MAP17 inhibits Myc-induced apoptosis through PI3K/AKT pathway activation

Exosomal LINC00853 promotes progression of gastric cancer via the MAP17/PDZK1/AKT signaling pathway

Although rare, there is ongoing research into biomarkers that predict the onset and recurrence of gastric cancer, particularly focusing on substances found in exosomes. Long non-coding RNAs (lncRNAs) have garnered attention for their potential in diagnosing gastric cancer. This study investigates the role of lncRNAs in gastric cancer, focusing on their presence in exosomes as potential biomarkers for the disease's onset and recurrence. We utilized the ArrayStar Human LncRNA array 2.0 to analyze lncRNA expression in tissues from early-stage gastric cancer patients. Our analysis highlighted LINC00853, which was significantly upregulated in cancer tissues and implicated in promoting epithelial-mesenchymal transition via the MAP17/PDZK1/AKT pathway. Functional studies on AGS and MKN74 gastric cancer cell lines demonstrated that LINC00853 facilitates cell proliferation, invasion, and migration. Additionally, RNA immunoprecipitation and electrophoretic mobility shift assays confirmed LINC00853 interaction with MAP17. Importantly, LINC00853 was also detected in exosomes from both patient samples and cell lines, and its downregulation led to decreased tumorigenicity in AGS cells. These findings suggest that both cellular and exosomal LINC00853 contribute to gastric cancer pathogenesis and may serve as valuable biomarkers for the disease.

MAP17 Expression in Colorectal Cancer Is a Prognostic Factor for Disease Recurrence and Dismal Prognosis Already in Early Stage Disease

BACKGROUND

Disease recurrence in colorectal cancer constitutes a major cause of significant cancer-associated morbidity and mortality. MAP17 is a small protein, and its overexpression in malignant tumors has been correlated with aggressive tumor phenotypes. The aim of the present study was to investigate the expression patterns of MAP17 in colorectal cancer specimens and to assess its clinical significance.

PATIENTS AND METHODS

Surgical specimens of 111 patients with primary resectable colorectal cancer constituted the study population. Expression of MAP17 was assessed by immunohistochemistry, and the results were correlated with clinical and survival data.

RESULTS

MAP17 was expressed in cancer cells and endothelial cells of tumor blood vessels. Expression of MAP17 more than 10% was correlated with advanced disease stage (p < 0.001), higher T classification (p = 0.007), the presence of lymph node metastasis (p < 0.001), vascular (p = 0.013) and perineural invasion (p = 0.012). Patients exhibiting MAP17 expression of more than 30% in cancer cells compared to those expressing MAP17 less than 10% demonstrated a significantly worse 3-year progression-free survival (35.2 vs. 91%, p < 0.001) and 5-year overall survival (40.8 vs. 91%, p < 0.001). Cox regression analysis confirmed MAP17 expression of more than 30% as a prognostic marker of progression free survival (HR 0.136, 95% CI = 0.056-0.329, p < 0.001) and overall survival (HR 0.144 [95% CI) = 0.049-0.419, p < 0.001) independent of other clinicopathological characteristics. Statistically significantly worse 3-year progression-free survival and 5-year overall survival was demonstrated in the subgroup analysis of patients with early stage cancer only and high expression of MAP17.

CONCLUSIONS

High MAP17 expression in patients with colorectal cancer is a significant risk factor for cancer-associated morbidity and mortality already in early stage disease.

Hypoxia-dependent expression of MAP17 coordinates the Warburg effect to tumor growth in hepatocellular carcinoma

Background

Reprogrammed glucose metabolism, also known as the Warburg effect, which is essential for tumor progression, is regarded as a hallmark of cancer. MAP17, a small 17-kDa non-glycosylated membrane protein, is frequently dysregulated in human cancers. However, its role in hepatocellular carcinoma (HCC) remains largely unknown.

Methods

Immunohistochemistry was used to analyze the expression pattern of MAP17 in HCC. Loss-of-function and gain-of-function studies were performed to investigate the oncogenic roles of MAP17 in vitro and in vivo. RNA sequencing, co-immunoprecipitation, immunofluorescence and western blotting were used to study the molecular mechanism of MAP17 affecting the tumor growth and glycolytic phenotype of HCC.

