Molecular Signatures of the Insulin-like Growth Factor 1-mediated Epithelial-Mesenchymal Transition in Breast, Lung and Gastric Cancers

High expression of SMYD3 indicates poor survival outcome and promotes tumour progression through an IGF-1R/AKT/E2F-1 positive feedback loop in bladder cancer

The AKT/mTOR pathway is critical for bladder cancer (BC) pathogenesis and is hyper-activated during BC progression. In the present study, we identified a novel positive feedback loop involving oncogenic factors histone methyltransferase SMYD3, insulin-like growth factor-1 receptor (IGF-1R), AKT, and E2F-1. SMYD3 expression was significantly up-regulated in BC tumors and positively associated with histological grade, lymph node metastasis, and shorter patient survival. Depletion of SMYD3 inhibited BC cell proliferation, colony formation, migration, invasion, and xenograft tumor growth. Mechanistically, SMYD3 inhibition led to the diminished AKT/mTOR signaling activity, thereby triggering deleterious effects on BC cells. Furthermore, SMYD3 directly activates the expression of IGF-1R, a critical activator of AKT in BC, by inducing hyper-methylation of histone H3-K4 and subsequent chromatin remodeling in the IGF-1R promoter region. On the other hand, E2F-1, a downstream factor of the AKT pathway, binds to the E2F-1 binding motifs at the SMYD3 promoter and consequently induces SMYD3 transcription and expression. Thus, SMYD3/IGF-1R/AKT/E2F-1 forms a positive feedback loop leading to the hyper-activated AKT signaling. Our findings provide not only profound insights into SMYD3-mediated oncogenic activity but also present a unique avenue for treating BC by directly disrupting this signaling circuit.

PM2.5, Fine Particulate Matter: A Novel Player in the Epithelial-Mesenchymal Transition?

Epithelial-mesenchymal transition (EMT) refers to the conversion of epithelial cells to mesenchymal phenotype, which endows the epithelial cells with enhanced migration, invasion, and extracellular matrix production abilities. These characteristics link EMT with the pathogenesis of organ fibrosis and cancer progression. Recent studies have preliminarily established that fine particulate matter with an aerodynamic diameter of less than 2.5 μm (PM_2.5) is correlated with EMT initiation. In this pathological process, PM_2.5 particles, excessive reactive oxygen species (ROS) derived from PM_2.5, and certain components in PM_2.5, such as ions and polyaromatic hydrocarbons (PAHs), have been implicated as potential EMT mediators that are linked to the activation of transforming growth factor β (TGF-β)/SMADs, NF-κB, growth factor (GF)/extracellular signal-regulated protein kinase (ERK), GF/phosphatidylinositol 3-kinase (PI3K)/Akt, wingless/integrated (Wnt)/β-catenin, Notch, Hedgehog, high mobility group box B1 (HMGB1)-receptor for advanced glycation end-products (RAGE), and aryl hydrocarbon receptor (AHR) signaling cascades and to cytoskeleton rearrangement. These pathways directly and indirectly transduce pro-EMT signals that regulate EMT-related gene expression in epithelial cells, finally inducing the characteristic alterations in morphology and functions of epithelia. In addition, novel associations between autophagy, ATP citrate lyase (ACLY), and exosomes with PM_2.5-induced EMT have also been summarized. However, some debates and paradoxes remain to be consolidated. This review discusses the potential molecular mechanisms underlying PM_2.5-induced EMT, which might account for the latent role of PM_2.5 in cancer progression and fibrogenesis.

