NOVA1 expression is associated with clinicopathological characteristics and prognosis in patients with small cell lung cancer

Investigation of RNA-binding protein NOVA1 in silico: Comparison of the modern human V197 with the archaic I197 variant present in Neanderthals

By comparing the high-coverage archaic genome sequences to those of modern humans, specific genetic differences have been identified. For example, a human-specific substitution has been found in neuro-oncological ventral antigen 1 (NOVA1) - an RNA-binding protein that regulates the alternative splicing of neuronal pre-mRNA. The amino acid substitution results in an isoleucine-to-valine change at position 197 in NOVA1 (archaic: I197, modern human: V197). Previous studies have utilised gene editing technology to compare the archaic and modern human forms of NOVA1 in cortical organoids, however, the structural and molecular details require further investigation. Using an in silico approach, the modern human (WT) and archaic (V197I) structures of NOVA1 were generated. Moreover, the structure of NOVA1 containing a glycine-to-valine substitution at position 68 (G68V), which occurs at the RNA-binding interface, was examined for comparison. Protein-RNA docking was subsequently performed to model the interaction of NOVA1 variants with RNA and the complexes were evaluated further using classical molecular dynamics (MD) simulations. Based on the MM-PBSA analysis, the binding free energies were similar between the WT (-956.8 ± 32.6 kcal/mol), V197I (-975.4 ± 65.6 kcal/mol), and G68V (-946.7 ± 34.3 kcal/mol) complexes. The findings highlight the binding and stability of protein-RNA complexes with only modest structural changes observed in the archaic and G68V variants compared to the WT NOVA1 protein. Further clarification is required to enhance our understanding of the impact of NOVA1 mutations on alternative splicing and disease development. In particular, delineating the effect of multiple mutations in the NOVA1 gene is of importance.

Oncogenic NOVA1 expression dysregulates alternative splicing in breast cancer

Neuro-Oncological Ventral Antigen 1 (NOVA1) is best known for its role in mediating an alternative splicing (AS) program in neurons, yet was first discovered as an antigen expressed in breast tumors, causing rare autoimmune reactions and paraneoplastic neurological disorders (PNDs). The PND model suggests a plausible role of the tumor antigen expression in tumor suppression, whereas it has emerged that NOVA may function as an oncogene in a variety of cancers. In addition, whether NOVA mediates AS in breast cancer remains unanswered. Here we examine the AS profiles of breast invasive carcinoma (BRCA) tumor samples and demonstrate that ectopic NOVA1 expression led to the activation of neuron-like splicing patterns in many genes, including exons targeted by NOVA in the brain. The splicing dysregulation is especially prevalent in cell periphery and cytoskeleton genes related to cell-cell communication, actin-based movement, and neuronal functions. We find that NOVA1-mediated AS is most prominent in Luminal A tumors and high NOVA1 expression in this subtype is associated with poorer prognosis. Our results suggest that ectopic NOVA1 in tumors has regulatory activity affecting pathways with high relevance to tumor progression and that this might be a more general mechanism for PND antigens.

Upregulation of FGF9 and NOVA1 in cancer-associated fibroblasts promotes cell proliferation, invasion and migration of triple negative breast cancer

Cancer-associated fibroblasts (CAFs) play a pivotal role in cancer progression. This study aimed to explore the roles of CAFs-derived Fibroblast growth factor 9 (FGF9) and Neuro-oncological ventral antigen 1 (NOVA1) in triple negative breast cancer (TNBC) progression. MDA-MB-231 and BT-549 cells were cocultured with CAF conditioned-medium (CAF-CM) or normal fibroblasts conditioned-medium (NF-CM). MTT, EdU, colony formation, wound healing, transwell migration, and invasion assays were employed to determine cell proliferation, migration and invasion, respectively. Western blot and RT-qPCR were carried out to examine the protein and mRNA expression of FGF9 and NOVA1. Xenograft tumor experiments were conducted to evaluate the effects of CAFs, FGF9, and NOVA1 on tumor growth in vivo. Our results showed that CAFs significantly promoted the proliferation, invasion, and migration of TNBC cells. FGF9 and NOVA1 were significantly upregulated in TNBC CAFs, tissues and cells. CAF-CM also could increase the expression of FGF9 and NOVA1 in TNBC cells. Knockdown of FGF9 or NOVA1 could hamper cell proliferation, invasion, migration, and EMT of TNBC cells. Moreover, CAFs with FGF9/NOVA1 knockdown also could inhibit TNBC progression. Besides, CAFs significantly accelerated tumor growth in vivo, which was blocked by FGF9/NOVA1 knockdown in nude mice. In conclusion, our results indicated the tumor-promoting role of CAFs in TNBC progression. FGF9 and NOVA1 upregulation in CAFs induced cell proliferation, migration and invasion in vitro, and facilitated tumor growth in vivo in TNBC development.

NOVA1 promotes NSCLC proliferation and invasion by activating Wnt/β-catenin signaling

BACKGROUND

Neuro-oncological ventral antigen 1 (NOVA1) is a neuron-specific RNA-binding protein which regulates alternative splicing in the developing nervous system. Recent research has found that NOVA1 plays a significant role in carcinogenesis. In this paper, we examine the role of NOVA1 in non-small cell lung cancer (NSCLC) and its underlying molecular mechanisms.

METHODS

The expression of NOVA1 in NSCLC was detected by immunohistochemistry and correlations between NOVA1 expression and clinicopathological factors were analyzed by chi-square tests. Kaplan-Meier survival analysis and the Cox regression model were used to evaluate the predictive effect of prognostic factors. Western blotting, Cell Counting Kit-8, colony formation, apoptosis, migration and invasion assays were used to detect the effects of silencing (si)NOVA1 RNA on Wnt/β-catenin signaling and biological behavior in NSCLC cell lines.

RESULTS

Our study showed that expression of NOVA1 was up-regulated and significantly correlated with poor differentiation (p = 0.020), advanced TNM stage (P = 0.001), T stage (P = 0.001) and lymph node metastasis (P = 0.000) as well as the expression of β-catenin (P = 0.012) in NSCLC. The down-regulation of NSCLC by siRNA significantly inhibited proliferation, migration and invasion and promoted apoptosis in NSCLC cells. Expression of Wnt signaling molecules, including β-catenin, activated β-catenin, cyclin D1, matrix metalloproteinase (MMP)-2 and MMP-7, was also significantly reduced by siNOVA1. The inhibition of Wnt/β-catenin signaling in A549 and H1299 cells by siNOVA1 was reversed after treatment with a β-catenin expression plasmid.

CONCLUSION

The present study suggests that NOVA1 may serve as a potential prognosis biomarker in NSCLC. High NOVA1 expression was associated with poor survival rate. Finally, in vitro experiments verified that NOVA1 promotes NSCLC cell proliferation and invasion by regulating Wnt/β-catenin signaling.