Results

An integrative analysis showed that MAP17, a small 17-kDa non-glycosylated membrane protein, is significantly related to the glycolytic phenotype of hepatocellular carcinoma (HCC). Firstly, we found that MAP17 expression is hypoxia-dependent and predicts a poor prognosis in HCC. Genetic silencing of MAP17 reduced the rate of glucose uptake, lactate release, extracellular acidification rate, and expression of glycolytic genes. Ectopic expression of wild type MAP17 but not its PDZ binding domain mutant MAP17-PDZm increased tumor glycolysis. Further research showed that MAP17 knockdown markedly retarded in vivo tumor growth in HCC. Importantly, attenuation of tumor glycolysis by galactose largely hijacked the growth-promoting role of MAP17 in HCC cells. RNA sequencing analysis revealed that MAP17 knockdown leads to transcriptional changes in the ROS metabolic process, cell surface receptor signaling, cell communication, mitotic cell cycle progression, and regulation of cell differentiation. Mechanistically, MAP17 exerted an increased tumoral phenotype associated with an increase in reactive oxygen species (ROS), which activates downstream effectors AKT and HIF1α to enhance the Warburg effect. In HCC clinical samples, there is a close correlation between MAP17 expression and HIF1α or phosphorated level of AKT.

Conclusions

Our results show that MAP17 is a novel glycolytic regulator, and targeting MAP17/ROS pathway may be an alternative approach for the prevention and treatment of HCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01927-5.

MAP17 contributes to non-small cell lung cancer progression via suppressing miR-27a-3p expression and p38 signaling pathway

PROBLEM AND AIM

The overexpression of MAP17 has been reported in various human carcinomas. However, its molecular mechanism in non-small cell lung cancer (NSCLC) has not been fully understood. Our study aimed to reveal the molecular mechanism of NSCLC that involved MAP17 and identify its target miRNA.

METHODS

RT-qPCR and immunoblot assays were conducted to measure the expression of mRNA and protein in NSCLC tissues and cell lines. Meanwhile, the A549 cells (an NSCLC cell line) were randomly assigned to the MAP17 overexpression group, the MAP17 knockdown group and negative control group to study the roles of MAP17 in cell viability, cell proliferation, migration, invasion, and apoptosis by performing Trypan blue exclusion, MTT, colony formation, transwell, wound healing and flow-cytometric apoptosis assays. The luciferase reporter assay was conducted to confirm the target relationship between MAP17 and miR-27a-3p.

RESULTS

The upregulation of MAP17 mRNA and protein was observed in NSCLC tissues and cell lines. In vitro, the positive roles of MAP17 on cell viability, migration, and invasion were confirmed in A549 cells. It was also found that MAP17 could inhibit cell apoptosis by suppressing the activation of the p38 pathway. This research eventually proved the target relationship between MAP17 and miR-27a-3p, and that miR-27a-3p reversed the effects of MAP17 in A549 cells by directly targeting MAP17.

CONCLUSIONS

MAP17 plays an oncogenic role in NSCLC by suppressing the activation of the p38 pathway. Apart from that, the miR-27a-3p can inhibit the expression of MAP17 to suppress the NSCLC progression.

Breast tumor cells promotes the horizontal propagation of EMT, stemness, and metastasis by transferring the MAP17 protein between subsets of neoplastic cells

MAP17 (PDZK1IP1) is a small protein regulating inflammation and tumor progression, upregulated in a broad range of carcinomas. MAP17 levels increase during tumor progression in a large percentage of advanced tumors. In the present work, we explored the role of this protein shaping tumor evolution. Here we show that in breast cancer, cells increased MAP17 levels in tumors by demethylation induced multiple changes in gene expression through specific miRNAs downregulation. These miRNA changes are dependent on Notch pathway activation. As a consequence, epithelial mesenchymal transition (EMT) and stemness are induced promoting the metastatic potential of these cells both in vitro and in vivo. Furthermore, MAP17 increased the exosomes in tumor cells, where MAP17 was released as cargo, and this horizontal propagation also increased the EMT in the recipient cells. Importantly, an antibody against MAP17 in the media reduces the EMT and stemness alterations promoted by the conditioned media from MAP17-expressing cells. Therefore, MAP17 expression promotes the horizontal propagation of EMT and metastasis by transferring the MAP17 protein between subsets of neoplastic cells. Thus, MAP17 can be used to describe a new mechanism for cell malignity at distance, without the involvement of genetic or epigenetic modifications. MAP17 can also be taken in consideration as new target for metastatic high-grade breast tumors.

