Mucin 1 (MUC1) is a novel partner for MAL2 in breast carcinoma cells

Simple recombinant monoclonal antibody production from Escherichia coli

Antibodies are valuable biological reagents used in a wide range of discovery research, biotechnology, diagnostic and therapeutic applications. Currently, both commercial and laboratory-scale antibody production is reliant on expression from mammalian cells, which can be time-consuming and requires the use of specialist facilities and costly growth reagents. Here, we describe a simple, rapid and cheap method for producing and isolating functional monoclonal antibodies and antibody fragments from bacterial cells that can be used in a range of laboratory applications. This simple method only requires access to basic microbial cell culture and molecular biology equipment, making scalable in-house antibody production accessible to the global diagnostics, therapeutics and molecular bioscience research communities.

TPD52 as a Potential Prognostic Biomarker and its Correlation with Immune Infiltrates in Uterine Corpus Endometrial Carcinoma: Bioinformatic Analysis and Experimental Verification

BACKGROUND

Aberrant expression of tumor protein D52 (TPD52) is associated with some tumors. The role of TPD52 in uterine corpus endometrial carcinoma (UCEC) remains uncertain.

OBJECTIVE

We aimed to investigate the involvement of TPD52 in the pathogenesis of UCEC.

METHODS

We employed bioinformatics analysis and experimental validation in our study.

RESULTS

Our findings indicated that elevated TPD52 expression in UCEC was significantly associated with various clinical factors, including clinical stage, race, weight, body mass index (BMI), histological type, histological grade, surgical approach, and age (p < 0.01). Furthermore, high TPD52 expression was a predictor of poorer overall survival (OS), progress-free survival (PFS), and disease-specific survival (DSS) (p = 0.011, p = 0.006, and p = 0.003, respectively). TPD52 exhibited a significant correlation with DSS (HR: 2.500; 95% CI: 1.153-5.419; p = 0.02). TPD52 was involved in GPCR ligand binding and formation of the cornified envelope in UCEC. Moreover, TPD52 expression was found to be associated with immune infiltration, immune checkpoints, tumor mutation burden (TMB)/ microsatellite instability (MSI), and mRNA stemness indices (mRNAsi). The somatic mutation rate of TPD52 in UCEC was 1.9%. A ceRNA network of AC011447.7/miR-1-3p/TPD52 was constructed. There was excessive TPD52 protein expression. The upregulation of TPD52 expression in UCEC cell lines was found to be statistically significant.

CONCLUSION

TPD52 is upregulated in UCEC and may be a useful patent for prognostic biomarkers of UCEC, which may have important value for clinical treatment and supervision of UCEC patients.

Research advances of MAL family members in tumorigenesis and tumor progression (Review)

The myelin and lymphocyte protein (MAL) family is a novel gene family first identified and characterized in 2002. This family is comprised of seven members, including MAL, MAL2, plasmolipin, MALL, myeloid differentiation‑associated marker (MYADM), MYADML2 and CMTM8, which are located on different chromosomes. In addition to exhibiting extensive activity during transcytosis, the MAL family plays a vital role in the neurological, digestive, respiratory, genitourinary and other physiological systems. Furthermore, the intimate association between MAL and the pathogenesis, progression and metastasis of malignancies, attributable to several mechanisms such as DNA methylation has also been elucidated. In the present review, an overview of the structural and functional properties of the MAL family and the latest research findings regarding the relationship between several MAL members and various cancers is provided. Furthermore, the potential clinical and scientific significance of MAL is discussed and directions for future research are summarized.

The MAL Family of Proteins: Normal Function, Expression in Cancer, and Potential Use as Cancer Biomarkers

The MAL family of integral membrane proteins consists of MAL, MAL2, MALL, PLLP, CMTM8, MYADM, and MYADML2. The best characterized members are elements of the machinery that controls specialized pathways of membrane traffic and cell signaling. This review aims to help answer the following questions about the MAL-family genes: (i) is their expression regulated in cancer and, if so, how? (ii) What role do they play in cancer? (iii) Might they have biomedical applications? Analysis of large-scale gene expression datasets indicated altered levels of MAL-family transcripts in specific cancer types. A comprehensive literature search provides evidence of MAL-family gene dysregulation and protein function repurposing in cancer. For MAL, and probably for other genes of the family, dysregulation is primarily a consequence of gene methylation, although copy number alterations also contribute to varying degrees. The scrutiny of the two sources of information, datasets and published studies, reveals potential prognostic applications of MAL-family members as cancer biomarkers-for instance, MAL2 in breast cancer, MAL2 and MALL in pancreatic cancer, and MAL and MYADM in lung cancer-and other biomedical uses. The availability of validated antibodies to some MAL-family proteins sanctions their use as cancer biomarkers in routine clinical practice.

