Apoptosis of human carcinoma cells in the presence of inhibitors of glycosphingolipid biosynthesis: I. Treatment of Colo-205 and SKBR3 cells with isomers of PDMP and PPMP

Multimolecular characteristics of cell-death related hub genes in human cancers: a comprehensive pan-cancer analysis

Failure of the normal process of cell death pathways contributes to the defection of immune systems and the occurrence of cancers. The key genes, the multimolecular mechanisms, and the immune functions of these genes in pan-cancers remain unclear. Using online databases of The Cancer Genome Atlas, GEPIA2, TISIDB, HPA, Kaplan-Meier Plotter, PrognoScan, cBioPortal, GSCALite, TIMER, and Sangerbox, we identified the key genes from the six primary cell death-related pathways and performed a comprehensive analysis to investigate the multimolecular characteristics and immunological functions of the hub genes in 33 human cancers. We identified five hub genes in the six primary cell death-related pathways (JUN, NFKB1, CASP3, PARP1, and TP53). We found that CASP3, PARP1, and TP53 were overexpressed in 28, 23, and 27 cancers. The expression of the five genes was associated with the development and prognosis of many cancers. Particularly, JUN, NFKB1, CASP3, and TP53 have prognostic values in Brain Lower Grade Glioma (LGG), while PARP1 and CASP3 could predict the survival outcomes in Adrenocortical carcinoma (ACC). In addition, an extensive association between five genes' expression, DNA methylation, and tumor-immune system interactions was noticed. The five cell death-related hub genes could function as potential biomarkers for various cancers, particularly LGG and ACC. The immunological function analysis of the five genes also proposes new targets for developing immunosuppressants and improving the immunotherapy efficacy of cancers. However, further extensive clinical and experimental research are required to validate their clinical values.

Blockade of Glycosphingolipid Synthesis Inhibits Cell Cycle and Spheroid Growth of Colon Cancer Cells In Vitro and Experimental Colon Cancer Incidence In Vivo

Colorectal cancer (CRC) is one of the most frequently diagnosed cancers in humans. At early stages CRC is treated by surgery and at advanced stages combined with chemotherapy. We examined here the potential effect of glucosylceramide synthase (GCS)-inhibition on CRC biology. GCS is the rate-limiting enzyme in the glycosphingolipid (GSL)-biosynthesis pathway and overexpressed in many human tumors. We suppressed GSL-biosynthesis using the GCS inhibitor Genz-123346 (Genz), NB-DNJ (Miglustat) or by genetic targeting of the GCS-encoding gene UDP-glucose-ceramide-glucosyltransferase- (UGCG). GCS-inhibition or GSL-depletion led to a marked arrest of the cell cycle in Lovo cells. UGCG silencing strongly also inhibited tumor spheroid growth in Lovo cells and moderately in HCT116 cells. MS/MS analysis demonstrated markedly elevated levels of sphingomyelin (SM) and phosphatidylcholine (PC) that occurred in a Genz-concentration dependent manner. Ultrastructural analysis of Genz-treated cells indicated multi-lamellar lipid storage in vesicular compartments. In mice, Genz lowered the incidence of experimentally induced colorectal tumors and in particular the growth of colorectal adenomas. These results highlight the potential for GCS-based inhibition in the treatment of CRC.

Protective effects of Schisandrin B against D-GalN-induced cell apoptosis in human hepatocyte (L02) cells via modulating Bcl-2 and Bax

Schisandrin B is a dibenzocyclooctadiene derivative extracted fromSchisandra chinensis (Turcz.) Baill., that exhibits anti-oxidation, anti-inflammation, anti-tumor and hepatoprotective activities. To understand the hepatoprotective mechanism of schisandrin B, this study investigated the efficacy of schisandrin B on L02 cells after treatment with D-GalN. Following pretreatment with 40 μM schisandrin B, L02 cells were stimulated with 40 mM D-GalN. Cell viability, apoptosis, the expression levels of genes associated with apoptosis, and the intracellular oxidative stress indexes were measured. The viability of L02 cells was determined using MTT assay, and the Annexin V-FITC/PI assay kit was utilized for the assessment of apoptosis. The activities of GSH-Px and SOD, the level of MDA were assessed, separately, using relative detection kits. Moreover, RT-PCR as well as Western blot was applied to measure the mRNA and protein expression of Bax and Bcl-2. The results indicated that schisandrin B significantly prevented D-GalN‑induced oxidative damage in L02 cells (P<0.05), decreased GSH-Px and SOD activities (P<0.05), increased MDA content (P<0.05). Furthermore, schisandrin B inhibited D-GalN-induced apoptosis in L02 cells (P<0.05), regulated the expression of Bax and Bcl-2 (P<0.05). The results indicated that schisandrin B decreased the D-GalN-induced intracellular oxidative stress indexes generation, and inhibited the down-regulation of Bcl-2 and up-regulation of Bax induced by D-GalN. In conclusion, schisandrin B was shown to exert protective effect against oxidative damage of L02 cells, which, in part, was achieved by regulating the mRNA and protein levels of Bax and Bcl-2.