Proteasome activation by insulin-like growth factor-1/nuclear factor erythroid 2-related factor 2 signaling promotes exercise-induced neurogenesis

Physical exercise-induced enhancement of learning and memory and alleviation of age-related cognitive decline in humans have been widely acknowledged. However, the mechanistic relationship between exercise and cognitive improvement remains largely unknown. In this study, we found that exercise-elicited cognitive benefits were accompanied by adaptive hippocampal proteasome activation. Voluntary wheel running increased hippocampal proteasome activity in adult and middle-aged mice, contributing to an acceleration of neurogenesis that could be reversed by intrahippocampal injection of the proteasome inhibitor MG132. We further found that increased levels of insulin-like growth factor-1 (IGF-1) in both serum and hippocampus may be essential for exercise-induced proteasome activation. Our in vitro study demonstrated that IGF-1 stimulated proteasome activity in cultured adult neural progenitor cells (NPCs) by promoting nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2), followed by elevated expressions of proteasome subunits such as PSMB5. In contrast, pretreating adult mice with the selective IGF-1R inhibitor picropodophyllin diminished exercise-induced neurogenesis, concurrent with reduced Nrf2 nuclear translocation and proteasome activity. Likewise, lowering Nrf2 expression by RNA interference with bilateral intrahippocampal injections of recombinant adeno-associated viral particles significantly suppressed exercise-induced proteasome activation and attenuated cognitive function. Collectively, our work demonstrates that proteasome activation in hippocampus through IGF-1/Nrf2 signaling is a key adaptive mechanism underlying exercise-related neurogenesis, which may serve as a potential targetable pathway in neurodegeneration.

STEAP2 is down-regulated in breast cancer tissue and suppresses PI3K/AKT signaling and breast cancer cell invasion in vitro and in vivo

The six-transmembrane epithelial antigen of prostate 2 (STEAP2) protein was identified in advanced prostate cancer, and is highly over-expressed in various types of cancer. This study aimed to investigate the prognostic value and the function of STEAP2 in breast cancer. STEAP2 mRNA and protein expressions in breast normal and cancer tissues, breast cancer cell lines (MCF-7, BT-549, BT-474, MDA-MB-361, HCC1937, and MDA-MB-468) and normal mammary epithelial cell lines (HBL-100 and MCF-10A) were evaluated by immunohistochemistry, real time RT-qPCR and western blotting. The expression of STEAP2 in breast cancer tissues and its value of evaluating the prognosis of breast cancer patients was validated in the Public Databases (Oncomine and Kaplan-Meier plotter database). Lentiviral vectors with STEAP2 cDNA and shRNA were constructed and used to infect breast cancer cell lines and normal mammary epithelial cell line to investigate the effects of STEAP2 up- and down- regulation on the biological behavior of breast cells. The low expression of STEAP2 was detected in breast cancer tissues, which was associated with malignant phenotype and poor prognosis of breast cancer. The public databases analyses were consistent with our findings. STEAP2 up-regulation hindered cellular proliferation, invasion and metastasis abilities by inhibiting EMT process and suppressing PI3K/AKT/mTOR signaling pathway. On the other hand, STEAP2 down-regulation could promote cell proliferation and invasion by inducing EMT and activating the PI3K/AKT/mTOR signaling pathway. Collectively, STEAP2 acted as an anti-oncogene in breast cancer development, which suggested a new research objective for the future studies.

Hypoxic Gene Signature of Primary and Metastatic Melanoma Cell Lines: Focusing on HIF-1β and NDRG-1

Background:

Hypoxia is an important microenvironmental factor significantly affecting tumor proliferation and progression. The importance of hypoxia is, however, not well known in oncogenesis of malignant melanoma.

Aims:

To evaluate the difference of hypoxic gene expression signatures in primary melanoma cell lines and metastatic melanoma cell lines and to find the expression changes of hypoxia-related genes in primary melanoma cell lines at experimental hypoxic conditions.

Study Design:

Cell study.

Methods:

The mRNA expression levels of hypoxia-related genes in primary melanoma cell lines and metastatic melanoma cell lines and at experimental hypoxic conditions in primary melanoma cell lines were evaluated by using real-time polymerase chain reaction. Depending on the experimental data, we focused on two genes/proteins, the hypoxia-inducible factor-1 beta and the N-myc downstream regulated gene-1. The expression levels of the two proteins were investigated by immunohistochemistry methods in 16 primary and metastatic melanomas, 10 intradermal nevi, and a commercial tissue array comprised of 208 cores including 192 primary and metastatic malignant melanomas.

