RIN1 is a breast tumor suppressor gene

Expression of RAS and RAB interactor 1 (RIN1) in head and neck tumors at selected hospital in Ghana

BACKGROUND

Head and neck tumors (HNT) are tumors of the paranasal sinuses, the salivary glands and the upper aerodigestive tract. RIN1 is a Ras effector protein regulating epithelial cell properties and has been implicated in a number of cancers.

METHOD

The aim of this study was to investigate the expression of RIN1 in head and neck tumors. RIN1 expression was assessed using quantitative real-time PCR (qRT-PCR) and immunohistochemical staining on archival head and neck tissue samples between 2014 and 2020.

RESULTS

RIN1 expression was low in tissue samples as compared with the normal head and neck tissues. High and low RIN1 levels were compared with ages ≤40, >40 in the head and neck tumors of p-value 0.02. There was a significant difference with p-values of 0.001 when poor and well-moderate malignant tumors were compared.

CONCLUSION

Our data suggests that RIN1may play an important role in head and neck tumor progression and that its expression may provide baseline data to facilitate identification of new molecular targeted therapeutics.

Discovery of pan-cancer related genes via integrative network analysis

Identification of cancer-related genes is helpful for understanding the pathogenesis of cancer, developing targeted drugs and creating new diagnostic and therapeutic methods. Considering the complexity of the biological laboratory methods, many network-based methods have been proposed to identify cancer-related genes at the global perspective with the increasing availability of high-throughput data. Some studies have focused on the tissue-specific cancer networks. However, cancers from different tissues may share common features, and those methods may ignore the differences and similarities across cancers during the establishment of modeling. In this work, in order to make full use of global information of the network, we first establish the pan-cancer network via differential network algorithm, which not only contains heterogeneous data across multiple cancer types but also contains heterogeneous data between tumor samples and normal samples. Second, the node representation vectors are learned by network embedding. In contrast to ranking analysis-based methods, with the help of integrative network analysis, we transform the cancer-related gene identification problem into a binary classification problem. The final results are obtained via ensemble classification. We further applied these methods to the most commonly used gene expression data involving six tissue-specific cancer types. As a result, an integrative pan-cancer network and several biologically meaningful results were obtained. As examples, nine genes were ultimately identified as potential pan-cancer-related genes. Most of these genes have been reported in published studies, thus showing our method's potential for application in identifying driver gene candidates for further biological experimental verification.

Transcriptome Profiling of Human Follicle Dermal Papilla Cells in response to Porphyra-334 Treatment by RNA-Seq

Porphyra-334 is a kind of mycosporine-like amino acid absorbing ultraviolet-A. Here, we characterized porphyra-334 as a potential antiaging agent. An in vitro assay revealed that porphyra-334 dramatically promoted collagen synthesis in fibroblast cells. The effect of porphyra-334 on cell proliferation was dependent on the cell type, and the increase of cell viability by porphyra-334 was the highest in keratinocyte cells among the three tested cell types. An in vivo clinical test with 22 participants demonstrated the possible role of porphyra-334 in the improvement of periorbital wrinkles. RNA-sequencing using human follicle dermal papilla (HFDP) cells upon porphyra-334 treatment identified the upregulation of metallothionein- (MT-) associated genes, confirming the antioxidant role of porphyra-334 with MT. Moreover, the expression of genes involved in nuclear chromosome segregation and the encoding of components of kinetochores was upregulated by porphyra-334 treatment. Furthermore, we found that several genes associated with the hair follicle cycle, the hair follicle structure, the epidermal structure, and stem cells were upregulated by porphyra-334 treatment, suggesting the potential role of porphyra-334 in hair follicle growth and maintenance. In summary, we provided several new pieces of evidence of porphyra-334 as a potential antiaging cosmetic agent and elucidated the expression network in HFDP cells upon porphyra-334.