Targeting KK-LC-1 inhibits malignant biological behaviors of triple-negative breast cancer

BACKGROUND

Cancer/testis antigens (CTAs) participate in the regulation of malignant biological behaviors in breast cancer. However, the function and mechanism of KK-LC-1, a member of the CTA family, in breast cancer are still unclear.

METHODS

Bioinformatic tools, immunohistochemistry, and western blotting were utilized to detect the expression of KK-LC-1 in breast cancer and to explore the prognostic effect of KK-LC-1 expression in breast cancer patients. Cell function assays, animal assays, and next-generation sequencing were utilized to explore the function and mechanism of KK-LC-1 in the malignant biological behaviors of triple-negative breast cancer. Small molecular compounds targeting KK-LC-1 were also screened and drug susceptibility testing was performed.

RESULTS

KK-LC-1 was significantly highly expressed in triple-negative breast cancer tissues than in normal breast tissues. KK-LC-1 high expression was related to poor survival outcomes in patients with breast cancer. In vitro studies suggested that KK-LC-1 silencing can inhibit triple-negative breast cancer cell proliferation, invasion, migration, and scratch healing ability, increase cell apoptosis ratio, and arrest the cell cycle in the G0-G1 phase. In vivo studies have suggested that KK-LC-1 silencing decreases tumor weight and volume in nude mice. Results showed that KK-CL-1 can regulate the malignant biological behaviors of triple-negative breast cancer via the MAL2/MUC1-C/PI3K/AKT/mTOR pathway. The small-molecule compound Z839878730 had excellent KK-LC-1 targeting ability and cancer cell killing ability. The EC50 value was 9.7 μM for MDA-MB-231 cells and 13.67 µM for MDA-MB-468 cells. Besides, Z839878730 has little tumor-killing effect on human normal mammary epithelial cells MCF10A and can inhibit the malignant biological behaviors of triple-negative breast cancer cells by MAL2/MUC1-C/PI3K/AKT/mTOR pathway.

CONCLUSIONS

Our findings suggest that KK-LC-1 may serve as a novel therapeutic target for triple-negative breast cancer. Z839878730, which targets KK-LC-1, presents a new path for breast cancer clinical treatment.

Identification of epigenetic dysregulation gene markers and immune landscape in kidney renal clear cell carcinoma by comprehensive genomic analysis

Kidney cancer is one the most lethal cancers of the urinary system, but current treatments are limited and its prognosis is poor. This study focused on kidney renal clear cell carcinoma (KIRC) and analyzed the relationship between epigenetic alterations and KIRC prognosis, and explored the prognostic significance of these findings in KIRC patients. Based on multi-omics data, differentially expressed histone-modified genes were identified using the R package limma package. Gene enhancers were detected from data in the FANTOM5 database. Gene promoters were screened using the R package ChIPseeker, and the Bumphunter in the R package CHAMP was applied to screen differentially methylated regions (DMR). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and Gene Ontology (GO) functional enrichment analysis of genes was performed using the R package clusterProfiler. We identified 51 dysregulated epigenetic protein coding genes (epi-PCGs) from 872 epi-PCGs, and categorized three molecular subtypes (C1, C2, and C3) of KIRC samples with significantly different prognosis. Notably, among the three molecular subtypes, we found a markedly differential immune features in immune checkpoints, cytokines, immune signatures, and immune cell distribution. C2 subtype had significantly lower enrichment score of IFNγ, cytotoxic score (CYT), and angiogenesis. In addition, an 8-gene signature containing 8 epi-PCGs (ETV4, SH2B3, FATE1, GRK5, MALL, HRH2, SEMA3G, and SLC10A6) was developed for predicting KIRC prognosis. Prognosis of patients with a high 8-gene signature score was significantly worse than those with a low 8-gene signature score, which was also validated by the independent validation data. The 8-gene signature had a better performance compared with previous signatures of KIRC. Overall, this study highlighted the important role of epigenetic regulation in KIRC development, and explored prognostic epi-PCGs, which may provide a guidance for exploiting further pathological mechanisms of KIRC and for developing novel drug targets.

