Lysosomal transmembrane protein LAPTM4B promotes autophagy and tolerance to metabolic stress in cancer cells

Lysosomal-associated protein transmembrane 4 Beta-35 overexpression is a novel independent prognostic marker for gastric carcinoma

OBJECTIVE

The purpose of this work was to analyze the relationships between the expression status of Lysosomal-associated protein transmembrane-4 beta 35 (LAPTM4B-35) in cancerous tissues and clinicopathological characteristics and prognosis of the patients with gastric carcinoma (GC).

METHODS

The GC samples from 157 patients in a discovery cohort and 148 patients in a testing cohort with follow-up data were used to validate the feasibility of expression of LAPTM4B-35 protein in predicting GC prognosis. Immunohistochemical staining was used to determine the expression of LAPTM4B-35 protein in precancerous gastric lesions and gastric carcinomas. The correlation between the expression of LAPTM4B-35 and clinicopathologic characteristics of patients with gastric carcinoma was analyzed using chi-square test. Univariate and multivariate analyses were performed to determine the association between LAPTM4B-35 expression and prognosis.

RESULTS

LAPTM4B-35 expression was increased steadily in sequential stages of precancerous gastric lesions. Positive LAPTM4B-35 expression was more frequently detected in patients with distant metastasis (P = 0.023) and III+IV TNM stages (P = 0.042) in the discovery cohort. Kaplan-Meier survival curves and univariate analysis showed that expression of LAPTM4B-35 had a significant impact on overall survival of patients with gastric carcinoma in discovery cohort (P<0.001) and testing cohort (P = 0.001). LAPTM4B-35 expression was an independent prognostic indicator for the overall survival of patients with gastric carcinoma in both cohorts.

CONCLUSIONS

The present research demonstrated that LAPTM4B-35 over-expression was an independent factor in gastric carcinoma prognosis. LAPTM4B gene may be a useful target of interventions slowing the progression of precancerous gastric lesions and a new therapy method to improve the prognosis of gastric carcinoma.

Relationship Between LAPTM4B Gene Polymorphism and Susceptibility of Malignant Melanoma in Chinese Patients

Lysosomal-associated protein transmembrane 4 beta (LAPTM4B) is known as an oncogene associated with many human malignant tumors. There are two alleles of the gene, LAPTM4B*1 and LAPTM4B*2. Previous studies have shown that LAPTM4B polymorphism contributes to the risk of many cancers. This case-control study was to investigate the relationship between LAPTM4B gene polymorphism and susceptibility of malignant melanoma. The genotypes of LAPTM4B were determined in 617 control subjects and 220 patients with malignant melanoma by utilizing polymerase chain reaction based on specific primers. The genotypic distribution of LAPTM4B and Hardy–Weinberg equilibrium were analyzed by χ² test. Odds ratio and 95% confidence interval was calculated by unconditional logistic regression. The distributions of LAPTM4B genotypes were significantly different between melanoma patients (45.9% for *1/1, 46.4% for *1/2 and 7.7 for *2/2) and controls (54.5% for *1/1, 39.9% for *1/2 and 5.7 for *2/2). LAPTM4B *1/2 and LAPTM4B *2/2 had a 1.396-fold and 1.619-fold higher risk for melanoma occurrence than *1/1, and subjects with LAPTM4B*2 have a 1.308-fold higher risk than LAPTM4B*1 carriers. No association between LAPTM4B genotypes and gender, age, subtype, Clark level of invasion, Breslow thickness, ulceration, clinical stage, and C-KIT, BRAF gene mutation status was observed. LAPTM4B*2 is associated with the high risk of malignant melanoma and carrying LAPTM4B *2 may be a susceptible factor to Chinese melanoma patients.

