CXCL12/CXCR4 transactivates HER2 in lipid rafts of prostate cancer cells and promotes growth of metastatic deposits in bone

Lipid rafts, caveolae, and epidermal growth factor receptor family: friends or foes?

Lipid rafts are dynamic microdomains enriched with cholesterol and sphingolipids that play critical roles in cellular processes by organizing and concentrating specific proteins involved in signal transduction. The interplay between lipid rafts, raft-associated caveolae and the human epidermal growth factor receptors has significant implications in cancer biology, particularly in breast and gastric cancer therapy resistance. This review examines the structural and functional characteristics of lipid rafts, their involvement in EGFR and HER2 signaling, and the impact of lipid rafts/CXCL12/CXCR4/HER2 axis on bone metastasis. We also discuss the potential of targeting lipid rafts and caveolin-1 to enhance therapeutic strategies against HER2-positive cancers and the impact of co-localization of trastuzumab or antibody drug conjugates with caveolin-1 on therapy response. Emerging evidence suggests that disrupting lipid raft integrity or silencing caveolin-1, through several strategies including cholesterol-lowering molecules, can influence HER2 availability and internalization, enhancing anti-HER2 targeted therapy and offering a novel approach to counteract drug resistance and improve treatment efficacy.

Revisiting HER2 in Prostate Cancer from an Inclusive Perspective: From Biomarkers to Omics

Human epidermal growth factor receptor 2 (HER2) is a major driver of disease progression, treatment resistance, and worse survival for patients with various types of cancers, including prostate cancer. However, key bench studies and clinical trials have failed to evaluate the role of HER2 in prostate cancer using racially diverse experimental designs and protocols. This lack of diversity represents what has been the status quo of cancer research in the United States for decades. In the case of prostate cancer, homogenic study designs are problematic as Black men are much more likely to be diagnosed and die from aggressive and incurable forms of the disease. Therefore, the strategic inclusion of biospecimens collected from Black patients as well as the recruitment and enrollment of Black men into prostate cancer clinical trials is necessary to comprehensively evaluate genetic and molecular factors that contribute to variable outcomes in this high-risk population. Additionally, a higher prevalence of HER2 expression in Black men was recently reported in a small cohort of prostate cancer patients and may contribute to worsened prognosis. In this review, we carefully consider the role of HER2 in prostate cancer while, for the first time, taking into account the influences of race and genetic ancestry.

Statins as anti-tumor agents: A paradigm for repurposed drugs

BACKGROUND

Statins, frequently prescribed medications, work by inhibiting the rate-limiting enzyme HMG-CoA reductase (HMGCR) in the mevalonate pathway to reduce cholesterol levels. Due to their multifaceted benefits, statins are being adapted for use as cost-efficient, safe and effective anti-cancer treatments. Several studies have shown that specific types of cancer are responsive to statin medications since they rely on the mevalonate pathway for their growth and survival.

RECENT FINDINGS

Statin are a class of drugs known for their potent inhibition of cholesterol production and are typically prescribed to treat high cholesterol levels. Nevertheless, there is growing interest in repurposing statins for the treatment of malignant neoplastic diseases, often in conjunction with chemotherapy and radiotherapy. The mechanism behind statin treatment includes targeting apoptosis through the BCL2 signaling pathway, regulating the cell cycle via the p53-YAP axis, and imparting epigenetic modulations by altering methylation patterns on CpG islands and histone acetylation by downregulating DNMTs and HDACs respectively. Notably, some studies have suggested a potential chemo-preventive effect, as decreased occurrence of tumor relapse and enhanced survival rate were reported in patients undergoing long-term statin therapy. However, the definitive endorsement of statin usage in cancer therapy hinges on population based clinical studies with larger patient cohorts and extended follow-up periods.

CONCLUSIONS

The potential of anti-cancer properties of statins seems to reach beyond their influence on cholesterol production. Further investigations are necessary to uncover their effects on cancer promoting signaling pathways. Given their distinct attributes, statins might emerge as promising contenders in the fight against tumorigenesis, as they appear to enhance the efficacy and address the limitations of conventional cancer treatments.

Adaptor proteins mediate CXCR4 and PI4KA crosstalk in prostate cancer cells and the significance of PI4KA in bone tumor growth

The chemokine receptor, CXCR4 signaling regulates cell growth, invasion, and metastasis to the bone-marrow niche in prostate cancer (PCa). Previously, we established that CXCR4 interacts with phosphatidylinositol 4-kinase IIIα (PI4KIIIα encoded by PI4KA) through its adaptor proteins and PI4KA overexpressed in the PCa metastasis. To further characterize how the CXCR4-PI4KIIIα axis promotes PCa metastasis, here we identify CXCR4 binds to PI4KIIIα adaptor proteins TTC7 and this interaction induce plasma membrane PI4P production in prostate cancer cells. Inhibiting PI4KIIIα or TTC7 reduces plasma membrane PI4P production, cellular invasion, and bone tumor growth. Using metastatic biopsy sequencing, we found PI4KA expression in tumors correlated with overall survival and contributes to immunosuppressive bone tumor microenvironment through preferentially enriching non-activated and immunosuppressive macrophage populations. Altogether we have characterized the chemokine signaling axis through CXCR4-PI4KIIIα interaction contributing to the growth of prostate cancer bone metastasis.

Statins in Cancer Prevention and Therapy

Statins, a class of HMG-CoA reductase inhibitors best known for their cholesterol-reducing and cardiovascular protective activity, have also demonstrated promise in cancer prevention and treatment. This review focuses on their potential applications in head and neck cancer (HNC), a common malignancy for which established treatment often fails despite incurring debilitating adverse effects. Preclinical and clinical studies have suggested that statins may enhance HNC sensitivity to radiation and other conventional therapies while protecting normal tissue, but the underlying mechanisms remain poorly defined, likely involving both cholesterol-dependent and -independent effects on diverse cancer-related pathways. This review brings together recent discoveries concerning the anticancer activity of statins relevant to HNC, highlighting their anti-inflammatory activity and impacts on DNA-damage response. We also explore molecular targets and mechanisms and discuss the potential to integrate statins into conventional HNC treatment regimens to improve patient outcomes.

A Novel Interaction between Chemokine and Phosphoinositide Signaling in Metastatic Prostate Cancer

Prostate cancer commonly metastasizes to bone due to its favorable microenvironment for cell growth and survival. Currently, the standard of care for metastatic prostate cancer is medical castration in conjunction with chemotherapeutic agents and newer anti-androgen/androgen receptor therapies. While these therapies aim to improve the quality of life in patients with advanced disease, resistance to these therapies is inevitable prompting the development of newer therapies to contain disease progression. The CXCL12/CXCR4 axis has previously been shown to be involved in prostate cancer cell homing to bone tissue, and new investigations found a novel interaction of Phosphatidyl Inositol 4 kinase IIIa (PI4KA) downstream of chemokine signaling. PI4KA phosphorylates at the 4th position on phosphatidylinositol (PI), to produce PI4P and is localized to the plasma membrane (PM). At the PM, PI4KA provides precursors for the generation of PI(4,5)P2, and PI(3,4,5)P3 and helps maintain PM identity through the recruitment of lipids and signaling proteins. PI4KA is recruited to the PM through evolutionarily conserved adaptor proteins, and in PC cells, CXCR4 binds with adaptor proteins to recruit PI4KA to the PM. The objective of this review is to summarize our understanding of the role that phosphatidyl inositol lipid messengers in cancer cells.

Adaptor proteins mediate CXCR4 and PI4KA crosstalk in prostate cancer cells and the significance of PI4KA in bone tumor growth

The chemokine receptor, CXCR4 signaling regulates cell growth, invasion, and metastasis to the bone-marrow niche in prostate cancer (PCa). Previously, we established that CXCR4 interacts with phosphatidylinositol 4-kinase IIIα (PI4KIIIα encoded by PI4KA) through its adaptor proteins and PI4KA overexpressed in the PCa metastasis. To further characterize how the CXCR4-PI4KIIIα axis promotes PCa metastasis, here we identify CXCR4 binds to PI4KIIIα adaptor proteins TTC7 and this interaction induce plasma membrane PI4P production in prostate cancer cells. Inhibiting PI4KIIIα or TTC7 reduces plasma membrane PI4P production, cellular invasion, and bone tumor growth. Using metastatic biopsy sequencing, we found PI4KA expression in tumors correlated with overall survival and contributes to immunosuppressive bone tumor microenvironment through preferentially enriching non-activated and immunosuppressive macrophage populations. Altogether we have characterized the chemokine signaling axis through CXCR4-PI4KIIIα interaction contributing to the growth of prostate cancer bone metastasis.

