ASOs have wide applications for different anticancer treatments, including lung cancer (LC). The effects of anti-angiogenic treatments for lung squamous cell carcinoma are limited and associated with adverse side effects. Recent evidence has demonstrated the role of long non-coding RNAs in tumor progression and VEGF modulation, driving the potential of RNA-based therapies for the development of LC and anti-angiogenic strategies. Overexpression of LINC00173.v1 has been associated with proliferation, tumorigenesis, migration of vascular endothelial cells and poor overall survival in squamous cell carcinoma patients. LINC000173.v1 upregulates VEGFA expression by miR-511-5p sponge, and inhibition of LINC000173.v1 using ASOs results in decreased tumor growth and increased cisplatin sensitivity. A recent study demonstrated the potential of ASOs to downregulate metadherin expression, which is involved in T cell depletion and WNT signaling.
In cell lines using locked nucleic acid (LNA) modified ASOs and in spontaneous mouse models, down-regulation of metadherin was found to significantly reduce LC progression and metastasis. Similarly, miR-21 is among the most differently regulated microRNAs in NSCLC and regulates cell growth, proliferation, migration, invasion, apoptosis, and drug resistance. Ge et al recently reported the use of phosphorothioate ASOs to inhibit miR-21 expression, found that these ASOs reduce the proliferation of NSCLC cells and induce apoptosis through caspase-8 pathway activation. KRAS is a gene that is frequently mutated in different cancers, and activating mutations in KRAS occur in 20% of human tumors, including NSCLC. KRAS is a highly accepted target for cancer therapy, and however, the development of pharmacological small molecules for mutant KRAS continues to be challenging. In addition, most of the inhibitors identified are still in early-stage clinical trials.
AZD4785 is a high affinity KRAS mRNA targeting therapeutic ASO that selectively reduces mutant KRAS mRNA as well as protein. Unlike inhibitors of RAS-MAPK pathways, this depletion did not activate the feedback loop of the MAPK pathway. AZD4785 down-regulates the effector pathways and selectively reduces the proliferation of cells harboring the mutant KRAS. Systemic injection of AZD4785 into NSCLC mice xenografts and patient-derived xenografts harboring mutant KRAS inhibited KRAS expression and induced potent anti-tumor activity. It has been suggested that AZD4785 and other novel ASOs are innovative therapeutic approaches for treating KRAS and other mutated oncogenes. Wang et al. Reported the construction of new polyethylene glycol (PEG) linked antisense therapeutic oligonucleotides that form a bottle brush-like structure composed of PEG side chains, DNA backbone and overhangs of antisense oligonucleotides. These formulations have a high concentration of PEG at the surface, which reduces the unwanted interactions of ASOs with DNA and proteins (protects them from enzymatic degradation) and increases the chance of antisense spurs to hybridize with the target mRNA, thereby reducing protein expression.
This study evaluated KRAS targeting by these PEGylated ASOs in lung cancer. These modified ASOs have higher inhibitory effects than traditional hairpins and antisense molecules reduce the proliferation of the LC cell line expressing the mutant KRAS (G12C) gene. These ASOs have shown increased retention time in vivo (due to the high biocompatibility of PEG), representing an important strategy to improve the biopharmaceutical efficacy and translation applicability of ASOs mediated therapies. ADP-ribosylation factor such as 4C (ARL4C), a member of the small GTP binding protein family, is often overexpressed in adenomatous hyperplasic lesions (precursors of adenocarcinoma) and lung cancer. ARL4C promotes cell proliferation and is a potential therapeutic target for lung cancer.
Its expression is directly associated with different histological stages (adenocarcinoma, minimally invasive adenocarcinoma and invasive adenocarcinoma) and with poor prognosis. ASOs targeting ARL4C (ASO-1316) showed reduced RAS-associated substrate activity in lung cancer cell lines carrying KRAS and EGFR mutations. It also inhibited cell proliferation and migration and suppressed nuclear import of Yes-associated protein-1 (YAP-1). In addition, in ASO-1316 orthotopic mouse models, KRAS and EGFR reduced tumorigenesis of mutated lung cancer cell lines. This study identified the role of ARL4C in the initiation of premalignant lesions, tumor progression and development, and demonstrated the utility of ASO-1316 as a potential therapeutic agent for LC patients with ARL4C overexpression regardless of mutation status.