BRCA1-mediated inflammation and growth activated & inhibited transition mechanisms between no-tumor hepatitis/cirrhotic tissues and HCC

To understand breast cancer 1 early onset (BRCA1)-mediated inflammation and growth activated and inhibited transition mechanisms between no-tumor hepatitis/cirrhotic tissues (HBV or HCV infection) and human hepatocellular carcinoma (HCC), BRCA1-activated different complete (all no positive correlation, Pearson correlation coefficient <0.25) and uncomplete (partly no positive correlation except BRCA1, Pearson <0.25) networks were identified in higher HCC compared with lower no-tumor hepatitis/cirrhotic tissues (HBV or HCV infection) from the corresponding BRCA1-stimulated (Pearson ≥0.25) or inhibited (Pearson ≤-0.25) overlapping molecules of Pearson and GRNInfer, respectively. This result was verified by the corresponding scatter matrix. As visualized by GO, KEGG, GenMAPP, BioCarta, and disease database integration, we proposed mainly that BRCA1-stimulated different complete network was involved in BRCA1 activation with integral to membrane killer cell lectin-like receptor C to nucleus interferon regulatory factor 5-induced inflammation, whereas the corresponding inhibited network participated in BRCA1 repression with matrix roundabout axon guidance receptor homolog 1 to plasma membrane versican-induced growth in lower no-tumor hepatitis/cirrhotic tissues (HBV or HCV infection). However, BRCA1-stimulated network contained BRCA1 activation with endothelium-specific to lysosomal transmembrane and carbamoyl synthetase to tastin, histone cluster and cyclin-induced growth, whereas the corresponding inhibited different complete network included BRCA1 repression with ovalbumin, thyroid stimulating hormone beta and Hu antigen C to cytochrome P450 to transducin-induced inflammation in higher HCC. Our BRCA1 different networks were verified by BRCA1-activated or -inhibited complete and uncomplete networks within and between no-tumor hepatitis/cirrhotic tissues (HBV or HCV infection) or (and) HCC.

Therapeutic targeting of autophagy in cancer. Part I: molecular pathways controlling autophagy

Autophagy is a process in which cells can generate energy and building materials, by degradation of redundant and/or damaged organelles and proteins. Especially during conditions of stress, autophagy helps to maintain homeostasis. In addition, autophagy has been shown to influence malignant transformation and cancer progression. The precise molecular events in autophagy are complex and the core autophagic machinery described to date consists of nearly thirty proteins. Apart from these factors that execute the process of autophagy, several signalling pathways are involved in converting internal and external stimuli into an autophagic response. In this review we provide an overview of the signalling pathways that influence autophagy, particularly in cancer cells. We will illustrate that interference with multiple of these signalling pathways can have significant effects on cancer cell survival.

Drug resistance mediated by AEG-1/MTDH/LYRIC

AEG-1/MTDH/LYRIC has been shown to promote cancer progression and development. Overexpression of AEG-1/MTDH/LYRIC correlates with angiogenesis, metastasis, and chemoresistance to various chemotherapy agents in cancer cells originating from a variety of tissues. In this chapter, we focus on the role of AEG-1/MTDH/LYRIC in drug resistance. Mechanistic studies have shown that AEG-1/MTDH/LYRIC is involved in classical oncogenic pathways including Ha-Ras, myc, NFκB, and PI3K/Akt. AEG-1/MTDH/LYRIC also promotes protective autophagy by activating AMP kinase and autophagy-related gene 5. Another reported mechanism by which AEG-1/MTDH/LYRIC regulates drug resistance is by increasing loading of multidrug resistance gene (MDR) 1 mRNA to the polysome, thereby facilitating MDR1 protein translation. More recently, a novel function for AEG-1/MTDH/LYRIC as an RNA-binding protein was elucidated, which has the potential to impact expression of drug sensitivity or resistance genes. Finally, AEG-1/MTDH/LYRIC acts in microRNA-directed gene silencing via an interaction with staphylococcal nuclease and tudor domain containing 1, a component of the RNA-induced silencing complex. Altered microRNA expression and activity induced by AEG-1/MTDH/LYRIC represent an additional way that AEG-1/MTDH/LYRIC may cause drug resistance in cancer. The multiple functions of AEG-1/MTDH/LYRIC in drug resistance highlight that it is a viable target as an anticancer agent for a wide variety of cancers.