Osteoid cell-derived chemokines drive bone-metastatic prostate cancer

One of the greatest challenges in improving prostate cancer (PCa) survival is in designing new therapies to effectively target bone metastases. PCa regulation of the bone environment has been well characterized; however, bone-targeted therapies have little impact on patient survival, demonstrating a need for understanding the complexities of the tumor-bone environment. Many factors contribute to creating a favorable microenvironment for prostate tumors in bone, including cell signaling proteins produced by osteoid cells. Specifically, there has been extensive evidence from both past and recent studies that emphasize the importance of chemokine signaling in promoting PCa progression in the bone environment. Chemokine-focused strategies present promising therapeutic options for treating bone metastasis. These signaling pathways are complex, with many being produced by (and exerting effects on) a plethora of different cell types, including stromal and tumor cells of the prostate tumor-bone microenvironment. ​This review highlights an underappreciated molecular family that should be interrogated for treatment of bone metastatic prostate cancer (BM-PCa).

A Novel Mechanism Underlying the Inhibitory Effects of Trastuzumab on the Growth of HER2-Positive Breast Cancer Cells

To improve the efficacy of trastuzumab, it is essential to understand its mechanism of action. One of the significant issues that makes it difficult to determine the precise mechanism of trastuzumab action is the formation of various HER receptor dimers in HER2-positive breast cancer cells. So far, studies have focused on the role of HER2-HER3 heterodimers, and little is known regarding EGFR-HER2 heterodimers. Here, we study the role of trastuzumab on the cell signaling and cell proliferation mediated by EGFR-HER2 heterodimers in BT474 and SRBR3 cells. EGF stimulates the formation of both EGFR homodimer and EGFR-HER2 heterodimer. Trastuzumab only binds to HER2, not EGFR. Therefore, any effects of trastuzumab on EGF-induced activation of EGFR, HER2, and downstream signaling proteins, as well as cell proliferation, are through its effects on EGFR-HER2 heterodimers. We show that trastuzumab inhibits EGF-induced cell proliferation and cell cycle progression in BT474 and SKBR3 cells. Interestingly trastuzumab strongly inhibits EGF-induced Akt phosphorylation and slightly inhibits EGF-induced Erk activation, in both BT474 and SKBR3 cells. These data suggest the presence of a novel mechanism that allows trastuzumab to inhibit EGR-induced Akt activation and cell proliferation, without blocking EGF-induced EGFR-HER2 heterodimerization and activation. We show that trastuzumab inhibits EGF-induced lipid raft localization of the EGFR-HER2 heterodimer. Disruption of the lipid raft with MβCD blocks HER2-mediated AKT activation in a similar way to trastuzumab. MβCD and trastuzumab synergically inhibit AKT activation. We conclude that trastuzumab inhibits EGF-induced lipid raft localization of EGFR-HER2 heterodimer, which leads to the inhibition of Akt phosphorylation and cell proliferation, without blocking the formation and phosphorylation of the EGFR-HER2 heterodimer.

Antimetastatic Effects of Curcumin in Oral and Gastrointestinal Cancers

Gastrointestinal (GI) cancers are known as frequently occurred solid malignant tumors that can cause the high rate mortality in the world. Metastasis is a significant destructive feature of tumoral cells, which directly correlates with decreased prognosis and survival. Curcumin, which is found in turmeric, has been identified as a potent therapeutic natural bioactive compound (Curcuma longa). It has been traditionally applied for centuries to treat different diseases, and it has shown efficacy for its anticancer properties. Numerous studies have revealed that curcumin inhibits migration and metastasis of GI cancer cells by modulating various genes and proteins, i.e., growth factors, inflammatory cytokines and their receptors, different types of enzymes, caspases, cell adhesion molecules, and cell cycle proteins. Herein, we summarized the antimetastatic effects of curcumin in GI cancers, including pancreatic cancer, gastric cancer, colorectal cancer, oral cancer, and esophageal cancer.

Therapeutic effect of curcumin in gastrointestinal cancers: A comprehensive review

Gastrointestinal (GI) cancers with a high global prevalence are a leading cause of morbidity and mortality. Accordingly, there is a great need to develop efficient therapeutic approaches. Curcumin, a naturally occurring agent, is a promising compound with documented safety and anticancer activities. Recent studies have demonstrated the activity of curcumin in the prevention and treatment of different cancers. According to systematic studies on curcumin use in various diseases, it can be particularly effective in GI cancers because of its high bioavailability in the gastrointestinal tract. Nevertheless, the clinical applications of curcumin are largely limited because of its low solubility and low chemical stability in water. These limitations may be addressed by the use of relevant analogues or novel delivery systems. Herein, we summarize the pharmacological effects of curcumin against GI cancers. Moreover, we highlight the application of curcumin's analogues and novel delivery systems in the treatment of GI cancers.

The nonreceptor protein tyrosine kinase Src participates in every step of cancer-induced bone pain

Cancer-induced bone pain (CIBP) is a refractory form of pain that has a high incidence in advanced tumors. Src protein tyrosine kinase is mainly composed of six domains, with two states of automatic inhibition and activation. The modular domain allows Src to conveniently regulate by and communicate with a variety of proteins, directly or indirectly participate in each step of the CIBP process. Src is beneficial to the growth and proliferation of tumor cells, and it can promote the metastases of primary tumors to bone. In the microenvironment of bone metastasis, it mainly mediates bone resorption, activates related peripheral receptors to participate in the formation of pain signals, and may promote the generation of pathological sensory nerve fibers. In the process of pain signal transmission, it mainly mediates NMDAR and central glial cells to regulate pain signal intensity and central sensitization, but it is not limited to these two aspects. Both basic experimentation and clinical research have shown encouraging potential, providing new ideas and inspiration for the prevention and treatment of CIBP.

The multifaceted roles of the chemokines CCL2 and CXCL12 in osteophilic metastatic cancers

Breast and prostate cancers have a great propensity to metastasize to long bones. The development of bone metastases is life-threatening, incurable, and drastically reduces patients' quality of life. The chemokines CCL2 and CXCL12 and their respective receptors, CCR2 and CXCR4, are central instigators involved in all stages leading to cancer cell dissemination and secondary tumor formation in distant target organs. They orchestrate tumor cell survival, growth and migration, tumor invasion and angiogenesis, and the formation of micrometastases in the bone marrow. The bone niche is of particular importance in metastasis formation, as it expresses high levels of CCL2 and CXCL12, which attract tumor cells and contribute to malignancy. The limited number of available effective treatment strategies highlights the need to better understand the pathophysiology of bone metastases and reduce the skeletal tumor burden in patients diagnosed with metastatic bone disease. This review focuses on the involvement of the CCL2/CCR2 and CXCL12/CXCR4 chemokine axes in the formation and development of bone metastases, as well as on therapeutic perspectives aimed at targeting these chemokine-receptor pairs.

Role of Cholesterol and Lipid Rafts in Cancer Signaling: A Promising Therapeutic Opportunity?

Cholesterol is a lipid molecule that plays an essential role in a number of biological processes, both physiological and pathological. It is an essential structural constituent of cell membranes, and it is fundamental for biosynthesis, integrity, and functions of biological membranes, including membrane trafficking and signaling. Moreover, cholesterol is the major lipid component of lipid rafts, a sort of lipid-based structures that regulate the assembly and functioning of numerous cell signaling pathways, including those related to cancer, such as tumor cell growth, adhesion, migration, invasion, and apoptosis. Considering the importance of cholesterol metabolism, its homeostasis is strictly regulated at every stage: import, synthesis, export, metabolism, and storage. The alterations of this homeostatic balance are known to be associated with cardiovascular diseases and atherosclerosis, but mounting evidence also connects these behaviors to increased cancer risks. Although there is conflicting evidence on the role of cholesterol in cancer development, most of the studies consistently suggest that a dysregulation of cholesterol homeostasis could lead to cancer development. This review aims to discuss the current understanding of cholesterol homeostasis in normal and cancerous cells, summarizing key findings from recent preclinical and clinical studies that have investigated the role of major players in cholesterol regulation and the organization of lipid rafts, which could represent promising therapeutic targets.