Sarcoma stratification by combined pH2AX and MAP17 (PDZK1IP1) levels for a better outcome on doxorubicin plus olaparib treatment

Sarcomas constitute a rare heterogeneous group of tumors, including a wide variety of histological subtypes. Despite advances in our understanding of the pathophysiology of the disease, first-line sarcoma treatment options are still limited and new treatment approaches are needed. Histone H2AX phosphorylation is a sensitive marker for double strand breaks and has recently emerged as biomarker of DNA damage for new drug development. In this study, we explored the role of H2AX phosphorylation at Ser139 alone or in combination with MAP17 protein, an inducer of DNA damage through ROS increase, as prognostic biomarkers in sarcoma tumors. Next, we proposed doxorubicin and olaparib combination as potential therapeutic strategies against sarcomas displaying high level of both markers. We evaluate retrospectively the levels of pH2AX (Ser139) and MAP17 in a cohort of 69 patients with different sarcoma types and its relationship with clinical and pathological features. We found that the levels of pH2AX and MAP17 were related to clinical features and poor survival. Next, we pursued PARP1 inhibition with olaparib to potentiate the antitumor effect of DNA damaging effect of the DNA damaging agent doxorubicin to achieve an optimal synergy in sarcoma. We demonstrated that the combination of olaparib and doxorubicin was synergistic in vitro, inhibiting cell proliferation and enhancing pH2AX intranuclear accumulation, as a result of DNA damage. The synergism was corroborated in patient-derived xenografts (PDX) where the combination was effective in tumors with high levels of pH2AX and MAP17, suggesting that both biomarkers might potentially identify patients who better benefit from this combined therapy.

Combined Fascin-1 and MAP17 Expression in Breast Cancer Identifies Patients with High Risk for Disease Recurrence

BACKGROUND AND OBJECTIVE

Breast cancer stem cells are considered to be a major cause of disease recurrence in breast cancer as they appear to be chemoresistant. Fascin-1 and MAP17 are stem cell markers whose excessive expression in tumors is associated with aggressive tumor phenotypes. The aim of the present study was to investigate the expression patterns of fascin-1 and MAP17 in breast cancer and to assess their clinical significance.

METHODS

Expression of fascin-1 and MAP17 was assessed via immunohistochemistry in surgical specimens of a cohort comprised of 127 patients with resectable breast cancer. Results were correlated with clinicopathological characteristics and survival data. Progression-free survival (PFS) was defined as the primary outcome of the present study.

RESULTS

Fascin-1 and MAP17 expression were strongly associated with the presence of triple-negative cancers (p < 0.0001). Tumors displaying high expression of fascin-1 presented correlations with high tumor grade (p = 0.002) and high expression of Ki-67 (p = 0.004). PFS of patients exhibiting high expression of fascin-1 and MAP17 in cancer cells in the first 5 years after surgery was significantly worse than in patients with low expression of the two markers (47.8%, 95% confidence interval [CI] 33-51 vs. 80.5%, 95% CI 47-56; p = 0.012) and independent of other clinicopathological characteristics (hazard ratio 0.171, 95% CI 0.034-0.869; p = 0.033).

CONCLUSION

Combined expression of fascin-1 and MAP17 in breast cancer cells is associated with a significantly worse 5-year PFS, therefore recognizing a group of patients with high risk for early disease recurrence.

PDZK1-interacting protein 1 (PDZK1IP1) traps Smad4 protein and suppresses transforming growth factor-β (TGF-β) signaling

Transforming growth factor (TGF)-β signaling in humans is stringently regulated to prevent excessive TGF-β signaling. In tumors, TGF-β signaling can both negatively and positively regulate tumorigenesis dependent on tumor type, but the reason for these opposite effects is unclear. TGF-β signaling is mainly mediated via the Smad-dependent pathway, and herein we found that PDZK1-interacting protein 1 (PDZK1IP1) interacts with Smad4. PDZK1IP1 inhibited both the TGF-β and the bone morphogenetic protein (BMP) pathways without affecting receptor-regulated Smad (R-Smad) phosphorylation. Rather than targeting R-Smad phosphorylation, PDZK1IP1 could interfere with TGF-β- and BMP-induced R-Smad/Smad4 complex formation. Of note, PDZK1IP1 retained Smad4 in the cytoplasm of TGF-β-stimulated cells. To pinpoint PDZK1IP1's functional domain, we created several PDZK1IP1 variants and found that its middle region, from Phe⁴⁰ to Ala⁴⁹, plays a key role in its Smad4-regulating activity. PDZK1IP1 knockdown enhanced the expression of the TGF-β target genes Smad7 and prostate transmembrane protein androgen-induced (TMEPAI) upon TGF-β stimulation. In contrast, PDZK1IP1 overexpression suppressed TGF-β-induced reporter activities, cell migration, and cell growth inhibition. In a xenograft tumor model in which TGF-β was previously shown to elicit tumor-promoting effects, PDZK1IP1 gain of function decreased tumor size and increased survival rates. Taken together, these findings indicate that PDZK1IP1 interacts with Smad4 and thereby suppresses the TGF-β signaling pathway.