Transcriptomic architecture of the adjacent airway field cancerization in non-small cell lung cancer

BACKGROUND

Earlier work identified specific tumor-promoting abnormalities that are shared between lung cancers and adjacent normal bronchial epithelia. We sought to characterize the yet unknown global molecular and adjacent airway field cancerization (FC) in early-stage non-small cell lung cancer (NSCLC).

METHODS

Whole-transcriptome expression profiling of resected early-stage (I-IIIA) NSCLC specimens (n = 20) with matched tumors, multiple cytologically controlled normal airways with varying distances from tumors, and uninvolved normal lung tissues (n = 194 samples) was performed using the Affymetrix Human Gene 1.0 ST platform. Mixed-effects models were used to identify differentially expressed genes among groups. Ordinal regression analysis was performed to characterize site-dependent airway expression profiles. All statistical tests were two-sided, except where noted.

RESULTS

We identified differentially expressed gene features (n = 1661) between NSCLCs and airways compared with normal lung tissues, a subset of which (n = 299), after gene set enrichment analysis, statistically significantly (P < .001) distinguished large airways in lung cancer patients from airways in cancer-free smokers. In addition, we identified genes (n = 422) statistically significantly and progressively differentially expressed in airways by distance from tumors that were found to be congruently modulated between NSCLCs and normal lung tissues. Furthermore, LAPTM4B, with statistically significantly increased expression (P < .05) in airways with shorter distance from tumors, was upregulated in human immortalized cells compared with normal bronchial epithelial cells (P < .001) and promoted anchorage-dependent and -independent lung cancer cell growth.

CONCLUSIONS

The adjacent airway FC comprises both site-independent profiles as well as gradient and localized airway expression patterns. Profiling of the airway FC may provide new insights into NSCLC oncogenesis and molecular tools for detection of the disease.

New potential therapeutic approach for the treatment of B-Cell malignancies using chlorambucil/hydroxychloroquine-loaded anti-CD20 nanoparticles

Current B-cell disorder treatments take advantage of dose-intensive chemotherapy regimens and immunotherapy via use of monoclonal antibodies. Unfortunately, they may lead to insufficient tumor distribution of therapeutic agents, and often cause adverse effects on patients. In this contribution, we propose a novel therapeutic approach in which relatively high doses of Hydroxychloroquine and Chlorambucil were loaded into biodegradable nanoparticles coated with an anti-CD20 antibody. We demonstrate their ability to effectively target and internalize in tumor B-cells. Moreover, these nanoparticles were able to kill not only p53 mutated/deleted lymphoma cell lines expressing a low amount of CD20, but also circulating primary cells purified from chronic lymphocitic leukemia patients. Their safety was demonstrated in healthy mice, and their therapeutic effects in a new model of Burkitt's lymphoma. The latter serves as a prototype of an aggressive lympho-proliferative disease. In vitro and in vivo data showed the ability of anti-CD20 nanoparticles loaded with Hydroxychloroquine and Chlorambucil to increase tumor cell killing in comparison to free cytotoxic agents or Rituximab. These results shed light on the potential of anti-CD20 nanoparticles carrying Hydroxychloroquine and Chlorambucil for controlling a disseminated model of aggressive lymphoma, and lend credence to the idea of adopting this therapeutic approach for the treatment of B-cell disorders.