Multi-Omics Analysis of the Therapeutic Value of MAL2 Based on Data Mining in Human Cancers

Recent studies have reported that T-cell differentiation protein 2 (MAL2) is an important regulator in cancers. Here, we downloaded data from multiple databases to analyze MAL2 expression and function in pan-cancers, especially in ovarian cancer (OC). Gene Expression Profiling Interactive Analysis (GEPIA) databases was used to examine MAL2 expression in 13 types of cancer. Kaplan–Meier plotter database was used to analyze the overall survival rate of MAL2 in pan-cancers. The Catalog of Somatic Mutations in Cancer (COSMIC), cBioPortal, and UCSC databases were used to examine MAL2 mutation in human cancers. Metascape, STRING, and GeneMANIA websites were used to explore MAL2 function in OC. Furthermore, ggplot2 package and ROC package were performed to analyze hub gene expression and undertake receiver operating characteristic (ROC) analysis. Drug sensitivity of MAL2 in OC was examined by the GSCALite database. In order to verify the results from databases above, real-time quantitative polymerase chain reaction (qRT-PCR) and western blotting were conducted to detect the expression of MAL2 in OC cells. CRISPR/Cas9 system was used to knockout the MAL2 gene in the OC cell lines HO8910 and OVCAR3, using specific guide RNA targeting the exons of MAL2. Then, we performed proliferation, colony formation, migration, and invasion assays to investigate the impact of MAL2 in OC cell lines in vivo and in vitro. Epithelial-mesenchymal transition (EMT)-associated biomarkers were significantly altered in vitro via western blotting and qRT-PCR. Taken together, we observed that MAL2 was remarkably dysregulated in multiple cancers and was related to patient overall survival (OS), mutation, and drug sensitivity. Furthermore, experimental results showed that MAL2 deletion negatively regulated the proliferation, migration, invasion, and EMT of OC, indicating that MAL2 is a novel oncogene that can activate EMT, significantly promote both the proliferation and migration of OC in vitro and in vivo, and provide new clues for treatment strategies.

Myelin and lymphocyte protein 2 regulates cell proliferation and metastasis through the Notch pathway in prostate adenocarcinoma

Background

Myelin and lymphocyte protein 2 (MAL2) is a proven oncogene in some human tumors. However, currently, little is known about the function of MAL2 in prostate adenocarcinoma (PRAD). This study sought to investigate the role of MAL2 on PRAD progression.

Methods

MAL2 expression in PRAD was first analyzed by the Gene Expression Profiling Interactive Analysis (GEPIA) database. The reverse transcription-quantitative polymerase chain reaction (RT-qPCR) assay and Western blot assay were used to detect the expression of MAL2 in PRAD tissues and cell lines. Additionally, immunohistochemistry (IHC) straining was used to detect the expression of MAL2 in PRAD pathological tissues. The Cell Counting Kit-8 (CCK-8) assay, clone formation assay and Flow cytometry were performed to investigate the effect of MAL2 on PRAD cell proliferation and cell apoptosis. Cell migration and invasion were measured by Transwell assay. The effect of MAL2 on epithelial-mesenchymal transition (EMT) progression and the Notch signaling pathway in PRAD was also investigated.

Results

MAL2 was discovered to be obviously upregulated in PRAD tissues and cell lines. The upregulation of MAL2 was closely associated with tumor, nodes and metastases (TNM) stage, the Gleason score and metastasis of PRAD patients, and affected the prognosis of PRAD patients. Functionally, the depletion of MAL2 suppressed cell proliferation, migration, invasion, and EMT progression, and promoted cell apoptosis of PRAD cells. In an in vivo experiment, MAL2 knockdown significantly suppressed tumor growth in mice. Further, inhibiting the Notch pathway reversed the effect of MAL2 knockdown on PRAD progression.

Conclusions

In sum, MAL2 was found to be upregulated in PRAD, and appears to act as a carcinogen in PRAD. Additionally, MAL2 appears to regulate PRAD progression through the Notch signaling pathway.