A Modified Tripeptide Motif of RS1 (RSC1A1) Down-Regulates Exocytotic Pathways of Human Na+-d-glucose Cotransporters SGLT1, SGLT2, and Glucose Sensor SGLT3 in the Presence of Glucose

A domain of protein RS1 (RSC1A1) called RS1-Reg down-regulates the plasma membrane abundance of Na⁺-d-glucose cotransporter SGLT1 by blocking the exocytotic pathway at the trans-Golgi. This effect is blunted by intracellular glucose but prevails when serine in a QSP (Gln-Ser-Pro) motif is replaced by glutamate [RS1-Reg(S20E)]. RS1-Reg binds to ornithine decarboxylase (ODC) and inhibits ODC in a glucose-dependent manner. Because the ODC inhibitor difluoromethylornithine (DFMO) acts like RS1-Reg(S20E), and DFMO and RS1-Reg(S20E) are not cumulative, we raised the hypothesis that RS1-Reg(S20E) down-regulates the exocytotic pathway of SGLT1 at the trans-Golgi by inhibiting ODC. We investigated whether QEP down-regulates human SGLT1 (hSGLT1) like hRS1-Reg(S20E) and whether human Na⁺-d-glucose cotransporter hSGLT2 and the human glucose sensor hSGLT3 are also addressed. We expressed hSGLT1, hSGLT1 linked to yellow fluorescent protein (hSGLT1-YFP), hSGLT2-YFP and hSGLT3-YFP in oocytes of Xenopus laevis, injected hRS1-Reg(S20E), QEP, DFMO, and/or α-methyl-d-glucopyranoside (AMG), and measured AMG uptake, glucose-induced currents, and plasma membrane-associated fluorescence after 1 hour. We also performed in vitro AMG uptake measurements into small intestinal mucosa of mice and human. The data indicate that QEP down-regulates the exocytotic pathway of SGLT1 similar to hRS1-Reg(S20E). Our results suggests that both peptides also down-regulate hSGLT2 and hSGLT3 via the same pathway. Thirty minutes after application of 5 mM QEP in the presence of 5 mM d-glucose, hSGLT1-mediated AMG uptake into small intestinal mucosa was decreased by 40% to 50%. Thus oral application of QEP in a formulation that optimizes uptake into enterocytes but prevents entry into the blood is proposed as novel antidiabetic therapy.

MAP17 predicts sensitivity to platinum-based therapy, EGFR inhibitors and the proteasome inhibitor bortezomib in lung adenocarcinoma

Background

The high incidence and mortality of lung tumours is a major health problem. Therefore, the identification both of biomarkers predicting efficacy for therapies in use and of novel efficacious therapeutic agents is crucial to increase patient survival. MAP17 (PDZK1IP1) is a small membrane-bound protein whose upregulation is reported as a common feature in tumours from diverse histological origins. Furthermore, MAP17 is correlated with tumour progression.

Methods

We assessed the expression of MAP17 in preclinical models, including cell lines and patient-derived xenografts (PDXs), assessing its correlation with sensitivity to different standard-of-care drugs in lung adenocarcinoma, as well as novel drugs. At the clinical level, we subsequently correlated MAP17 expression in human tumours with patient response to these therapies.

Results

We show that MAP17 expression is induced during lung tumourigenesis, particularly in lung adenocarcinomas, and provide in vitro and in vivo evidence that MAP17 levels predict sensitivity to therapies currently under clinical use in adenocarcinoma tumours, including cisplatin, carboplatin and EGFR inhibitors. In addition, we show that MAP17 expression predicts proteasome inhibitor efficacy in this context and that bortezomib, an FDA-approved drug, may be a novel therapeutic approach for MAP17-overexpressing lung adenocarcinomas.

