Lymphatics-associated genes are downregulated at transcription level in non-small cell lung cancer

Advances in lymphatic metastasis of non-small cell lung cancer

Lung cancer is a deeply malignant tumor with high incidence and mortality. Despite the rapid development of diagnosis and treatment technology, abundant patients with lung cancer are still inevitably faced with recurrence and metastasis, contributing to death. Lymphatic metastasis is the first step of distant metastasis and an important prognostic indicator of non-small cell lung cancer. Tumor-induced lymphangiogenesis is involved in the construction of the tumor microenvironment, except promoting malignant proliferation and metastasis of tumor cells, it also plays a crucial role in individual response to treatment, especially immunotherapy. Thus, this article reviews the current research status of lymphatic metastasis in non-small cell lung cancer, in order to provide some insights for the basic research and clinical and translational application in this field.

The Role of PROX1 in Neoplasia: A Key Player Often Overlooked

The human PROX1 gene (Prospero homeobox gene 1) is a member of the homeobox transcription factor family. PROX1 plays a key role in the development of the lymphatic system and is primarily used as a lymphatic vessel marker. However, as the accumulating evidence indicates that PROX1 is also implicated in the tumorigenesis of various cancer types, the scientific community has attempted to elucidate its complicated function in neoplasia pathogenesis, as well as its utility in cancer diagnosis, prognosis, and therapy. PROX1 has been shown to participate in the complex molecular mechanisms affecting tumorigenesis and has been associated with a plethora of clinicopathological parameters, including tumor stage and patients’ overall survival. Depending on the specific organ affected, PROX1 has exhibited both tumor-promoting and tumor-suppressing properties, with its inhibition and reactivation representing possible novel therapeutic interventions, respectively. Moreover, researchers have reported PROX1 as a useful tool in the fields of diagnosis and prognosis assessment. The current study aims to summarize and present the existing data that render PROX1 a novel and useful diagnostic and prognostic biomarker, as well as a possible therapeutic target.

Lymph Leakage Promotes Immunosuppression by Enhancing Anti-Inflammatory Macrophage Polarization

Lymphatic vasculature is a network of capillaries and vessels capable of draining extracellular fluid back to blood circulation and to facilitate immune cell migration. Although the role of the lymphatic vasculature as coordinator of fluid homeostasis has been extensively studied, the consequences of abnormal lymphatic vasculature function and impaired lymph drainage have been mostly unexplored. Here, by using the Prox1+/- mice with defective lymphatic vasculature and lymphatic leakage, we provide evidence showing that lymph leakage induces an immunosuppressive environment by promoting anti-inflammatory M2 macrophage polarization in different inflammatory conditions. In fact, by using a mouse model of tail lymphedema where lymphatic vessels are thermal ablated leading to lymph accumulation, an increasing number of anti-inflammatory M2 macrophages are found in the lymphedematous tissue. Moreover, RNA-seq analysis from different human tumors shows that reduced lymphatic signature, a hallmark of lymphatic dysfunction, is associated with increased M2 and reduced M1 macrophage signatures, impacting the survival of the patients. In summary, we show that lymphatic vascular leakage promotes an immunosuppressive environment by enhancing anti-inflammatory macrophage differentiation, with relevance in clinical conditions such as inflammatory bowel diseases or cancer.

Novel genetic variants of SYK and ITGA1 related lymphangiogenesis signaling pathway predict non-small cell lung cancer survival

Although lymphangiogenesis is a vital step in lung cancer metastasis, the association between lymphangiogenesis and non-small cell lung cancer (NSCLC) survival remains unclear. Since single-nucleotide polymorphisms (SNPs) have been reported to predict NSCLC survival, we investigated associations between SNPs in lymphangiogenesis-related pathway genes and NSCLC survival in a discovery genotyping dataset of 1,185 patients from the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial and validated the findings in another genotyping dataset of 984 patients from the Harvard Lung Cancer Susceptibility Study. We evaluated associations between 34,509 genetic variants (3252 genotyped and 31,257 imputed) in 247 genes involved in lymphangiogenesis-related pathway and NSCLC survival. After validation, we finally identified two independent SNPs (SYK rs11787670 A>G and ITGA1 rs67715745 T>C) to be significantly associated with NSCLC overall survival (OS), with adjusted hazards ratios of 0.77 and 0.83 (95% confidence interval =0.66-0.90, P=7.20×10^-4) and 0.84 (95% confidence interval =0.75-0.92, P=3.50×10^-4), respectively. Moreover, an increasing number of combined protective alleles of these two SNPs was significantly associated with an improved NSCLC OS and disease-specific survival (DSS) in the PLCO dataset (P _trend=0.011 and 0.006, respectively). Furthermore, the addition of these protective alleles to the prediction model for the 5-year survival increased the time-dependent area under the curve both from 87% to 87.67% for OS (P=0.029) and from 88.54% to 89.06% for DSS (P=0.022). Subsequent expression quantitative trait loci (eQTL) functional analysis revealed that the rs11787670 G allele was significantly associated with an elevated SYK mRNA expression in normal tissues. Additional analyses suggested a suppressor role for both SYK and ITGA1 in NSCLC survival. Collectively, these findings indicated that SYK rs11787670 A>G and ITGA1 rs67715745 T>C may be independent prognostic factors for NSCLC survival once further validated.

