Tumor cell cholesterol depletion and V-ATPase inhibition as an inhibitory mechanism to prevent cell migration and invasiveness in melanoma

Softening the tumor matrix through cholesterol depletion breaks the physical barrier for enhanced antitumor therapy

The tumor develops defense tactics, including conversing the mechanical characteristics of tumor cells and their surrounding environment. A recent study reported that cholesterol depletion stiffens tumor cells, which could enhance adaptive T-cell immunotherapy. However, it remains unclear whether reducing the cholesterol in tumor cells contributes to re-educating the stiff tumor matrix, which serves as a physical barrier against drug penetration. Herein, we found that depleting cholesterol from tumor cells can demolish the intratumor physical barrier by disrupting the mechanical signal transduction between tumor cells and the extracellular matrix through the destruction of lipid rafts. This disruption allows nanoparticles (H/S@hNP) to penetrate deeply, resulting in improved photodynamic treatment. Our research also indicates that cholesterol depletion can inhibit the epithelial-mesenchymal transition and repolarize tumor-associated macrophages from M2 to M1, demonstrating the essential role of cholesterol in tumor progression. Overall, this study reveals that a cholesterol-depleted, softened tumor matrix reduces the difficulty of drug penetration, leading to enhanced antitumor therapeutics.

Unraveling lipid metabolism reprogramming for overcoming drug resistance in melanoma

Cutaneous melanoma is the deadliest form of skin cancer, and its incidence is continuing to increase worldwide in the last decades. Traditional therapies for melanoma can easily cause drug resistance, thus the treatment of melanoma remains a challenge. Various studies have focused on reversing the drug resistance. As tumors grow and progress, cancer cells face a constantly changing microenvironment made up of different nutrients, metabolites, and cell types. Multiple studies have shown that metabolic reprogramming of cancer is not static, but a highly dynamic process. There is a growing interest in exploring the relationship between melanoma andmetabolic reprogramming, one of which may belipid metabolism. This review frames the recent research progresses on lipid metabolism in melanoma.In addition, we emphasize the dynamic ability of metabolism during tumorigenesis as a target for improving response to different therapies and for overcoming drug resistance in melanoma.

Mining key circRNA-associated-ceRNA networks for milk fat metabolism in cows with varying milk fat percentages

BACKGROUND

Cow milk fat is an essential indicator for evaluating and measuring milk quality and cow performance. Growing research has identified the molecular functions of circular RNAs (circRNAs) necessary for mammary gland development and lactation in mammals.

METHOD

The present study analyzed circRNA expression profiling data in mammary epithelial cells (MECs) from cows with highly variable milk fat percentage (MFP) using differential expression analysis and weighted gene co-expression network analysis (WGCNA).

RESULTS

A total of 309 differentially expressed circRNAs (DE-circRNAs) were identified in the high and low MFP groups. WGCNA analysis revealed that the pink module was significantly associated with MFP (r = - 0.85, P = 0.007). Parental genes of circRNAs in this module were enriched mainly in lipid metabolism-related signaling pathways, such as focal adhesion, ECM-receptor interaction, adherens junction and AMPK. Finally, six DE-circRNAs were screened from the pink module: circ_0010571, circ_0007797, circ_0002746, circ_0003052, circ_0004319, and circ_0012840. Among them, circ_0002746, circ_0003052, circ_0004319, and circ_0012840 had circular structures and were highly expressed in mammary tissues. Subcellular localization revealed that these four DE-circRNAs may play a regulatory role in the mammary glands of dairy cows, mainly as competitive endogenous RNAs (ceRNAs). Seven hub target genes (GNB1, GNG2, PLCB1, PLCG1, ATP6V0C, NDUFS4, and PIGH) were obtained by constructing the regulatory network of their ceRNAs and then analyzed by CytoHubba and MCODE plugins in Cytoscape. Functional enrichment analysis revealed that these genes are crucial and most probable ceRNA regulators in milk fat metabolism.

CONCLUSIONS

Our study identified several vital circRNAs and ceRNAs affecting milk fat synthesis, providing new research ideas and a theoretical basis for cow lactation, milk quality, and breed improvement.