Conclusions

Our results indicate a potential prognostic role for MAP17 in lung tumours, with particular relevance in lung adenocarcinomas, and highlight the predictive pot0065ntial of this membrane-associated protein for platinum-based therapy and EGFR inhibitor efficacy. Furthermore, we propose bortezomib treatment as a novel and efficacious therapy for lung adenocarcinomas exhibiting high MAP17 expression.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0871-7) contains supplementary material, which is available to authorized users.

Efficacy of bortezomib in sarcomas with high levels of MAP17 (PDZK1IP1)

Sarcomas are malignant tumors accounting for a high percentage of cancer morbidity and mortality in children and young adults. Surgery and radiation therapy are the accepted treatments for most sarcomas; however, patients with metastatic disease are treated with systemic chemotherapy. Many tumors display marginal levels of chemoresponsiveness, and new treatment approaches are needed. MAP17 is a small non-glycosylated membrane protein overexpressed in carcinomas. The levels of MAP17 could be used as a prognostic marker to predict the response to bortezomib in hematological malignancies and in breast tumors. Therefore, we analyzed the expression of this oncogene in sarcomas and its relationship with clinico-pathological features, as well as tested whether it can be used as a new biomarker to predict the therapeutic response to bortezomib and new therapies for sarcomas. We found that the levels of MAP17 were related to clinical features and poor survival in a cohort of 69 patients with different sarcoma types, not being restricted to any special subtype of tumor. MAP17 expression is associated with poor overall survival (p<0.001) and worse disease-free survival (p=0.002). Cell lines with high levels of MAP17 show a better response to bortezomib in vitro. Furthermore, patient-derived xenografts (PDX) with high levels of MAP17 respond to bortezomib in vivo. Our results showed that this response is due to the lower levels of NFκB and autophagy activation. Therefore, we suggest that MAP17 is a new biomarker to predict the efficacy of bortezomib as a new therapy for sarcomas.

The cargo protein MAP17 (PDZK1IP1) regulates the immune microenvironment

Inflammation is a complex defensive response activated after various harmful stimuli allowing the clearance of damaged cells and initiating healing and regenerative processes. Chronic, or pathological, inflammation is also one of the causes of neoplastic transformation and cancer development. MAP17 is a cargo protein that transports membrane proteins from the endoplasmic reticulum. Therefore, its overexpression may be linked to an excess of membrane proteins that may be recognized as an unwanted signal, triggering local inflammation. Therefore, we analyzed whether its overexpression is related to an inflammatory phenotype. In this work, we found a correlation between MAP17 expression and inflammatory phenotype in tumors and in other inflammatory diseases such as Crohn's disease, Barrett's esophagus, COPD or psoriasis. MAP17 expression correlated also with the markers of inflammation HLAs, BBS10, HERC2, ADNP and PYCARD. Furthermore, we found that MAP17 expression directly regulates NFAT2 and IL-6 activation, inducing the differentiation of monocytes to dendritic cells and suggesting a causal role of MAP17 in inflammation. Immunohistochemistry confirms local inflammation, mainly CD45⁺ cells, at the site of expression of MAP17, at least in tumors, Crohn's and psoriasis. Therefore, our data indicates that the overexpression of the protein MAP17 plays important role in diseases involving chronic inflammation.

The Cargo Protein MAP17 (PDZK1IP1) Regulates the Cancer Stem Cell Pool Activating the Notch Pathway by Abducting NUMB

Purpose: Cancer stem cells (CSC) are self-renewing tumor cells, with the ability to generate diverse differentiated tumor cell subpopulations. They differ from normal stem cells in the deregulation of the mechanisms that normally control stem cell physiology. CSCs are the origin of metastasis and highly resistant to therapy. Therefore, the understanding of the CSC origin and deregulated pathways is important for tumor control.Experimental Design: We have included experiments in vitro, in cell lines and tumors of different origins. We have used patient-derived xenografts (PDX) and public transcriptomic databases of human tumors.Results: MAP17 (PDZKIP1), a small cargo protein overexpressed in tumors, interacts with NUMB through the PDZ-binding domain activating the Notch pathway, leading to an increase in stem cell factors and cancer-initiating-like cells. Identical behavior was mimicked by inhibiting NUMB. Conversely, MAP17 downregulation in a tumor cell line constitutively expressing this gene led to Notch pathway inactivation and a marked reduction of stemness. In PDX models, MAP17 levels directly correlated with tumorsphere formation capability. Finally, in human colon, breast, or lung there is a strong correlation of MAP17 expression with a signature of Notch and stem cell genes.Conclusions: MAP17 overexpression activates Notch pathway by sequestering NUMB. High levels of MAP17 correlated with tumorsphere formation and Notch and Stem gene transcription. Its direct modification causes direct alteration of tumorsphere number and Notch and Stem pathway transcription. This defines a new mechanism of Notch pathway activation and Stem cell pool increase that may be active in a large percentage of tumors. Clin Cancer Res; 23(14); 3871-83. ©2017 AACR.