Acetylation of KLF5 maintains EMT and tumorigenicity to cause chemoresistant bone metastasis in prostate cancer

Advanced prostate cancer (PCa) often develops bone metastasis, for which therapies are very limited and the underlying mechanisms are poorly understood. We report that bone-borne TGF-β induces the acetylation of transcription factor KLF5 in PCa bone metastases, and acetylated KLF5 (Ac-KLF5) causes osteoclastogenesis and bone metastatic lesions by activating CXCR4, which leads to IL-11 secretion, and stimulating SHH/IL-6 paracrine signaling. While essential for maintaining the mesenchymal phenotype and tumorigenicity, Ac-KLF5 also causes resistance to docetaxel in tumors and bone metastases, which is overcome by targeting CXCR4 with FDA-approved plerixafor. Establishing a mechanism for bone metastasis and chemoresistance in PCa, these findings provide a rationale for treating chemoresistant bone metastasis of PCa with inhibitors of Ac-KLF5/CXCR4 signaling.

Androgen-Driven Fusion Genes and Chimeric Transcripts in Prostate Cancer

Androgens are steroid hormones governing the male reproductive development and function. As such, androgens and the key mediator of their effects, androgen receptor (AR), have a leading role in many diseases. Prostate cancer is a major disease where AR and its transcription factor function affect a significant number of patients worldwide. While disease-related AR-driven transcriptional programs are connected to the presence and activity of the receptor itself, also novel modes of transcriptional regulation by androgens are exploited by cancer cells. One of the most intriguing and ingenious mechanisms is to bring previously unconnected genes under the control of AR. Most often this occurs through genetic rearrangements resulting in fusion genes where an androgen-regulated promoter area is combined to a protein-coding area of a previously androgen-unaffected gene. These gene fusions are distinctly frequent in prostate cancer compared to other common solid tumors, a phenomenon still requiring an explanation. Interestingly, also another mode of connecting androgen regulation to a previously unaffected gene product exists via transcriptional read-through mechanisms. Furthermore, androgen regulation of fusion genes and transcripts is not linked to only protein-coding genes. Pseudogenes and non-coding RNAs (ncRNAs), including long non-coding RNAs (lncRNAs) can also be affected by androgens and de novo functions produced. In this review, we discuss the prevalence, molecular mechanisms, and functional evidence for androgen-regulated prostate cancer fusion genes and transcripts. We also discuss the clinical relevance of especially the most common prostate cancer fusion gene TMPRSS2-ERG, as well as present open questions of prostate cancer fusions requiring further investigation.

Post-Translational Modifications That Drive Prostate Cancer Progression

While a protein primary structure is determined by genetic code, its specific functional form is mostly achieved in a dynamic interplay that includes actions of many enzymes involved in post-translational modifications. This versatile repertoire is widely used by cells to direct their response to external stimuli, regulate transcription and protein localization and to keep proteostasis. Herein, post-translational modifications with evident potency to drive prostate cancer are explored. A comprehensive list of proteome-wide and single protein post-translational modifications and their involvement in phenotypic outcomes is presented. Specifically, the data on phosphorylation, glycosylation, ubiquitination, SUMOylation, acetylation, and lipidation in prostate cancer and the enzymes involved are collected. This type of knowledge is especially valuable in cases when cancer cells do not differ in the expression or mutational status of a protein, but its differential activity is regulated on the level of post-translational modifications. Since their driving roles in prostate cancer, post-translational modifications are widely studied in attempts to advance prostate cancer treatment. Current strategies that exploit the potential of post-translational modifications in prostate cancer therapy are presented.

Cholesterol and Sphingolipid Enriched Lipid Rafts as Therapeutic Targets in Cancer

Lipid rafts are critical cell membrane lipid platforms enriched in sphingolipid and cholesterol content involved in diverse cellular processes. They have been proposed to influence membrane properties and to accommodate receptors within themselves by facilitating their interaction with ligands. Over the past decade, technical advances have improved our understanding of lipid rafts as bioactive structures. In this review, we will cover the more recent findings about cholesterol, sphingolipids and lipid rafts located in cellular and nuclear membranes in cancer. Collectively, the data provide insights on the role of lipid rafts as biomolecular targets in cancer with good perspectives for the development of innovative therapeutic strategies.

Pro-inflammatory cytokines and chemokines initiate multiple prostate cancer biologic pathways of cellular proliferation, heterogeneity and metastasis in a racially diverse population and underlie the genetic/biologic mechanism of racial disparity: Update

Pro-inflammatory cytokine and chemokines genes drive prostate cancer progression and metastasis: molecular mechanism update and the science that underlies racial disparity. comprehensive review article. Isaac J. Powell, S. Chinni, S.S. Reddy, Alexander Zaslavsky, Navnath Gavande Introduction: In 2013 we reported that with the use of bioinformatics and ingenuity pathway network analysis we were able to identify functional driver genes that were differentially expressed among a large population of African American men (AAM) and European American men (EAM). Pro-inflammatory cytokine genes were found to be more interactive and more expressed among AAM and have been found to be functional drivers of aggressive prostate cancer (CaP) and aggressiveness in other solid tumors. We examined these genes and biological pathways initiated by these cytokines in primary CaP tissue. Method We unravel the gene network and identified biologic pathways that impacted activation of the androgen receptor, mesenchymal epithelial transition (invasion) and chemokines associated with metastasis in the CaP tissue from 639 radical prostatectomy specimens. Results Biologic pathways identified by unraveling pro-inflammatory genes from our network, more expressed among AAM compared to EAM, were tumor necrosis factor (TNF), IL1b, IL6, and IL8. IL6 and IL8 are downstream of TNF activity and are known activators of androgen receptor and through mediators promote CaP cell proliferation. TNF and IL1b mediate tumor cell invasiveness through the activation of MMP (matrix metalloproteinase) which down regulates E-Cadherin to initiate epithelial mesenchymal transition which allows cells to become invasive in the microenvironment. Ultimately our network analysis indicates that TNF and IL1b activate CXCR4 receptor on CaP cells, which facilitates metastatic progression reportedly by binding to CXCL12 on lipid rafts and tumor implantation in the bone marrow. Conclusion Our retrospective biologic mechanistic model reveals a set of pro-inflammatory cytokines and chemokines that drive CaP aggressiveness, tumor heterogeneity, progression and metastasis. A prospective multi-institutional study needs to be conducted for clinical validation as well consideration of targeted therapy.

The role of cholesterol and cholesterol-driven membrane raft domains in prostate cancer

Membrane rafts are heterogeneous and dynamic domains that are characterized by tight packing of lipids. They are enriched in cholesterol, sphingolipids, and certain types of proteins. Among these are various cell signaling proteins, which indicate that rafts play an important role in cell signal transduction pathways, including some involved in cancer development, progression, and invasiveness. Due to their increased cholesterol content, raft domains exhibit lower fluidity than the surrounding membrane. The cell membranes of some solid tumors, such as breast and prostate cancer, contain higher levels of cholesterol, which means larger raft domain can form in those membranes. This may stimulate signaling pathways to promote tumor growth and progression. This review focuses on the known raft-dependent regulatory mechanisms that promote prostate cancer progression.

Impact statement

Prostate cancer remains the most common malignancy and second most frequent cause of cancer-related death in men. Cholesterol levels are usually higher in prostate cancer cells. This affects the cell membrane composition, with cholesterol and sphingolipid-containing raft membrane domains becoming a greater component. In addition to polar lipids, these domains recruit and regulate certain types of protein, including various cell signaling proteins that are critical to cancer cell survival and invasiveness. This suggests that membrane rafts have a regulatory role in tumor progression, making them a potential target in prostate cancer treatment.

Enhanced mitochondrial fission suppresses signaling and metastasis in triple-negative breast cancer

BACKGROUND

Mitochondrial dynamics underlies malignant transformation, cancer progression, and response to treatment. Current research presents conflicting evidence for functions of mitochondrial fission and fusion in tumor progression. Here, we investigated how mitochondrial fission and fusion states regulate underlying processes of cancer progression and metastasis in triple-negative breast cancer (TNBC).