European mtDNA Variants Are Associated With Differential Responses to Cisplatin, an Anticancer Drug: Implications for Drug Resistance and Side Effects

Background: Cisplatin, a powerful antitumor agent, causes formation of DNA adducts, and activation of apoptotic pathways. Presently, cisplatin resistance develops in up to 70% of patients but the underlying molecular mechanism(s) are unclear and there are no markers to determine which patients will become resistant. Mitochondria play a significant role not only in energy metabolism but also retrograde signaling (mitochondria to nucleus) that modulates inflammation, complement, and apoptosis pathways. Maternally inherited mitochondrial (mt) DNA can be classified into haplogroups representing different ethnic populations that have diverse susceptibilities to diseases and medications. Methods: Transmitochondrial cybrids, where all cell lines possess identical nuclear genomes but either the H (Southern European) or J (Northern European) mtDNA haplogroups, were treated with cisplatin and analyzed for differential responses related to viability, oxidative stress, and expression levels of genes associated with cancer, cisplatin-induced nephrotoxicity and resistance, apoptosis and signaling pathways. Results: The cisplatin-treated-J cybrids showed greater loss of cell viability along with lower levels of reactive oxygen species and mitochondrial membrane potential compared to cisplatin-treated-H cybrids. After cisplatin treatment, J cybrids showed increased gene expression of BAX, CASP3, and CYP51A, but lower levels of SFRP1 compared to untreated-J cybrids. The cisplatin-treated-H cybrids had elevated expression of CDKN1A/P21, which has a role in cisplatin toxicity, compared to untreated-H cybrids. The cisplatin-treated H had higher transcription levels of ABCC1, DHRS2/HEP27, and EFEMP1 compared to cisplatin-treated-J cybrids. Conclusions: Cybrid cell lines that contain identical nuclei but either H mtDNA mitochondria or J mtDNA mitochondria respond differently to cisplatin treatments suggesting involvement of the retrograde signaling (from mitochondria to nucleus) in the drug-induced cell death. Varying toxicities and transcription levels of the H vs. J cybrids after cisplatin treatment support the hypothesis that mtDNA variants play a role in the expression of genes affecting resistance and side effects of cisplatin.

Induction of Apoptosis in Metastatic Breast Cancer Cells: XV. Downregulation of DNA Polymerase-α - Helicase Complex (Replisomes) and Glyco-Genes