Regulating Cholesterol in Tumorigenesis: A Novel Paradigm for Tumor Nanotherapeutics

During the past decade, "membrane lipid therapy", which involves the regulation of the structure and function of tumor cell plasma membranes, has emerged as a new strategy for cancer treatment. Cholesterol is an important component of the tumor plasma membrane and serves an essential role in tumor initiation and progression. This review elucidates the role of cholesterol in tumorigenesis (including tumor cell proliferation, invasion/metastasis, drug resistance, and immunosuppressive microenvironment) and elaborates on the potential therapeutic targets for tumor treatment by regulating cholesterol. More meaningfully, this review provides an overview of cholesterol-integrated membrane lipid nanotherapeutics for cancer therapy through cholesterol regulation. These strategies include cholesterol biosynthesis interference, cholesterol uptake disruption, cholesterol metabolism regulation, cholesterol depletion, and cholesterol-based combination treatments. In summary, this review demonstrates the tumor nanotherapeutics based on cholesterol regulation, which will provide a reference for the further development of "membrane lipid therapy" for tumors.

Dynamized ultra-low dilution of Ruta graveolens disrupts plasma membrane organization and decreases migration of melanoma cancer cell

Cutaneous melanoma is a cancer with a very poor prognosis mainly because of metastatic dissemination and therefore a deregulation of cell migration. Current therapies can benefit from complementary medicines as supportive care in oncology. In our study, we show that a dynamized ultra-low dilution of Ruta Graveolens leads to an in vitro inhibition of migration on fibronectin of B16F10 melanoma cells, as well as a decrease in metastatic dissemination in vivo. These effects appear to be due to a disruption of plasma membrane organization, with a change in cell and membrane stiffness, associated with a disorganization of the actin cytoskeleton and a modification of the lipid composition of the plasma membrane. Together, these results demonstrate, in in vitro and in vivo models of cutaneous melanoma, an anti-cancer and anti-metastatic activity of ultra-low dynamized dilution of Ruta graveolens and reinforce its interest as complementary medicine in oncology.

Vacuolar ATPase Is a Possible Therapeutic Target in Acute Myeloid Leukemia: Focus on Patient Heterogeneity and Treatment Toxicity

Vacuolar ATPase (V-ATPase) is regarded as a possible target in cancer treatment. It is expressed in primary acute myeloid leukemia cells (AML), but the expression varies between patients and is highest for patients with a favorable prognosis after intensive chemotherapy. We therefore investigated the functional effects of two V-ATPase inhibitors (bafilomycin A1, concanamycin A) for primary AML cells derived from 80 consecutive patients. The V-ATPase inhibitors showed dose-dependent antiproliferative and proapoptotic effects that varied considerably between patients. A proteomic comparison of primary AML cells showing weak versus strong antiproliferative effects of V-ATPase inhibition showed a differential expression of proteins involved in intracellular transport/cytoskeleton functions, and an equivalent phosphoproteomic comparison showed a differential expression of proteins that regulate RNA processing/function together with increased activity of casein kinase 2. Patients with secondary AML, i.e., a heterogeneous subset with generally adverse prognosis and previous cytotoxic therapy, myeloproliferative neoplasia or myelodysplastic syndrome, were characterized by a strong antiproliferative effect of V-ATPase inhibition and also by a specific mRNA expression profile of V-ATPase interactome proteins. Furthermore, the V-ATPase inhibition altered the constitutive extracellular release of several soluble mediators (e.g., chemokines, interleukins, proteases, protease inhibitors), and increased mediator levels in the presence of AML-supporting bone marrow mesenchymal stem cells was then observed, especially for patients with secondary AML. Finally, animal studies suggested that the V-ATPase inhibitor bafilomycin had limited toxicity, even when combined with cytarabine. To conclude, V-ATPase inhibition has antileukemic effects in AML, but this effect varies between patients.

Comprehensive analysis of the clinical and biological significances of cholesterol metabolism in lower-grade gliomas

BACKGROUND

As a component of membrane lipids and the precursor of oxysterols and steroid hormones, reprogrammed cholesterol metabolism contributes to the initiation and progression of multiple cancers. Thus, we aim to further investigate the significances of cholesterol metabolism in lower-grade gliomas (LGGs).