METHODS

We enforced mitochondrial fission and fusion states through chemical or genetic approaches and measured migration and invasion of TNBC cells in 2D and 3D in vitro models. We also utilized kinase translocation reporters (KTRs) to identify single cell effects of mitochondrial state on signaling cascades, PI3K/Akt/mTOR and Ras/Raf/MEK/ERK, commonly activated in TNBC. Furthermore, we determined effects of fission and fusion states on metastasis, bone destruction, and signaling in mouse models of breast cancer.

RESULTS

Enforcing mitochondrial fission through chemical or genetic approaches inhibited migration, invasion, and metastasis in TNBC. Breast cancer cells with predominantly fissioned mitochondria exhibited reduced activation of Akt and ERK both in vitro and in mouse models of breast cancer. Treatment with leflunomide, a potent activator of mitochondrial fusion proteins, overcame inhibitory effects of fission on migration, signaling, and metastasis. Mining existing datasets for breast cancer revealed that increased expression of genes associated with mitochondrial fission correlated with improved survival in human breast cancer.

CONCLUSIONS

In TNBC, mitochondrial fission inhibits cellular processes and signaling pathways associated with cancer progression and metastasis. These data suggest that therapies driving mitochondrial fission may benefit patients with breast cancer.

New Insights on the Emerging Genomic Landscape of CXCR4 in Cancer: A Lesson from WHIM

Deciphering the molecular alterations leading to disease initiation and progression is currently crucial to identify the most relevant targets for precision therapy in cancer patients. Cancers express a complex chemokine network influencing leucocyte infiltration and angiogenesis. Moreover, malignant cells also express a selective repertoire of chemokine receptors that sustain their growth and spread. At present, different cancer types have been shown to overexpress C-X-C chemokine receptor type 4 (CXCR4) and to respond to its ligand C-X-C motif chemokine 12 (CXCL12). The CXCL12/CXCR4 axis influences cancer biology, promoting survival, proliferation, and angiogenesis, and plays a pivotal role in directing migration of cancer cells to sites of metastases, making it a prognostic marker and a therapeutic target. More recently, mutations in the C-terminus of CXCR4 have been identified in the genomic landscape of patients affected by Waldenstrom's macroglobulinemia, a rare B cell neoplasm. These mutations closely resemble those occurring in Warts, Hypogammaglobulinemia, Immunodeficiency, and Myelokathexis (WHIM) syndrome, an immunodeficiency associated with CXCR4 aberrant expression and activity and with chemotherapy resistance in clinical trials. In this review, we summarize the current knowledge on the relevance of CXCR4 mutations in cancer biology, focusing on its importance as predictors of clinical presentation and response to therapy.

Modulation of CXC-motif chemokine receptor 7, but not 4, expression is related to migration of the human prostate cancer cell LNCaP: regulation by androgen and inflammatory stimuli

OBJECTIVE

To elucidate the regulation, function of the chemokine CXC-motif ligand 12 (CXCL12) and its receptors (CXCR) 4 and 7 in prostate cancer tumor microenvironment.

MATERIAL

In-silico-analysis of expression in prostate cancer tissues. In-vitro comparison, testing of regulation in human prostate cancer cells LNCaP, DU145, and PC3.

TREATMENT

Dihydrotestosterone (DHT) treatments (0-10 nM) were for 0-48 h. The inflammatory agent Flagellin treatment (20 ng/ml) was for 2 h. Migration assays were performed for 24 h using 10 ng/ml CXCL12.

METHODS

Real-time PCR, western analysis, and migration assays were used to determine mRNA, protein, and functional changes, respectively.

RESULTS

Malignant prostate cancer tissues exhibit higher CXCR4/7 mRNA ratio, and higher CXCR7 mRNA levels were detected in the androgen-responsive LNCaP cells. Putative androgen-responsive elements were identified in CXCR4, 7 gene, and exposure to DHT, flagellin increased CXCR4 mRNA but decreased CXCR7 mRNA levels in LNCaP cells. Androgen receptor siRNA significantly attenuated the effects of DHT on CXCR4, 7 mRNA in LNCaP cells. However, DHT and flagellin only decrease CXCR7 protein and additively increased migration of LNCaP cells towards CXCL12.

CONCLUSIONS

Down regulation of CXCR7 protein by DHT and flagellin increased migration, supporting CXCR7 as decoy receptor counteracting CXCL12/CXCR4-mediated migration in prostate cancer cells.

Cholesterol impacts chemokine CCR5 receptor ligand-binding activity

The chemokine CCR5 receptor is target of maraviroc, a negative allosteric modulator of CCR5 that blocks the HIV protein gp120 from associating with the receptor, thereby inhibiting virus cellular entry. As noted with other G-protein-coupled receptor family members, the role of the lipid environment in CCR5 signaling remains obscure and very modestly investigated. Controversial literature on the impact of cholesterol (Chol) depletion in HIV infection and CCR5 signaling, including the hypothesis that Chol depletion could inhibit HIV infection, lead us to focus on the understanding of Chol impact in the first stages of receptor activation. To address this aim, the approach chosen was to employ reconstituted model lipid systems of controlled lipid composition containing CCR5 from two distinct expression systems: Pichia pastoris and cell-free expression. The characterization of receptor/ligand interaction in terms of total binding or competition binding assays was independently performed by plasmon waveguide resonance and fluorescence anisotropy, respectively. Maraviroc, a potent receptor antagonist, was the ligand investigated. Additionally, coarse-grained molecular dynamics simulation was employed to investigate Chol impact in the receptor-conformational flexibility and dynamics. Results obtained with receptor produced by different expression systems and using different biophysical approaches clearly demonstrate a considerable impact of Chol in the binding affinity of maraviroc to the receptor and receptor-conformational dynamics. Chol considerably decreases maraviroc binding affinity to the CCR5 receptor. The mechanisms by which this effect occurs seem to involve the adoption of distinct receptor-conformational states with restrained structural dynamics and helical motions in the presence of Chol.

How Prostate Cancer Cells Use Strategy Instead of Brute Force to Achieve Metastasis

Akin to many other cancers, metastasis is the predominant cause of lethality in prostate cancer (PCa). Research in the past decade or so has revealed that although metastatic manifestation is a multi-step and complex process that is orchestrated by distinct cellular and molecular mechanisms, the process in itself is an extremely inefficient one. It is now becoming increasingly evident that PCa cells employ a plethora of strategies to make the most of this inefficient process. These strategies include priming the metastatic sites ahead of colonization, devising ways to metastasize to specific organs, outsmarting the host defense surveillance, lying in a dormant state at the metastatic site for prolonged periods, and widespread reprogramming of the gene expression to suit their needs. Based on established, recent, and evolving lines of research, this review is an attempt to understand PCa metastasis from the perspective of military combat, wherein strategic maneuvering instead of brute force often plays a decisive role in the outcome.

CXCL12/CXCR4 signal transduction in diseases and its molecular approaches in targeted-therapy

Chemokines are small molecules called "chemotactic cytokines" and regulate many processes like leukocyte trafficking, homing of immune cells, maturation, cytoskeletal rearrangement, physiology, migration during development, and host immune responses. These proteins bind to their corresponding 7-membrane G-protein-coupled receptors. Chemokines and their receptors are anti-inflammatory factors in autoimmune conditions, so consider as potential targets for neutralization in such diseases. They also express by cancer cells and function as angiogenic factors, and/or survival/growth factors that enhance tumor angiogenesis and development. Among chemokines, the CXCL12/CXCR4 axis has significantly been studied in numerous cancers and autoimmune diseases. CXCL12 is a homeostatic chemokine, which is acts as an anti-inflammatory chemokine during autoimmune inflammatory responses. In cancer cells, CXCL12 acts as an angiogenic, proliferative agent and regulates tumor cell apoptosis as well. CXCR4 has a role in leukocyte chemotaxis in inflammatory situations in numerous autoimmune diseases, as well as the high levels of CXCR4, observed in different types of human cancers. These findings suggest CXCL12/CXCR4 as a potential therapeutic target for therapy of autoimmune diseases and open a new approach to targeted-therapy of cancers by neutralizing CXCL12 and CXCR4. In this paper, we reviewed the current understanding of the role of the CXCL12/CXCR4 axis in disease pathology and cancer biology, and discuss its therapeutic implications in cancer and diseases.

