Fluorescence imaging of MALAT1 expression using a Cy5.5-labeled antisense oligonucleotide in lung cancer and epidermal carcinoma cells.

Background: The long noncoding RNA Metastasis Associated Lung Adenocarcinoma Transcript 1 (MALAT1) has been extensively studied as an oncogenic factor. Antisense oligonucleotides (ASOs) labeled with the Cyanine5.5 (Cy5.5) dye enable effective in vivo imaging using near-infrared fluorescence.

Methods: Pan-cancer research on MALAT1 expression levels was conducted through The Cancer Genome Atlas (TCGA) database analysis. The selectivity and specificity of MALAT1-ASO were validated in lung cancer and epidermal carcinoma cell lines (A549, A431, PC9GR, and PC9) using cellular fluorescence and flow cytometry. Corresponding xenograft models were created for these cell lines, and near-infrared fluorescence imaging assessed tumor imaging effectiveness and the biodistribution of Cy5.5-labeled MALAT1 ASOs.

Results: MALAT1 expression levels were found to be upregulated in various tumors and high MALAT1 expression level correlated to poor prognosis in some tumors. The high expression of MALAT1 was confirmed in tumor cell lines. In vitro fluorescent intensity correlated with MALAT1 expression within cells. The fluorescence intensity also exhibited concentration dependence. In vivo experiments revealed a significant contrast between tumor tissues and normal tissues within 24 h. Tumors exhibited varied probe uptake corresponding to their MALAT1 expression levels. Ex vivo experiments shows high probe uptake in kidney, liver and intestine tissues.

Conclusion: MALAT1 is highly expressed in various cancer tissues and associated with poor prognosis. In xenograft models of lung cancer and epidermal carcinoma cell lines A549, A431, PC9GR, and PC9, Cy5.5-labeled ASOs exhibit evident binding specificity and discernible imaging effect in both in vitro and in vivo, effectively reflecting MALAT1 expression levels in tumors.