Integration of autophagy and anoikis resistance in solid tumors

Macroautophagy or autophagy is a lysosome-dependent process in which enzymatic degradation and recycling of cytosolic components occurred due to stressful conditions. This cellular arrangement imparts anoikis resistance in solid tumors. Anoikis, a special form of apoptosis occurring when cells detach from the extracellular matrix, is a critical mechanism in maintaining tissue homeostasis and development. Anoikis resistance facilitates tumorigenesis and metastasis. However, the complexity of the role of autophagy in tumor is underscored by evidence that autophagy can function as both a pro-survival or pro-death depending on the context and the stimuli, which are likely exploitable for tumor therapy. This review focuses on recent progress in understanding anoikis resistance and autophagy signaling, paying particular attention to its relevance in solid tumor metastasis.

Expression of the lysosomal-associated membrane protein-1 (LAMP-1) in astrocytomas

Targeting of lysosomes is a novel therapeutic anti-cancer strategy for killing the otherwise apoptosis-resistant cancer cells. Such strategies are urgently needed for treatment of brain tumors, especially the glioblastoma, which is the most frequent and most malignant type. The aim of the present study was to investigate the presence of lysosomes in astrocytic brain tumors focussing also on the therapy resistant tumor stem cells. Expression of the lysosomal marker LAMP-1 (lysosomal-associated membrane protein-1) was investigated by immunohistochemistry in 112 formalin fixed paraffin embedded astrocytomas and compared with tumor grade and overall patient survival. Moreover, double immunofluorescence stainings were performed with LAMP-1 and the astrocytic marker GFAP and the putative stem cell marker CD133 on ten glioblastomas. Most tumors expressed the LAMP-1 protein in the cytoplasm of the tumor cells, while the blood vessels were positive in all tumors. The percentage of LAMP-1 positive tumor cells and staining intensities increased with tumor grade but variations in tumors of the same grade were also found. No association was found between LAMP-1 expression and patient overall survival in the individual tumor grades. LAMP-1/GFAP showed pronounced co-expression and LAMP-1/CD133 was co-expressed as well suggesting that tumor cells including the proposed tumor stem cells contain lysosomes. The results suggest that high amounts of lysosomes are present in glioblastomas and in the proposed tumor stem cells. Targeting of lysosomes may be a promising novel therapeutic strategy against this highly malignant neoplasm.

Impact of tumor HER2/ERBB2 expression level on HER2-targeted liposomal doxorubicin-mediated drug delivery: multiple low-affinity interactions lead to a threshold effect

Numerous targeted nanotherapeutics have been described for potential treatment of solid tumors. Although attention has focused on antigen selection and molecular design of these systems, there has been comparatively little study of how cellular heterogeneity influences interaction of targeted nanoparticles with tumor cells. Antigens, such as HER2/ERBB2, are heterogeneously expressed across different indications, across patients, and within individual tumors. Furthermore, antigen expression in nontarget tissues necessitates optimization of the therapeutic window. Understanding the performance of a given nanoparticle under different regimens of antigen expression has the ability to inform patient selection and clinical development decisions. In this work, HER2-targeted liposomal doxorubicin was used as a model-targeted nanoparticle to quantitatively investigate the effect of HER2 expression levels on delivery of doxorubicin to the nucleus. We find quantitatively greater nuclear doxorubicin delivery with increasing HER2 expression, exhibiting a threshold effect at approximately 2 × 10(5) HER2 receptors/cell. Kinetic modeling indicated that the threshold effect arises from multiple low-affinity interactions between the targeted liposome and HER2. These results support previous data showing little or no uptake into human cardiomyocytes, which express levels of HER2 below the threshold. Finally, these results suggest that HER2-targeted liposomal doxorubicin may effectively target tumors that fall below traditional definitions of HER2-positive tumors, thereby expanding the potential population of patients that might benefit from this agent.

