Reciprocal regulation of forkhead box C1 and L1 cell adhesion molecule contributes to triple-negative breast cancer progression.

PURPOSE: The potential of targeting forkhead box C1 (FOXC1) as a therapeutic approach for triple-negative breast cancer (TNBC) is promising. However, a comprehensive understanding of FOXC1 regulation, particularly upstream factors, remains elusive. Expression of the L1 cell adhesion molecule (L1CAM), a transmembrane glycoprotein associated with brain metastasis, was observed to be positively associated with FOXC1 transcripts. Thus, this study aims to investigate their relationship in TNBC progression. METHODS: Publicly available FOXC1 and L1CAM transcriptomic data were obtained, and their corresponding proteins were analyzed in four TNBC cell lines. In BT549 cells, FOXC1 and L1CAM were individually silenced, while L1CAM was overexpressed in BT549-shFOXC1, MDA-MB-231, and HCC1937 cells. CCK-8, transwell, and wound healing assays were performed in these cell lines, and immunohistochemical staining was conducted in tumor samples. RESULTS: A positive correlation between L1CAM and FOXC1 transcripts was observed in publicly available datasets. In BT549 cells, knockdown of FOXC1 led to reduced L1CAM expression at both the transcriptional and protein levels, and conversely, silencing of L1CAM decreased FOXC1 protein levels, but interestingly, FOXC1 transcripts remained largely unaffected. Overexpressing L1CAM resulted in increased FOXC1 protein expression without significant changes in FOXC1 mRNA levels. This trend was also observed in BT549-shFOXC1, MDA-MB-231-L1CAM, and HCC1937-L1CAM cells. Notably, alterations in FOXC1 or L1CAM levels corresponded to changes in cell proliferation, migration, and invasion capacities. Furthermore, a positive correlation between L1CAM and FOXC1 protein expression was detected in human TNBC tumors. CONCLUSION: FOXC1 and L1CAM exhibit co-regulation at the protein level, with FOXC1 regulating at the transcriptional level and L1CAM regulating at the post-transcriptional level, and together they positively influence cell proliferation, migration, and invasion in TNBC.

Clinical significance of L1CAM expression and its biological role in the progression of oral squamous cell carcinoma.

L1 cell adhesion molecule (L1CAM) has been implicated in the progression and metastasis of numerous cancers. However, the role of L1CAM in oral squamous cell carcinoma (OSCC) is not well characterized. In the present study, the expression of L1CAM was examined in oral tongue squamous cell carcinoma (OTSCC) tissue samples by immunohistochemistry, the clinicopathological significance of L1CAM expression was evaluated by chi­squared test, and the overall survival (OS) rate was analyzed using Kaplan­Meier method according to the expression of L1CAM. In addition, it was aimed to elucidate the biological role of L1CAM and the underlying molecular mechanisms by which L1CAM functions in OSCC cells in relation to epithelial­mesenchymal transition (EMT) and PI3K/AKT/ERK signaling pathways. Thus, the functions of L1CAM on the OSCC cell proliferation, migration and invasion, and the activation of EMT and PI3K/AKT/ERK signaling pathways were investigated in vitro. Positive L1CAM expression was found in 32.5% of OTSCC cases and was significantly correlated with high histologic grade, greater depth of invasion, lymph node metastasis, perineural invasion, advanced stage, and survival status. Patients with positive L1CAM expression had significantly lower OS rate. Particularly in patients with early OTSCC, L1CAM expression was strongly associated with worse prognosis. Overexpression of the recombinant human L1CAM protein significantly increased cell proliferation, migration and invasion. By contrast, L1CAM knockdown using small interfering RNA significantly inhibited cell proliferation, migration, invasion and EMT. Moreover, phosphorylated (p)­PI3K, p­AKT and p­ERK expression levels were significantly reduced by L1CAM knockdown. Taken together, the findings of the present study suggested that L1CAM could be a potential prognostic marker and a promising therapeutic target in OSCC.

Role of L1CAM in retinoblastoma tumorigenesis: identification of novel therapeutic targets.