MAP17 Is a Necessary Activator of Renal Na+/Glucose Cotransporter SGLT2

The renal proximal tubule reabsorbs 90% of the filtered glucose load through the Na⁺-coupled glucose transporter SGLT2, and specific inhibitors of SGLT2 are now available to patients with diabetes to increase urinary glucose excretion. Using expression cloning, we identified an accessory protein, 17 kDa membrane-associated protein (MAP17), that increased SGLT2 activity in RNA-injected Xenopus oocytes by two orders of magnitude. Significant stimulation of SGLT2 activity also occurred in opossum kidney cells cotransfected with SGLT2 and MAP17. Notably, transfection with MAP17 did not change the quantity of SGLT2 protein at the cell surface in either cell type. To confirm the physiologic relevance of the MAP17-SGLT2 interaction, we studied a cohort of 60 individuals with familial renal glucosuria. One patient without any identifiable mutation in the SGLT2 coding gene (SLC5A2) displayed homozygosity for a splicing mutation (c.176+1G>A) in the MAP17 coding gene (PDZK1IP1). In the proximal tubule and in other tissues, MAP17 is known to interact with PDZK1, a scaffolding protein linked to other transporters, including Na⁺/H⁺ exchanger 3, and to signaling pathways, such as the A-kinase anchor protein 2/protein kinase A pathway. Thus, these results provide the basis for a more thorough characterization of SGLT2 which would include the possible effects of its inhibition on colocalized renal transporters.

Overexpression of PDZK1IP1, EEF1A2 and RPL41 genes in intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (iCCA) is an aggressive malignancy in the liver, which is associated with a poor prognosis. However, the molecular pathogenesis of iCCA remains unclear. RNA-Seq for tumor and para-tumor sample pairs enables the characterization of changes in the gene expression profiles of patients with iCCA. The present study analyzed RNA‑Seq data of seven iCCA para‑tumor and tumor sample pairs. Differential gene expression analysis demonstrated significant upregulation of PDZK1IP1, EEF1A2 and RPL41 (ENSG00000279483) genes in the iCCA samples when compared with the matched para‑tumor samples. Furthermore, genes associated with the immune system, metabolism and metabolic energy were significantly downregulated in the iCCA tumor tissues, indicating that this is involved in the pathogenesis of iCCA. The present study aimed to elucidate the gene expression patterns associated with the tumorigenesis of iCCA by comparing tumor and normal tissues, in order to isolate novel diagnostic factors for iCCA.

MAP17 (PDZKIP1) as a novel prognostic biomarker for laryngeal cancer

Larynx cancer organ preservation treatments with chemo and radiotherapy have substantially improved laryngoesophageal dysfunction-free survival. However, both of them lead to a high incidence of acute and chronic toxicities and a significant number of patients relapse. To date, there is no evidence available to establish the group of patients that may benefit from preservation approaches and clinical criteria such as primary tumor extension or pretreatment tracheotomy are not validated. MAP17 is a small non-glycosylated membrane protein overexpressed in carcinomas. The tumoral behavior induced by MAP17 is associated with reactive oxygen species production in which SGLT1 seems involved. In this study we found that the levels of MAP17 were related to clinical findings and survival in a cohort of 58 patients with larynx cancer. MAP17 expression is associated with overall survival (p<0.001) and laryngoesophageal dysfunction-free survival (p=0.002). Locoregional control in patients with high MAP17 showed better outcomes than those with low MAP17 (p=0.016). Besides, a positive correlation was observed between MAP17 expression and SGLT (p=0.022) and the combination of high levels of MAP17/SGLT also led to an increased overall survival (p=0,028). These findings suggest that MAP17, alone or in combination with SGLT1, may become a novel predictive biomarker for laryngeal carcinoma.