Macrofluidic recirculating model of skeletal metastasis

While microfluidic systems model aspects of metastasis, they are limited to artificially created tissues of limited complexity. We set out to develop an in vitro model of tumor cell migration from a primary tumor to a distant site that allows use of tissue. Accordingly, we created a macrofluidic model using culture plate wells connected with type I collagen-coated large bore tubing and has recirculating media. Green fluorescent protein-positive prostate carcinoma cells in a hydrogel or excised tumor xenografts from mice were placed into primary tumor sites and either human bone stromal cells (HS-5) in a hydrogel or human-derived bone chips were seeded into metastatic sites. Cells from the primary sites migrated to and grew in metastatic sites. Bone enhanced growth at metastatic sites and established a CXCL12 gradient that was higher in metastatic versus primary sites. AMD3100-mediated inhibition of CXCL12 function reduced the number of cells targeting the bone at the metastatic sites. In summary, we have developed a macrofluidic metastasis model that allows incorporation of tumor and metastatic microenvironment tissues and models chemotaxis. This system allows for incorporation of tumor heterogeneity and inclusion of an intact microenvironment. These features will facilitate identification of mechanisms and therapeutics for bone metastasis.

Stromal fibroblasts induce metastatic tumor cell clusters via epithelial-mesenchymal plasticity

Emerging evidence supports the hypothesis that multicellular tumor clusters invade and seed metastasis. However, whether tumor-associated stroma induces epithelial-mesenchymal plasticity in tumor cell clusters, to promote invasion and metastasis, remains unknown. We demonstrate herein that carcinoma-associated fibroblasts (CAFs) frequently present in tumor stroma drive the formation of tumor cell clusters composed of two distinct cancer cell populations, one in a highly epithelial (E-cadherinhiZEB1lo/neg: Ehi) state and another in a hybrid epithelial/mesenchymal (E-cadherinloZEB1hi: E/M) state. The Ehi cells highly express oncogenic cell-cell adhesion molecules, such as carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) and CEACAM6 that associate with E-cadherin, resulting in increased tumor cell cluster formation and metastatic seeding. The E/M cells also retain associations with Ehi cells, which follow the E/M cells leading to collective invasion. CAF-produced stromal cell-derived factor 1 and transforming growth factor-β confer the Ehi and E/M states as well as invasive and metastatic traits via Src activation in apposed human breast tumor cells. Taken together, these findings indicate that invasive and metastatic tumor cell clusters are induced by CAFs via epithelial-mesenchymal plasticity.

High-Density Lipoproteins Decrease Proinflammatory Activity and Modulate the Innate Immune Response

Atherosclerosis, a chronic inflammatory disease of the arterial wall, is the leading cause of cardiac disorders and stroke. The onset and progression of these diseases are linked with the inflammatory response, especially NLRP3 inflammasome activation, inducing the production of proinflammatory cytokines, such as interleukin 1β (IL-1β). Because high-density lipoproteins (HDLs) have shown significant antiatherogenic and anti-inflammatory properties, we evaluated their immunomodulatory activity in response to cholesterol crystals and other innate immune activators. Human primary monocyte-derived macrophages, THP-1 cells, and murine macrophages were stimulated to activate NLRP3 inflammasome and other pattern recognition receptors, in the presence or absence of HDL. Then, HDL immunomodulatory effects were evaluated through IL-1β and IL-6 production by enzyme-linked immunosorbent assay. Furthermore, in vivo HDL anti-inflammatory effects were evaluated in a murine model of peritoneal inflammatory infiltration. HDLs have an immunomodulatory effect on different cellular models, including peripheral blood mononuclear cells, THP-1 cells, and murine macrophages, by affecting the activity of innate immunity sensors, such as Toll-like receptors (TLRs), dectin-1, and inflammasomes. HDL reduces the proinflammatory role of cholesterol crystals, nigericin, and other NLRP3 and AIM2 inflammasome agonists, and several TLR agonists, leading to a decreased production of IL-1β and IL-6. The results suggest that HDLs are highly important in the regulation of the innate immune response and may have a beneficial role in controlling diseases associated with the inflammatory response.

Clathrin Heavy Chain Knockdown Impacts CXCR4 Signaling and Post-translational Modification

Recent research has implicated endocytic pathways as important regulators of receptor signaling. However, the role of endocytosis in regulating chemokine CXC receptor 4 (CXCR4) signaling remains largely unknown. In the present work we systematically investigate the impact of clathrin knockdown on CXCR4 internalization, signaling, and receptor post-translational modification. Inhibition of clathrin-mediated endocytosis (CME) significantly reduced CXCR4 internalization. In contrast to other receptors, clathrin knockdown increased CXCL12-dependent ERK1/2 signaling. Simultaneous inhibition of CME and lipid raft disruption abrogated this increase in ERK1/2 phosphorylation suggesting that endocytic pathway compensation can influence signaling outcomes. Interestingly, using an antibody sensitive to CXCR4 post-translational modification, we also found that our ability to detect CXCR4 was drastically reduced upon clathrin knockdown. We hypothesize that this effect was due to differences in receptor post-translational modification as total CXCR4 protein and mRNA levels were unchanged. Lastly, we show that clathrin knockdown reduced CXCL12-dependent cell migration irrespective of an observed increase in ERK1/2 phosphorylation. Altogether, this work supports a complex model by which modulation of endocytosis affects not only receptor signaling and internalization but also receptor post-translational modification.

ErbB-2 signaling in advanced prostate cancer progression and potential therapy

Currently, prostate cancer (PCa) remains the most commonly diagnosed solid tumor and the second leading cause of cancer-related deaths in US men. Most of these deaths are attributed to the development of castration-resistant (CR) PCa. ErbB-2 and ErbB family members have been demonstrated to contribute to the progression of this lethal disease. In this review, we focus on updating the role of ErbB-2 in advanced PCa progression and its regulation, including its regulation via ligand activation, miRNAs and protein phosphorylation. We also discuss its downstream signaling pathways, including AKT, ERK1/2 and STATs, involved in advanced PCa progression. Additionally, we evaluate the potential of ErbB-2, focusing on its protein hyper-phosphorylation status, as a biomarker for aggressive PCa as well as the effectiveness of ErbB-2 as a target for the treatment of CR PCa via a multitude of approaches, including orally available inhibitors, intratumoral expression of cPAcP, vaccination and immunotherapy.

Ping-Pong-Tumor and Host in Pancreatic Cancer Progression

Metastasis is the main cause of high pancreatic cancer (PaCa) mortality and trials dampening PaCa mortality rates are not satisfying. Tumor progression is driven by the crosstalk between tumor cells, predominantly cancer-initiating cells (CIC), and surrounding cells and tissues as well as distant organs, where tumor-derived extracellular vesicles (TEX) are of major importance. A strong stroma reaction, recruitment of immunosuppressive leukocytes, perineural invasion, and early spread toward the peritoneal cavity, liver, and lung are shared with several epithelial cell-derived cancer, but are most prominent in PaCa. Here, we report on the state of knowledge on the PaCIC markers Tspan8, alpha6beta4, CD44v6, CXCR4, LRP5/6, LRG5, claudin7, EpCAM, and CD133, which all, but at different steps, are engaged in the metastatic cascade, frequently via PaCIC-TEX. This includes the contribution of PaCIC markers to TEX biogenesis, targeting, and uptake. We then discuss PaCa-selective features, where feedback loops between stromal elements and tumor cells, including distorted transcription, signal transduction, and metabolic shifts, establish vicious circles. For the latter particularly pancreatic stellate cells (PSC) are responsible, furnishing PaCa to cope with poor angiogenesis-promoted hypoxia by metabolic shifts and direct nutrient transfer via vesicles. Furthermore, nerves including Schwann cells deliver a large range of tumor cell attracting factors and Schwann cells additionally support PaCa cell survival by signaling receptor binding. PSC, tumor-associated macrophages, and components of the dysplastic stroma contribute to perineural invasion with signaling pathway activation including the cholinergic system. Last, PaCa aggressiveness is strongly assisted by the immune system. Although rich in immune cells, only immunosuppressive cells and factors are recovered in proximity to tumor cells and hamper effector immune cells entering the tumor stroma. Besides a paucity of immunostimulatory factors and receptors, immunosuppressive cytokines, myeloid-derived suppressor cells, regulatory T-cells, and M2 macrophages as well as PSC actively inhibit effector cell activation. This accounts for NK cells of the non-adaptive and cytotoxic T-cells of the adaptive immune system. We anticipate further deciphering the molecular background of these recently unraveled intermingled phenomena may turn most lethal PaCa into a curatively treatable disease.