Stoichiogenomics reveal oxygen usage bias, key proteins and pathways associated with stomach cancer

Stomach cancer involves hypoxia-specific microenvironments. Stoichiogenomics explores environmental resource limitation on biological macromolecules in terms of element usages. However, the patterns of oxygen usage by proteins and the ways that proteins adapt to a cancer hypoxia microenvironment are still unknown. Here we compared the oxygen and carbon contents ([C]) between proteomes of stomach cancer (hypoxia) and two stomach glandular cells (normal). Key proteins, genome locations, pathways, and functional dissection associated with stomach cancer were also studied. An association of oxygen content ([O]) and protein expression level was revealed in stomach cancer and stomach glandular cells. For differentially expressed proteins (DEPs), oxygen contents in the up regulated proteins were3.2%higherthan that in the down regulated proteins in stomach cancer. A total of 1,062 DEPs were identified; interestingly none of these proteins were coded on Y chromosome. The up regulated proteins were significantly enriched in pathways including regulation of actin cytoskeleton, cardiac muscle contraction, pathway of progesterone-mediated oocyte maturation, etc. Functional dissection of the up regulated proteins with high oxygen contents showed that most of them were cytoskeleton, cytoskeleton associated proteins, cyclins and signaling proteins in cell cycle progression. Element signature of resource limitation could not be detected in stomach cancer for oxygen, just as what happened in plants and microbes. Unsaved use of oxygen by the highly expressed proteins was adapted to the rapid growth and fast division of the stomach cancer cells. In addition, oxygen usage bias, key proteins and pathways identified in this paper laid a foundation for application of stoichiogenomics in precision medicine.

On The Role of Myelin and Lymphocyte Protein (MAL) In Cancer: A Puzzle With Two Faces

Myelin and lymphocyte protein (MAL) is an integral membrane protein constituent of lipid rafts, and it is implicated in apical transport of proteins in polarized epithelial cells. However, beyond the involvement of MAL in apical sorting and as its function as a raft stabilizer, it is still not totally clear how MAL participates in cell proliferating processes. More controversial and interesting is the fact that MAL has been implicated in carcinogenesis in two opposite ways. First, this protein is overexpressed in ovarian cancer and some kinds of lymphomas where it seems to favor cancer progression. Conversely, it has been reported that downregulation of the MAL gene by promoter hypermethylation is a hallmark of several adenocarcinomas. So far, there is not enough experimental evidence to help us understand this phenomenon, and no MAL mutations or MAL isoforms have been associated with these opposite functions. This review provides an updated summary of the structure and functions of MAL, and we will discuss the possible mechanisms underlying its roles as a tumor suppressor and a tumor progression factor.

MiR-129 regulates growth and invasion by targeting MAL2 in papillary thyroid carcinoma

MAL2, a member of the MAL proteolipid family, is essential for raft-mediated transport. In this study, we investigated the roles and underlying mechanism of MAL2 in the development of papillary thyroid carcinoma (PTC). Up-regulation of MAL2 was found in human PTC tissues and significantly correlated with poor overall survival (OS). Knockdown of MAL2 dramatically suppressed PTC cell proliferation and invasion in vitro and inhibited tumor growth in vivo. We further found that miR-129 suppressed the expression of MLA through directly binding to the 3' untranslated region (3' UTR). While forced miR-129 expression suppressed growth and invasion of PTC cells, re-expression of MAL2 rescued these effects. Taken together, our data indicated that MAL2 acted as an oncogene and was negatively regulated by miR-129, supporting the potential therapeutic strategy against PTC by targeting miR-129-MAL2 axis.

The four-transmembrane protein MAL2 and tumor protein D52 (TPD52) are highly expressed in colorectal cancer and correlated with poor prognosis

