MicroRNAs (miRNAs) are short non-coding RNA molecules playing regulatory roles by repressing translation or cleaving RNA transcripts. Although the number of verified human miRNA is still expanding, only few have been functionally described. However, emerging evidences suggest the potential involvement of altered regulation of miRNA in pathogenesis of cancers and these genes are thought to function as both tumours suppressor and oncogenes.

PURPOSE: The survivin gene is a novel apoptosis inhibitor, related to the baculovirus gene, which is believed to play a pivotal role in fetal development and in cancer. We hypothesised that survivin would be expressed in tumors of patients with non–small-cell lung cancer (NSCLC), and we attempted to determine the influence of survivin re-expression on clinical outcome in patients with up to stage IIIA NSCLC who had undergone radical surgery. METHODS: We designed a reverse transcriptase polymerase chain reaction (RT-PCR) assay to study the expression of the survivin gene in 83 NSCLC tumor samples and compared the results with relevant clinical and pathologic data. RESULTS: The RT-PCR identified survivin gene transcript in 71 (85.5%) of the tumor samples and in only 10 (12%) of the paired, histopathologically normal lung samples. There was no relationship between histologic subtype (squamous v nonsquamous) and survivin gene expression. The 12 patients without survivin expression had significantly better overall survival than the 71 patients with survivin expression (P = .01 by univariate analysis; relative risk, 2.1). There was no significant correlation between survivin expression and age, sex, cigarette smoking, histologic subtype, tumor differentiation, tumor size, or the presence of mediastinal lymph node metastases in surgical specimens. CONCLUSION: The survivin gene was expressed in a vast majority of NSCLC tumors. We conclude that survivin transcript is a defining diagnostic marker for NSCLC that may also yield prognostic information and, as an apoptosis inhibitor, be an important target in cancer therapy.

Background: The p53 transcription factor is located at the core of a complex wiring of signaling pathways that are critical for the preservation of cellular homeostasis. Only recently it has become clear that p53 regulates the expression of several long intergenic noncoding RNAs (lincRNAs). However, relatively little is known about the role that lincRNAs play in this pathway. Results: Here we characterize a lincRNA named Pint (p53 induced noncoding transcript). We show that Pint is a ubiquitously expressed lincRNA that is finely regulated by p53. In mouse cells, Pint promotes cell proliferation and survival by regulating the expression of genes of the TGF-β, MAPK and p53 pathways. Pint is a nuclear lincRNA that directly interacts with the Polycomb repressive complex 2 (PRC2), and is required for PRC2 targeting of specific genes for H3K27 tri-methylation and repression. Furthermore, Pint functional activity is highly dependent on PRC2 expression. We have also identified Pint human ortholog (PINT), which presents suggestive analogies with the murine lincRNA. PINT is similarly regulated by p53, and its expression significantly correlates with the same cellular pathways as the mouse ortholog, including the p53 pathway. Interestingly, PINT is downregulated in colon primary tumors, while its overexpression inhibits the proliferation of tumor cells, suggesting a possible role as tumor suppressor. Conclusions: Our results reveal a p53 autoregulatory negative mechanism where a lincRNA connects p53 activation with epigenetic silencing by PRC2. Additionally, we show analogies and differences between the murine and human orthologs, identifying a novel tumor suppressor candidate lincRNA.

MicroRNAs (miRNAs) have been identified as promising prognostic markers in non-small-cell lung cancer (NSCLC) since they play an important role in oncogenesis. The miR-34 family is composed of three miRNAs (miR-34a, miR-34b and miR-34c) that are part of the p53 network and whose expression is directly induced by p53 in response to DNA damage or oncogenic stress. We have analyzed the impact of miR-34 expression on relapse and overall survival in surgically resected NSCLC patients. For this purpose, we used stem-loop reverse transcription–polymerase chain reaction to analyze the expression of the miR-34 family in paired tumor and normal tissue from 70 surgically resected NSCLC patients who received no postsurgical treatment until relapse. In addition, in patients with sufficient tumor tissue, we assessed p53 mutations and the methylation status of the MIRN34A gene promoter region and correlated these findings with miR-34a expression. Molecular findings were correlated with relapse and overall survival. The miR-34 family was downregulated in tumor compared with normal tissue, and low levels of miR-34a expression were correlated with a high probability of relapse ( P = 0.04). A relation was also found between MIRN34A methylation and miR-34a expression ( P = 0.008). Patients with both p53 mutations and low miR-34a levels had the highest probability of relapse ( P = 0.001). In the multivariate analysis, miR-34a expression emerged as an independent prognostic marker for relapse. In summary, we have identified miR-34a as a novel prognostic marker in NSCLC patients, providing a potential mechanism for estimating a patient's risk of disease recurrence and a useful tool to help guide treatment decisions.

PURPOSE: The mechanisms that cause chemoresistance in non–small-cell lung cancer (NSCLC) patients have yet to be clearly elucidated. Paclitaxel is a tubulin-disrupting agent that binds preferentially to beta-tubulin. Tubulins are guanosine triphosphate (GTP)–binding proteins. Beta-tubulin is a GTPase, whereas alpha-tubulin has no enzyme activity. We reasoned that polymerase chain reaction (PCR) and DNA sequencing of the beta-tubulin gene could reveal more information regarding the connection between beta-tubulin mutations and primary paclitaxel resistance. PATIENTS AND METHODS: Constitutional genomic DNA and paired tumor DNA were isolated from 49 biopsies from 43 Spanish and six American stage IIIB and IV NSCLC patients who had been treated with a 3-hour, 210 mg/m² paclitaxel infusion and a 24-hour, 200 mg/m² infusion, respectively. Oligonucleotides specific to beta-tubulin were designed for PCR amplification and sequencing of GTP- and paclitaxel-binding beta-tubulin domains. RESULTS: Of 49 patients with NSCLC, 16 (33%; 95% confidence interval [CI], 20.7% to 45.3%) had beta-tubulin mutations in exons 1 (one patient) or 4 (15 patients). None of the patients with beta-tubulin mutations had an objective response, whereas 13 of 33 (39.4%; 95% CI, 22.8% to 56%; P = 0.01) patients without beta-tubulin mutations had complete or partial responses. Median survival was 3 months for the 16 patients with beta-tubulin mutations and 10 months for the 33 patients without beta-tubulin mutations (P = .0001). CONCLUSION: We have identified beta-tubulin gene mutations as a strong predictor of response to the antitubulin drug paclitaxel; these mutations may represent a novel mechanism of resistance and should be examined prospectively in future trials of taxane-based therapy in NSCLC.