Targeting CXCL12/CXCR4 Axis in Tumor Immunotherapy

Chemokines, which have chemotactic abilities, are comprised of a family of small cytokines with 8-10 kilodaltons. Chemokines work in immune cells by trafficking and regulating cell proliferation, migration, activation, differentiation, and homing. CXCR-4 is an alpha-chemokine receptor specific for stromal-derived-factor-1 (SDF-1, also known as CXCL12), which has been found to be expressed in more than 23 different types of cancers. Recently, the SDF-1/CXCR-4 signaling pathway has emerged as a potential therapeutic target for human tumor because of its critical role in tumor initiation and progression by activating multiple signaling pathways, such as ERK1/2, ras, p38 MAPK, PLC/ MAPK, and SAPK/ JNK, as well as regulating cancer stem cells. CXCL12/CXCR4 antagonists have been produced, which have shown encouraging results in anti-cancer activity. Here, we provide a brief overview of the CXCL12/CXCR4 axis as a molecular target for cancer treatment. We also review the potential utility of targeting CXCL12/CXCR4 axis in combination of immunotherapy and/or chemotherapy based on up-to-date literature and ongoing research progress.

Regulatory signaling network in the tumor microenvironment of prostate cancer bone and visceral organ metastases and the development of novel therapeutics

This article describes cell signaling network of metastatic prostate cancer (PCa) to bone and visceral organs in the context of tumor microenvironment and for the development of novel therapeutics. The article focuses on our recent progress in the understanding of: 1) The plasticity and dynamics of tumor–stroma interaction; 2) The significance of epigenetic reprogramming in conferring cancer growth, invasion and metastasis; 3) New insights on altered junctional communication affecting PCa bone and brain metastases; 4) Novel strategies to overcome therapeutic resistance to hormonal antagonists and chemotherapy; 5) Genetic-based therapy to co-target tumor and bone stroma; 6) PCa-bone-immune cell interaction and TBX2-WNTprotein signaling in bone metastasis; 7) The roles of monoamine oxidase and reactive oxygen species in PCa growth and bone metastasis; and 8) Characterization of imprinting cluster of microRNA, in tumor–stroma interaction. This article provides new approaches and insights of PCa metastases with emphasis on basic science and potential for clinical translation. This article referenced the details of the various approaches and discoveries described herein in peer-reviewed publications. We dedicate this article in our fond memory of Dr. Donald S. Coffey who taught us the spirit of sharing and the importance of focusing basic science discoveries toward translational medicine.

A novel cross-talk between CXCR4 and PI4KIIIα in prostate cancer cells

Chemokine signaling regulates cell migration and tumor metastasis. CXCL12, a member of the chemokine family, and its receptor, CXCR4, a G protein coupled receptor (GPCR), are key mediators of prostate-cancer (PC) bone metastasis. In PC cells androgens activate CXCR4 gene expression and receptor signaling on lipid rafts, which induces protease expression and cancer cell invasion. To identify novel lipid-raft-associated CXCR4 regulators supporting invasion/metastasis, we performed a SILAC-based quantitative proteomic analysis of lipid-rafts derived from PC3 stable cell lines with overexpression or knockdown of CXCR4. This analysis identified the evolutionarily conserved phosphatidylinositol 4-kinase IIIα (PI4KIIIα), and SAC1 phosphatase that dephosphorylates phosphatidylinositol-4-phosphate as potential candidate CXCR4 regulators. CXCR4 interacted with PI4KIIIα membrane targeting machinery recruiting them to the plasma membrane for PI4P production. Consistent with this interaction, PI4KIIIα was found tightly linked to the CXCR4 induced PC cell invasion. Thus, ablation of PI4KIIIα in CXCR4-expressing PC3 cells reduced cellular invasion in response to a variety of chemokines. Immunofluorescence microscopy in CXCR4 expressing cells revealed localized production of PI4P on the invasive projections. Human tumor studies documented increased PI4KIIIα expression in metastatic tumors vs. the primary tumor counterparts, further supporting the PI4KIIIα role in tumor metastasis. Furthermore, we also identified an unexpected function of PI4KIIIα in GPCR signaling where CXCR4 regulates PI4KIIIα activity and mediate tumor metastasis. Together, our study identifies a novel cross-talk between PI4KIIIα and CXCR4 in promoting tumor metastasis and suggests that PI4KIIIα pharmacological targeting may have therapeutic benefit for advanced prostate cancer patients.

Caveolin‑1 enhances RANKL‑induced gastric cancer cell migration

The classical pathway involving receptor activator of nuclear factor‑κB (RANK) and its ligand (RANKL) induces the activation of osteoclasts and the migration of a variety of tumor cells, including breast and lung cancer. In our previous study, the expression of RANK was identified on the surface of gastric cancer cells, however, whether the RANKL/RANK pathway is involved in the regulation of gastric cancer cell migration remains to be fully elucidated. Lipid rafts represent a major platform for the regulation of cancer signaling; however, their involvement in RANKL‑induced migration remains to be elucidated. To investigate the potential roles and mechanism of RANKL/RANK in gastric cancer migration and metastasis, the present study examined the expression of RANK by western blot analysis and the expression of caveolin‑1 (Cav‑1) in gastric cancer tissues by immunohistochemistry, in addition to cell migration which is measured by Transwell migration assay. The aggregation of lipid reft was observed by fluorescence microscopy and western blotting was used to measure signaling changes in associated pathways. The results showed that RANKL induced gastric cancer cell migration, accompanied by the activation of Cav‑1 and aggregation of lipid rafts. Nystatin, a lipid raft inhibitor, inhibited the activation of Cav‑1 and markedly reversed RANKL‑induced gastric cancer cell migration. The RANKL‑induced activation of Cav‑1 has been shown to occur with the activation of proto‑oncogene tyrosine‑protein kinase Src (c‑Src). The c‑Src inhibitor, PP2, inhibited the activation of Cav‑1 and lipid raft aggregation, and reversed RANKL‑induced gastric cancer cell migration. Furthermore, it was demonstrated that Cav‑1 was involved in RANKL‑induced cell migration in lung, renal and breast cancer cells. These results suggested that RANKL induced gastric cancer cell migration, likely through mechanisms involving the c‑Src/Cav‑1 pathway and lipid raft aggregation.

The Chemokine Receptor CXCR4 and c-MET Cooperatively Promote Epithelial-Mesenchymal Transition in Gastric Cancer Cells

The C-X-C motif chemokine receptor 4 (CXCR4) pathway can promote tumor metastasis but is dependent on cross talk with other signaling pathways. The MET proto-oncogene (c-MET) participates in metastasis and is highly expressed in gastric cancer. However, the relationship between CXCR4 and c-MET signaling and their mechanisms of action in gastric cancer metastasis remain unclear. In this study, in vitro experiments demonstrated that C-X-C motif chemokine ligand 12 (CXCL12)/CXCR4 induces epithelial-mesenchymal transition (EMT) and promotes migration in gastric cancer cells, which is accompanied by c-MET activation. These phenomena were reversed by c-MET inhibition. Further investigation revealed that c-MET activation correlated with its interaction with caveolin 1 in lipid rafts, induced by CXCL12. In clinical samples, we observed a significant positive association between CXCR4 expression and c-MET phosphorylation (r = 0.259, P = .005). Moreover, samples expressing both receptors were found to indicate significantly poorer patient prognosis (P < .001). These results suggest that CXCL12 induces EMT at least partially through cross talk between CXCR4 and c-MET signaling. In addition, changes in these pathways could have clinical importance for the treatment of gastric cancer.

