The Enhanced Efficacy of Intracellular Delivery of Doxorubicin/C6-Ceramide Combination Mediated by the F3 Peptide/Nucleolin System Is Supported by the Downregulation of the PI3K/Akt Pathway

Targeting multiple cellular populations is of high therapeutic relevance for the tackling of solid tumors heterogeneity. Herein, the ability of pegylated and pH-sensitive liposomes, functionalized with the nucleolin-binding F3 peptide and containing doxorubicin (DXR)/C6-ceramide synergistic combination, to target, in vitro, ovarian cancer, including ovarian cancer stem cells (CSC), was assessed. The underlying molecular mechanism of action of the nucleolin-mediated intracellular delivery of C6-ceramide to cancer cells was also explored. The assessment of overexpression of surface nucleolin expression by flow cytometry was critical to dissipate differences identified by Western blot in membrane/cytoplasm of SKOV-3, OVCAR-3 and TOV-112D ovarian cancer cell lines. The former was in line with the significant extent of uptake into (bulk) ovarian cancer cells, relative to non-targeted and non-specific counterparts. This pattern of uptake was recapitulated with putative CSC-enriched ovarian SKOV-3 and OVCAR-3 sub-population (EpCAMhigh/CD44high). Co-encapsulation of DXR:C6-ceramide into F3 peptide-targeted liposomes improved cytotoxic activity relative to liposomes containing DXR alone, in an extent that depended on the intrinsic resistance to DXR and on the incubation time. The enhanced cytotoxicity of the targeted combination was mechanistically supported by the downregulation of PI3K/Akt pathway by C6-ceramide, only among the nucleolin-overexpressing cancer cells presenting a basal p-Akt/total Akt ratio lower than 1.

C6 Ceramide (d18:1/6:0) as a Novel Treatment of Cutaneous T Cell Lymphoma

Cutaneous T cell lymphomas (CTCLs) represent a heterogeneous group of T cell lymphomas that primarily affect the skin. The most frequent forms of CTCL are mycosis fungoides and Sézary syndrome. Both are characterized by frequent recurrence, developing chronic conditions and high mortality with a lack of a curative treatment. In this study, we evaluated the effect of short-chain, cell-permeable C6 Ceramide (C6Cer) on CTCL cell lines and keratinocytes. C6Cer significantly reduced cell viability of CTCL cell lines and induced cell death via apoptosis and necrosis. In contrast, primary human keratinocytes and HaCaT keratinocytes were less affected by C6Cer. Both keratinocyte cell lines showed higher expressions of ceramide catabolizing enzymes and HaCaT keratinocytes were able to metabolize C6Cer faster and more efficiently than CTCL cell lines, which might explain the observed protective effects. Along with other existing skin-directed therapies, C6Cer could be a novel well-tolerated drug for the topical treatment of CTCL.

C6-Ceramide Induces Apoptosis in Lung Non-Small Cell Lung Cancer and Suppresses Brain Metastasis by Downregulating The PI3K/AKT/mTOR Signaling Pathway

Background: The membrane lipid ceramide plays important roles in regulating tumor growth, chemotherapy drug resistance, and apoptosis. However, the mechanisms through which ceramide induces apoptosis are still unclear. In this study, we explored the biological functions and underlying mechanism of C6-ceramide in brain metastasis (BM) arising from non-small cell lung cancer (NSCLC).Methods: The effects of C6-ceramide on cell apoptosis were studied by flow cytometry. Cell Counting Kit-8 assays, wound-healing assays, and flow cytometry were performed to investigate the biological functions of C6-ceramide. An in vitro blood-brain barrier (BBB) model was constructed, and its effectiveness and availability were tested by evaluating horse radish peroxidase activity and junction-related protein expression. The underlying signaling pathways of C6-ceramide were detected by western blotting, and further verification was performed using pathway inhibitors. RNA sequencing was used to confirm the involvement of C6-ceramide and associated pathways in BM arising from NSCLC.Results: C6-ceramide induced apoptosis in NSCLC cells, and the optimal working concentration of C6-ceramide was 50 μM. C6-ceramide not only suppressed cell proliferation and migration but also arrested cells at the G1/S transition. An in vitro BBB model constructed using human umbilical vein endothelial cells and human astrocytes cells showed the lowest permeability and the strongest tight junction connections when cells were cocultured for 72 h. Moreover, C6-ceramide suppressed the passage of cells through the BBB model. C6-ceramide at least partially influenced NSCLC biological functions by downregulating the phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway, which was further confirmed by rescue assays and RNA sequencing. Conclusions: C6-ceramide functioned as a tumor suppressor by inducing NSCLC cell apoptosis and BM through the PI3K/AKT/mTOR signal pathway. Thus, this pathway may serve as a novel potential therapeutic target for patients with BM arising from NSCLC.