EnABLing Tumor Growth and Progression: Recent progress in unraveling the functions of ABL kinases in solid tumor cells

Purpose of Review

The goal of this review is to summarize our current knowledge regarding how ABL family kinases are activated in solid tumors and impact on solid tumor development/progression, with a focus on recent advances in the field.

Recent Findings

Although ABL kinases are known drivers of human leukemia, emerging data also implicates the kinases in a large number of solid tumor types where they promote diverse processes such as proliferation, survival, cytoskeletal reorganization, cellular polarity, EMT (epithelial-mesenchymal-transition), metabolic reprogramming, migration, invasion and metastasis via unique signaling pathways. ABL1 and ABL2 appear to have overlapping but also unique roles in driving these processes. In some tumor types, the kinases may act to integrate pro- and anti-proliferative and -invasive signals, and also may serve as a switch during EMT/MET (mesenchymal-epithelial) transitions.

Conclusions

Most data indicate that targeting ABL kinases may be effective for reducing tumor growth and preventing metastasis; however, ABL kinases also may have a tumor suppressive role in some tumor types and in some cellular contexts. Understanding the functions of ABL kinases in solid tumors is critical for developing successful clinical trials aimed at targeting ABL kinases for the treatment of solid tumors.

Promoter DNA methylation analysis reveals a novel diagnostic CpG-based biomarker and RAB25 hypermethylation in clear cell renel cell carcinoma

Clear-cell renal cell carcinoma (ccRCC) is a common aggressive urinary malignant tumor that cannot be easily diagnosed at an early stage. The DNA methylation occurs within promoter before precancerous lesion plays a pivotal role that could help us in diagnosing and understanding ccRCC. In this study, based on a whole-genome promoter DNA methylation profiling, we used shrunken centroids classifier method to identify a CpG-based biomarker that is capable of differentiating between ccRCC tumor and adjacent tissues. The biomarker was validated in 19 ccRCCs and three public datasets. We found that both CYP4B1 and RAB25 are downregulated with promoter hypermethylation and CA9 is upregulated with promoter hypomethylation, and we validated their mRNA differential expressions in 19 ccRCCs and 10 GEO datasets. We further confirmed that hypermethylated RAB25 is inversely correlated with its mRNA level. Log-rank test showed that ccRCC patients with low levels of CA9 promoter methylation had a higher survival rate. This reveals clinically a potential biomarker for use in early detection for ccRCC, and provides a better understanding of carcinogenesis.

Identifying Cancer Driver Genes Using Replication-Incompetent Retroviral Vectors

Identifying novel genes that drive tumor metastasis and drug resistance has significant potential to improve patient outcomes. High-throughput sequencing approaches have identified cancer genes, but distinguishing driver genes from passengers remains challenging. Insertional mutagenesis screens using replication-incompetent retroviral vectors have emerged as a powerful tool to identify cancer genes. Unlike replicating retroviruses and transposons, replication-incompetent retroviral vectors lack additional mutagenesis events that can complicate the identification of driver mutations from passenger mutations. They can also be used for almost any human cancer due to the broad tropism of the vectors. Replication-incompetent retroviral vectors have the ability to dysregulate nearby cancer genes via several mechanisms including enhancer-mediated activation of gene promoters. The integrated provirus acts as a unique molecular tag for nearby candidate driver genes which can be rapidly identified using well established methods that utilize next generation sequencing and bioinformatics programs. Recently, retroviral vector screens have been used to efficiently identify candidate driver genes in prostate, breast, liver and pancreatic cancers. Validated driver genes can be potential therapeutic targets and biomarkers. In this review, we describe the emergence of retroviral insertional mutagenesis screens using replication-incompetent retroviral vectors as a novel tool to identify cancer driver genes in different cancer types.

