No abstract

BACKGROUND: Epigenetic reprogramming of the methylome has been implicated in all stages of cancer evolution. It is now well accepted that cancer cells exploit epigenetic reprogramming, a mechanism that regulates stem/progenitor cell renewal and differentiation, to promote cancer initiation and progression. The oncogene FOXM1 has been implicated in all major forms of human cancer. METHODS: We have recently shown that aberrant upregulation of FOXM1 orchestrated a DNA methylation signature that mimics the cancer methylome landscape, from which we have identified a number of FOXM1-induced epigenetic markers. Differential promoter methylation and gene expression in clinical specimens were measured using commercially available bisulfite conversion kits and absolute quantitative PCR, respectively. RESULTS: Here, we investigated 8 FOXM1-induced differentially methylated genes, SPCS1, FLNA, CHPF, GLT8D1, C6orf136, MGAT1, NDUFA10, and PAFAH1B3, using human head and neck tissue specimens donated by 2 geographically independent patient cohorts from Norway and the United Kingdom. Two genes (GLT8D1 and C6orf136) were found to be differentially expressed in head and neck squamous cell carcinomas (HNSCCs). Using methylationspecific quantitative PCR, we confirmed that the promoters of GLT8D1 and C6orf136 were hypo-and hypermethylated, respectively, in HNSCC tissues. CONCLUSIONS: Given that epigenetic change precedes gene expression, methylation status of candidate genes identified from this study may represent a signature of premalignancy, rendering them potentially useful predictive biomarkers for precancer screening and/or therapeutic targets for cancer prevention. Cancer 2013;119:4249-58.

We earlier reported that cell-projection pumping transfers fibroblast contents to cancer cells and this alters the cancer cell phenotype. Here, we report on single-cell tracking of time lapse recordings from co-cultured fluorescent fibroblasts and SAOS-2 osteosarcoma cells, tracking 5201 cells across 7 experiments. The fluorescent lipophilic marker DiD was used to label fibroblast organelles and to trace the transfer of fibroblast cytoplasm into SAOS-2 cells. We related SAOS-2 phenotypic change to levels of fluorescence transfer from fibroblasts to SAOS-2 cells, as well as what we term ‘compensated fluorescence’, that numerically projects mother cell fluorescence post-mitosis into daughter cells. The comparison of absolute with compensated fluorescence allowed us to deduct if the phenotypic effects in mother SAOS-2 cells were inherited by their daughters. SAOS-2 receipt of fibroblast fluorescence correlated by Kendall’s tau with cell-profile area and without evidence of persistence in daughter cells (median tau = 0.51, p < 0.016); negatively and weakly with cell circularity and with evidence of persistence (median tau = −0.19, p < 0.05); and very weakly with cell migration velocity and without evidence of persistence (median tau = 0.01, p < 0.016). In addition, mitotic SAOS-2 cells had higher rates of prior fluorescence uptake (median = 64.9 units/day) than non-dividing cells (median = 35.6 units/day, p < 0.016) and there was no evidence of persistence post-mitosis. We conclude that there was an appreciable impact of cell-projection pumping on cancer cell phenotype relevant to cancer histopathological diagnosis, clinical spread and growth, with most effects being ‘reset’ by cancer cell mitosis.