METHODS

The present study included 413 LGG samples from TCGA RNA-seq dataset (training cohort) and 172 LGG samples from CGGA RNA-seq dataset (validation cohort). The cholesterol metabolism-related signature was identified by the LASSO regression model. Bioinformatics analyses were performed to explore the functional roles of this signature in LGGs. Kaplan-Meier and Cox regression analyses were enrolled to estimate prognostic value of the risk signature.

RESULTS

Our findings suggested that cholesterol metabolism was tightly associated clinicopathologic features and genomic alterations of LGGs. Bioinformatics analyses revealed that cholesterol metabolism played a key role in immunosuppression of LGGs, mainly by promoting macrophages polarization and T cell exhaustion. Kaplan-Meier curve and Cox regression analysis showed that cholesterol metabolism was an independent prognostic indicator for LGG patients. To improve the clinical application value of the risk signature, we also constructed a nomogram model to predict the 1-, 3- and 5-year survival of LGG patients.

CONCLUSION

The cholesterol metabolism was powerful prognostic indicator and could serve as a promising target to enhance personalized treatment of LGGs.

Lactoferrin perturbs intracellular trafficking, disrupts cholesterol-rich lipid rafts and inhibits glycolysis of highly metastatic cancer cells harbouring plasmalemmal V-ATPase

The milk-derived bovine lactoferrin (bLf) is an iron-binding glycoprotein with remarkable selective anticancer activity towards highly metastatic cancer cells displaying the proton pump V-ATPase at the plasma membrane. As studies aiming to dissect the bLf mechanisms of action are critical to improve its efficacy and boost its targeted clinical use, herein we sought to further uncover the molecular basis of bLf anticancer activity. We showed that bLf co-localizes with V-ATPase and cholesterol-rich lipid rafts at the plasma membrane of highly metastatic cancer cells. Our data also revealed that bLf perturbs cellular trafficking, induces intracellular accumulation of cholesterol and lipid rafts disruption, downregulates PI3K, and AKT or p-AKT and inhibits glycolysis of cancer cells harbouring V-ATPase at the plasma membrane lipid rafts. Altogether, our results can lay the foundation for future bLf-based targeted anticancer strategies as they unravel a novel cascade of molecular events that explains and further reinforces bLf selectivity for cancer cells displaying plasmalemmal V-ATPase.

The Lysosome in Malignant Melanoma: Biology, Function and Therapeutic Applications

Lysosomes are membrane-bound vesicles that play roles in the degradation and recycling of cellular waste and homeostasis maintenance within cells. False alterations of lysosomal functions can lead to broad detrimental effects and cause various diseases, including cancers. Cancer cells that are rapidly proliferative and invasive are highly dependent on effective lysosomal function. Malignant melanoma is the most lethal form of skin cancer, with high metastasis characteristics, drug resistance, and aggressiveness. It is critical to understand the role of lysosomes in melanoma pathogenesis in order to improve the outcomes of melanoma patients. In this mini-review, we compile our current knowledge of lysosomes' role in tumorigenesis, progression, therapy resistance, and the current treatment strategies related to lysosomes in melanoma.

MYC Enhances Cholesterol Biosynthesis and Supports Cell Proliferation Through SQLE

Oncogene c-Myc (referred in this report as MYC) promotes tumorigenesis in multiple human cancers. MYC regulates numerous cellular programs involved in cell growth and cell metabolism. Tumor cells exhibit obligatory dependence on cholesterol metabolism, which provides essential membrane components and metabolites to support cell growth. To date, how cholesterol biosynthesis is delicately regulated to promote tumorigenesis remains unclear. Here, we show that MYC enhances cholesterol biosynthesis and promotes cell proliferation. Through transcriptional upregulation of SQLE, a rate-limiting enzyme in cholesterol synthesis pathway, MYC increases cholesterol production and promotes tumor cell growth. SQLE overexpression restores the cellular cholesterol levels in MYC-knockdown cells. More importantly, in SQLE-depleted cells, enforced expression of MYC has no effect on cholesterol levels. Therefore, our findings reveal that SQLE is critical for MYC-mediated cholesterol synthesis, and further demonstrate that SQLE may be a potential therapeutic target in MYC-amplified cancers.