In normal and cancer cells, successful cell division requires accurate duplication of chromosomal DNA. All cells require a multiprotein DNA duplication system (replisomes) for their existence. However, death of normal cells in our body occurs through the apoptotic process. During apoptotic process several crucial genes are downregulated with the upregulation of caspase pathways, leading to ultimate degradation of genomic DNA. In metastatic cancer cells (SKBR-3, MCF -7, and MDA-462), this process is inhibited to achieve immortality as well as overexpression of the enzymes for the synthesis of marker molecules. It is believed that the GSL of the lacto family such as Le^X, SA-Le^X, Le^Y, Le^a, and Le^b are markers on the human colon and breast cancer cells. Recently, we have characterized that a few apoptotic chemicals (cis-platin, L-PPMP, D-PDMP, GD3 ganglioside, GD1b ganglioside, betulinic acid, tamoxifen, and melphalan) in low doses kill metastatic breast cancer cells. The apoptosis-inducing agent (e.g., cis-platin) showed inhibition of DNA polymerase/helicase (part of the replisomes) and also modulated (positively) a few glycolipid-glycosyltransferase (GSL-GLTs) transcriptions in the early stages (within 2 h after treatment) of apoptosis. These Lc-family GSLs are also present on the surfaces of human breast and colon carcinoma cells. It is advantageous to deliver these apoptotic chemicals through the metastatic cell surfaces containing high concentration of marker glycolipids (Lc-GSLs). Targeted application of apoptotic chemicals (in micro scale) to kill the cancer cells would be an ideal way to inhibit the metastatic growth of both breast and colon cancer cells. It was observed in three different breast cancer lines (SKBR-3, MDA-468, and MCF-7) that in 2 h very little apoptotic process had started, but predominant biochemical changes (including inactivation of replisomes) started between 6 and 24 h of the drug treatments. The contents of replisomes (replisomal complexes) during induction of apoptosis are not known. It is known that DNA helicase activities (major proteins catalyze the melting of dsDNA strands) change during apoptotic induction process. Previously DNA Helicase-III was characterized as a component of the replication complexes isolated from carcinoma cells and normal rapid growing embryonic chicken brain cells. Helicase activities were assayed by a novel method (combined immunoprecipitation-ROME assay), and DNA polymerase-alpha activities were determined by regular chain extension of nicked "ACT-DNA," by determining values obtained from +/- aphidicolin added to the incubation mixtures. Very little is known about the stability of the "replication complexes" (or replisomes) during the apoptotic process. DNA helicases are motor proteins that catalyze the melting of genomic DNA during replication, repair, and recombination processes. In all three breast carcinoma cell lines (SKBR-3, MCF-7, and MDA-468), a common trend, decrease of activities of DNA polymerase-alpha and Helicase-III (estimated and detected with a polyclonal antibody), was observed, after cis-platin- and L-PPMP-induced apoptosis. Previously our laboratory has documented downregulation (within 24-48 h) of several GSL-GLTs with these apoptotic reagents in breast and colon cancer cells also. Perhaps induced apoptosis would improve the prognosis in metastatic breast and colon cancer patients.

Inhibition of hepatocellular carcinoma growth by blockade of glycosphingolipid synthesis

Hepatocellular carcinoma (HCC) is one of the most frequent cancers. In vitro studies suggest that growth and response to therapy of human carcinomas may depend on glycosphingolipid (GSL) expression. Glucosylceramide synthase (GCS), encoded by the gene Ugcg, is the basic enzyme required for the synthesis of GSLs. Gene array analysis implied that Ugcg is significantly overexpressed in human HCC as compared to non-tumorous liver tissue. Therefore we have investigated whether tumor - genesis and - growth is altered in the absence of GSLs. An endogenous liver cancer model has been initiated by application of diethylnitrosamine in mice lacking Ugcg specifically in hepatocytes. We have now shown that hepatocellular tumor initiation and growth in mice is significantly inhibited by hepatic GSL deficiency in vivo. Neither the expression of cell cycle proteins, such as cyclins and pathways such as the MAP-kinase/Erk pathway nor the mTOR/Akt pathway as well as the number of liver infiltrating macrophages and T cells were essentially changed in tumors lacking GSLs. Significantly elevated bi-nucleation of atypical hepatocytes, a feature for impaired cytokinesis, was detected in tumors of mice lacking liver-specific GSLs. A reduction of proliferation and restricted growth of tumor microspheres due to delayed, GSL-dependent cytokinesis, analogous to the histopathologic phenotype in vivo could be demonstrated in vitro. GSL synthesis inhibition may thus constitute a potential therapeutic target for hepatocellular carcinoma.

Comparative lipidomic study of urothelial cancer models: association with urothelial cancer cell invasiveness

A joint NMR/LC-MS approach allows to establish significant differences in the lipidoma of invasive urothelial carcinoma cells (T24) with respect to noninvasive urothelial cells (RT4).

Sphingolipids: key regulators of apoptosis and pivotal players in cancer drug resistance

Drug resistance elicited by cancer cells still constitutes a huge problem that frequently impairs the efficacy of both conventional and novel molecular therapies. Chemotherapy usually acts to induce apoptosis in cancer cells; therefore, the investigation of apoptosis control and of the mechanisms used by cancer cells to evade apoptosis could be translated in an improvement of therapies. Among many tools acquired by cancer cells to this end, the de-regulated synthesis and metabolism of sphingolipids have been well documented. Sphingolipids are known to play many structural and signalling roles in cells, as they are involved in the control of growth, survival, adhesion, and motility. In particular, in order to increase survival, cancer cells: (a) counteract the accumulation of ceramide that is endowed with pro-apoptotic potential and is induced by many drugs; (b) increase the synthesis of sphingosine-1-phosphate and glucosylceramide that are pro-survivals signals; (c) modify the synthesis and the metabolism of complex glycosphingolipids, particularly increasing the levels of modified species of gangliosides such as 9-O acetylated GD3 (αNeu5Ac(2-8)αNeu5Ac(2-3)βGal(1-4)βGlc(1-1)Cer) or N-glycolyl GM3 (αNeu5Ac (2-3)βGal(1-4)βGlc(1-1)Cer) and de-N-acetyl GM3 (NeuNH(2)βGal(1-4)βGlc(1-1)Cer) endowed with anti-apoptotic roles and of globoside Gb3 related to a higher expression of the multidrug resistance gene MDR1. In light of this evidence, the employment of chemical or genetic approaches specifically targeting sphingolipid dysregulations appears a promising tool for the improvement of current chemotherapy efficacy.

