Abstract
Lung cancer is the most common cancer in the world and several miRNAs are associated with it. MiRNA sponges are presented as tools to inhibit miRNAs. We designed a system to capture miRNAs based on circular RNAs (circRNA). To demonstrate its usefulness, we chose miR-21, which is upregulated and implicated in lung cancer. We constructed a miR-21 sponge and inserted it into a vector that facilitates circular RNA production (Circ-21) to study its effect on growth, colony formation, and migration in lung cancer cell lines and multicellular tumor spheroids (MTS). Circ-21 induced a significant and time-dependent decrease in the growth of A549 and LL2 cells, but not in L132 cells. Furthermore, A549 and LL2 cells transfected with Circ-21 showed a lower number of colonies and migration than L132. Similar findings were seen in A549 and LL2 Circ-21 MTS, which showed a significant decrease in volume growth, but not in L132 Circ-21 MTS. Based on this, the miR-21 circular sponge may suppress the processes of tumorigenesis and progression. Therefore, our system based on circular sponges seems to be effective, as a tool for the capture of other miRNAs.
Highlights
Lung cancer is the cancer that occurs most frequently in the world, and the most in men, and the third most in women in terms of mortality [1]
Cell colony formation exhibited a lower colony number in A549 and LL2 cells transfected with Circ-21 (p < 0.01 and p < 0.1, respectively) compared with both cell lines transfected with Circ-enhanced green fluorescence protein (EGFP) or no transfection (Figure 6)
We studied the expression level of miR-21 in A549 human lung adenocarcinoma epithelial cell line, LL2 mouse Lewis lung carcinoma cell line, and L132 human embryonic lung cell line. has-miR-103-3p and has-miR-191-5p were used for housekeeping in quantitative real time-polymerase chain reaction (qPCR)
Summary
Lung cancer is the cancer that occurs most frequently in the world, and the most in men, and the third most in women in terms of mortality [1] It has a low survival rate because the disease is generally advanced or metastatic at the time of diagnosis. Non-small cell lung cancer (NSCLC) represents 80–85% of all lung cancer diagnoses, with a five-year survival rate of 5% [2] This aggressiveness and the need of more effective treatments have led to the study of miRNAs, which are found suppressed or overexpressed in this type of cancer. The miRNAs are involved in diverse biological processes such as cell cycle control [5], cellular differentiation [6], development [7], and metabolism [8]. Deregulation in the expression of miRNAs has been related to the appearance of several cancers [13–15] similar to lung cancer, both with oncogenic and tumor suppressor functions (Table S1)
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