Potent Antitumor Activity of a Novel Cationic Pyridinium-Ceramide Alone or in Combination with Gemcitabine against Human Head and Neck Squamous Cell Carcinomas in Vitro and in Vivo

Abstract

In this study, a cationic water-soluble ceramide analog L-threo-C 6 -pyridinium-ceramide-bromide (L-t-C 6 -Pyr-Cer), which exhibits high solubility and bioavailability, inhibited the growth of various human head and neck squamous cell carcinoma (HNSCC) cell lines at low IC 50 concentrations, independent of their p53 status. Consistent with its design to target negatively charged intracellular compartments, L-t-C 6 -Pyr-Cer accumulated mainly in mitochondria-, and nuclei-enriched fractions upon treatment of human UM-SCC-22A cells [human squamous cell carcinoma (SCC) of the hypopharynx] at 1 to 6 h. In addition to its growth-inhibitory function as a single agent, the supra-additive interaction of L-t-C 6 -Pyr-Cer with gemcitabine (GMZ), a chemotherapeutic agent used in HNSCC, was determined using isobologram studies. Then, the effects of this ceramide, alone or in combination with GMZ, on the growth of UM-SCC-22A xenografts in SCID mice was assessed following the determination of preclinical parameters, such as maximum tolerated dose, clearance from the blood, and bioaccumulation. Results demonstrated that treatment with L-t-C 6 -PyrCer in combination with GMZ significantly prevented the growth of HNSCC tumors in vivo. The therapeutic efficacy of L-t-C 6 -Pyr-Cer/ GMZ combination against HNSCC tumors was approximately 2.5-fold better than that of the combination of 5-fluorouracil/cisplatin. In addition, liquid chromatography/mass spectroscopy analysis showed that the levels of L-t-C 6 -Pyr-Cer in HNSCC tumors weresignificantly higher than its levels in the liver and intestines; interestingly, the combination with GMZ increased the sustained accumulation of this ceramide by approximately 40%. Moreover, treatment with L-t-C 6 -Pyr-Cer/GMZ combination resulted in a significant inhibition of telomerase activity and decrease in telomere length in vivo, which are among downstream targets of ceramide.Human head and neck squamous cell carcinomas (HNSCCs) are among the five most common cancers in the world. Global occurrence of HNSCC is high, and it is estimated that approximately 780,000 new patients are diagnosed with HNSCC each year in the adult population. There are approximately 41,000 new HNSCC cases diagnosed annually in the United States in 2004, and the overall 5-year survival of patients with stage III and IV disease remains less than 50% (Her, 2001;Jemal et al., 2004).Historically, chemotherapy did not play a curative role in the treatment of HNSCC but was reserved for palliative therapy. Surgery and radiation therapy remained the primary curative options; however, complications of these ther-

A novel mechanism of dasatinib-induced apoptosis in chronic myeloid leukemia; ceramide synthase and ceramide clearance genes

“…Statistical significance was determined using two-way analysis of variance, and p<0.05 was considered to be significant significant increase in apoptosis was observed in combination of dasatinib and C8:ceramide. It was also shown previously by our group and Senkal et al that exogenous ceramide analog applications increased apoptotic effects of different anticancer agents in various types of cancers [37,38].…”

“…The antiproliferative and apoptotic effects of exogenous ceramides has been demonstrated in different human cancer cells [37,38]. Struckhoff et al have shown apoptotic effects of ceramide analogs on breast cancer cells while some other structural ceramide analogs also showed antiproliferative effects on adriamycin-resistant SKBr3 and MCF-7 human breast cancer cells [45,46].…”

Role of human longevity assurance gene 1 and C18-ceramide in chemotherapy-induced cell death in human head and neck squamous cell carcinomas

“…Conventional short-chain ceramides, such as C 2 -and C 6 -ceramides, were shown to induce cell death in a variety of cancers. However, because of poor solubility and bioavailability of the conventional ceramides, novel pyridinium ceramides (Pyr-Cer) have been synthesized with greater water solubility and cell permeability (26,35,36). In addition, the positively charged pyridinium ring of these novel ceramides permits them to target and accumulate in negatively charged intracellular compartments, especially the mitochondria and nucleus (37).…”

“…In addition, the positively charged pyridinium ring of these novel ceramides permits them to target and accumulate in negatively charged intracellular compartments, especially the mitochondria and nucleus (37). L-t-C 6 -Pyr-Cer, alone or in combination with gemcitabine, has been shown in vivo to preferentially accumulate in the tumor site and modulate telomerase, decrease telomeric length, and inhibit HNSCC tumor growth (26).…”

“…Statistical Analysis Statistical significance of the data from the xenografts was analyzed using Tukey's Student's test as described previously (26). Treatment of animals was done according to the approved procedures by the Institutional Animal Care and Use Committee at the Medical University of South Carolina.…”