Cannabinoids synergize with carfilzomib, reducing multiple myeloma cells viability and migration

Several studies showed a potential anti-tumor role for cannabinoids, by modulating cell signaling pathways involved in cancer cell proliferation, chemo-resistance and migration. Cannabidiol (CBD) was previously noted in multiple myeloma (MM), both alone and in synergy with the proteasome inhibitor bortezomib, to induce cell death. In other type of human cancers, the combination of CBD with Δ⁹-tetrahydrocannabinol (THC) was found to act synergistically with other chemotherapeutic drugs suggesting their use in combination therapy. In the current study, we evaluated the effects of THC alone and in combination with CBD in MM cell lines. We found that CBD and THC, mainly in combination, were able to reduce cell viability by inducing autophagic-dependent necrosis. Moreover, we showed that the CBD-THC combination was able to reduce MM cells migration by down-regulating expression of the chemokine receptor CXCR4 and of the CD147 plasma membrane glycoprotein. Furthermore, since the immuno-proteasome is considered a new target in MM and also since carfilzomib (CFZ) is a new promising immuno-proteasome inhibitor that creates irreversible adducts with the β5i subunit of immuno-proteasome, we evaluated the effect of CBD and THC in regulating the expression of the β5i subunit and their effect in combination with CFZ. Herein, we also found that the CBD and THC combination is able to reduce expression of the β5i subunit as well as to act in synergy with CFZ to increase MM cell death and inhibits cell migration. In summary, these results proved that this combination exerts strong anti-myeloma activities.

The MRPS18-2 protein levels correlate with prostate tumor progression and it induces CXCR4-dependent migration of cancer cells

We have earlier found abnormal expression of the mitochondrial ribosomal protein S18-2 (MRPS18-2, S18-2) in endometrial cancer, compared to the expression in hyperplasia and in normal endometrium. Here we report that expression of S18-2 was increased with disease progression in clinical specimens of prostate cancer (PCa). The level of induction of epithelial to mesenchymal cell transition (EMT) correlated with the expression level of S18-2 in PCa cell lines. Moreover, cells acquired increased ability of migration upon S18-2 overexpression, as was evaluated in zebrafish embryo model and in trans-well assay. We found that this is due to increased CXCR4 cell surface expression. Neutralizing CXCR4 protein or abrogating S18-2 expression in cells significantly reduced their migratory ability directed toward CXCL12. The mRNA expression of TWIST2, encoding one of transcription factors that induce EMT upon CXCR4 increase, positively correlated with the S18-2 protein level. Together, these data suggest that the S18-2 protein induces EMT through the TWIST2/E-cadherin signalling and, consequently, CXCR4-mediated migration of PCa cells.

CXCL12/SDF-1α induces migration via SRC-mediated CXCR4-EGFR cross-talk in gastric cancer cells

Metastasis is the primary cause of mortality in patients with advanced gastric carcinoma, and multiple signaling pathways promote the development of this condition. Stromal cell-derived factor-1 (SDF-1α/CXCL12), the main ligand for CXC chemokine receptor-4 (CXCR4), serves an important role in gastric cancer cell migration. Previous studies have demonstrated that CXCL12 could also stimulate the secretion of epidermal growth factor receptor (EGFR) ligands, including amphiregulin and heparin-binding epidermal growth factor-like growth factor, from gastric cancer cells, resulting in an increase in the ability of migration. However, it remains to be elucidated whether CXCL12 activates EGFR intracellular signaling and therefore stimulates migration in gastric cancer. The present study demonstrated that three gastric cancer cell lines, SGC-7901, MGC-803 and BGC-823, all expressed CXCR4. The increased chemotactic migratory ability stimulated by CXCL12 was effectively abrogated by the CXCR4 antagonist, AMD3100. Furthermore, a rapid phosphorylation of Akt/extracellular signal-regulated kinase (ERK)/EGFR was demonstrated to be involved in CXCL12/CXCR4-induced gastric cancer cell migration. Knockdown of EGFR gene or the use of a monoclonal antibody against EGFR (C225) blocked the activation of ERK/Akt and partially prevented the ability of migration induced by CXCL12, which indicated that EGFR signaling is located downstream of CXCL12. In addition, it was also revealed that the activation of non-receptor tyrosine kinase c-steroid receptor co-activator (SRC) and the formation of the SRC/EGFR heterodimer are promoted by CXCL12, whereas the SRC inhibitor, PP2, blocks the SRC/EGFR heterodimer and the activation of EGFR, as well as CXCR4-meditated migration induced by CXCL12. The present results indicated that SRC mediates a potential CXCR4-EGFR cross-talk, and thereby utilizes the EGFR-Akt/ERK axis to promote cellular migration. The present study provided a novel insight into the underlying regulatory mechanisms of the CXCL12/CXCR4 pathway in gastric cancer cell migration.

Dissecting major signaling pathways in prostate cancer development and progression: Mechanisms and novel therapeutic targets

Prostate cancer (PCa) is the most frequently diagnosed non-cutaneous malignancy and leading cause of cancer mortality in men. At the initial stages, prostate cancer is dependent upon androgens for their growth and hence effectively combated by androgen deprivation therapy (ADT). However, most patients eventually recur with an androgen deprivation-resistant phenotype, referred to as castration-resistant prostate cancer (CRPC), a more aggressive form for which there is no effective therapy presently available. The current review is an attempt to cover and establish an understanding of some major signaling pathways implicated in prostate cancer development and castration-resistance, besides addressing therapeutic strategies that targets the key signaling mechanisms.

Real time monitoring of membrane GPCR reconstitution by plasmon waveguide resonance: on the role of lipids

G-protein coupled receptors (GPCRs) are important therapeutic targets since more than 40% of the drugs on the market exert their action through these proteins. To decipher the molecular mechanisms of activation and signaling, GPCRs often need to be isolated and reconstituted from a detergent-solubilized state into a well-defined and controllable lipid model system. Several methods exist to reconstitute membrane proteins in lipid systems but usually the reconstitution success is tested at the end of the experiment and often by an additional and indirect method. Irrespective of the method used, the reconstitution process is often an intractable and time-consuming trial-and-error procedure. Herein, we present a method that allows directly monitoring the reconstitution of GPCRs in model planar lipid membranes. Plasmon waveguide resonance (PWR) allows following GPCR lipid reconstitution process without any labeling and with high sensitivity. Additionally, the method is ideal to probe the lipid effect on receptor ligand binding as demonstrated by antagonist binding to the chemokine CCR5 receptor.

Pharmacological targeting of CXCL12/CXCR4 signaling in prostate cancer bone metastasis

Background

The CXCL12/CXCR4 axis transactivates HER2 and promotes intraosseous tumor growth. To further explore the transactivation of HER2 by CXCL12, we investigated the role of small GTP protein G_αi2 in Src and HER2 phosphorylation in lipid raft membrane microdomains and the significance of CXCR4 in prostate cancer bone tumor growth.

Methods

We used a variety of methods such as lipid raft isolation, invasion assays, an in vivo model of intratibial tumor growth, bone histomorphometry, and immunohistochemistry to determine the role of CXCR4 signaling in lipid raft membrane microdomains and effects of targeting of CXCR4 for bone tumor growth.

Results

We determined that (a) CXCL12/CXCR4 transactivation of EGFR and HER2 is confined to lipid raft membrane microdomains, (b) CXCL12 activation of HER2 and Src is mediated by small GTP proteins in lipid rafts, (c) inhibition of the CXCL12/CXCR4 axis through plerixafor abrogates the initial establishment of tumor growth without affecting the growth of established bone tumors, and (d) inhibition of EGFR signaling through gefitinib leads to inhibition of established bone tumor growth.

Conclusions

These data suggest that lipid raft membrane microdomains are key sites for CXCL12/CXCR4 transactivation of HER2 via small GTP binding protein G_αi2 and Src kinase. The initial establishment of prostate cancer is supported by the endosteal niche, and blocking the CXCL12/CXCR4 axis of this niche along with its downstream signaling severely compromises initial establishment of tumors in the bone microenvironment, whereas expanding bone tumors are sensitive only to the members of growth factor receptor inhibition.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-016-0552-0) contains supplementary material, which is available to authorized users.

