Non-small cell lung cancer (NSCLC) is one of the most common malignancies worldwide, and it occurs at a higher frequency in males. HOXD-AS1 could negatively regulate the expression of miR-147a. buy 502632-66-8 miR-147a inhibition abrogated the effect of HOXD-AS1 knockdown on the proliferation and apoptosis of NSCLC cells. Furthermore, HOXD-AS1 positively regulated the expression of pRB (a buy 502632-66-8 tumor suppressor protein) in NSCLC cells. Taken together, our data indicated that HOXD-AS1 might be an oncogenic lncRNA that promotes proliferation of NSCLC and could be a therapeutic target in NSCLC. Keywords: non-small cell lung cancer, HOXD-AS1, proliferation, miR-147a Introduction Lung cancer is a common malignancy, and it has the mortality of cancer-related deaths worldwide. Lung cancer can be classified into small cell lung cancer and non-small cell lung cancer (NSCLC) based on their degrees of differentiation and morphologic characteristics. Among all lung cancer patients, 85% are NSCLC.1 Accumulating evidence has shown that there are many important molecules and processes involved in the occurrence and development of NSCLC, such as the altered gene expression induced by epigenetic regulation.2,3 At present, the involvement of noncoding genes in NSCLC has buy 502632-66-8 been well documented, and they consist mainly of miRNAs. They can affect the stability of mRNAs and regulate both the transcription of mRNA and, subsequently, the expression of protein-encoding genes at the translational level. It has been shown that miRNAs can regulate various biologic processes and play a critical role in the development and metastasis of cancers.4,5 Long noncoding RNAs (lncRNAs) account for the greatest proportion of the mammalian gene transcriptome and are different from many protein-encoding genes or microRNAs. lncRNAs, still belonging to the dark matter in genomics, are not well studied to date, and attempts to understand their function and mechanism are underway.6,7 In recent years, several lncRNAs have TSPAN2 been demonstrated to be directly involved in the process of tumor development and metastasis.8,9 HOTAIR is the first lncRNA proved to have a transregulatory effect on transcription. By mediating chromatin remodeling, binding to polycomb repressive complex 2 (PRC2) and histone demethylation complex 1 (LSD1), and mediating the binding of these two protein complexes to specific sites on the genome, HOTAIR allows lysine methylation on specific residues of histones, resulting in gene silencing.10 It has been found that the expression of HOTAIR in various tumor tissues, including lung cancer, is closely related to tumor metastasis, recurrence, and clinical prognosis.11C13 In this study, we focused on a novel lncRNA, HOXD Cluster Antisense RNA 1 (HOXD-AS1), which is encoded by a member of the same gene family that encodes HOTAIR (the HOX gene family). The HOX gene family, first discovered in the study of homeosis in Drosophila, contains a series of evolutionarily conserved genes and plays an important role in embryonic development.14 Human HOX genes can be divided into A, B, C, and D gene clusters, which are located on different chromosomes. Each gene cluster contains 9C11 genes.15 It was found that the mutation in HOX genes may cause developmental disorders and abnormal formation of tissues and organs. HOX gene mutations can even induce cell malignant transformation to form tumors.16,17 A total of 231 lncRNAs have been annotated buy 502632-66-8 in the four HOX gene clusters,18 including HOTAIR, which is located between HOXC 11 and HOXC 12 genes and is on the antisense strand. HOXD-AS1, another lncRNA that has been annotated, is located between the HOXD1 and HOSD3 genes and is also located on the antisense strand. In addition to their proximity on the genome, HOXD-AS1, like HOTAIR, also plays an important role in the occurrence and progression of tumors, especially in the regulation of tumor metastasis. A recent study demonstrated that HOXD-AS1 is upregulated in bladder cancer and may be involved in the apoptosis and metastasis of tumor cells.19 However, neither the role of HOXD-AS1 in NSCLC nor its underlying mechanism has been elucidated. Studies have shown that 50% of miRNAs are located in the fragile sites or tumor-related gene regions, which are often amplified, deleted, or rearranged in cancer cells, suggesting that some miRNAs may act as oncogenes or tumor suppressor genes. 20C23 miR-147a was cloned and characterized by Lagos-Quintana et al in 2002 from mouse spleen tissue. Its homologous sequence was also found in the human genome at 9q33. 2 and was originally named miR-147. 24 Another member of the family, miR-147b, was identified on 15q21.1 in 2011.25.