Emerging insights on the role of V-ATPase in human diseases: Therapeutic challenges and opportunities

The control of the intracellular pH is vital for the survival of all organisms. Membrane transporters, both at the plasma and intracellular membranes, are key players in maintaining a finely tuned pH balance between intra- and extracellular spaces, and therefore in cellular homeostasis. V-ATPase is a housekeeping ATP-driven proton pump highly conserved among prokaryotes and eukaryotes. This proton pump, which exhibits a complex multisubunit structure based on cell type-specific isoforms, is essential for pH regulation and for a multitude of ubiquitous and specialized functions. Thus, it is not surprising that V-ATPase aberrant overexpression, mislocalization, and mutations in V-ATPase subunit-encoding genes have been associated with several human diseases. However, the ubiquitous expression of this transporter and the high toxicity driven by its off-target inhibition, renders V-ATPase-directed therapies very challenging and increases the need for selective strategies. Here we review emerging evidence linking V-ATPase and both inherited and acquired human diseases, explore the therapeutic challenges and opportunities envisaged from recent data, and advance future research avenues. We highlight the importance of V-ATPases with unique subunit isoform molecular signatures and disease-associated isoforms to design selective V-ATPase-directed therapies. We also discuss the rational design of drug development pipelines and cutting-edge methodological approaches toward V-ATPase-centered drug discovery. Diseases like cancer, osteoporosis, and even fungal infections can benefit from V-ATPase-directed therapies.

Lipid metabolic Reprogramming: Role in Melanoma Progression and Therapeutic Perspectives

Simple Summary

Melanoma is a devastating skin cancer characterized by an impressive metabolic plasticity. Melanoma cells are able to adapt to the tumor microenvironment by using a variety of fuels that contribute to tumor growth and progression. In this review, the authors summarize the contribution of the lipid metabolic network in melanoma plasticity and aggressiveness, with a particular attention to specific lipid classes such as glycerophospholipids, sphingolipids, sterols and eicosanoids. They also highlight the role of adipose tissue in tumor progression as well as the potential antitumor role of drugs targeting critical steps of lipid metabolic pathways in the context of melanoma.

Abstract

Metabolic reprogramming contributes to the pathogenesis and heterogeneity of melanoma. It is driven both by oncogenic events and the constraints imposed by a nutrient- and oxygen-scarce microenvironment. Among the most prominent metabolic reprogramming features is an increased rate of lipid synthesis. Lipids serve as a source of energy and form the structural foundation of all membranes, but have also emerged as mediators that not only impact classical oncogenic signaling pathways, but also contribute to melanoma progression. Various alterations in fatty acid metabolism have been reported and can contribute to melanoma cell aggressiveness. Elevated expression of the key lipogenic fatty acid synthase is associated with tumor cell invasion and poor prognosis. Fatty acid uptake from the surrounding microenvironment, fatty acid β-oxidation and storage also appear to play an essential role in tumor cell migration. The aim of this review is (i) to focus on the major alterations affecting lipid storage organelles and lipid metabolism. A particular attention has been paid to glycerophospholipids, sphingolipids, sterols and eicosanoids, (ii) to discuss how these metabolic dysregulations contribute to the phenotype plasticity of melanoma cells and/or melanoma aggressiveness, and (iii) to highlight therapeutic approaches targeting lipid metabolism that could be applicable for melanoma treatment.

Cholesterol metabolism in cancer: mechanisms and therapeutic opportunities

Cholesterol metabolism produces essential membrane components as well as metabolites with a variety of biological functions. In the tumour microenvironment, cell-intrinsic and cell-extrinsic cues reprogram cholesterol metabolism and consequently promote tumourigenesis. Cholesterol-derived metabolites play complex roles in supporting cancer progression and suppressing immune responses. Preclinical and clinical studies have shown that manipulating cholesterol metabolism inhibits tumour growth, reshapes the immunological landscape and reinvigorates anti-tumour immunity. Here, we review cholesterol metabolism in cancer cells, its role in cancer progression and the mechanisms through which cholesterol metabolites affect immune cells in the tumour microenvironment. We also discuss therapeutic strategies aimed at interfering with cholesterol metabolism, and how the combination of such approaches with existing anti-cancer therapies can have synergistic effects, thus offering new therapeutic opportunities.

