lncRNA FOXD3‑AS1 promotes the progression of non‑small cell lung cancer by regulating the miR‑135a‑5p/CDK6 axis

Abstract

Long non-coding RNA (lncRNA) is essential to the development and progression of malignant human cancer. Growing evidence suggests that the lncRNA forkhead box D3 antisense 1 (FOXD3-AS1) is a crucial regulatory effector for multiple cancer types and is closely associated with poor prognosis. However, in most cases, the molecular mechanism underlying the role of FOXD3-AS1 in cancer development has not yet been fully elucidated. The present study focused on non-small cell lung cancer (NSCLC) in order to gain insight into how FOXD3-AS1 drives cancer progression. First, FOXD3-AS1 expression in NSCLC tissue samples was detected using reverse transcription-quantitative (RT-qPCR). Moreover, cell proliferation and apoptosis were determined using Cell Counting Kit-8 assays and flow cytometry, respectively. A luciferase reporter assay was then performed to determine whether there was a direct binding association between FOXD3-AS1 and microRNA (miR)-135a-5p. Lastly, a tumor subcutaneous xenograft model was established to examine the role of FOXD3-AS1 in tumor growth. FOXD3-AS1 was significantly overexpressed in NSCLC tissue samples and cell lines compared with normal tissue samples and cells. FOXD3-AS1 silencing expression significantly inhibited A549 and H1229 cell proliferation while inducing apoptosis compared with sh-NC group. The luciferase reporter assay demonstrated the direct binding interaction between FOXD3-AS1 and miR-135a-5p. Moreover, FOXD3-AS1 silencing led to the upregulation of miR-135a-5p in A549 and H1229 cells compared with sh-NC group. It was also demonstrated that miR-135a-5p could bind to the 3′ untranslated region of cyclin-dependent kinase 6 (CDK6) and negatively modulate its transcription. miR-135a-5p knockdown or CDK6 overexpression reversed the inhibition on cell proliferation and apoptosis following FOXD3-AS1 knockdown. Altogether, the present study suggests that FOXD3-AS1 sponges miR-135a-5p to promote cell proliferation and concomitantly inhibit apoptosis by regulating CDK6 expression in NSCLC cells.

Evaluation of lncRNA FOXD3-AS1 as a Biomarker for Early-Stage Lung Cancer Diagnosis and Subtype Identification

“…Through the PI3K/Akt pathway, FOXD3-AS1 interacts with and activates RNA-binding protein ELAV-like RNA-binding protein 1, causing LC cell proliferation, invasion, and 5-fluorouracil resistance [ 20 ]. FOXD3-AS1 has also been shown to keep mediator subunit 28, murine double minute 2, and cyclin-dependent kinase 6 expressions in NSCLC by sequestering miRNAs [ 21 – 23 ]. We confirmed that FOXD3-AS1 is overexpressed in both blood and tissues of LUAD, LUSC, and SCLC samples when compared to control in the current study, based on hints from the Cancer Genome Atlas (TCGA) lung adenocarcinoma projects, lung squamous carcinoma projects, and Gene Expression Omnibus (GEO) datasets (GSE60052) as well as our RT-qPCR assays.…”

Emerging Roles and Mechanisms of lncRNA FOXD3-AS1 in Human Diseases

“…Increasing evidence has shown that lncRNA FOXD3-AS1 is abnormally expressed in various human diseases, including lung cancer (24)(25)(26)(27)(28), breast cancer (29,30), cervical cancer (31,32), nasopharyngeal carcinoma (33,34), osteosarcoma (35), colorectal cancer (36), melanoma (37,38), liver cancer (39), thyroid cancer (40), neuroblastoma (41), glioma (42), allergic rhinitis (43), retinal infection with Toxoplasma gondii-ocular toxoplasmosis (44), ischemic stroke (45), myocardial ischemia (46,47) and acute respiratory distress syndrome (48). Further studies demonstrated that aberrant expression of FOXD3-AS1 is closely associated to clinicopathological characteristics, such as tumor size, tumor grade, distant lymph node metastasis, differentiation of tumor tissues, overall survival, progressionfree survival, and survival time of patients (Table 1).…”

“…Despite advancements in early detection and treatment of NSCLC, the identification of molecular markers associated with patient survival is still necessary (53,(58)(59)(60). Multiple studies have demonstrated that FOXD3-AS1 is overexpressed in NSCLC tissues and cell lines (H1299, A549 and SPC-A1 cells) (24,(26)(27)(28). In addition, FOXD3-AS1 exerts pro-cancer effects in vitro and in vivo by regulating cell proliferation, migration, apoptosis as well as chemo-resistance.…”

“…Apoptosis is a type of programed cell death that has been implicated in the development and occurrence of cancers (159)(160)(161)(162)(163). FOXD3-AS1 was demonstrated to suppress the apoptosis of NSCLC A549 and H1229 cells through functioning as a ceRNA for miR-135a-5p and elevating CDK6 expression (24). Similarly, in cervical cancer HeLa and C33A cells, FOXD3-AS1 acts as an oncogene and competitively binds to miR-296-5p, which dramatically increases the levels of HMGA1, thus restraining tumor cells apoptosis (32).…”

“…FOXD3-AS1 is abnormally expressed in multitude diseases, including NSCLC (24)(25)(26)(27)(28), breast cancer (29,30), cervical cancer (31,32), nasopharyngeal carcinoma (33,34), osteosarcoma (35), colon adenocarcinoma (36), melanoma (37,38), hepatocellular carcinoma (39), thyroid cancer (40), neuroblastoma (41), glioma (42), ischemic stroke (45), myocardial ischemia (46,47), acute respiratory distress syndrome (48), allergic rhinitis (43) and retinal infection with toxoplasma gondii-ocular toxoplasmosis (44). Differential expression of FOXD3-AS1 on specific tissues is able to distinguish pathological tissues from adjacent normal ones, suggesting that FOXD3-AS1 can be a promising diagnostic marker for the early diagnosis of diseases.…”