Podoplanin is a useful prognostic marker and indicates better differentiation in lung squamous cell cancer patients? A systematic review and meta-analysis

Background

The CSC (cancer stem cell) markers often indicate poor prognosis and more cell invasion or migration of cancer patients. Podoplanin was assumed as a candidate CSC marker and predict poor prognosis among squamous cancers. Whereas, the prognostic value of podoplanin among lung squamous cancer (LUSC) patients remains controversial.

Methods

A search of databases including PubMed, Embase and Web of Science was performed. Eligible articles studying the prognostic significance of podoplanin were selected. Odds ratio and HR (hazard ratio) were used to assess the relationships between podoplanin and clinical characteristics, as well as to quantify its prognostic role. The heterogeneity was estimated by I² Statistic and P values from sensitivity analysis. Begg’s funnel plots were used to estimate possible publication bias.

Results

8 eligible studies containing 725 I-IV LUSC patients were included. Podoplanin expression showed no significant correlations with TNM stage, vascular invasion, lymphatic invasion, lymph node metastasis, pleural metastasis of tumor and gender of patients. However, podoplanin showed significant associations with better differentiation (pooled OR = 2.64, 95% CI 1.53–4.56, P = 0.0005, fixed effect) and better overall survival (HR = 2.14, 95% CI 1.45–3.15, P = 0.0001, fixed effect) and progression-free survival (HR = 1.73, 95% CI: 1.01–2.98, P = 0.05, fixed effect) of LUSC. Funnel plots illustrated no evidence of publication bias in our results.

Conclusions

Podoplanin could be a useful prognostic marker and indicates better differentiation for LUSC patients, and the value of PDPN expression as a marker for cancer stem cells in LUSC should be critically evaluated in future studies.

Genome-wide profiling reveals alternative polyadenylation of mRNA in human non-small cell lung cancer

BACKGROUND

Lung cancer is the second most common cancer with an extremely poor overall survival rate. Post-transcriptional regulation of gene expression play many important roles in human cancer, and one of the potential mechanisms underlying this is alternative mRNA maturation at its 3' untranslated regions (3'-UTRs).

METHODS

Cancer tissues and paired adjacent normal lung tissues from 26 patients diagnosed with non-small cell lung cancer (NSCLC) were analyzed by in vitro transcription-sequencing alternative polyadenylation sites (IVT-SAPAS). 41,773,101 reads in average were obtained from each paired sample. A potential regulation of Cleavage Stimulation Factor Subunit 2 (CSTF2) on 3'UTR length of genes was tested in H460 cells.

RESULTS

1439 (10.26%) genes showed up-regulated expression and 1364 (9.72%) genes showed down-regulated expression in lung cancer tissue versus normal lung tissue, and shorten 3'UTR in cancer tissue was detected in cancer tissues collected from 96.2% (25/26) patients, indicating lung cancer tend to have shortened 3'UTRs of these identified genes. KEGG analysis showed 1855 genes with shorten 3'UTR were enriched in mTOR signaling, ubiquitin mediated proteolysis and RNA degradation. Knocking down CSTF2 expression in H460 cells results in 3'UTR elongation of genes that was identified to be with shortened length in cancer tissues.

CONCLUSION

Alternative polyadenylation (APA) site-switching of 3'UTRs is prevalent in NSCLC, and CSTF2 may serve as an oncogene regulates the 3'UTR length of cancer related genes in NSCLC.

[Changes of lymphatic vessel density in lung adenocarcinoma in situ, minimally invasive adenocarcinoma, and invasive adenocarcinoma and the regulatory factors]

OBJECTIVE

To analyze the changes in tumor lymphatic vessel density (LVD) in patients with lung adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA), and invasive adenocarcinoma (IA) and explore the regulatory factors of LVD.

METHODS

Complete clinicopathological data were collected form a total of 301 patients with lung adenocarcinoma, including 28 (9.3%) with AIS, 86 (28.6%) with MIA, and 187 (62.1%) with IA. The LVD of all the adenocarcinomas were calculated after D2-40 immunohistochemical staining, and MT1-MMP and VEGF-C expression levels were also evaluated. The differences in LVD among the groups and the correlations of tumor LVD with the expressions of MT1-MMP and VEGF-C and the clinicopathological factors were analyzed.

RESULTS

The LVD differed significantly among AIS, MIA, and IA groups (P= 0.000). The LVDs was significantly correlated with the level of VEGF-C protein expression (r=0.917, P=0.009), tumor size (r= 0.686, P=0.017), lymph node metastasis (r=0.739, P=0.000), and clinical stage (r=0.874, P=0.012) of the patients.

CONCLUSIONS

Tumor lymphangiogenesis plays an important role in lung adenocarcinoma progression, and VEGF-C may promote this process.