MAP17 (PDZKIP1) Expression Determines Sensitivity to the Proteasomal Inhibitor Bortezomib by Preventing Cytoprotective Autophagy and NFκB Activation in Breast Cancer

MAP17 is a small nonglycosylated membrane protein that is overexpressed in a high percentage of carcinomas. High levels of MAP17 enhance the tumorigenic properties of tumor cells by increasing oxidative stress, which is dependent on Na(+)-coupled cotransport. Here, we show that MAP17 is associated with proteins involved in protein degradation and that proteasome inhibition induces autophagy. To analyze whether MAP17 could also alter this process, we used the proteasome inhibitor bortezomib (Velcade, PS-341), which is approved for the treatment of multiple myeloma and mantle cell lymphoma, although it has a high rate of resistance emergence and poor efficacy in solid tumors. We provide evidence that bortezomib induces a cytoprotective effect by activating autophagy and NFκB nuclear translocation, responses that are repressed in the presence of high levels of MAP17 both in vitro and in vivo. Indeed, patients with multiple myeloma treated with bortezomib showed higher response rates and a longer time to progression associated with increased levels of MAP17 expression. The MAP17-induced sensitivity to bortezomib is dependent on the oxidative status of the cells and the activity of Na(+)-coupled transporters because treatment with antioxidants or the inhibitor furosemide restores the cytoprotective activity induced by bortezomib. Therefore, bortezomib induces a prosurvival response through cytoprotective autophagy and NFκB nuclear translocation, which is repressed by high levels of MAP17. We propose that the levels of MAP17 could be used as a prognostic marker to predict the response to bortezomib in hematologic malignancies and in other tissues that are not commonly responsive to the drug.

MAP17 and SGLT1 protein expression levels as prognostic markers for cervical tumor patient survival

MAP17 is a membrane-associated protein that is overexpressed in human tumors. Because the expression of MAP17 increases reactive oxygen species (ROS) generation through SGLT1 in cancer cells, in the present work, we investigated whether MAP17 and/or SGLT1 might be markers for the activity of treatments involving oxidative stress, such as cisplatin or radiotherapy. First, we confirmed transcriptional alterations in genes involved in the oxidative stress induced by MAP17 expression in HeLa cervical tumor cells and found that Hela cells expressing MAP17 were more sensitive to therapies that induce ROS than were parental cells. Furthermore, MAP17 increased glucose uptake through SGLT receptors. We then analyzed MAP17 and SGLT1 expression levels in cervical tumors treated with cisplatin plus radiotherapy and correlated the expression levels with patient survival. MAP17 and SGLT1 were expressed in approximately 70% and 50% of cervical tumors of different types, respectively, but they were not expressed in adenoma tumors. Furthermore, there was a significant correlation between MAP17 and SGLT1 expression levels. High levels of either MAP17 or SGLT1 correlated with improved patient survival after treatment. However, the patients with high levels of both MAP17 and SGLT1 survived through the end of this study. Therefore, the combination of high MAP17 and SGLT1 levels is a marker for good prognosis in patients with cervical tumors after cisplatin plus radiotherapy treatment. These results also suggest that the use of MAP17 and SGLT1 markers may identify patients who are likely to exhibit a better response to treatments that boost oxidative stress in other cancer types.

MAP17, a ROS-dependent oncogene

MAP17 is a small 17 kDa non-glycosylated membrane protein previously identified as being overexpressed in carcinomas. Breast tumor cells that overexpress MAP17 show an increased tumoral phenotype with enhanced proliferative capabilities both in the presence or the absence of contact inhibition, decreased apoptotic sensitivity, and increased migration. MAP17-expressing clones also grow better in nude mice. The increased malignant cell behavior induced by MAP17 is associated with an increase in reactive oxygen species (ROS) production, and the treatment of MAP17-expressing cells with antioxidants results in a reduction in the tumorigenic properties of these cells. The MAP17-dependent increase in ROS and tumorigenesis relies on its PDZ-binding domain because disruption of this sequence by point mutations abolishes the ability of MAP17 to enhance ROS production and tumorigenesis. MAP17 is overexpressed in a great variety of human carcinomas, including breast tumors. Immunohistochemical analysis of MAP17 during cancer progression demonstrates that overexpression of the protein strongly correlates with tumoral progression. Generalized MAP17 overexpression in human carcinomas indicates that MAP17 can be a good marker for tumorigenesis and, especially, for malignant progression.