A novel gammaretroviral shuttle vector insertional mutagenesis screen identifies SHARPIN as a breast cancer metastasis gene and prognostic biomarker

Breast cancer (BC) is the second leading cause of malignancy among U.S. women. Metastasis results in a poor prognosis and increased mortality, but the molecular mechanisms by which metastatic tumors occur are not well understood. Identifying the genes that drive the metastatic process could provide targets for improved therapy and biomarkers to improve BC patient outcomes. Using a forward mutagenesis screen, BC cells mutagenized with a replication-incompetent gammaretroviral vector (γRV) were xenotransplanted into the mammary fat pad of immunodeficient mice. In this approach the vector provirus dysregulates nearby genes, providing a selective advantage to transduced cells to form metastases. Metastatic tumors were analyzed for proviral integration sites to identify nearby candidate metastasis genes. The γRV has a transgene cassette that allows for rescue in bacteria and rapid identification of vector integration sites. Using this approach, we identified the previously described metastasis gene WWTR1 (TAZ), and three other novel candidate metastasis genes including SHARPIN. SHARPIN was independently validated in vivo as a BC metastasis gene. Analysis of patient data showed that SHARPIN expression predicts metastasis-free survival after adjuvant therapy. Our approach has broad potential to identify genes involved in oncogenic processes for BC and other cancers. We show here it can identify both known (WWTR1) and novel (SHARPIN) BC metastasis genes.

A CpG-methylation-based assay to predict survival in clear cell renal cell carcinoma

Clear cell renal cell carcinomas (ccRCCs) display divergent clinical behaviours. Molecular markers might improve risk stratification of ccRCC. Here we use, based on genome-wide CpG methylation profiling, a LASSO model to develop a five-CpG-based assay for ccRCC prognosis that can be used with formalin-fixed paraffin-embedded specimens. The five-CpG-based classifier was validated in three independent sets from China, United States and the Cancer Genome Atlas data set. The classifier predicts the overall survival of ccRCC patients (hazard ratio=2.96−4.82; P=3.9 × 10⁻⁶−2.2 × 10⁻⁹), independent of standard clinical prognostic factors. The five-CpG-based classifier successfully categorizes patients into high-risk and low-risk groups, with significant differences of clinical outcome in respective clinical stages and individual ‘stage, size, grade and necrosis' scores. Moreover, methylation at the five CpGs correlates with expression of five genes: PITX1, FOXE3, TWF2, EHBP1L1 and RIN1. Our five-CpG-based classifier is a practical and reliable prognostic tool for ccRCC that can add prognostic value to the staging system.

Using molecular markers is a useful way to predict the prognosis of cancer patients. Here, Wei et al. describe a five gene methylation signature that can predict the prognosis of renal clear cell cancer and validate its use in multiple patient cohorts.

Reduced Expression of TET1, TET2, TET3 and TDG mRNAs Are Associated with Poor Prognosis of Patients with Early Breast Cancer

Purpose

The purpose of this study was to determine the prognostic role of ten eleven translocation (TET) family proteins and DNA glycosylase (TDG) in patients with early breast cancer (EBC).

Methods

Expression of mRNAs encoding TET1–3 and TDG in 162 breast cancer tissues was quantified using real-time polymerase chain reaction analysis. The general characteristics of patients and clinicopathologic factors were collected. Estimation of patient survival was calculated using the Kaplan–Meier method, and independent prognostic indicators were analyzed using Cox regression analysis.

Results

The level of TET1 mRNA was significantly related to overall survival (OS) (P = 0.022). Multivariate analysis shows that the TNM stage was an independent predictor of disease-free survival (DFS) (HR = 1.761, 95% CI: 1.124–2.761, P = 0.014) and OS (HR = 2.135, 95% CI: 1.070–4.263, P = 0.032). Further, in patients with EBC who were treated with anthracyclines, Kaplan–Meier analysis indicates that the levels of TET3 and TDG mRNAs were related to DFS (P = 0.026 and 0.030, respectively), and multivariate analysis reveals that high levels of TET3 (HR = 1.944, 95% CI: 1.029–3.672, P = 0.040) and TDG (HR = 2.178, 95% CI: 1.140–4.163, P = 0.018) mRNAs were independent indicators of favorable DFS.