Results:

The real-time polymerase chain reaction study showed that hypoxic gene expression signature was different between metastatic melanoma cell lines and primary melanoma cell lines. Hypoxic experimental conditions significantly affected the hypoxic gene expression signature. In immunohistochemical study, N-myc downstream regulated gene-1 expression was found to be lower in primary cutaneous melanoma compared to in intradermal nevi (p=0.001). In contrast, the cytoplasmic expression of hypoxia-inducible factor-1 beta was higher in primary cutaneous melanoma than in intradermal nevi (p=0.001). We also detected medium/strong significant correlations between the two proteins studied in the study groups.

Conclusion:

Hypoxic response consists of closely related proteins in more complex pathways. These findings will shed light on hypoxic processes in melanoma and unlock a Pandora’s box for development of new therapeutic strategies.

Communication between EMT and PD-L1 signaling: New insights into tumor immune evasion

Immune checkpoint blockage has been considered a breakthrough in cancer treatment, achieving encouraging anti-tumor effects in some advanced solid malignancies. However, low response rate and therapeutic resistance represent significant challenges in this field. In addition to its typical role in embryonic development and tissue fibrosis, epithelial-mesenchymal transition (EMT) plays a pivotal role in tumor immunosuppression and immune evasion. Previous studies revealed that EMT is associated with activation of different immune checkpoint molecules, including PD-L1. EMT-induced immune escape promotes cancer progression and may also provide a platform for discovery of novel therapeutic approaches and predictive biomarkers for checkpoint inhibitor therapeutic response. Here, we summarize recent findings focused on EMT-induced immune suppression and evasion in the tumor microenvironment (TME). EMT transcription factors (EMT-TFs), immune cells, cell plasticity and their regulatory role in the immune response are thoroughly reviewed. Bidirectional regulation between EMT and PD-L1 signaling is discussed in terms of cancer immune escape and possible combined therapies. Additionally, we investigated the value of preclinical or clinical trials using EMT targeted therapy combined with PD-L1 inhibitors. This review may help to further understand the role of EMT and PD-L1 signaling in cancer immune evasion. Meanwhile, additional molecular mechanistic studies and clinical trials are urgently needed.

SphK1 functions downstream of IGF-1 to modulate IGF-1-induced EMT, migration and paclitaxel resistance of A549 cells: A preliminary in vitro study

Insulin-like growth factor-1 (IGF-1) -induced epithelial-mesenchymal transition (EMT) plays a key role in the metastasis and drug resistance of non-small cell lung cancer (NSCLC). Sphingosine kinase-1 (SphK1) is also involved in EMT of NSCLC. However, the interaction between SphK1 and IGF-1 in the EMT of NSCLC is largely unknown. To clarify this issue, we examined the involvement of SphK1 in IGF-1-induced EMT using human lung cancer cell line A549, and its paclitaxel-resistant subline. Cell viability was evaluated by cell counting kit-8 assay; Migratory ability was examined using scratch wound healing test; Protein expression levels of SphK1, vimentin, fibronectin, N-cadherin and E-cadherin were detected by western blot analysis, respectively. The results showed that, IGF-1 treatment of A549 cells stimulated the expression of SphK1, the activation of ERK and AKT, the cell migration, and the expression of EMT hallmark proteins, while inhibition of SphK1 by its specific inhibitor SKI-II suppressed all the above changes and increased the sensitivity of A549 cells to paclitaxel. Our data demonstrate that SphK1 acts as a downstream effector of IGF-1 and plays a critical role in IGF-1-induced EMT, cell migration and paclitaxel resistance of A549 cells, suggesting that SphK1 might be a potential therapeutic target for NSCLC.