The study presented focuses on the role of the neuronal cell adhesion molecule L1 cell adhesion molecule (L1CAM) in retinoblastoma (RB), the most common malignant intraocular childhood tumor. L1CAM is differentially expressed in a variety of human cancers and has been suggested as a promising therapeutic target. We likewise observed differential expression patterns for L1CAM in RB cell lines and patient samples. The two proteases involved in ectodomain shedding of L1CAM (L1CAM sheddases: ADAM10 and ADAM17) were likewise differentially expressed in the RB cell lines investigated, and an involvement in L1CAM processing in RB cells could be verified. We also identified ezrin, galectin-3, and fibroblast growth factor basic as L1CAM signaling target genes in RB cells. Lentiviral L1CAM knockdown induced apoptosis and reduced cell viability, proliferation, growth, and colony formation capacity of RB cells, whereas L1CAM-overexpressing RB cells displayed the opposite effects. Chicken chorioallantoic membrane assays revealed that L1CAM depletion decreases the tumorigenic and migration potential of RB cells in vivo. Moreover, L1CAM depletion decreased viability and tumor growth of etoposide-resistant RB cell lines upon etoposide treatment in vitro and in vivo. Thus, L1CAM and its processing sheddases are potential novel targets for future therapeutic RB approaches.

Adhesion molecule L1 binds to amyloid beta and reduces Alzheimer's disease pathology in mice.

Alzheimer's disease (AD) is a devastating neurodegenerative disorder and the most common cause of elderly dementia. In an effort to contribute to the potential of molecular approaches to reduce degenerative processes we have tested the possibility that the neural adhesion molecule L1 ameliorates some characteristic cellular and molecular parameters associated with the disease in a mouse model of AD. Three-month-old mice overexpressing mutated forms of amyloid precursor protein and presenilin-1 under the control of a neuron-specific promoter received an injection of adeno-associated virus encoding the neuronal isoform of full-length L1 (AAV-L1) or, as negative control, green fluorescent protein (AAV-GFP) into the hippocampus and occipital cortex. Four months after virus injection, the mice were analyzed for histological and biochemical parameters of AD. AAV-L1 injection decreased the Aß plaque load, levels of Aß42, Aß42/40 ratio and astrogliosis compared with AAV-GFP controls. AAV-L1 injected mice also had increased densities of inhibitory synaptic terminals on pyramidal cells in the hippocampus when compared with AAV-GFP controls. Numbers of microglial cells/macrophages were similar in both groups, but numbers of microglial cells/macrophages per plaque were increased in AAV-L1 injected mice. To probe for a molecular mechanism that may underlie these effects, we analyzed whether L1 would directly and specifically interact with Aß. In a label-free binding assay, concentration dependent binding of the extracellular domain of L1, but not of the close homolog of L1 to Aß40 and Aß42 was seen, with the fibronectin type III homologous repeats 1-3 of L1 mediating this effect. Aggregation of Aß42 in vitro was reduced in the presence of the extracellular domain of L1. The combined observations indicate that L1, when overexpressed in neurons and glia, reduces several histopathological hallmarks of AD in mice, possibly by reduction of Aß aggregation. L1 thus appears to be a candidate molecule to ameliorate the pathology of AD, when applied in therapeutically viable treatment schemes.

The injured and regenerating nervous system: immunoglobulin superfamily members as key players.

Understanding restricted functional recovery and designing efficient treatments to alleviate dysfunction after injury of the nervous system remain major challenges in neuroscience and medicine. Numerous molecules of potential significance in neural repair have been identified in vitro, but only few of these have proved to be of major importance in vivo up to now. Among the molecules involved in regeneration are several members of the immunoglobulin superfamily, most notably the neural cell adhesion molecules L1, its close homologue CHL1, and NCAM and, in particular, its polysialic acid glycan moiety. Sufficient evidence is now available to justify the statement that these molecules are major players not only in nervous system development but also in the adult during neural repair and synaptic plasticity. Importantly, insights into the functions of these molecules in promoting or inhibiting functional recovery have allowed the design and assessment of therapeutic approaches in animal models of central nervous system injury that could prove to be applicable in clinical settings.

Optic nerve regeneration in polyglycolic acid-chitosan conduits coated with recombinant L1-Fc.

Autografts have been extensively studied to facilitate optic nerve (ON) regeneration in animal experiments, but the clinical application of this approach to aid autoregeneration has not yet been attempted. This study aims to explore the guided regeneration by an artificial polyglycolic acid-chitosan conduit coated with recombinant L1-Fc. Consistent with previous studies; in vitro assay showed that both chitosan, a natural biomaterial, and the neural cell adhesion molecule L1-Fc enhanced neurite outgrowth. Rat optic nerve transection was used as an in vivo model. The implanted PGA-chitosan conduit was progressively degraded and absorbed, accompanied by significant axonal regeneration as revealed by immunohistochemistry, anterograde and retrograde tracing. The polyglycolic acid-chitosan conduit coated with L1-Fc showed more effective to promote axonal regeneration and remyelination. Taken together, our observations demonstrated that the L1-Fc coated PGA-chitosan conduits provided a compatible and supportive canal to guild the injured nerve regeneration and remyelination.