C6-ceramide treatment inhibits the proangiogenic activity of multiple myeloma exosomes via the miR-29b/Akt pathway

Background: The increased bone marrow angiogenesis is involved in the progression of multiple myeloma (MM) with the underlying mechanism poorly understood. Cancer-released exosomes could play an important role in the pathological angiogenesis through exosomal microRNAs (miRs) delivery. MiR-29b has been reported in regulating the tumor angiogenesis. Methods: In this study, we explored the role of C6-ceramide (C6-cer, a Ceramide pathway activator) in the angiogenic effect of MM exosomes and its potential mechanism. MM cells (OPM2 and RPMI-8226) treated with C6-cer were studied for its effects on the endothelial cell (EC) functions . Results: Our results showed that exosomes released from MM cells treated by C6-cer ( Exo C6-cer ) significantly inhibited the proliferation, migration and tube formation of ECs. For mechanism studies, we found that the level of miR-29b was increased in ECs treated by exo C6-cer , while mRNA and protein expressions of Akt3, PI3K and VEGFA were decreased in ECs, indicating the involvement of Akt pathway. Furthermore, downregulation of miR-29b by inhibitor administration could prevent the exo C6-cer -induced cell proliferation, migration and angiogenesis of ECs, accompanied with the increased expressions of Akt3, PI3K and VEGFA. Conclusions: Collectively, our data suggest that exo C6-cer -mediated miR-29b expression participates in the progression of MM through suppressing the proliferation, migration and angiogenesis of ECs by targeting Akt signal pathway.

C6-ceramide treatment inhibits the proangiogenic activity of multiple myeloma exosomes via the miR-29b/Akt pathway

Background: The increased bone marrow angiogenesis is involved in the progression of multiple myeloma (MM) with the underlying mechanism poorly understood. Cancer-released exosomes could play an important role in the pathological angiogenesis through exosomal microRNAs (miRs) delivery. MiR-29b has been reported in regulating the tumor angiogenesis. Methods: In this study, we explored the role of C6-ceramide (C6-cer, a Ceramide pathway activator) in the angiogenic effect of MM exosomes and its potential mechanism. MM cells (OPM2 and RPMI-8226) treated with C6-cer were studied for its effects on the endothelial cell (EC) functions . Results: Our results showed that exosomes released from MM cells treated by C6-cer ( Exo C6-cer ) significantly inhibited the proliferation, migration and tube formation of ECs. For mechanism studies, we found that the level of miR-29b was increased in ECs treated by exo C6-cer , while mRNA and protein expressions of Akt3, PI3K and VEGFA were decreased in ECs, indicating the involvement of Akt pathway. Furthermore, downregulation of miR-29b by inhibitor administration could prevent the exo C6-cer -induced cell proliferation, migration and angiogenesis of ECs, accompanied with the increased expressions of Akt3, PI3K and VEGFA. Conclusions: Collectively, our data suggest that exo C6-cer -mediated miR-29b expression participates in the progression of MM through suppressing the proliferation, migration and angiogenesis of ECs by targeting Akt signal pathway.

Inhibition of glycosphingolipid biosynthesis reverts multidrug resistance by differential modulation of ABC transporters on chronic myeloid leukemias

ABSTRACTMultidrug resistance (MDR) in cancer manifests due to cross-resistance to chemotherapeutic drugs with neither structural nor functional relationship, markedly by increased expression and activity of ABC superfamily transporters. Evidences indicate sphingolipids as substrates to ABC proteins in processes such as cell signaling, membrane biosynthesis and inflammation, and products of its biosynthetic route were shown to favor cancer progression. Glucosylceramide (GlcCer) is a ubiquitous glycosphingolipid (GSL) generated by glucosylceramide synthase, a key cell regulator enzyme encoded by the UDP-glucose ceramide glucosyltransferase (UGCG) gene. Under stress, cells increase de novo biosynthesis of ceramides, which return to sub-toxic levels after assimilation into GlcCer by UGCG. Given that cancer cells seem to mobilize UGCG and increase GSL contents for the clearance of ceramides ultimately contributing to treatment failure, we studied how inhibiting GSL biosynthesis would affect the MDR phenotype of chronic myeloid leukemias. Results indicate that MDR associates to higher expression of UGCG and to a complex GSL profile. Inhibition of this glucosyltransferase greatly reduced GM1 expression, and cotreatment with standard chemotherapeutics sensitized cells leading to mitochondrial membrane potential loss and apoptosis. Despite reducing ABCB1 expression, only the ABCC-mediated efflux activity was affected. Consistently, efflux of C6-ceramide, one byproduct of UGCG downregulation, was reduced after inhibition of ABCC-mediated transport. Overall, UGCG inhibition impaired the malignant glycophenotype of MDR leukemias, overcoming drug resistance through distinct mechanisms. This work brings more comprehension about the involvement of GSL for chemotherapy failure, and modulation of its contents emerges as an intervention targeted to MDR leukemias.

Sphingolipid metabolism determines the therapeutic efficacy of nanoliposomal ceramide in acute myeloid leukemia

Key Points Distinct sphingolipid metabolism of AML with MDS-related changes defines unique sensitivity to nanoliposomal C6-ceramide. Vinblastine alters sphingolipid metabolism to enhance the sensitivity of AML to nanoliposomal C6-ceramide.