A recent study showed that ASOs bound with deoxyadenosine (dA 40) can form complex with glucan schizophila (SPG) and the ASOs-dA 40 / SPG complex can be recognized by Dectin-1 (a glucan receptor). This is expressed on lung cancer cells and antigen presenting cells (APCs). ASOs -dA 40 / SPG targeting KRAS inhibited KRAS expression in LC cells expressing Dectin-1 and consequently decreased cell growth. This ASOs-dA40 / SPG complex increased the cytotoxic effect of gemcitabine due to the ability of dA 40. Interestingly, after internalization, this interaction dissolves and gemcitabine is easily released from the complex. It means that conjugation of ASOs carrying SPG and dA40 can serve as potential carriers for gemcitabine and other structurally similar drugs. Due to this dual ability of ASOs-dA40 / SPG complexes to target KRAS and increase gemcitabine activity, these formulations are of interest to be evaluated in clinical trials.
The signal converter and transcription 3 activator (STAT3) is a central molecule for oncogenic and non-oncogenic signaling. STAT3 overexpression is associated with the progression of various cancers, including LC, making it a potential target for cancer therapy. AZD9150, an advanced ASO composed of ethyl modifications, was designed to target STAT3 as it is difficult to target transcription factors through small molecule inhibitors. Preclinical evaluations found that AZD9150 reduced the expression of STAT3, exhibiting pronounced antitumor effects in various preclinical cancer models of lymphoma and LC. In a phase I clinical trial (NCT01563302) for diffuse large B cell lymphoma (DL-BCL), AZD9150 demonstrated efficacy in a subgroup of well tolerated and well-treated patients. Currently, combination studies of AZD9150 with immune checkpoint inhibitors are ongoing.
Therapeutic silencing of STAT3 can also be achieved by targeting STAT3 to bind to target sites. CS3D is a cyclic 15-mer oligonucleotide trap corresponding to the response element of STAT3 target genes. The CS3D trap, tested on EGFR inhibitor resistant NSCLC cells, resulted in down-regulation of the STAT3 targeted c-MYC gene at mRNA and protein levels. In addition, CS3D inhibited cell proliferation, colonization, increased apoptosis in vitro, and decreased tumor growth along with in vivo expression of c-MYC. Therefore, targeting STAT3 with RNA-based oligonucleotides is a promising alternative to develop effective therapies for LC for small molecule chemical inhibitors.
High expression of Bcl2 and Akt1 promotes growth, proliferation and apoptotic abduction in LC, and Bcl2 is a potential therapeutic target for both NSCLC and SCLC. G3139 and RX-0201 are ASOs targeting Bcl2 and Akt-1, respectively, but have shown limited efficacy in clinical studies due to their insufficiency. These ASOs were modified using the Gapmer strategy and 2′-O-methyl modifications at the 5 ‘and 3 ′ ends. To improve targeting and delivery, cancer cell-specific lipid nanoparticles have been synthesized with these modified ASOs. Co-loaded nanoparticles of ASO exhibited improved colloidal stability, higher encapsulation with smaller particle size, and higher cellular uptake. T7-ASO-lipid nanoparticles reduced the expression of LC cell lines of Bcl2 and Akt-1, exhibited superior antitumor effects and improved overall survival (OS) in mice bearing LC xenografts. The activity of G3139 ASO Lipid nanoparticles relative to gapmer for Bcl2 in vitro was also evaluated. G3139-GAP (with 2’-O-methyl nucleotides) was incorporated into DOTAP, egg PC, cholesterol and Tween 80 lipid nanoparticles, anticancer activity was studied in A549 cells and xenograft mouse models. These gap-based ASOs reduced Bcl2 expression in mRNA as well as protein level in lipid nanoparticles, cell lines and tumors, inhibited tumor growth and improved OS.
Self-regenerating tumor-initiating cells (TICs) or cancer stem cells mainly resist tumor initiation, recurrence, and treatment. Overexpression and activity of glycine decarboxylase (GLDC) preserves TICs and is likely responsible for tumorigenesis of NSCLC. GLDC is an important member of the glycine and serine metabolic pathway, which regulates pyrimidine metabolism and cancer cell proliferation. Also, no therapeutic molecules are available for GLDC. Insertion-modulating steric block ASOs were created to induce exon skipping to disrupt the open reading frame of GLDC encoding transcripts and induce nonsense-mediated degradation. These GLDC steric blocks inhibited cell proliferation, colonization of LC cell lines, and tumor spheres derived from NSCLC TICs. Candidate GLDC ASOs reduced tumor growth of xenografts derived from TICs in mice. Overall, these reports show promise in designing and developing RNA-based therapeutic regimes for the LC of ASOs.
Writer: Ozlem Guvenc Agaoglu