LAPTM4B is associated with poor prognosis in NSCLC and promotes the NRF2-mediated stress response pathway in lung cancer cells

LAPTM4B counteracts ferroptosis via suppressing the ubiquitin-proteasome degradation of SLC7A11 in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a leading cause of cancer-related deaths worldwide, necessitating the identification of novel therapeutic targets. Lysosome Associated Protein Transmembrane 4B (LAPTM4B) is involved in biological processes critical to cancer progression, such as regulation of solute carrier transporter proteins and metabolic pathways, including mTORC1. However, the metabolic processes governed by LAPTM4B and its role in oncogenesis remain unknown. In this study, we conducted unbiased metabolomic screens to uncover the metabolic landscape regulated by LAPTM4B. We observed common metabolic changes in several knockout cell models suggesting of a role for LAPTM4B in suppressing ferroptosis. Through a series of cell-based assays and animal experiments, we demonstrate that LAPTM4B protects tumor cells from erastin-induced ferroptosis both in vitro and in vivo. Mechanistically, LAPTM4B suppresses ferroptosis by inhibiting NEDD4L/ZRANB1 mediated ubiquitination and subsequent proteasomal degradation of the cystine-glutamate antiporter SLC7A11. Furthermore, metabolomic profiling of cancer cells revealed that LAPTM4B knockout leads to a significant enrichment of ferroptosis and associated metabolic alterations. By integrating results from cellular assays, patient tissue samples, an animal model, and cancer databases, this study highlights the clinical relevance of the LAPTM4B-SLC7A11-ferroptosis signaling axis in NSCLC progression and identifies it as a potential target for the development of cancer therapeutics.

Long Non-Coding RNA TP73-AS1 Promotes the Development of Lung Cancer by Targeting the miR-27b-3p/LAPTM4B Axis

Purpose

Long non-coding RNA P73 antisense RNA 1T (TP73-AS1) is a newly discovered lncRNA involved in the occurrence and development of several cancers. However, its role in lung cancer has not been well investigated yet.

Methods

The expressions of TP73-AS1, microRNA-27b-3p (miR-27b-3p) and lysosomal-associated protein transmembrane-4 Beta (LAPTM4B) were detected by quantitative real-time polymerase chain reaction (qRT-PCR). The cell proliferation, apoptosis, migration and invasion were detected by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), Annexin V-FITC/PI and transwell assays, respectively. Tumor xenografts were applied to explore the role of TP73-AS1 in vivo. The target relationship was predicted by StarBase v.2.0 or TargetScan and confirmed by luciferase reporter assay. Pearson's coefficient assay was applied to assess the expression correlation between two groups. Protein expression levels were detected by Western blot.

Results

We found that TP73-AS1 was strikingly up-regulated in lung cancer tissues and cells. TP73-AS1 depletion inhibited the growth and metastasis of lung cancer cells in vitro. Furthermore, TP73-AS1 could act as an endogenous sponge by directly binding miR-27b-3p, and a notable inverse correlation between them was also discovered. Importantly, knockdown of miR-27b-3p could reverse the inhibitory effects of TP73-AS1 depletion on the growth and metastasis of lung cancer cells. Besides, LAPTM4B was directly targeted by miR-27b-3p and could be co-regulated by TP73-AS1 and miR-27b-3p in lung cancer cells. Silencing TP73-AS1 hampered tumor growth by regulating miR-27b-3p/LAPTM4B axis in vivo.

Conclusion

TP73-AS1 promoted the progression of lung cancer through regulating miR-27b-3p/LAPTM4B axis and it might be a potential target for diagnosis and treatment of lung cancer.

LAPTM4B knockdown increases the radiosensitivity of EGFR-overexpressing radioresistant nasopharyngeal cancer cells by inhibiting autophagy

Purpose

Nasopharyngeal carcinoma (NPC) is a malignant tumor that commonly occurs in southern China and Southeast Asia. Radiation therapy is the main treatment for patients with NPC, and the radioresistance of NPC is an unresolved clinical problem. This study focuses on the mechanism of NPC radioresistance and explores therapeutic targets and research directions for increasing the radiosensitivity of radioresistant cells.

Methods

We used a gradient dose model to establish radioresistant strains of 6-10B and CNE-2 human NPC cells. Plate colony formation assays were used to verify the radioresistance of the cells. We evaluated the expression of epidermal growth factor receptor (EGFR), lysosome-associated transmembrane protein 4β (LAPTM4B), Beclin1 and the autophagy-related proteins p62, LC3I, and LC3II by Western blot and observed GFP-LC3 puncta by confocal microscopy. The interaction between proteins was verified by immunofluorescence and coimmunoprecipitation analyses. Flow cytometry was performed to detect differences related to the apoptosis of radioresistant strains.