Multi-cancer V-ATPase molecular signatures: A distinctive balance of subunit C isoforms in esophageal carcinoma

Background

V-ATPases are hetero-oligomeric enzymes consisting of 13 subunits and playing key roles in ion homeostasis and signaling. Differential expression of these proton pumps has been implicated in carcinogenesis and metastasis. To elucidate putative molecular signatures underlying these phenomena, we evaluated the expression of V-ATPase genes in esophageal squamous cell carcinoma (ESCC) and extended the analysis to other cancers.

Methods

Expression of all V-ATPase genes were analyzed in ESCC by a microarray data and in different types of tumors available from public databases. Expression of C isoforms was validated by qRT-PCR in paired ESCC samples.

Findings

A differential expression pattern of V-ATPase genes was found in different tumors, with combinations in up- and down-regulation leading to an imbalance in the expression ratios of their isoforms. Particularly, a high C1 and low C2 expression pattern accurately discriminated ESCC from normal tissues. Structural modeling of C2a isoform uncovered motifs for oncogenic kinases in an additional peptide stretch, and an actin-biding domain downstream to this sequence.

Interpretation

Altogether these data revealed that the expression ratios of subunits/isoforms could form a conformational code that controls the H⁺ pump regulation and interactions related to tumorigenesis. This study establishes a paradigm change by uncovering multi-cancer molecular signatures present in the V-ATPase structure, from which future studies must address the complexity of the onco-related V-ATPase assemblies as a whole, rather than targeting changes in specific subunit isoforms.

Funding

This work was supported by grants from CNPq and FAPERJ-Brazil.

Lipid droplet velocity is a microenvironmental sensor of aggressive tumors regulated by V-ATPase and PEDF

Lipid droplets (LDs) utilize microtubules (MTs) to participate in intracellular trafficking of cargo proteins. Cancer cells accumulate LDs and acidify their tumor microenvironment (TME) by increasing the proton pump V-ATPase. However, it is not known whether these two metabolic changes are mechanistically related or influence LD movement. We postulated that LD density and velocity are progressively increased with tumor aggressiveness and are dependent on V-ATPase and the lipolysis regulator pigment epithelium-derived factor (PEDF). LD density was assessed in human prostate cancer (PCa) specimens across Gleason scores (GS) 6-8. LD distribution and velocity were analyzed in low and highly aggressive tumors using live-cell imaging and in cells exposed to low pH and/or treated with V-ATPase inhibitors. The MT network was disrupted and analyzed by α-tubulin staining. LD density positively correlated with advancing GS in human tumors. Acidification promoted peripheral localization and clustering of LDs. Highly aggressive prostate, breast, and pancreatic cell lines had significantly higher maximum LD velocity (LDVmax) than less aggressive and benign cells. LDVmax was MT-dependent and suppressed by blocking V-ATPase directly or indirectly with PEDF. Upon lowering pH, LDs moved to the cell periphery and carried metalloproteinases. These results suggest that acidification of the TME can alter intracellular LD movement and augment velocity in cancer. Restoration of PEDF or blockade of V-ATPase can normalize LD distribution and decrease velocity. This study identifies V-ATPase and PEDF as new modulators of LD trafficking in the cancer microenvironment.

