Polyamine-stimulation of arsenic-transformed keratinocytes

Abstract

Tumor promotion is strongly associated with inflammation and increased polyamine levels. Our understanding of relevant mechanisms responsible for arsenic-induced cancer remains limited. Previous studies suggest that arsenic targets and dysregulates stem cell populations that remain dormant in the skin until promoted to be recruited out of the bulge stem cell region, thus giving rise to skin tumors. In this study, we explored a possible mechanism by which increased keratinocyte polyamine biosynthesis promotes tumorsphere formation and invasiveness of arsenic-transformed HaCaT keratinocytes (As-HaCaT). Unlike parental HaCaT cells, As-HaCaT cells were tumorigenic in athymic nude mice, and the CD45negative epithelial tumor cells had enriched expression of Toll-Like Receptor 4 (TLR4), CD34 and CXCR4 as did As-HaCaT tumorsphere cultures compared to As-HaCaT monolayer cultures. Ornithine decarboxylase (ODC) overexpressing keratinocytes (Ker/ODC) release increased levels of the alarmin high mobility group box 1 (HMGB1). Ker/ODC conditioned medium (CM) stimulated As-HaCaT but not parental HaCaT tumorsphere formation, and this was inhibited by glycyrrhizin, an inhibitor of HMGB1, and by TAK242, an inhibitor of the HMGB1 receptor TLR4. Compared to parental HaCaT cells, As-HaCaT cells demonstrated greater invasiveness across a Matrigel-coated filter using either fibroblast CM or SDF-1α as chemoattractants. Addition of Ker/ODC CM or HMGB1 dramatically increased As-HaCaT invasiveness. Glycyrrhizin and TAK242 inhibited this Ker/ODC CM-stimulated invasion of As-HaCaT cells but not HaCaT cells. These results show that polyamine-dependent release of HMGB1 promotes the expansion of stem cell-like subpopulations in arsenic-transformed keratinocytes while also increasing their invasiveness, suggesting that polyamines may be a potential therapeutic target for the prevention and treatment of arsenic-initiated skin cancers.

Ectoine Globally Hypomethylates DNA in Skin Cells and Suppresses Cancer Proliferation

“…To study the possibility of ectoineinduced tumors in HaCaT keratinocytes, we treated cells with ectoine for 30 weeks and xenografted them into athymic nude mice. This experiment was modified from the previous studies [69,70]. Approximately 5 × 10 6 HaCaT cells treated with ectoine for 24 weeks were subcutaneously injected into the dorsal flank of athymic nude mice.…”

Ectoine Globally Hypomethylates DNA in Skin Cells and Suppresses Cancer Proliferation

“…To study the possibility of ectoine-induced tumors in HaCaT keratinocytes, we treated cells with ectoine for 30 weeks and xenografted them into athymic nude mice. This experiment was modified from the previous studies [38,39]. Approximately 5 × 106 HaCaT cells treated with ectoine for 24 weeks were subcutaneously injected into the dorsal flank of athymic nude mice.…”

Targeting HMGB1 in the Treatment of Non-Small Cell Lung Adenocarcinoma

“…Glycyrrhizin inhibits HMGB1 accumulation in the extracellular space, and prevents its interaction with proinflammatory receptors like TLR4, TLR2, and RAGE receptors [82][83][84][85]. Diseases where inflammation is a major factor in pathogenesis such as oncogenic transformation, bacterial infection, or diet-induced symbiosis are also sensitive to treatment with glycyrrhizin [46,49,52,53]. Conversely, the anti-inflammatory transforming growth factor (TGF-B1) pathway has been implicated in the cellular retention of HMGB1.…”