Conclusions

Our study indicates that EBC patients with decreased expression of TET1 mRNA had worse OS and that the levels of TET3 and TDG mRNAs were independent prognostic factors for patients who received anthracycline chemotherapy.

DNA methylation profiling reveals novel diagnostic biomarkers in renal cell carcinoma

BACKGROUND

Renal cell carcinoma (RCC) is the tenth most commonly diagnosed cancer in the United States. While it is usually lethal when metastatic, RCC is successfully treated with surgery when tumors are confined to the kidney and have low tumor volume. Because most early stage renal tumors do not result in symptoms, there is a strong need for biomarkers that can be used to detect the presence of the cancer as well as to monitor patients during and after therapy.

METHODS

We examined genome-wide DNA methylation alterations in renal cell carcinomas of diverse histologies and benign adjacent kidney tissues from 96 patients.

RESULTS

We observed widespread methylation differences between tumors and benign adjacent tissues, particularly in immune-, G-protein coupled receptor-, and metabolism-related genes. Additionally, we identified a single panel of DNA methylation biomarkers that reliably distinguishes tumor from benign adjacent tissue in all of the most common kidney cancer histologic subtypes, and a second panel does the same specifically for clear cell renal cell carcinoma tumors. This set of biomarkers were validated independently with excellent performance characteristics in more than 1,000 tissues in The Cancer Genome Atlas clear cell, papillary, and chromophobe renal cell carcinoma datasets.

CONCLUSIONS

These DNA methylation profiles provide insights into the etiology of renal cell carcinoma and, most importantly, demonstrate clinically applicable biomarkers for use in early detection of kidney cancer.

The RAB5-GEF function of RIN1 regulates multiple steps during Listeria monocytogenes infection

Listeria monocytogenes is a food-borne pathogenic bacterium that invades intestinal epithelial cells through a phagocytic pathway that relies on the activation of host cell RAB5 GTPases. Listeria monocytogenes must subsequently inhibit RAB5, however, in order to escape lysosome-mediated destruction. Relatively little is known about upstream RAB5 regulators during L. monocytogenes entry and phagosome escape processes in epithelial cells. Here we identify RIN1, a RAS effector and RAB5-directed guanine nucleotide exchange factor (GEF), as a host cell factor in L. monocytogenes infection. RIN1 is rapidly engaged following L. monocytogenes infection and is required for efficient invasion of intestinal epithelial cells. RIN1-mediated RAB5 activation later facilitates the fusion of phagosomes with lysosomes, promoting clearance of bacteria from the host cell. These results suggest that RIN1 is a host cell regulator that performs counterbalancing functions during early and late stages of L. monocytogenes infection, ultimately favoring pathogen clearance.

Low RIN1 expression in HCC is associated with tumor invasion and unfavorable prognosis

OBJECTIVES

To explore the association between the expression of Ras and Rab interactor 1 (RIN1) and the prognosis of hepatocellular carcinoma (HCC).

METHODS

RIN1 expression was detected in paired HCC tissues by real-time polymerase chain reaction, Western blot analysis, and immunohistochemistry. Transfection was applied to analyze the RIN1 function.

RESULTS

We found that expression of the RIN1 protein was downregulated in the HCC samples compared with the corresponding normal tissues. Downregulation of RIN1 expression was also associated with invasion and poor overall survival (OS). The results of our multivariate analysis indicated that the RIN1 status is a significant prognostic factor for OS. RIN1 overexpression also inhibited cell invasion in HepG2 cells. The expression between RIN1 and ABL2 may present a positive correlation.

CONCLUSIONS

Our results demonstrate that RIN1 suppresses tumor invasion in HCC patients and that a poor prognosis for HCC is expected when RIN1 expression is downregulated.