Apoptosis of human breast carcinoma cells in the presence of cis-platin and L-/D-PPMP: IV. Modulation of replication complexes and glycolipid: Glycosyltransferases

Apoptosis of human breast carcinoma cells (SKBR-3, MCF-7, and MDA-468) has been observed after treatment of these cells with anti-cancer drug cis-platin and glycosphingolipid biosynthesis inhibitor L- and D-PPMP, respectively. These drugs initiated apoptosis in a dose-dependent manner as measured by phenotypic morphological changes, by binding of a fluorescent phophatidyl serine-specific dye (PSS-380) onto the outer leaflet of the cell membranes, and by activation of caspases, -3, -8, and -9. It was observed that in two hours very little apoptotic process had started but predominant biochemical changes occurred after 6 h. DNA degradation started after 24 hours of drug treatment. However, very little is known about the stability of the ';Replication Complexes'' during the apoptotic process. DNA helicases are motor proteins that catalyze the melting of genomic DNA during its replication, repair, and recombination processes. Previously, DNA helicase-III was characterized as a component of the replication complexes isolated from embryonic chicken brains as well as breast and colon carcinoma cells. Helicase activities were measured by a novel method (ROME assay), and DNA polymerase-alpha activities were determined by regular chain extension of the nicked ACT-DNA, by determining values obtained from +/- aphidicolin-treated incubation mixtures. In all three breast carcinoma cell lines, a common trend was observed: a decrease of activities of DNA polymerase-alpha and Helicase III. A sharp decrease of activities of the glycolipid sialyltransferases: SAT-2 (CMP-NeuAc; GD3 alpha2-8 sialyltransferase) and SAT-4 (CMP-NeuAc: GM1a alpha2-3 sialyltransferase) was observed in the apoptotic carcinoma cells treated with L-PPMP compared with cis-platin.

Apoptosis of human carcinoma cells in the presence of potential anti-cancer drugs: III. Treatment of Colo-205 and SKBR3 cells with: cis -platin, Tamoxifen, Melphalan, Betulinic acid, L-PDMP, L-PPMP, and GD3 ganglioside

Breast cancer is the most common type of cancer, predominantly among women over 20, whereas colo-rectal cancer occurs in both men and women over the age of 50. Chemotherapy of both cancers affect rapidly growing normal as well as cancer cells. Cancer cells are non-apoptotic. Seven anti-cancer agents (cis -platin, Tamoxifen, Melphalan, Betulinic acid, D-PDMP, L-PPMP, and GD3) have been tested with human breast (SKBR3) and colon (Colo-205) carcinoma cells for their apoptotic effect and found to be positive by several assay systems. Colo-205 cells were obtained from ATCC, and the SKBR3 cells were a gift from the Cleveland Clinic. All of these six agents killed those two cell lines in a dose-dependent manner. In the early apoptotic stage (6 h), these cells showed only a flopping of phosphatidylserine on the outer lamella of the plasma membranes as evidenced by the binding of a novel fluorescent dye PSS-380. After 24 h of the treatment, those apoptotic cells showed damage of the plasma as well as the nuclear membrane as evidenced by binding of propidium iodide to the nuclear DNA. DNA laddering assay viewed further breakdown of DNA by 1% agarose gel electrophoresis analysis. It is concluded that during apoptosis the signaling by Mitochondrial Signaling Pathway (MSP) is stimulated by some of these agents. Caspase 3 was activated with the concomitant appearance of its p17 polypeptide as viewed by Westernblot analyses. Incorporation of radioactivity from [U-(14)C]-L-serine in total sphingolipid mixture was observed between 2 and 4 micromolar concentrations of most of the agents except ci s-platin. However, apoptosis in carcinoma cells in the presence of cis -platin is induced by a caspase 3 activation pathway without any increase in synthesis of ceramide.