Copper blocks V-ATPase activity and SNARE complex formation to inhibit yeast vacuole fusion

The accumulation of copper in organisms can lead to altered functions of various pathways and become cytotoxic through the generation of reactive oxygen species. In yeast, cytotoxic metals such as Hg⁺ , Cd²⁺ and Cu²⁺ are transported into the lumen of the vacuole through various pumps. Copper ions are initially transported into the cell by the copper transporter Ctr1 at the plasma membrane and sequestered by chaperones and other factors to prevent cellular damage by free cations. Excess copper ions can subsequently be transported into the vacuole lumen by an unknown mechanism. Transport across membranes requires the reduction of Cu²⁺ to Cu⁺ . Labile copper ions can interact with membranes to alter fluidity, lateral phase separation and fusion. Here we found that CuCl₂ potently inhibited vacuole fusion by blocking SNARE pairing. This was accompanied by the inhibition of V-ATPase H⁺ pumping. Deletion of the vacuolar reductase Fre6 had no effect on the inhibition of fusion by copper. This suggests that Cu²⁺ is responsible for the inhibition of vacuole fusion and V-ATPase function. This notion is supported by the differential effects of chelators. The Cu²⁺ -specific chelator triethylenetetramine rescued fusion, whereas the Cu⁺ -specific chelator bathocuproine disulfonate had no effect on the inhibited fusion.

Novel urokinase-plasminogen activator inhibitor SPINK13 inhibits growth and metastasis of hepatocellular carcinoma in vivo

Advanced hepatocellular carcinoma (HCC) is a highly aggressive malignancy that is a serious threat to the public health system of China. Urokinase-plasminogen activator (uPA) can promote the invasive growth and metastasis of HCC cells by activating matrix metalloproteinases (MMPs), leading to the breakage of the extra-cellular matrix. uPA is a promising target for advanced HCC treatment. In this stuy the expression of uPA was examined by quantitative polymerase chain reaction in hepatic cell lines. Protein interaction between uPA and SPINK13 was identified by immunoprecipitation. In vitro biochemical assay was used to examine the inhibitory effect of the SPINK13 on the direct cleaving of the recombinant pro-MMP9 by uPA. The antitumor effect of SPINK13 was examined by transwell assay or the nude mice tumor model.The expression of uPA was much higher in highly aggressive HCC cell lines than in lowly aggressive HCC cell lines or non-tumor hepatic cell lines. SPINK13 interacted with uPA in HCC cells and directly inhibited the cleaving of MMP9 by uPA. Treatment of the recombinant SPINK13 protein inhibited the invasion of HCC cells in several experiments, such as transwell experiments or the intrahepatic growth model. The results of the study indicated that SPINK13 could function as a promising therapeutic approach for patients with advanced HCC.

A novel long-sustaining system of apatinib for long-term inhibition of the proliferation of hepatocellular carcinoma cells

Background

Apatinib is a newly approved antitumor drug (molecular targeted agent/small molecular kinase inhibitor) for advanced hepatocellular carcinoma (HCC) treatment. However, current oral administration of apatinib could induce the even distribution of drugs in the body and cause the concentration of apatinib in the HCC location to be limited or insufficient. Therefore, it is urgent to develop novel formulations of apatinib to improve its efficiency.

Materials and methods

Apatinib was prepared to form a stable and even dispersion with cyclodextrin (a clathrate complex/inclusion complex named Apa-Cyc). A temperature-sensitive phase-change hydrogel of apatinib (named Apa-Gel) was prepared using apatinib–cyclodextrin and poloxamer 407. Apa-Gel was injected into HCC tissues in nude mice to examine the long-term antitumor effect.

Results

Apa-Gel can transform from liquid to hydrogel at near body temperature and maintain slow release of apatinib in HCC tumor tissues. When injected subcutaneously, one-time administration of Apa-Gel has a long-acting antitumor effect on the subcutaneous growth or epithelial–mesenchymal transition process of HCC cells.

Conclusion

This novel slow-releasing system allows apatinib to be released effectively on the long term and facilitates tissue attachment, thereby preserving the efficiency of apatinib over the long term.

