Spermidine Suppresses Oral Carcinogenesis through Autophagy Induction, DNA Damage Repair, and Oxidative Stress Reduction.

Autophagy has been proposed to play a dual role in cancer-as a tumor suppressor in early stages and oncogenic in late stages of tumorigenesis. This study investigated the role of autophagy in oral carcinogenesis using the model of oral squamous cell carcinoma (OSCC) induced by carcinogen 4-nitroquinoline 1-oxide (4NQO), mimicking molecular and histopathologic aspects of human OSCC. The induction of autophagy by spermidine (SPD) treatment reduced the severity of lesions and the incidence of OSCC in mice exposed to 4NQO. On the other hand, autophagy inhibition by chloroquine treatment had no protection. The comet assay indicated that SPD reduced 4NQO-induced DNA damage, likely related to the activation of DNA repair and the decrease of reactive oxygen species. As sphingolipid alterations have been reported in OSCC, sphingolipids in the tongue and plasma of animals were analyzed and plasma C16 ceramide levels were shown to increase proportionally to lesion severity, indicating its potential as a biomarker. Mice exposed to 4NQO plus SPD had lower levels of C16 ceramide than the 4NQO group, which indicated SPD's ability to prevent the 4NQO-induced carcinogenesis. Together, these data indicate that activation of autophagy has a tumor suppressor role during the early stages of oral carcinogenesis. Because of its ability to induce autophagy accompanied by reduced oxidative stress and DNA damage, SPD may have a protective action against chemically induced oral cancer.

Accumulated SET protein up-regulates and interacts with hnRNPK, increasing its binding to nucleic acids, the Bcl-xS repression, and cellular proliferation.

SET and hnRNPK are proteins involved in gene expression and regulation of cellular signaling. We previously demonstrated that SET accumulates in head and neck squamous cell carcinoma (HNSCC); hnRNPK is a prognostic marker in cancer. Here, we postulate that SET and hnRNPK proteins interact to promote tumorigenesis. We performed studies in HEK293 and HNSCC (HN6, HN12, and HN13) cell lines with SET/hnRNPK overexpression and knockdown, respectively. We found that SET and/or hnRNPK protein accumulation increased cellular proliferation. SET accumulation up-regulated hnRNPK mRNA and total/phosphorylated protein, promoted hnRNPK nuclear location, and reduced Bcl-x mRNA levels. SET protein directly interacted with hnRNPK, increasing both its binding to nucleic acids and Bcl-xS repression. We propose that hnRNPK should be a new target of SET and that SET-hnRNPK interaction, in turn, has potential implications in cell survival and malignant transformation.

Accumulation of the SET protein in HEK293T cells and mild oxidative stress: cell survival or death signaling.

SET protein (I2PP2A) is an inhibitor of PP2A, which regulates the phosphorylated Akt (protein kinase B) levels. We assessed the effects of SET overexpression in HEK293T cells, both in the presence and the absence of mild oxidative stress induced by 50 µM tert-butyl hydroperoxide. Immunoblotting assays demonstrated that SET accumulated in HEK293T cells and increased the levels of phosphorylated Akt and PTEN; in addition, SET decreased glutathione antioxidant defense of cell and increased expression of genes encoding antioxidant defense proteins. Immunofluorescence analysis demonstrated that accumulated SET was equally distributed in cytoplasm and nucleus; however, in cells that had been exposed to oxidative stress, SET was found in large aggregates in the cytoplasm. SET accumulation in HEK293T cells correlated with inhibition of basal apoptosis as evidenced by a decrease in annexin V staining and activity of caspases; under mild oxidative stress, SET accumulation correlated with caspase-independent cell death, as evidenced by increased PI and annexin V/PI double staining. The results suggest that accumulated SET could act via Akt/PTEN either as cell survival signal or as oxidative stress sensor for cell death.

Systemic leukocyte alterations are associated with invasive uterine cervical cancer.

OBJECTIVE: The aim of the study was to evaluate blood leukocyte counts in patients with uterine cervical neoplasia. METHODS: Patients treated at a university hospital were reviewed retrospectively. Disease progression was monitored, beginning in 1990 to 2002, for at least 5 years. Blood count parameters included absolute leukocyte, neutrophil and lymphocyte counts, leukocytosis (white blood cells > 10³/µL), neutrophilia (neutrophils ≥ 70% of leukocytes), lymphopenia (lymphocytes ≤ 15% of leukocytes), and the neutrophil-lymphocyte ratio (NLR), categorized as less than 5 or 5 or greater. RESULTS: A total of 315 patients were enrolled: 182 (57.8%) with preinvasive neoplasia (cervical intraepithelial neoplasia [CIN] group), 95 (30.1%) with stages I to II (early group), and 38 patients (12.1%) with stages III to IV neoplasia (advanced group). Neutrophil and lymphocyte counts were elevated and reduced, respectively, at advanced stages compared with the CIN group (P < 0.05). Leukocytosis, neutrophilia, lymphopenia, and an NLR of 5 or greater were more frequent at advanced stages compared with the CIN and early-stage groups (P < 0.05). Moreover, neutrophilia was also significantly more frequent at early stage compared with the CIN group. The advanced group with neutrophilia had increased frequency of recidivism and metastasis than patients in the CIN group with neutrophilia (P < 0.05). CONCLUSIONS: Patients with advanced cervical cancer had significantly higher frequency of leukocyte alterations, although they may occur apart from the preinvasive stages. Overall, neutrophilia was the best indicator of cancer invasiveness.