Results

The EGFR and LAPTM4B expression levels and autophagic flux were higher in radioresistant cells than in nonradioresistant cells, suggesting that EGFR and LAPTM4B are associated with autophagy levels. We observed that EGFR and LAPTM4B interact and stabilize each other in endosomes by confocal microscopy. LAPTM4B knockdown decreased the survival fraction of radioresistant cells and increased apoptosis after exposure to radiation. Coimmunoprecipitation experiments demonstrated that LAPTM4B interacts with Beclin1, which in turn promotes the initiation of autophagy.

Conclusion

This study illustrates a relationship among EGFR, LAPTM4B and autophagy in radioresistant NPC cell lines. LAPTM4B interacts with EGFR and Beclin 1, which promotes autophagy. LAPTM4B knockdown decreases radioresistance by inhibiting autophagy. This study proposes a possible mechanism for NPC radioresistance and provides a new research direction and theoretical basis for addressing the radioresistance of NPC.

LAPTM4B is a novel diagnostic and prognostic marker for lung adenocarcinoma and associated with mutant EGFR

Background

Lysosomal-associated protein transmembrane-4 beta (LAPTM4B), a novel oncogene, promotes tumorigenesis and may be a potential prognostic biomarker in several cancers. This study was to determine the clinical significance and biological roles of LAPTM4B in lung adenocarcinoma (LAC).

Methods

LAPTM4B expression was analyzed by immunohistochemistry (IHC) of 63 LAC tumors. Serum levels of LAPTM4B were measured by enzyme-linked immuosorbent assays (ELISA). The study included untreated group (n = 216), chemotherapy group (n = 29), chemotherapy efficacy group (n = 179), EGFR-TKIs group (n = 57) and 68 healthy controls. Statistical analysis was performed to explore the correlation between LAPTM4B expression and clinicopathological parameters in LAC. Kaplan-Meier analysis was performed to assess the prognostic significance of LAPTM4B in LAC. In vitro assays were performed to assess the biological roles of LAPTM4B in LAC cells. Western blotting assays were examined to identify the underlying pathways involved in the tumor-promoting role of LAPTM4B.

Results

We found LAPTM4B was upregulated in LAC tissues and high LAPTM4B expression was significantly correlated with poor prognosis. Serum LAPTM4B levels were significantly decreased after chemotherapy. Patients in invalid response group showed higher LAPTM4B levels than the valid response group. Overexpression of LAPTM4B promoted, while silencing of LAPTM4B inhibited proliferation, invasion and migration of LAC cells via PI3K/AKT and EMT signals. LAPTM4B expression level was associated with epidermal growth factor receptor (EGFR) gene mutations. In addition, LAPTM4B plays important roles in EGFR-promoted cell proliferation, migration and invasion and gefitinib-induced apoptosis.

Conclusions

Collectively, our data propose that LAPTM4B may be a cancer biomarker for LAC and a potential therapeutic target which facilitates the development of a novel therapeutic strategy against LAC.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5506-7) contains supplementary material, which is available to authorized users.

LAPTM4B facilitates tumor growth and induces autophagy in hepatocellular carcinoma

Background: Hepatocellular carcinoma (HCC) is one of the most frequent cancers and the third leading cause of cancer-related deaths. It has been reported that lysosomal associated transmembrane protein LAPTM4B expression is significantly upregulated in human cancers and closely associated with tumor initiation and progression.

Purpose: We aimed to reveal the relevance of LAPTM4B and the pathogenesis of HCC. Methods: Cell viability assessment, colony formation assay, in vivo xenograrft model, microarray, real-time PCR, immunofluorescence and western blot analysis were applied.

Results: Our results demonstrated that LAPTM4B promoted HCC cell proliferation in vitro and tumorigenesis in vivo. Additionally, upon starvation conditions, LAPTM4B facilitated cell survival, inhibited apoptosis and induced autophagic flux. Expression profiling coupled with gene ontology (GO) analysis revealed that 159 gene downregulated by LAPTM4B silencing was significantly enriched in response to nutrient and some metabolic processes. Moreover, LAPTM4B activated ATG3 transcription to modulate HCC cell apoptosis and autophagy.

