Overexpression of MEOX2 and TWIST1 is associated with H3K27me3 levels and determines lung cancer chemoresistance and prognosis

Lung cancer is the leading cause of death from malignant diseases worldwide, with the non-small cell (NSCLC) subtype accounting for the majority of cases. NSCLC is characterized by frequent genomic imbalances and copy number variations (CNVs), but the epigenetic aberrations that are associated with clinical prognosis and therapeutic failure remain not completely identify. In the present study, a total of 55 lung cancer patients were included and we conducted genomic and genetic expression analyses, immunohistochemical protein detection, DNA methylation and chromatin immunoprecipitation assays to obtain genetic and epigenetic profiles associated to prognosis and chemoresponse of NSCLC patients. Finally, siRNA transfection-mediated genetic silencing and cisplatinum cellular cytotoxicity assays in NSCLC cell lines A-427 and INER-37 were assessed to describe chemoresistance mechanisms involved. Our results identified high frequencies of CNVs (66–51% of cases) in the 7p22.3–p21.1 and 7p15.3–p15.2 cytogenetic regions. However, overexpression of genes, such as MEOX2, HDAC9, TWIST1 and AhR, at 7p21.2–p21.1 locus occurred despite the absence of CNVs and little changes in DNA methylation. In contrast, the promoter sequences of MEOX2 and TWIST1 displayed significantly lower/decrease in the repressive histone mark H3K27me3 and increased in the active histone mark H3K4me3 levels. Finally these results correlate with poor survival in NSCLC patients and cellular chemoresistance to oncologic drugs in NSCLC cell lines in a MEOX2 and TWIST1 overexpression dependent-manner. In conclusion, we report for the first time that MEOX2 participates in chemoresistance irrespective of high CNV, but it is significantly dependent upon H3K27me3 enrichment probably associated with aggressiveness and chemotherapy failure in NSCLC patients, however additional clinical studies must be performed to confirm our findings as new probable clinical markers in NSCLC patients.

[Surgical treatment of non-malignant tracheoesophageal fistula]

Tracheoesophageal fistula is a complication of endotracheal canulas with pressure balloon during mechanical ventilation, for which treatment is surgical closure. There are approximately 80 reported cases in the world literature. Here we report our experience at the National Institute of Respiratory Diseases of Mexico. We performed surgical treatment of 7 patients (4 males, 3 females, 17 to 65 years of age) with tracheoesophageal fistula from 1991 to 1995, referred from other hospitals. Six had a history of prolonged orotracheal intubation, and the seventh had a traumatic lesion of the neck. Preoperatory management varied from 1 to 8 weeks, with treatment of malnutrition and infections. Esophagus was sutured with polyglactin 000 in two layers, the inner with interrupted, and the superficial with continuous sutures. The area was covered with a muscle strap. In six patients, simple suture of trachea was performed. In the seventh, due to an extensive tracheal defect, we decided to use a second muscle strap to occlude it. Six patients have had a follow up of 15 months to 5 years with satisfactory evolution. One patient died due to abdominal sepsis. We conclude that this technique provides a good prognosis for this disorder.