of specific types of dairy, specific types of meat, and dietary calcium and vitamin D were also null. The associations were not modified by reproductive (e.g., parity) or lifestyle factors (e.g., smoking). Associations with estrogen receptor (ER) positive (+), ER negative (-), progesterone receptor (PR) +, PR-, ER+/PR+, and ER-/PR- breast cancer were generally null.

CONCLUSIONS

This analysis of African-American women provides little support for associations of dairy and meat intake with breast cancer risk.

Evidence for the Possible Biological Significance of the igf-1 Gene Alternative Splicing in Prostate Cancer

Insulin-like growth factor-I (IGF-I) has been implicated in the pathogenesis of prostate cancer (PCa), since it plays a key role in cell proliferation, differentiation, and apoptosis. The IGF-I actions are mediated mainly via its binding to the type I IGF receptor (IGF-IR), however IGF-I signaling via insulin receptor (IR) and hybrid IGF-I/IR is also evident. Different IGF-I mRNA splice variants, namely IGF-IEa, IGF-IEb, and IGF-IEc, are expressed in human cells and tissues. These transcripts encode several IGF-I precursor proteins which contain the same bioactive product (mature IGF-I), however, they differ by the length of their signal peptides on the amino-terminal end and the structure of the extension peptides (E-peptides) on the carboxy-terminal end. There is an increasing interest in the possible different role of the IGF-I transcripts and their respective non-(mature)IGF-I products in the regulation of distinct biological activities. Moreover, there is strong evidence of a differential expression profile of the IGF-I splice variants in normal versus PCa tissues and PCa cells, implying that the expression pattern of the various IGF-I transcripts and their respective protein products may possess different functions in cancer biology. Herein, the evidence that the IGF-IEc transcript regulates PCa growth via Ec peptide specific and IGF-IR/IR-independent signaling is discussed.

Apigenin Modulates Insulin-like Growth Factor Axis: Implications for Prevention and Therapy of Prostate Cancer

Aberrant changes to the insulin-like growth factor (IGF) axis promote prostate cancer development and progression, adaptation for growth and survival in a castrate environment, and invasive metastasis. Natural and/or synthetic compounds that target the IGF axis to prevent or reverse theses abnormalities may be extremely useful in the chemoprevention and/or chemotherapy of prostate cancer. Apigenin, a naturally-occurring flavone found in many fruits and vegetables, is one such compound that can correctively modulate the IGF axis to induce growth arrest and apoptosis in many pre-clinical in vitro and in vivo models of prostate cancer. Because of its known mechanism of action, low toxicity, and effectiveness at physiologically relevant levels in animal models of prostate cancer, apigenin is an excellent candidate for a pilot study to determine the effect of apigenin supplementation on prostate cancer development and progression in humans.

Androgens, diabetes and prostate cancer

Metabolic disorders such as diabetes, obesity and the metabolic syndrome have been shown to modulate prostate cancer (PCa) risk and aggressiveness in population-based and experimental studies. While associations between these conditions are modest and complex, two consistent findings have emerged. First, there is observational evidence that obesity and associated insulin excess are linked to increased PCa aggressiveness and worse outcomes. Secondly and somewhat paradoxically, long-standing diabetes may be protective against PCa development. This apparent paradox may be due to the fact that long-standing diabetes is associated with insulin depletion and decreased IGF1 signalling. Men with obesity or diabetes have moderate reductions in their androgen levels. The interconnectedness of metabolic and androgen status complicates the dissection of the individual roles of these factors in PCa development and progression. Metabolic factors and androgens may promote prostate carcinogenesis via multiple mechanisms including inflammation, adipokine action, fatty acid metabolism and IGF signalling. Moreover, androgen deprivation, given to men with PCa, has adverse metabolic consequences that need to be taken into account when estimating the risk benefit ratio of this therapy. In this review, we will discuss the current epidemiological and mechanistic evidence regarding the interactions between metabolic conditions, sex steroids and PCa risk and management.

The insulin and igf-I pathway in endocrine glands carcinogenesis

Endocrine cancers are a heterogeneous group of diseases that may arise from endocrine cells in any gland of the endocrine system. These malignancies may show an aggressive behavior and resistance to the common anticancer therapies. The etiopathogenesis of these tumors remains mostly unknown. The normal embryological development and differentiation of several endocrine glands are regulated by specific pituitary tropins, which, in adult life, control the function and trophism of the endocrine gland. Pituitary tropins act in concert with peptide growth factors, including the insulin-like growth factors (IGFs), which are considered key regulators of cell growth, proliferation, and apoptosis. While pituitary TSH is regarded as tumor-promoting factor for metastatic thyroid cancer, the role of other pituitary hormones in endocrine cancers is uncertain. However, multiple molecular abnormalities of the IGF system frequently occur in endocrine cancers and may have a role in tumorigenesis as well as in tumor progression and resistance to therapies. Herein, we will review studies indicating a role of IGF system dysregulation in endocrine cancers and will discuss the possible implications of these findings for tumor prevention and treatment, with a major focus on cancers from the thyroid, adrenal, and ovary, which are the most extensively studied.