Conclusion: Our findings demonstrate that LAPTM4B acts as an oncogene that promotes HCC tumorigenesis and autophagy, and indicate that LAPTM4B may be used as a novel therapeutic target for HCC treatment.

Prognostic Values of LAPTM4B-35 in Human Cancer: A Meta-analysis

Background: Lysosome-associated protein transmembrane-4β-35(LAPTM4B-35) has been observed overexpressed in multiple malignant tumors. However, the prognostic value of LAPTM4B-35 remains controversial. Therefore, we conducted a meta-analysis to evaluate the prognostic value of LAPTM4B-35 in human cancers. Methods: The relevant publications were obtained by systematically searching the PubMed, Web of Science, Embase, Wanfang, and China National Knowledge Infrastructure (CNKI) databases. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated for the prognosis value of LAPTM4B-35 for cancer patient. Results: Our result suggest that LAPTM4B-35 overexpression is significantly associated with poor overall survival (OS) (HR = 2.49, 95% CI = 1.87-3.32, p < 0.001), disease-free survival (DFS) (HR = 2.43, 95% CI = 1.35-4.35, p = 0.003), and progression-free survival (PFS) (HR = 4.12, 95% CI = 2.30-7.37, p < 0.001). Moreover, subgroup analysis revealed significant association with poor OS in lung (HR = 2.05, 95% CI = 1.37-3.06, p < 0.001), gastric carcinoma (HR = 1.88, 95% CI = 1.01-3.50, p < 0.047) and ovarian cancer (HR = 4.94, 95% CI = 1.44-16.94, p = 0.011). Conclusion: LAPTM4B-35 may be a novel predictive biomarker and a potential target for treatment.

Regulation of Eclipta prostrata L. components on cigarette smoking-induced autophagy of bronchial epithelial cells via keap1-Nrf2 pathway

Cigarette smoking extract (CSE)-induced autophagic injury has been regarded as an important contributor to the pathogenesis of lung cancer. We previously found that Eclipta prostrata L. component (CCE) reduced CSE-induced bronchial epithelial cells damage. However, the mechanism remains unknown. Human normal bronchial epithelial cells (NHBE) were exposed to CSE to establish stress model. Nrf2-siRNA and Keap1-siRNA transfection were performed. mRFP-GFP-LC3 dual fluorescence and transmission electron microscopy were used to observe the autophagic characteristics. CCE prevented CSE-induced Nrf2 transfer into cytoplasm and up-regulated Keap1 level of NHBE cells. Furthermore, CCE significantly increased p-p16, p-p21 and p-p53 phosphorylation levels in Nrf2-siRNA- or Keap1-siRNA-transfected cells. As demonstrated by transmission electron microscopy and mRFP-GFP-LC3 dual fluorescence assays, CCE mitigated autophagic injury, and also down-regulated autophagy-related Beclin-1, LC3II/LC3I ratio, Atg5 and ATF4 levels. Our findings showed the attenuation of CCE on CSE-induced NHBE cells injury was associated with Nrf-2-mediated oxidative signaling pathway.

Increased levels of LAPTM4B, VEGF and survivin are correlated with tumor progression and poor prognosis in breast cancer patients

Objective

This study explored the relationships among the expression of LAPTM4B, VEGF, and survivin and clinicopathological characteristics and prognosis in breast cancer patients.

Methods

The expression of these three molecules in 110 stage I-III breast cancer patients with clinicopathological and follow-up data was detected via immunohistochemistry. Kaplan-Meier and Cox proportional hazard regression analyses were performed to assess the prognostic significance of these markers in breast cancer. Moreover, expression levels of these markers were evaluated in 5 breast cell lines via Western blot analysis.

Results

LAPTM4B, VEGF, and survivin were over-expressed in breast cancer specimens and highly expressed in MDA-MB-231 cells. VEGF and nuclear survivin expression was significantly correlated with LAPTM4B expression, and high levels of all three were associated with a tumor size >2cm, TNM stage II+III and lymph node metastasis, which had worse impacts on overall survival and progression-free survival in breast cancer patients. A multivariate Cox analysis identified LAPTM4B over-expression as an independent prognostic marker in breast cancer.

Conclusions

These findings suggest that LAPTM4B, VEGF, and nuclear survivin expression are significantly correlated in breast cancer, which may be predictive of prognosis as well as effective therapeutic targets for new anticancer therapies.