MAP17 and the double-edged sword of ROS

Reactive oxygen species, ROS, are beneficially involved in many signaling pathways that control development and maintain cellular homeostasis. In physiological conditions, a tightly regulated redox balance protects cells from injurious ROS activity, but if the balance is altered, it promotes various pathological conditions including cancer. Understanding the duality of ROS as cytotoxic molecules and key mediators in signaling cascades may provide novel opportunities for improved cancer therapy. MAP17 is a small 17-kDa non-glycosylated membrane protein that is overexpressed in many tumors of different origins, including carcinomas. Immunohistochemical analysis of MAP17 during cancer progression demonstrates that overexpression of the protein strongly correlates with the progression of most types of tumor. Tumor cells that overexpress MAP17 show an increased tumoral phenotype associated with an increase in ROS. However, in non-tumor cells MAP17 increases ROS, resulting in senescence or apoptosis. Therefore, in tumor cells, MAP17 could be a marker for increased oxidative stress and could define new therapeutic approaches. Here, we review the role of MAP17 as a putative oncogene, as well as its role in cancer and anticancer therapies.

AKT promotes rRNA synthesis and cooperates with c-MYC to stimulate ribosome biogenesis in cancer

Precise regulation of ribosome biogenesis is fundamental to maintain normal cell growth and proliferation, and accelerated ribosome biogenesis is associated with malignant transformation. Here, we show that the kinase AKT regulates ribosome biogenesis at multiple levels to promote ribosomal RNA (rRNA) synthesis. Transcription elongation by RNA polymerase I, which synthesizes rRNA, required continuous AKT-dependent signaling, an effect independent of AKT's role in activating the translation-promoting complex mTORC1 (mammalian target of rapamycin complex 1). Sustained inhibition of AKT and mTORC1 cooperated to reduce rRNA synthesis and ribosome biogenesis by additionally limiting RNA polymerase I loading and pre-rRNA processing. In the absence of growth factors, constitutively active AKT increased synthesis of rRNA, ribosome biogenesis, and cell growth. Furthermore, AKT cooperated with the transcription factor c-MYC to synergistically activate rRNA synthesis and ribosome biogenesis, defining a network involving AKT, mTORC1, and c-MYC as a master controller of cell growth. Maximal activation of c-MYC-dependent rRNA synthesis in lymphoma cells required AKT activity. Moreover, inhibition of AKT-dependent rRNA transcription was associated with increased lymphoma cell death by apoptosis. These data indicate that decreased ribosome biogenesis is likely to be a fundamental component of the therapeutic response to AKT inhibitors in cancer.

Influence of amine ligands on the aquation and cytotoxicity of trans-diamine platinum(II) anticancer complexes

Three (15)N-labelled trans-Pt(ii) amine complexes with isopropylamine ((15)N-ipa), methylamine ((15)N-ma) and dimethylamine ((15)N-dma) have been prepared and characterized. 2D [(1)H,(15)N] HSQC NMR spectroscopy was used to obtain the rate and equilibrium constants for the aquation of trans-[PtCl(2)((15)N-ipa)((15)N-ma)] ((15)N-1), trans-[PtCl(2)((15)N-dma)((15)N-ma)] ((15)N-2) and trans-[PtCl(2)((15)N-dma)((15)N-ipa)] ((15)N-) in 100 mM NaClO(4) solutions at 298 K. New (15)N shift ranges for H(2)N-Pt(II)-N and HN-Pt(II)-N groups are reported. Formation of the diaqua complex was not observed for and accounted for <2% of the species at equilibrium for 1 and 2 . The first aquation step is significantly faster for 2 (k(1) = 14 x 10(-5) s(-1)) than for the two complexes with the bulkier ipa ligand (k(1) = 5.5 x 10(-5) s(-1) (), 6.1 x 10(-5) s(-1) (3)), but 2 is the least aquated of the three complexes at equilibrium. The pK(a) values for the monoaqua adducts of 1-3 are similar (5.98, 5.85 and 5.91, respectively) and 0.4 pH units lower than the related cis complex cis-[PtCl(2)(dma)(2)], indicating a smaller proportion of more reactive aqua species will exist at physiological pH. The pK(a) values for the diaqua adduct of 2 (4.59 and 7.98) are 0.3-0.6 pH units higher than those of 1(4.31 and 7.30) and 3 (4.28 and 7.29), which have very similar values. The speciation profiles of 1-3 , calculated on the basis of the calculated equilibrium and dissociation constants, indicate that <1% hydrolyzed species will exist under physiological conditions in cancer cells. The cytotoxicity of 1-3 (non-(15)N-labelled) was assessed in three cancer lines (SF268, MCF-7 and NCI-H460). The new trans-Pt(ii) diamine complex 2 is more active than 1 and 3 in all cases and is more potent than cisplatin in the MCF-7 adenocarcinoma cell line.