Bone Sialoprotein Shows Enhanced Expression in Early, High-Proliferation Stages of Three-Dimensional Spheroid Cell Cultures of Breast Cancer Cell Line MDA-MB-231

Normally, bone sialoprotein (BSP) is an important contributor to bone micro-calcification. However, it is also highly expressed in bone-metastatic malignancies, including prostate, lung, and breast cancer. In these disorders, BSP correlates with poor prognosis. Its expression in triple-negative breast cancer cells is enhanced by the transcription factor RUNX2, and both, BSP and RUNX2 are under control of IGF-1 and TGFβ1. Knockdown of BSP or its inactivation by specific antibodies were found to reduce the metastatic potential of MDA-MB-231 triple-negative breast cancer cells in xenografts. While the role of BSP in bone metastasis was studied using such in vivo models, valid in vitro test systems to investigate BSP biology have been lacking since this protein is expressed at very low levels in classical 2D cell cultures and the frequently used breast cancer cell line MDA-MB-231 is difficult to grow in 3D. Here, we have developed a long-term 3D spheroid culture model using MDA-MB-231 cells in a sandwich approach using cell embedding between a non-adherent surface and basement membrane extracts. This allowed consistent growth of spheroids for more than 21 days. Also, co-culturing of MDA-MB-231 with CCD-1137Sk fibroblasts yielded stably growing spheroids, suggesting the importance of extracellular matrix (ECM) in this process. In addition, we have set up a novel and simple open source analysis tool to characterize protein expression in 2D cultures and spheroids by immunofluorescence. Using this approach in combination with Western blot analysis, the expression profile of BSP was analyzed. BSP was enriched at the rims of spheroids, both in mono- and co-cultures and its abundance in general correlated with that of TGFβ1 under different conditions, including spheroid maturation, cytostatic treatment, and fibroblast co-culture. Conversely, correlation of IGF-1 and BSP was limited to mono-culture time course profiles. In conclusion, we present novel tools to study the regulation of gene expression in combination with cell proliferation and apoptosis in a long-term 3D model of breast cancer and find dynamic abundance profiles of the metastasis-relevant protein BSP and its regulators.

Human Insulin Therapy Is Associated With an Increased Risk of Lung Cancer: A Population-Based Retrospective Cohort Study

Background: Whether human insulin may affect lung cancer risk requires investigation. Methods: All patients with a diagnosis of diabetes mellitus from 1996 to 2009 were enrolled from Taiwan's National Health Insurance. An entry date was set on January 1, 2004, and 1,007,617 patients with type 2 diabetes mellitus diagnosed before 2004 were followed up for new-onset lung cancer until December 31, 2009. Incidence rates of lung cancer for never-users, ever-users, and tertiles of three dose-response exposure parameters (i.e., time since starting insulin, cumulative dose, and cumulative duration) were calculated. Adjusted hazard ratios were estimated by Cox proportional hazards models. The joint effect of insulin and chronic obstructive pulmonary disease was also evaluated. Results: There were 156,720 ever-users and 850,897 never-users. The respective case numbers of incident lung cancer were 3,007 (1.92%) and 13,677 (1.61%), and the respective incidence rates were 424.45 and 313.60 per 100,000 person-years. The adjusted hazard ratio comparing ever-users vs. never-users was 1.545 (95% confidence interval: 1.478-1.614). The hazard ratios for the different subgroups of the three dose-response parameters all suggested a significantly higher risk of lung cancer associated with insulin use (P trend < 0.0001). Compared to patients without insulin use and without chronic obstructive pulmonary disease, insulin users who also had chronic obstructive pulmonary disease had the highest risk of lung cancer (adjusted hazard ratio: 1.891, 95% confidence interval: 1.767-2.024). Conclusions: This study suggests a significant association between human insulin use and lung cancer risk in patients with type 2 diabetes mellitus.