Association of LAPTM4B gene polymorphism with nasopharyngeal carcinoma susceptibility in a Chinese population

Lysosome-associated protein transmembrane-4 beta (LAPTM4B) is a novel cancer-related gene. It has two alleles designated LAPTM4B 1 and LAPTM4B 2. Previous studies have revealed that LAPTM4B polymorphisms contribute to the risk of many cancers. The aim of this study was to investigate the association between different LAPTM4B alleles and the risk of nasopharyngeal carcinoma (NPC), one of the most common cancers in southern China. Using polymerase chain reaction (PCR) in a case-control study, we detected the LAPTM4B genotype in peripheral blood samples from 134 patients with NPC and 327 control subjects. The chi-square test was used to analyze differences of categorical variables and Hardy-Weinberg equilibrium. Odds ratios and 95 % CI were computed using an unconditional logistic regression model. The frequency of allele 2 was 26.87 % in the NPC group, which was not significantly different from that of the control group (27.98 %, P = 0.867). Using the LAPTM4B 1/1 genotype as a reference, we found that the 1/2, 2/2 and 1/2 + 2/2 genotype were also not associated with the risk of NPC. No association was observed between LAPTM4B gene polymorphisms and the risk of NPC adjusted by gender and age. The results of our study indicated that the polymorphism of LAPTM4B gene did not influence the susceptibility of NPC in the Chinese population. Large-scale studies are needed to confirm our findings.

LAPTM4B gene polymorphism and endometrial carcinoma risk and prognosis

A novel gene called LAPTM4B (lysosome-associated protein transmembrane 4 beta) plays several crucial roles in carcinogenesis. In this case-control study, we investigated the relationship between LAPTM4B gene polymorphism and susceptibility to endometrial carcinoma (EC). In an adjusted multivariate logistic regression analyses, subjects with the LAPTM4B*1/2 and *2/2 genotypes respectively exhibited 1.572-fold (95% confidence interval (CI) = 1.041-2.375) and 2.335-fold (95% CI = 1.365-3.995) increases in the risk of developing EC relative to those carrying LAPTM4B*1/1. Patients with LAPTM4B *2 had both significantly shorter overall survival (OS) and shorter disease-free survival (DFS) (both p < 0.001). Multivariate analysis showed that LAPTM4B genotype is an independent prognostic factor for OS and DFS (both p < 0.001). These results suggest that LAPTM4B polymorphisms might play an important role in the aetiology of EC.

Bufalin increases sensitivity to AKT/mTOR-induced autophagic cell death in SK-HEP-1 human hepatocellular carcinoma cells

Bufalin is the major component of Chan-Su (a traditional Chinese medicine, TCM) extracts from the venom of Bufo bufo gargarizan. In the present study, we investigated the pharmacological mechanisms of cell cycle arrest and autophagic cell death induced by bufalin in SK-HEP-1 human hepatocellular carcinoma cells in vitro. Bufalin inhibited cell survival by MTT assay and increased cell death by trypan blue exclusion assay in a concentration-dependent manner. In addition, bufalin induced G2/M phase arrest by reducing CDK1 activity. Bufalin triggered DNA fragmentation and apoptotic cell death in SK-HEP-1 cells by DNA gel electrophoresis, TUNEL and caspase-3 activity assay, while bufalin induced autophagic cell death by double-membrane vacuoles (transmission electron microscopy, TEM), acidic vesicular organelles (acridine orange staining) and cleavage of microtubule-associated protein 1 light chain 3 (LC3). Protein expression levels of cyclin A and B, CDK1, phospho-CDK1 (Thr161), Cdc25c, phospho-Cdc25c (Ser198), phospho-AKT (Thr308), phospho-AKT (Ser473), phospho‑mTOR (Ser2481) were downregulated. In contrast, protein expression levels of the Chk1, Wee1, LC3-II, Beclin-1, Atg 5, Atg 7 and Atg 12 were upregulated in SK-HEP-1 cells after bufalin treatment. Inhibition of autophagy by 3-methyladenine (an inhibitor of class III phosphatidylinositol-3 kinase; 3-MA) or bafilomycin A1 (an inhibitor of the vacuolar proton pump of lysosomes and endosomes) reduced the effect of bufalin on cell viability and enhanced the effect of bufalin on apoptosis. In conclusion, bufalin triggered autophagic cell death and G2/M phase arrest through the AKT/mTOR signaling pathway in SK-HEP-1 cells. Our findings showed that bufalin may be potentially efficacious in the treatment of human hepatocellular carcinoma.