V-ATPases and osteoclasts: ambiguous future of V-ATPases inhibitors in osteoporosis

Vacuolar ATPases (V-ATPases) play a critical role in regulating extracellular acidification of osteoclasts and bone resorption. The deficiencies of subunit a3 and d2 of V-ATPases result in increased bone density in humans and mice. One of the traditional drug design strategies in treating osteoporosis is the use of subunit a3 inhibitor. Recent findings connect subunits H and G1 with decreased bone density. Given the controversial effects of ATPase subunits on bone density, there is a critical need to review the subunits of V-ATPase in osteoclasts and their functions in regulating osteoclasts and bone remodeling. In this review, we comprehensively address the following areas: information about all V-ATPase subunits and their isoforms; summary of V-ATPase subunits associated with human genetic diseases; V-ATPase subunits and osteopetrosis/osteoporosis; screening of all V-ATPase subunits variants in GEFOS data and in-house data; spectrum of V-ATPase subunits during osteoclastogenesis; direct and indirect roles of subunits of V-ATPases in osteoclasts; V-ATPase-associated signaling pathways in osteoclasts; interactions among V-ATPase subunits in osteoclasts; osteoclast-specific V-ATPase inhibitors; perspective of future inhibitors or activators targeting V-ATPase subunits in the treatment of osteoporosis.

Myrtenal-induced V-ATPase inhibition - A toxicity mechanism behind tumor cell death and suppressed migration and invasion in melanoma

BACKGROUND

Metastatic tumor cells have acidic extracellular pH and differential electrochemical H⁺ gradients generated across their cell membranes by V-type H⁺-ATPases. This study shows that inhibition of the V-ATPases by the plant-derived monoterpene Myrtenal results in tumor cell death and decreased metastatic dissemination in mice.

METHODS

The Myrtenal anticancer toxicity was evaluated in vitro using murine (B16F0 and B16F10) and human (SkMel-5) melanoma cell lines, and in in vivo mouse metastatic dissemination model. Proton flux and extracellular acidification were directly evaluated at the surface of living cells using a non-invasive selective ion electrode approach.

RESULTS

The inhibition of V-ATPases by 100 μM Myrtenal disrupted the electrochemical H⁺ gradient across the cell membranes, strongly induced cell death (4-5 fold), and decreased tumor cells migration and invasion in vitro. Myrtenal (15 mg/kg) also significantly reduced metastasis induced by B16F10 in vivo, further reinforcing that V-ATPase is a molecular target to halt the progression of cancers.

CONCLUSIONS

These data revealed the therapeutic potential of Myrtenal as inhibitor of melanoma progression proposing a mechanism of action by which once inhibited by this monoterpene the proton pumps fail to activate cancer-related differential electrochemical gradients and H⁺ fluxes across the tumor cell membranes, disrupting pH signatures inherent in tumor progression, resulting in reprogrammed cell death and metastasis inhibition.

GENERAL SIGNIFICANCE

The work represents a new mechanistic strategy for contention of melanoma, the most aggressive and deadly form of cutaneous neoplasm, and highlights Myrtenal, other related monoterpenes and derivatives as promising proton pump inhibitors with high chemotherapeutic potential.

Silencing the expression of copine-III enhances the sensitivity of hepatocellular carcinoma cells to the molecular targeted agent sorafenib

Background

The application of the oral targeted therapeutic agent sorafenib provides new hope for patients suffering from advanced stages of hepatocellular carcinoma (HCC), but the prognosis of such patients remains poor due to the rapid development of the multidrug resistance process in cancer pathogenesis. The present work evaluated whether copine-III, a novel cancer regulator encoded by the CPNE3 gene, would be a potential indicator of sorafenib resistance in HCC treatment.

Materials and methods

The endogenous expression of copine-III in clinical specimens was examined by quantitative polymerase chain reaction. Copine-III siRNA was transfected into HCC cells to downregulate copine-III expression. The effect of copine-III on sorafenib’s antitumor activation was identified by in vitro and in vivo experiments (MTT, Transwell, and flow cytometry as well as a nude mice model).

Results

High levels of copine-III in clinical specimens are related to poor prognosis of advanced HCC patients on sorafenib treatment. Infection of Ad-siCPNE3 significantly decreased the endogenous expression of copine-III and enhanced the susceptibility of MHCC97-H cells to sorafenib: the IC₅₀ value decreased from 1.15±0.11 to 0.25±0.05 μmol/L. Moreover, silencing copine-III enhanced the effect of sorafenib on apoptosis, in vitro invasion/migration, and subcutaneous or intrahepatic growth of MHCC97-H cells in nude mice.

Conclusion

Copine-III is a novel potential indicator of prognosis for patients who received sorafenib for advanced HCC treatment.