Crocetin shifts autophagic cell survival to death of breast cancer cells in chemotherapy

The chemotherapy with fluorouracil is not always effective, in which some breast cancer cells may survive the fluorouracil treatment through enhanced autophagy. Crocetin is the major constituent of saffron, a Chinese traditional herb, which has recently found to have multiple pharmacological effects, including anticancer. However, the effects of Crocetin on the outcome of fluorouracil therapy for breast cancer have not been studied. Here, we showed that fluorouracil treatment inhibited the growth of breast cancer cells, in either a Cell Counting Kit-8 assay or an MTT assay. Inhibition of autophagy further suppressed breast cancer cell growth, suggesting that the breast cancer cells increased autophagic cell survival during fluorouracil treatment. However, Crocetin significantly increased the suppressive effects of fluorouracil on breast cancer cell growth, without affecting either cell apoptosis or autophagy. Inhibition of autophagy at the presence of Crocetin partially abolished the suppressive effects on breast cancer cell growth, suggesting that Crocetin may increase autophagic cell death in fluorouracil-treated breast cancer cells. Furthermore, Crocetin decreased Beclin-1 levels but increased ATG1 levels in fluorouracil-treated breast cancer cells. Together, these data suggest that Crocetin may shift autophagic cell survival to autophagic cell death in fluorouracil-treated breast cancer cells, possibly through modulation of the expression of ATG1 and Beclin-1.

Relationship between LAPTM4B Gene Polymorphism and Prognosis of Patients following Tumor Resection for Colorectal and Esophageal Cancers

BACKGROUND

Lysosome-associated transmembrane-4 beta (LAPTM4B) is an oncogene that participates tumorgenesis in a variety of human solid tumors, and it has two alleles named as LAPTM4B*1 and *2. The present study aimed to identify the association of LAPTM4B genotype with clinicopathological features and prognosis in colorectal and esophageal cancer patients.

METHOD

Genotypes of LAPTM4B were determined by PCR in 167 colon cancer cases (72 patients in a discovery cohort and 95 patients in a testing cohort), 160 rectal cancer cases and 164 esophageal cancer cases. Association between the LAPTM4B gene polymorphism and clinicopathological variables was calculated by Chi-square test or Fisher's exact test. Patient survival differences were calculated by the Kaplan-Meier method. Prognostic factors were determined with Log-rank test and Cox regression model.

RESULTS

LAPTM4B *1/1 was more frequently detected in colon cancer patients with lymph node metastasis and TNM III+IV stages in total colon cancer (discovery + testing cohorts). LAPTM4B *2/2 decreased in recurrent patients in total colon cancer patients (P = 0.045). Kaplan-Meier survival curves and Log-rank test showed that LAPTM4B*1 was correlated with shorter overall survival (OS) in discovery and testing cohorts of colon cancer (P = 0.0254 and 0.0292, respectively), but not in rectal and esophageal cancer cases (P = 0.7669 and 0.9356, respectively). Multivariate analysis showed that LAPTM4B genotype was an independent prognostic factor for OS in total colon cancer [P = 0.004, hazard ratio (HR) = 0.432; 95% confidence interval (CI) = 0.243-0.768], but not in rectal and esophageal cancers (P = 0.791, HR = 1.073, 95% CI = 0.638-1.804 and 0.998, HR = 1.000, 95% CI = 0.663-1.530, respectively).

CONCLUSION

These findings suggested that LAPTM4B allele *1 was a risk factor associated with poor prognosis in patients with colon cancer, but not in patients with rectal or esophageal cancers. LAPTM4B genotype status might be a useful prognostic indicator for patients that need surgical operation in colon cancer.

Early Events in the Molecular Pathogenesis of Lung Cancer

The majority of cancer-related deaths in the United States and worldwide are attributed to lung cancer. There are more than 90 million smokers in the United States who represent a significant population at elevated risk for lung malignancy. In other epithelial tumors, it has been shown that if neoplastic lesions can be detected and treated at their intraepithelial stage, patient prognosis is significantly improved. Thus, new strategies to detect and treat lung preinvasive lesions are urgently needed in order to decrease the overwhelming public health burden of lung cancer. Limiting these advances is a poor knowledge of the earliest events that underlie lung cancer development and that would constitute markers and targets for early detection and prevention. This review summarizes the state of knowledge of human lung cancer pathogenesis and the molecular pathology of premalignant lung lesions, with a focus on the molecular premalignant field that associates with lung cancer development. Lastly, we highlight new approaches and models to study genome-wide alterations in human lung premalignancy in order to facilitate the discovery of new markers for early detection and prevention of this fatal disease. Cancer Prev Res; 9(7); 518-27. ©2016 AACR.