The four-transmembrane protein MAL2 and tumor protein D52 (TPD52) have been shown to be involved in tumorigenesis of various cancers. However, their roles in colorectal cancer (CRC) remain unclear. In this study, we explored the expressions of MAL2 and TPD52 in tumor specimens resected from 123 CRC patients and the prognostic values of the two proteins in CRC. Immunohistochemical analyses showed that MAL2 (P<0.001) and TPD52 (P<0.001) were significantly highly expressed in primary carcinoma tissues compared with adjacent non-cancerous mucosa tissues. And TPD52 exhibited frequent overexpression in liver metastasis tissues relative to primary carcinoma tissues (P = 0.042), while MAL2 in lymphnode and liver metastasis tissues showed no significant elevation. Real-time quantitative PCR (RT-qPCR) showed the identical results. Correlation analyses by Pearson's chi-square test demonstrated that MAL2 in tumors was positively correlated with tumor status (pathological assessment of regional lymph nodes (pN, P = 0.024)), and clinic stage (P = 0.017). Additionally, the expression of TPD52 was detected under the same condition and was shown to be positively correlated withtumor status (pathological assessment of the primary tumor (pT, P = 0.035), distant metastasis (pM, P = 0.001)) and CRC clinicopathology(P = 0.024). Kaplan-Meier survival curves indicated that positive MAL2 (P<0.001) and TPD52 (P<0.001) expressions were associated with poor overall survival (OS) in CRC patients. Multivariate analysis showed that MAL2 and TPD52 expression was an independent prognostic factor for reduced OS of CRC patients. Moreover, overexpression of TPD52 in CRC SW480 cells showed an increased cell migration (P = 0.023) and invasion (P = 0.012) through inducing occurrence of epithelial-mesenchymal transition (EMT) and activating focal adhesion kinase (FAK)-mediated integrin signalling and PI3K⁄Akt signalling.Whereas TPD52-depleted cells showed the reverse effect. These data suggested that MAL2 and TPD52 might be potential biomarkers for clinical prognosis and might be a promising therapeutic target for CRC.

MUC1 (CD227): a multi-tasked molecule

Mucin 1 (MUC1 [CD227]) is a high-molecular weight (>400 kDa), type I membrane-tethered glycoprotein that is expressed on epithelial cells and extends far above the glycocalyx. MUC1 is overexpressed and aberrantly glycosylated in adenocarcinomas and in hematological malignancies. As a result, MUC1 has been a target for tumor immunotherapeutic studies in mice and in humans. MUC1 has been shown to have anti-adhesive and immunosuppressive properties, protects against infections, and is involved in the oncogenic process as well as in cell signaling. In addition, MUC1 plays a key role in the reproductive tract, in the immune system (affecting dendritic cells, monocytes, T cells, and B cells), and in chronic inflammatory diseases. Evidence for all of these roles for MUC1 is discussed herein and demonstrates that MUC1 is truly a multitasked molecule.

Serine/threonine kinase 16 and MAL2 regulate constitutive secretion of soluble cargo in hepatic cells

MAL2 (myelin and lymphocyte protein 2) is thought to regulate at least two steps in the hepatic apical transcytotic pathway. As vesicle budding and delivery at each step are driven by complex machineries, we predicted that MAL2 participates in several large protein complexes with multiple binding partners. To identify novel MAL2 interactors, we performed split-ubiquitin yeast two-hybrid assays and identified STK16 (serine/threonine kinase 16) as a putative interactor which we verified morphologically and biochemically. As STK16 is a Golgi-associated constitutively active kinase implicated in regulating secretion and because of the massive constitutive secretory capacity of hepatic cells, we tested whether MAL2 and STK16 function in secretion. Expression of a dominant-negative kinase-dead STK16 mutant (E202A) or knockdown of MAL2 impaired secretion that correlated with decreased expression of albumin and haptoglobin. By using 19°C temperature blocks and lysosome deacidification, we determined that E202A expression or MAL2 knockdown did not interfere with albumin synthesis or processing, but led to albumin lysosomal degradation. We conclude that MAL2 and the constitutively active STK16 function to sort secretory soluble cargo into the constitutive secretory pathway at the TGN (trans-Golgi network) in polarized hepatocytes.

Identification of PLP2 and RAB5C as novel TPD52 binding partners through yeast two-hybrid screening

Tumor protein D52 (TPD52) is overexpressed in different cancers, but its molecular functions are poorly defined. A large, low-stringency yeast two-hybrid screen using full-length TPD52 bait identified known partners (TPD52, TPD52L1, TPD52L2, MAL2) and four other preys that reproducibly bound TPD52 and TPD52L1 baits (PLP2, RAB5C, GOLGA5, YIF1A). PLP2 and RAB5 interactions with TPD52 were confirmed in pull down assays, with interaction domain mapping experiments indicating that both proteins interact with a novel binding region of TPD52. This study provides insights into TPD52 functions, and ways to maximise the efficiency of low-stringency yeast two-hybrid screens.