RIN1 regulates cell migration through RAB5 GTPases and ABL tyrosine kinases

Stimulation of a receptor tyrosine kinase (RTK), such as EGFR, leads to RAS activation followed by RIN1 activation. RIN1, in turn, activates RAB5 family GTPases, as well as ABL tyrosine kinases. As expected, RIN1 expression directly correlates with RAB5-mediated EGFR endocytosis. We previously showed that normal receptor endocytosis and internalized EGFR fate also depend on the ability of RIN1 to concomitantly activate ABL tyrosine kinases, consistent with the established role of ABL kinases in cytoskeleton remodeling and the growing evidence that such remodeling plays a role in endocytic processes. Here we report that growth factor-directed cell migration, a physiological process that involves receptor endocytosis and actin remodeling, also requires the ability of RIN1 to coordinate RAB5 GTPase and ABL tyrosine kinase pathways.

Multi-level control of actin dynamics by protein kinase D

Dynamic actin remodeling is fundamental to processes such as cell motility, vesicle trafficking, and cytokinesis. Protein kinase D (PKD) is a serine-threonine kinase known to be involved in diverse biological functions ranging from vesicle fission at the Golgi complex to regulation of cell motility and invasion. This review addresses the role of PKD in the organization of the actin cytoskeleton with a particular emphasis on the substrates associated with this function. We further highlight the multi-level control of actin dynamics by PKD and suggest that the tight spatio-temporal control of PKD activity is critical for the coordination of directed cell migration.

Activation of abl family kinases in solid tumors

Although c-Abl and Arg non-receptor tyrosine kinases are well known for driving leukemia development, their role in solid tumors has not been appreciated until recently. Accumulating evidence now indicates that c-Abl and/or Arg are activated in some solid tumor cell lines via unique mechanisms that do not involve gene mutation/translocation, and c-Abl/Arg activation promotes matrix degradation, invasion, proliferation, tumorigenesis, and/or metastasis, depending on the tumor type. However, some data suggest that c-Abl also may suppress invasion, proliferation, and tumorigenesis in certain cell contexts. Thus, c-Abl/Arg may serve as molecular switches that suppress proliferation and invasion in response to some stimuli (e.g., ephrins) or when inactive/regulated, or as promote invasion and proliferation in response to other signals (e.g., activated growth factor receptors, loss of inhibitor expression), which induce sustained activation. Clearly, more data are required to determine the extent and prevalence of c-Abl/Arg activation in primary tumors and during progression, and additional animal studies are needed to substantiate in vitro findings. Furthermore, c-Abl/Arg inhibitors have been used in numerous solid tumor clinical trials; however, none of these trials were restricted to patients whose tumors expressed highly activated c-Abl/Arg (targeted trial). Targeted trials are critical for determining whether c-Abl/Arg inhibitors can be effective treatment options for patients whose tumors are driven by c-Abl/Arg.

RIN1 orchestrates the activation of RAB5 GTPases and ABL tyrosine kinases to determine the fate of EGFR

Stimulation of epidermal growth factor receptor (EGFR) initiates RAS signaling simultaneously with EGFR internalization. Endocytosed EGFR is then either recycled or degraded. EGFR fate is determined in part by the RAS effector RIN1, a guanine nucleotide exchange factor (GEF) for RAB5 GTPases. EGFR degradation was slowed by RIN1 silencing, enhanced by RIN1 overexpression and accelerated by RIN1 localization to the plasma membrane. RIN1 also directly activates ABL tyrosine kinases, which regulate actin remodeling, a function not previously connected to endocytosis. We report that RIN1-RAB5 signaling favors EGFR downregulation over EGFR recycling, whereas RIN1-ABL signaling stabilizes EGFR and inhibits macropinocytosis. RIN1(QM), a mutant that blocks ABL activation, caused EGF-stimulated membrane ruffling, actin remodeling, dextran uptake and EGFR degradation. An ABL kinase inhibitor phenocopied these effects in cells overexpressing RIN1. EGFR activation also promotes RIN1 interaction with BIN1, a membrane bending protein. These findings suggest that RIN1 orchestrates RAB5 activation, ABL kinase activation and BIN1 recruitment to determine EGFR fate.

