LAUSR

Lung cancer continues to be the leading cause of cancer death in the United States, with more than 140,000 deaths per year. One of the main types of lung cancer is non-small cell lung cancer with lung adenocarcinoma (LUAD) being the most prominent subtype and is mainly due to oncogenic mutations like KRAS, which offers limited and unsuccessful treatments. The mucus barrier produced by mucins, particularly Mucin 5ac (Muc5ac) which is mainly expressed by lung epithelial cells, is essential for airway homeostasis. However, its overproduction can promote respiratory diseases such as chronic obstructive pulmonary disease (COPD), which is known to increase the risk of lung cancer by 3-10 fold. We have previously shown that Muc5ac is commonly expressed in patients with KRAS-driven LUAD and is associated with poor prognosis. Additionally, we found that lack of Muc5ac (genetic deletion) in mice with LUAD either induced chemically by urethane or genetically engineered with mutant KRAS presented with significantly reduced tumor burden. Therefore, we sought a translational approach by inhibiting Muc5ac in our KRAS-driven lung cancer mutant mouse model using an antisense oligonucleotide (ASO) against Muc5ac and hypothesized that the administration of this drug would result in decreased Muc5ac mRNA expression and reduced tumor burden. This was tested by intrapharyngeal administration of either ASO (5mg/kg) or vehicle (saline) twice a week to a cohort of six-week-old KRASG12D mutant mice for a total duration of eight weeks. Our results showed a 5-fold decrease in Muc5ac mRNA expression and a 42% reduction in overall tumor burden when compared to age and sex matched control mice. Additionally, analysis of bronchoalveolar lavage fluid showed a predominance of macrophages with significant downregulation of the protumorigenic M2 type macrophage polarization markers Fizz1 and Arg1 as well as significant upregulation of TNF-a, which suggests a mechanism mediated by direct tumor cytotoxic activity or apoptosis associated with a reduction in macrophage mediated immunosuppressive tumor microenvironment. In conclusion, our study suggests that administration of Muc5ac ASO effectively inhibits mucin production and ameliorates tumor progression, which ultimately could provide insight in both treatments and prevention against KRAS-driven LUAD. Citation Format: Walter V. Velasco Torrez, Shanshan Deng, Marco A. Ramos-Castaneda, Segundo W. Del Aguila-Soto, Seyed Moghaddam. Mucin 5ac as a potential therapeutic target for KRAS-driven lung adenocarcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4053.