Tumor protein D52 controls trafficking of an apical endolysosomal secretory pathway in pancreatic acinar cells

Zymogen granule (ZG) formation in acinar cells involves zymogen cargo sorting from trans-Golgi into immature secretory granules (ISGs). ISG maturation progresses by removal of lysosomal membrane and select content proteins, which enter endosomal intermediates prior to their apical exocytosis. Constitutive and stimulated secretion through this mechanism is termed the constitutive-like and minor-regulated pathways, respectively. However, the molecular components that control membrane trafficking within these endosomal compartments are largely unknown. We show that tumor protein D52 is highly expressed in endosomal compartments following pancreatic acinar cell stimulation and regulates apical exocytosis of an apically directed endolysosomal compartment. Secretion from the endolysosomal compartment was detected by cell-surface antigen labeling of lysosome-associated membrane protein LAMP1, which is absent from ZGs, and had incomplete overlap with surface labeling of synaptotagmin 1, a marker of ZG exocytosis. Although culturing (16-18 h) of isolated acinar cells is accompanied by a loss of secretory responsiveness, the levels of SNARE proteins necessary for ZG exocytosis were preserved. However, levels of endolysosomal proteins D52, EEA1, Rab5, and LAMP1 markedly decreased with culture. When D52 levels were restored by adenoviral delivery, the levels of these regulatory proteins and secretion of both LAMP1 (endolysosomal) and amylase was strongly enhanced. These secretory effects were absent in alanine and aspartate substitutions of serine 136, the major D52 phosphorylation site, and were inhibited by brefeldin A, which does not directly affect the ZG compartment. Our results indicate that D52 directly regulates apical endolysosomal secretion and are consistent with previous studies, suggesting that this pathway indirectly regulates ZG secretion of digestive enzymes.

MAL2 expression predicts distant metastasis and short survival in pancreatic cancer

BACKGROUND

Pancreatic cancer is associated with a devastating prognosis, partially because of its aggressive metastatic ability. Identification of prognostic markers of metastasis would be useful in the clinical management of postoperative patients with pancreatic cancer. Mal, T-cell differentiation protein 2 (MAL2) has been identified as a molecule predictive of metastases; the clinical relevance of MAL2 in pancreatic cancer is unknown.

METHODS

Orthotopic human pancreatic cancer xenografts from the pancreatic cancer cell line SUIT-2 were established in nude mice. Only liver metastasis was harvested and cultured. These metastatic cycles were repeated 5 times to establish a highly metastatic cell line, termed metastatic SUIT-2 (MS). We investigated proliferation and motility of MS cells compared with those of the parent SUIT-2. Microarray analysis was performed to investigate differences in gene expression. We also performed immunohistochemical analysis of 89 formalin-fixed, paraffin-embedded human pancreatic cancer tissue samples to investigate the clinical significance of MAL2 expression.

RESULTS

MS cells showed a greater metastatic rate after orthotopic implantation than parental SUIT-2. MS cells had increased motility but decreased proliferation compared with parental SUIT-2. Microarray analyses showed that 26 genes were significantly upregulated (>10-fold) in MS cells compared with parental SUIT-2, particularly MAL2 expression. Immunohistochemical analysis showed that high expression of MAL2 was associated with a lesser survival of postoperative patients (P = .03) and a high rate of distant metastasis (P = .008).

CONCLUSION

We characterized a newly established pancreatic cancer cell line with highly metastatic potential. MAL2 is a promising predictive marker for distant metastasis and short survival in patients with resected pancreatic cancer.

MAL, but not MAL2, expression promotes the formation of cholesterol-dependent membrane domains that recruit apical proteins

Our recent studies have been aimed at understanding the mechanisms regulating apical protein sorting in polarized epithelial cells. In particular, we have been investigating how lipid rafts serve to sort apical proteins in the biosynthetic pathway. The recent findings that lipid domains are too small or transient to host apically destined cargo have led to newer versions of the hypothesis that invoke proteins required for lipid domain coalescence and stabilization. MAL (myelin and lymphocyte protein) and its highly conserved family member, MAL2, have emerged as possible regulators of this process in the direct and indirect apical trafficking pathways respectively. To test this possibility, we took a biochemical approach. We determined that MAL, but not MAL2, self-associates, forms higher-order cholesterol-dependent complexes with apical proteins and promotes the formation of detergent-resistant membranes that recruit apical proteins. Such biochemical properties are consistent with a role for MAL in raft coalescence and stabilization. These findings also support a model whereby hydrophobic mismatch between the long membrane-spanning helices of MAL and the short-acyl-chain phospholipids in the Golgi drive formation of lipid domains rich in raft components that are characterized by a thicker hydrophobic core to alleviate mismatch.