Synergic effect of OP449 and FTY720 on oral squamous cell carcinoma.

As SET protein is overexpressed and PP2A activity is reduced in oral squamous cell carcinoma (OSCC), this study aimed to assess the effects induced by OP449, a PP2A activator/SET inhibitor, on OSCC cells in vitro, and its potential either isolated or combined with FTY720, a PP2A activator/sphingosine kinase 1 antagonist, as antitumoral therapy in vivo. SET protein was analyzed in cells by immunoblotting and cancer stem cells by aldehyde dehydrogenase 1 assay (ALDH1). The cytotoxicity of OP449 was determined in five OSCC lineages by resazurin assay. Molecular actions of OP449 in SET targets were determined by immunoblotting. The coefficient of drug interaction (CDI) was used to characterize the synergism of OP449 and FTY720. The xenograft HN12 tumor model in nude mice was used to assess the antitumoral effect of OP449 and/or FTY720. HN12 (metastatic) cells showed higher SET and ALDH1 levels, and together with SCC9 cells were selected for molecular analysis. OP449 altered several SET functions/targets, such as histone H3 acetylation and NFkB. A synergism in cytotoxicity was observed when HN12 and SCC9 cells were pre-treated with 2 µM OP449 in combination with 15 µM FTY720 (CDI = 0.27 ± 0.088). Nude mice bearing xenograft HN12 tumors treated with OP449 and FTY720 showed reduced tumor mass. Moreover, NFkB was reduced in tumors after treatment. OP449 targets several SET functions, not only PP2A inhibition. Besides, OP449 plus FTY720 has a synergistic antitumoral effect on OSCC. Our results suggest new combined therapies and highlight SET and NFκB signaling as targets for OSCC therapy.

SET protein accumulates in HNSCC and contributes to cell survival: antioxidant defense, Akt phosphorylation and AVOs acidification.

OBJECTIVES: Determination of the SET protein levels in head and neck squamous cell carcinoma (HNSCC) tissue samples and the SET role in cell survival and response to oxidative stress in HNSCC cell lineages. MATERIALS AND METHODS: SET protein was analyzed in 372 HNSCC tissue samples by immunohistochemistry using tissue microarray and HNSCC cell lineages. Oxidative stress was induced with the pro-oxidant tert-butylhydroperoxide (50 and 250µM) in the HNSCC HN13 cell lineage either with (siSET) or without (siNC) SET knockdown. Cell viability was evaluated by trypan blue exclusion and annexin V/propidium iodide assays. It was assessed caspase-3 and -9, PARP-1, DNA fragmentation, NM23-H1, SET, Akt and phosphorylated Akt (p-Akt) status. Acidic vesicular organelles (AVOs) were assessed by the acridine orange assay. Glutathione levels and transcripts of antioxidant genes were assayed by fluorometry and real time PCR, respectively. RESULTS: SET levels were up-regulated in 97% tumor tissue samples and in HNSCC cell lineages. SiSET in HN13 cells (i) promoted cell death but did not induced caspases, PARP-1 cleavage or DNA fragmentation, and (ii) decreased resistance to death induced by oxidative stress, indicating SET involvement through caspase-independent mechanism. The red fluorescence induced by siSET in HN13 cells in the acridine orange assay suggests SET-dependent prevention of AVOs acidification. NM23-H1 protein was restricted to the cytoplasm of siSET/siNC HN13 cells under oxidative stress, in association with decrease of cleaved SET levels. In the presence of oxidative stress, siNC HN13 cells showed lower GSH antioxidant defense (GSH/GSSG ratio) but higher expression of the antioxidant genes PRDX6, SOD2 and TXN compared to siSET HN13 cells. Still under oxidative stress, p-Akt levels were increased in siNC HN13 cells but not in siSET HN13, indicating its involvement in HN13 cell survival. Similar results for the main SET effects were observed in HN12 and CAL 27 cell lineages, except that HN13 cells were more resistant to death. CONCLUSION: SET is potential (i) marker for HNSCC associated with cancer cell resistance and (ii) new target in cancer therapy.