[PLXNA1 is highly expressed in hepatocellular carcinoma and affects patients' survival and immune microenvironment]

OBJECTIVE

To investigate PLXNA1 expression in hepatocellular carcinoma (HCC) and explore its biological function and impacts on patients' survival outcomes and immune microenvironment.

METHODS

Bioinformatic analysis of highly expressed immune-related genes in HCC were performed using TCGA database and Immport website, and 7 genes associated with the survival outcomes of the patients were identified using univariate Cox regression analysis, Gene Expression Profiling Interactive Analysis, and Kaplan Meier plotter website. The expression profile of PLXNA1 in HCC was verified using GEO database. The impact of PLXNA1 expression on survival outcomes of HCC patients was analyzed using TCGA database, Kaplan Meier, and timeROC curve analyses, and its association with immune cell infiltration was explored using TIMER website, CIBERSORT, and ssGSEA. Immunohistochemmistry was used to detect PLXNA1 expression in clinical specimens of HCC and adjacent tissues, and the correlation of PLXNA1 expression level with the patients' survival was analyzed. RT-qPCR was used to examine PLXNA1 expressions in different HCC cell lines, and the effects of PLXNA1 knockdown on proliferation and migration of SMMC-7721 cells were evaluated using CCK-8 and Transwell assays.

RESULTS

Bioinformatic analyses suggested that PLXNA1 was highly expressed in HCC, and its high expression was associated with poor survival outcomes of the patients. PLXNA1 expression level was significantly correlated with immune cell infiltration in HCC. Immunohistochemmistry showed that compared with the adjacent tissues, HCC tissues had significantly higher PLXNA1 expressions, which were associated with a poor patient survival and served also as a diagnostic indicator for HCC (AUC= 0.9346). In cultured HCC cell lines, SMMC-7721 cells showed a higher PLXNA1 expression than HL-7702 cells, and PLXNA1 knockdown significantly suppressed proliferation and migration of SMMC-7721 cells.

CONCLUSION

PLXNA1 is highly expressed in HCC to promote tumor cell migration and proliferation and affect the patients' survival outcomes and immune microenvironment.

MicroRNA-134 prevents the progression of esophageal squamous cell carcinoma via the PLXNA1-mediated MAPK signalling pathway

BACKGROUND

MicroRNAs (miRNAs) are involved in oncogenesis of esophageal squamous cell carcinoma (ESCC). miR-134 is reported to have a tumour-suppressive role but its role in ESCC is not known. The present study was designed to examine whether miR-134 inhibits ESCC development and further explored relevant underlying mechanisms.

METHODS

Differentially expressed genes related to ESCC were identified from microarray gene expression profiles. Immunohistochemical staining and RT-qRCR assays identified elevated PLXNA1 expression levels and low miR-134. The relationship between miR-134 and PLXNA1 was predicted and further verified by a dual-luciferase reporter assay. The expression levels of miR-134 and PLXNA1 in ESCC cells were modified by miR-134 mimic/inhibitor and siRNA against PLXNA1, respectively. Thereafter, the expression of MAPK signalling pathway-related proteins, as well as the viability, migration, invasion, cell cycle and cell apoptosis of ESCC cells was investigated.

FINDINGS

The results showed that miR-134 could block the MAPK signalling pathway by downregulating PLXNA1. When miR-134 was overexpressed or PLXNA1 was silenced, cell apoptosis was enhanced, the cell cycle was retarded, and the cell proliferation, migration and invasion were suppressed. In vivo experiments confirmed that miR-134 overexpression or PLXNA1 silencing restrained tumour growth and lymph node metastasis.

INTERPRETATION

These findings demonstrate that cancer cell proliferation, migration, invasion, and tumour metastasis of ESCC can be suppressed by overexpression of miR-134 through downregulating PLXNA1, which subsequently blocks the MAPK signalling pathway. These results provide new potential targets and strategies for the treatment of ESCC.

Prevalence and associated phenotypes of PLXNA1 variants in normosmic and anosmic idiopathic hypogonadotropic hypogonadism

Idiopathic hypogonadotropic hypogonadism (IHH) can be divided into two major forms, normosmic IHH and Kallmann syndrome (KS). Genetic mutations are responsible for the majority of IHH. PLXNA1 has recently been implicated in the GnRH neuron migration and the etiology of KS. We aimed to investigate the prevalence and associated phenotypes of PLXNA1 variants in a large cohort of IHH patients. We screened the whole exome data of 215 IHH patients in a single center for causative PLXNA1 variants. Our studies showed eight novel (p.Arg836His, p.Lys1451Arg, p.Val287Met, p.Val536Ile, p.Ser1850Arg, p.Ile1701Val, p.Arg319Trp, and p.Pro485Leu) and two previously described (p.Arg528Trp and p.Gly720Glu) heterozygous PLXNA1 variants in nine affected individuals from seven unrelated families. Only three of nine patients were anosmic (KS) while the remaining patients showed normal olfactory function (nIHH). Seven of nine patients (77.7%) harbored additional one or two variants in other nIHH/KS-associated genes, including PROKR2, IGSF10, HS6ST1, SEMA3E, CCDC141, FGFR1, NRP1, POLR3A, and SRA1. Our findings indicate that PLXNA1 variants cause not only anosmic but also normosmic IHH with a relatively high prevalence (3.9%). Heterozygous missense PLXNA1 variants appear to be involved together with other IHH gene variants in bringing about the IHH disease phenotype.

PLXNA1 developmental encephalopathy with syndromic features: A case report and review of the literature

Developmental encephalopathies constitute a broad and genetically heterogeneous spectrum of disorders associated with global developmental delay, intellectual disability, frequent epilepsy, and other neurofunctional abnormalities. Here, we report a male presenting with infantile onset epilepsy and syndromic features resembling Dubowitz syndrome identified to have a de novo PLXNA1 variant by whole exome sequencing. This constitutes the second report of PLXNA1 sequence variation associated with early onset epilepsy, and the first to expand on the clinical features of this emerging disorder. This reports suggests that nonsynonymous de novo sequence variations in PLXNA1 are associated with a novel human phenotype characterized by intractable early onset epilepsy, intellectual disability, and syndromic features.