An in vitro model that recapitulates the epithelial to mesenchymal transition (EMT) in human breast cancer

The epithelial to mesenchymal transition (EMT) is a developmental program in which epithelial cells down-regulate their cell-cell junctions, acquire spindle cell morphology and exhibit cellular motility. In human breast cancer, invasion into surrounding tissue is the first step in metastatic progression. Here, we devised an in vitro model using selected cell lines, which recapitulates many features of EMT as observed in human breast cancer. By comparing the gene expression profiles of claudin-low breast cancers with the experimental model, we identified a 9-gene signature characteristic of EMT. This signature was found to distinguish a series of breast cancer cell lines that have demonstrable, classical EMT hallmarks, including loss of E-cadherin protein and acquisition of N-cadherin and vimentin expression. We subsequently developed a three-dimensional model to recapitulate the process of EMT with these cell lines. The cells maintain epithelial morphology when encapsulated in a reconstituted basement membrane, but undergo spontaneous EMT and invade into surrounding collagen in the absence of exogenous cues. Collectively, this model of EMT in vitro reveals the behaviour of breast cancer cells beyond the basement membrane breach and recapitulates the in vivo context for further investigation into EMT and drugs that may interfere with it.

MAL2 and tumor protein D52 (TPD52) are frequently overexpressed in ovarian carcinoma, but differentially associated with histological subtype and patient outcome

BACKGROUND

The four-transmembrane MAL2 protein is frequently overexpressed in breast carcinoma, and MAL2 overexpression is associated with gain of the corresponding locus at chromosome 8q24.12. Independent expression microarray studies predict MAL2 overexpression in ovarian carcinoma, but these had remained unconfirmed. MAL2 binds tumor protein D52 (TPD52), which is frequently overexpressed in ovarian carcinoma, but the clinical significance of MAL2 and TPD52 overexpression was unknown.

METHODS

Immunohistochemical analyses of MAL2 and TPD52 expression were performed using tissue microarray sections including benign, borderline and malignant epithelial ovarian tumours. Inmmunohistochemical staining intensity and distribution was assessed both visually and digitally.

RESULTS

MAL2 and TPD52 were significantly overexpressed in high-grade serous carcinomas compared with serous borderline tumours. MAL2 expression was highest in serous carcinomas relative to other histological subtypes, whereas TPD52 expression was highest in clear cell carcinomas. MAL2 expression was not related to patient survival, however high-level TPD52 staining was significantly associated with improved overall survival in patients with stage III serous ovarian carcinoma (log-rank test, p < 0.001; n = 124) and was an independent predictor of survival in the overall carcinoma cohort (hazard ratio (HR), 0.498; 95% confidence interval (CI), 0.34-0.728; p < 0.001; n = 221), and in serous carcinomas (HR, 0.440; 95% CI, 0.294-0.658; p < 0.001; n = 182).

CONCLUSIONS

MAL2 is frequently overexpressed in ovarian carcinoma, and TPD52 overexpression is a favourable independent prognostic marker of potential value in the management of ovarian carcinoma patients.

The formin INF2 regulates basolateral-to-apical transcytosis and lumen formation in association with Cdc42 and MAL2

Transcytosis is a widespread pathway for apical targeting in epithelial cells. MAL2, an essential protein of the machinery for apical transcytosis, functions by shuttling in vesicular carriers between the apical zone and the cell periphery. We have identified INF2, an atypical formin with actin polymerization and depolymerization activities, which is a binding partner of MAL2. MAL2-positive vesicular carriers associate with short actin filaments during transcytosis in a process requiring INF2. INF2 binds Cdc42 in a GTP-loaded-dependent manner. Cdc42 and INF2 regulate MAL2 dynamics and are necessary for apical transcytosis and the formation of lateral lumens in hepatoma HepG2 cells. INF2 and MAL2 are also essential for the formation of the central lumen in organotypic cultures of epithelial MDCK cells. Our results reveal a functional mechanism whereby Cdc42, INF2, and MAL2 are sequentially ordered in a pathway dedicated to the regulation of transcytosis and lumen formation.