Prognostic significance of RIN1 gene expression in human non-small cell lung cancer

Ras interaction/interference 1 (RIN1), originally identified as a Ras effector protein, has been implicated in tumorigenesis and development of human cancers. The aim of this study was to detect RIN1 expression in human non-small cell lung cancer (NSCLC) and to analyze its association with prognosis of NSCLC patients. Quantitative real-time RT-PCR was performed to examine the expression of RIN1 mRNA in 25 cases of NSCLC and corresponding non-tumor tissue samples. Immunohistochemistry was performed to detect the expression of RIN1 in 90 NSCLC tissues. We found that the expression levels of RIN1 mRNA in NSCLC tissues were significantly higher than those in corresponding non-tumor tissues. High-level RIN1 expression was observed in 53.3% (48 of 90 cases), and correlated with poor tumor differentiation (P=0.024), TNM stage (P=0.032), and lymph node metastasis (P=0.018). Patients with high expression levels of RIN1 showed lower overall survival rate than those with low expression levels (P=0.033). Multivariate analysis showed that high RIN1 protein expression was an independent prognostic factor for NSCLC patients (P=0.021). Our study suggests that over-expression of RIN1 may play an important role in the progression of NSCLC and RIN1 expression may offer a valuable marker for predicting the outcome of patients with NSCLC.

Deregulation of Rab and Rab effector genes in bladder cancer

Growing evidence indicates that Rab GTPases, key regulators of intracellular transport in eukaryotic cells, play an important role in cancer. We analysed the deregulation at the transcriptional level of the genes encoding Rab proteins and Rab-interacting proteins in bladder cancer pathogenesis, distinguishing between the two main progression pathways so far identified in bladder cancer: the Ta pathway characterized by a high frequency of FGFR3 mutation and the carcinoma in situ pathway where no or infrequent FGFR3 mutations have been identified. A systematic literature search identified 61 genes encoding Rab proteins and 223 genes encoding Rab-interacting proteins. Transcriptomic data were obtained for normal urothelium samples and for two independent bladder cancer data sets corresponding to 152 and 75 tumors. Gene deregulation was analysed with the SAM (significant analysis of microarray) test or the binomial test. Overall, 30 genes were down-regulated, and 13 were up-regulated in the tumor samples. Five of these deregulated genes (LEPRE1, MICAL2, RAB23, STXBP1, SYTL1) were specifically deregulated in FGFR3-non-mutated muscle-invasive tumors. No gene encoding a Rab or Rab-interacting protein was found to be specifically deregulated in FGFR3-mutated tumors. Cluster analysis showed that the RAB27 gene cluster (comprising the genes encoding RAB27 and its interacting partners) was deregulated and that this deregulation was associated with both pathways of bladder cancer pathogenesis. Finally, we found that the expression of KIF20A and ZWINT was associated with that of proliferation markers and that the expression of MLPH, MYO5B, RAB11A, RAB11FIP1, RAB20 and SYTL2 was associated with that of urothelial cell differentiation markers. This systematic analysis of Rab and Rab effector gene deregulation in bladder cancer, taking relevant tumor subgroups into account, provides insight into the possible roles of Rab proteins and their effectors in bladder cancer pathogenesis. This approach is applicable to other group of genes and types of cancer.