LAPTM5 protein is a positive regulator of proinflammatory signaling pathways in macrophages

LAPTM5 (lysosomal-associated protein transmembrane 5) is a protein that is preferentially expressed in immune cells, and it interacts with the Nedd4 family of ubiquitin ligases. Recent studies in T and B cells identified LAPTM5 as a negative regulator of T and B cell receptor levels at the plasma membrane. Here we investigated the function of LAPTM5 in macrophages. We demonstrate that expression of LAPTM5 is required for the secretion of proinflammatory cytokines in response to Toll-like receptor ligands. We also show that RAW264.7 cells knocked down for LAPTM5 or macrophages from LAPTM5(-/-) mice exhibit reduced activation of NF-κB and MAPK signaling pathways mediated by the TNF receptor, as well as multiple pattern recognition receptors in various cellular compartments. TNF stimulation of LAPTM5-deficient macrophages leads to reduced ubiquitination of RIP1 (receptor-interacting protein 1), suggesting a role for LAPTM5 at the receptor-proximate level. Interestingly, we find that macrophages from LAPTM5(-/-) mice display up-regulated levels of A20, a ubiquitin-editing enzyme responsible for deubiquitination of RIP1 and subsequent termination of NF-κB activation. Our studies thus indicate that, in contrast to its negative role in T and B cell activation, LAPTM5 acts as a positive modulator of inflammatory signaling pathways and hence cytokine secretion in macrophages. They also highlight a role for the endosomal/lysosomal system in regulating signaling via cytokine and pattern recognition receptors.

Overexpression of LAPTM4B-35 is associated with poor prognosis in colorectal carcinoma

BACKGROUND

The purpose of this study was to determine whether lysosome-associated protein transmembrane-4 beta (LAPTM4B) overexpression is associated with the prognosis in patients with colorectal cancer.

METHODS

LAPTM4B expression was evaluated in colorectal cancer patients by Western blot analysis and immunohistochemistry. Univariate and multivariate analyses were performed to determine the association between LAPTM4B expression and prognosis.

RESULTS

Among the 136 patients with colorectal cancer, 51 patients had low LAPTM4B expression, and 85 patients had high LAPTM4B expression. The sensitivity and specificity of LAPTM4B overexpression were 62.5% and 100%, respectively. The 5-year overall survival (OS) rates for patients with high and low LAPTM4B expression were 37.38% and 98.04%, respectively (hazard ratio = 22.774; 95% confidence interval [CI], 5.287-98.091; P < .0001). The 5-year disease-free survival rate was 21.15% for patients in the high-expression group and 91.82% for patients in the low-expression group (hazard ratio = 11.674; 95% CI, 3.562-38.263; P < .0001).

CONCLUSIONS

LAPTM4B overexpression is an independent factor in colorectal cancer prognosis, and it may be an important potential biomarker.

The amplified cancer gene LAPTM4B promotes tumor growth and tolerance to stress through the induction of autophagy

Autophagy is a fundamental salvage pathway that encapsulates damaged cellular components and delivers them to the lysosome for degradation and recycling. This pathway usually conducts a protective cellular response to nutrient deprivation and various stresses. Tumor cells live with metabolic stress and use autophagy for their survival during tumor progression and metastasis. Genomic instability in tumor cells may result in amplification of crucial gene(s) for autophagy and upregulate the autophagic pathway. We demonstrate that a cancer-associated gene, LAPTM4B, plays an important role in lysosomal functions and is critical for autophagic maturation. Its amplification and overexpression promote autophagy, which renders tumor cells resistant to metabolic and genotoxic stress and results in more rapid tumor growth.