PGE2 /EP4 Signaling Controls the Transfer of the Mammary Stem Cell State by Lipid Rafts in Extracellular Vesicles

Prostaglandin E₂ (PGE₂ )-initiated signaling contributes to stem cell homeostasis and regeneration. However, it is unclear how PGE₂ signaling controls cell stemness. This study identifies a previously unknown mechanism by which PGE₂ /prostaglandin E receptor 4 (EP₄ ) signaling regulates multiple signaling pathways (e.g., PI3K/Akt signaling, TGFβ signaling, Wnt signaling, EGFR signaling) which maintain the basal mammary stem cell phenotype. A shift of basal mammary epithelial stem cells (MaSCs) from a mesenchymal/stem cell state to a non-basal-MaSC state occurs in response to prostaglandin E receptor 4 (EP₄ ) antagonism. EP₄ antagonists elicit release of signaling components, by controlling their trafficking into extracellular vesicles/exosomes in a lipid raft/caveolae-dependent manner. Consequently, EP₄ antagonism indirectly inactivates, through induced extracellular vesicle/exosome release, pathways required for mammary epithelial stem cell homeostasis, e.g. canonical/noncanonical Wnt, TGFβ and PI3K/Akt pathways. EP₄ antagonism causes signaling receptors and signaling components to shift from non-lipid raft fractions to lipid raft fractions, and to then be released in EP₄ antagonist-induced extracellular vesicles/exosomes, resulting in the loss of the stem cell state by mammary epithelial stem cells. In contrast, luminal mammary epithelial cells can acquire basal stem cell properties following ingestion of EP₄ antagonist-induced stem cell extracellular vesicles/exosomes, and can then form mammary glands. These findings demonstrate that PGE₂ /EP₄ signaling controls homeostasis of mammary epithelial stem cells through regulating extracellular vesicle/exosome release. Reprogramming of mammary epithelial cells can result from EP₄ -mediated stem cell property transfer by extracellular vesicles/exosomes containing caveolae-associated proteins, between mammary basal and luminal epithelial cells. Stem Cells 2017;35:425-444.

Integrative Analysis of Subcellular Quantitative Proteomics Studies Reveals Functional Cytoskeleton Membrane-Lipid Raft Interactions in Cancer

Lipid rafts are dynamic membrane microdomains that orchestrate molecular interactions and are implicated in cancer development. To understand the functions of lipid rafts in cancer, we performed an integrated analysis of quantitative lipid raft proteomics data sets modeling progression in breast cancer, melanoma, and renal cell carcinoma. This analysis revealed that cancer development is associated with increased membrane raft-cytoskeleton interactions, with ∼40% of elevated lipid raft proteins being cytoskeletal components. Previous studies suggest a potential functional role for the raft-cytoskeleton in the action of the putative tumor suppressors PTRF/Cavin-1 and Merlin. To extend the observation, we examined lipid raft proteome modulation by an unrelated tumor suppressor opioid binding protein cell-adhesion molecule (OPCML) in ovarian cancer SKOV3 cells. In agreement with the other model systems, quantitative proteomics revealed that 39% of OPCML-depleted lipid raft proteins are cytoskeletal components, with microfilaments and intermediate filaments specifically down-regulated. Furthermore, protein-protein interaction network and simulation analysis showed significantly higher interactions among cancer raft proteins compared with general human raft proteins. Collectively, these results suggest increased cytoskeleton-mediated stabilization of lipid raft domains with greater molecular interactions as a common, functional, and reversible feature of cancer cells.

Cytokine Regulation of Metastasis and Tumorigenicity

The human body combats infection and promotes wound healing through the remarkable process of inflammation. Inflammation is characterized by the recruitment of stromal cell activity including recruitment of immune cells and induction of angiogenesis. These cellular processes are regulated by a class of soluble molecules called cytokines. Based on function, cell target, and structure, cytokines are subdivided into several classes including: interleukins, chemokines, and lymphokines. While cytokines regulate normal physiological processes, chronic deregulation of cytokine expression and activity contributes to cancer in many ways. Gene polymorphisms of all types of cytokines are associated with risk of disease development. Deregulation RNA and protein expression of interleukins, chemokines, and lymphokines have been detected in many solid tumors and hematopoetic malignancies, correlating with poor patient prognosis. The current body of literature suggests that in some tumor types, interleukins and chemokines work against the human body by signaling to cancer cells and remodeling the local microenvironment to support the growth, survival, and invasion of primary tumors and enhance metastatic colonization. Some lymphokines are downregulated to suppress tumor progression by enhancing cytotoxic T cell activity and inhibiting tumor cell survival. In this review, we will describe the structure/function of several cytokine families and review our current understanding on the roles and mechanisms of cytokines in tumor progression. In addition, we will also discuss strategies for exploiting the expression and activity of cytokines in therapeutic intervention.

Oncogenic roles and drug target of CXCR4/CXCL12 axis in lung cancer and cancer stem cell

Although the great progress has been made in diagnosis and therapeutic in lung cancer, it induces the most cancer death worldwide in both males and females. Chemokines, which have chemotactic abilities, contain up to 50 family members. By binding to G protein-coupled receptors (GPCR), holding seven-transmembrane domain, they function in immune cell trafficking and regulation of cell proliferation, differentiation, activation, and migration, homing under both physiologic and pathologic conditions. The alpha-chemokine receptor CXCR4 for the alpha-chemokine stromal cell-derived-factor-1 (SDF-1) is most widely expressed by tumors. In addition to human tissues of the bone marrow, liver, adrenal glands, and brain, the CXC chemokine SDF-1 or CXCL12 is also highly expressed in lung cancer tissues and is associated with lung metastasis. Lung cancer cells have the capabilities to utilize and manipulate the CXCL12/CXCR system to benefit growth and distant spread. CXCL12/CXCR4 axis is a major culprit for lung cancer and has a crucial role in lung cancer initiation and progression by activating cancer stem cell. This review provides an evaluation of CXCL12/CXCR4 as the potential therapeutic target for lung cancers; it also focuses on the synergistic effects of inhibition of CXCL12/CXCR4 axis and immunotherapy as well as chemotherapy. Together, CXCL12/CXCR4 axis can be a potential therapeutic target for lung cancers and has additive effects with immunotherapy.

Critical role of CAV1/caveolin-1 in cell stress responses in human breast cancer cells via modulation of lysosomal function and autophagy

CAV1 (caveolin 1, caveolae protein, 22kDa) is well known as a principal scaffolding protein of caveolae, a specialized plasma membrane structure. Relatively, the caveolae-independent function of CAV1 is less studied. Autophagy is a process known to involve various membrane structures, including autophagosomes, lysosomes, and autolysosomes for degradation of intracellular proteins and organelles. Currently, the function of CAV1 in autophagy remains largely elusive. In this study, we demonstrate for the first time that CAV1 deficiency promotes both basal and inducible autophagy. Interestingly, the promoting effect was found mainly in the late stage of autophagy via enhancing lysosomal function and autophagosome-lysosome fusion. Notably, the regulatory function of CAV1 in lysosome and autophagy was found to be caveolae-independent, and acts through lipid rafts. Furthermore, the elevated autophagy level induced by CAV1 deficiency serves as a cell survival mechanism under starvation. Importantly, downregulation of CAV1 and enhanced autophagy level were observed in human breast cancer cells and tissues. Taken together, our data reveal a novel function of CAV1 and lipid rafts in breast cancer development via modulation of lysosomal function and autophagy.

Simultaneous Activation of Induced Heterodimerization between CXCR4 Chemokine Receptor and Cannabinoid Receptor 2 (CB2) Reveals a Mechanism for Regulation of Tumor Progression

The G-protein-coupled chemokine receptor CXCR4 generates signals that lead to cell migration, cell proliferation, and other survival mechanisms that result in the metastatic spread of primary tumor cells to distal organs. Numerous studies have demonstrated that CXCR4 can form homodimers or can heterodimerize with other G-protein-coupled receptors to form receptor complexes that can amplify or decrease the signaling capacity of each individual receptor. Using biophysical and biochemical approaches, we found that CXCR4 can form an induced heterodimer with cannabinoid receptor 2 (CB2) in human breast and prostate cancer cells. Simultaneous, agonist-dependent activation of CXCR4 and CB2 resulted in reduced CXCR4-mediated expression of phosphorylated ERK1/2 and ultimately reduced cancer cell functions such as calcium mobilization and cellular chemotaxis. Given that treatment with cannabinoids has been shown to reduce invasiveness of cancer cells as well as CXCR4-mediated migration of immune cells, it is plausible that CXCR4 signaling can be silenced through a physical heterodimeric association with CB2, thereby inhibiting subsequent functions of CXCR4. Taken together, the data illustrate a mechanism by which the cannabinoid system can negatively modulate CXCR4 receptor function and perhaps tumor progression.