RIN1 exhibits oncogenic property to suppress apoptosis and its aberrant accumulation associates with poor prognosis in melanoma

Malignant melanoma is an increasing disease in China, and its molecular mechanisms of development and progression are limited. The objective of this study was to investigate the expression of Ras interaction/interference 1 (RIN1) protein and its clinical significance in human melanoma. Immunohistochemistry was performed to detect the expression of RIN1 in 81 melanoma patients with a 5-year follow-up. The prognosis of the patients, classified by the clinicopathologic features and RIN1 expression, was assessed by multivariate analysis. RIN1 levels were then analyzed with overall survival (OS), progression-free survival (PFS), and recurrence-free survival (RFS) in the cohort. The biological function was determined by proliferation assay, flow cytometry analysis through knocking down of RIN1 in melanoma cells A375, as well as caspase-3 activation and PARP cleavage were detected by western blot or fluorometric assay. Data showed that RIN1 was overexpressed in melanoma samples. High-level RIN1 expression was observed in 49.4 % (40 of 81 cases), associated with thickness grade (P = 0.008) and lymph node metastasis (P < 0.001). Two distinguished subgroups were segregated by RIN1 levels within this set comparing prognostication of OS, PFS, and RFS. Importantly, RIN1 level was revealed as the significant independent prognostic factor for death and progression but a weak contribution for recurrence. Moreover, knock down of RIN1 expression in A375 cells, suppressed cell proliferation and induced apoptosis through caspase-3 activation and PARP cleavage. RIN1 expression could be a potential prognostic predictor for the melanoma patients and provide a potential target therapy for melanoma treatment.

High RIN1 expression is associated with poor prognosis in patients with gastric adenocarcinoma

The aim of this study was to investigate the expression and prognostic significance of RIN1 in gastric adenocarcinoma. RIN1 expression was analyzed using quantitative real-time PCR (qRT-PCR), Western blotting, and immunohistochemical staining on tissue samples from a consecutive series of 315 gastric adenocarcinoma patients who underwent tumor resections between 2003 and 2006. The relationship between RIN1 expression, clinicopathological factors, and patient survival was investigated. qRT-PCR results showed that the RIN1 mRNA expression was higher in tumor tissue samples than in the adjacent normal tissues, and a corresponding increase in protein expression was confirmed by Western blotting. Immunohistochemical staining indicated that RIN1 is highly expressed in 54.3 % of gastric adenocarcinomas. RIN1 expression levels were closely associated with tumor size, histological differentiation, tumor stage, and lymph node involvement. Kaplan-Meier survival analysis showed that high RIN1 expression exhibited a significant correlation with poor prognosis for gastric adenocarcinoma patients. Multivariate analysis revealed that RIN1 expression is an independent prognostic parameter for the overall survival rate of gastric adenocarcinoma patients. Our data suggest that RIN1 plays an important role in gastric adenocarcinoma progression and that a high RIN1 expression predicts an unfavorable prognosis in gastric adenocarcinoma patients.

High RIN1 expression is associated with poor prognosis in patients with gastric adenocarcinoma

The aim of this study was to investigate the expression and prognostic significance of RIN1 in gastric adenocarcinoma. RIN1 expression was analyzed using quantitative real-time PCR (qRT-PCR), Western blotting, and immunohistochemical staining on tissue samples from a consecutive series of 315 gastric adenocarcinoma patients who underwent tumor resections between 2003 and 2006. The relationship between RIN1 expression, clinicopathological factors, and patient survival was investigated. qRT-PCR results showed that the RIN1 mRNA expression was higher in tumor tissue samples than in the adjacent normal tissues, and a corresponding increase in protein expression was confirmed by Western blotting. Immunohistochemical staining indicated that RIN1 is highly expressed in 54.3 % of gastric adenocarcinomas. RIN1 expression levels were closely associated with tumor size, histological differentiation, tumor stage, and lymph node involvement. Kaplan-Meier survival analysis showed that high RIN1 expression exhibited a significant correlation with poor prognosis for gastric adenocarcinoma patients. Multivariate analysis revealed that RIN1 expression is an independent prognostic parameter for the overall survival rate of gastric adenocarcinoma patients. Our data suggest that RIN1 plays an important role in gastric adenocarcinoma progression and that a high RIN1 expression predicts an unfavorable prognosis in gastric adenocarcinoma patients.

Overexpression of RIN1 associates with tumor grade and progression in patients of bladder urothelial carcinoma

Ras and Rab interactor 1 (RIN1) is an effector of H-Ras, which plays an important role in the development and progression of carcinomas, but it has not been reported in bladder cancer. Hence, the association of RIN1 expression with prognosis of bladder urothelial carcinoma (UC) was examined. RIN1 mRNA and protein expression in 20 paired UCs and the adjacent normal tissues was detected by quantitative reverse transcription polymerase chain reaction and Western blot. The expression of RIN1 protein in 96 specimens of UCs and 22 specimens of adjacent normal bladder tissues were analyzed by immunohistochemistry. The overall survival (OS) was assessed by univariate and multivariate analysis. Moreover, the progression-free survival (PFS) and recurrence-free survival (RFS), classified by the clinicopathologic features with RIN1 expression, were assessed by multivariate analysis. RIN1 mRNA and protein level was higher in UCs than in the adjacent normal tissues (P < 0.01). Enhanced RIN1 immunoexpression was associated with high histologic grades (P = 0.046), cancer progression (P = 0.047) as well as Ki-67 expression (P = 0.023). Furthermore, the 5-year survival rate was 29% in the subgroup with high level of RIN1 expression, while it was 43% in the subgroup with normal level of RIN1 expression (P < 0.05). Importantly, RIN1 level was revealed as the significant independent prognostic factor for death (P = 0.023) and progression (P = 0.003), but a weak contribution for recurrence (P = 0.063). Collectively, RIN1 expression could be a potential prognostic predictor for UC patients.

Protein kinase D: coupling extracellular stimuli to the regulation of cell physiology

Protein kinase D (PKD) mediates the actions of stimuli that promote diacylglycerol (DAG) biogenesis. By phosphorylating effectors that regulate transcription, fission and polarized transport of Golgi vesicles, as well as cell migration and survival after oxidative stress, PKDs substantially expand the range of physiological processes controlled by DAG. Dysregulated PKDs have been linked to pathologies including heart hypertrophy and cancer invasiveness. Our understanding of PKD regulation by trans- and autophosphorylation, as well as the subcellular dynamics of PKD substrate phosphorylation, have increased markedly. Selective PKD inhibitors provide new, powerful tools for elucidating the physiological roles of PKDs and potentially treating cardiac disease and cancer.

A novel protein kinase D phosphorylation site in the tumor suppressor Rab interactor 1 is critical for coordination of cell migration

RIN1 is a regulator of epithelial cell migration. We identify serine 292 as a novel phosphorylation site for PKD in RIN1. Phosphorylation at this site controls RIN1-mediated inhibition of cell migration by modulating the direct activation of Abl kinases.

The multifunctional signal adapter protein Ras and Rab interactor 1 (RIN1) is a Ras effector protein involved in the regulation of epithelial cell processes such as cell migration and endocytosis. RIN1 signals via two downstream pathways, namely the activation of Rab5 and Abl family kinases. Protein kinase D (PKD) phosphorylates RIN1 at serine 351 in vitro, thereby regulating interaction with 14–3-3 proteins. Here, we report the identification of serine 292 in RIN1 as an in vivo PKD phosphorylation site. PKD-mediated phosphorylation at this site was confirmed with a phospho-specific antibody and by mass spectrometry. We demonstrate that phosphorylation at serine 292 controls RIN1-mediated inhibition of cell migration by modulating the activation of Abl kinases. We further provide evidence that RIN1 in vivo phosphorylation at serine 351 occurs independently of PKD. Collectively, our data identify a novel PKD signaling pathway through RIN1 and Abl kinases that is involved in the regulation of actin remodeling and cell migration.

p67/MetAP2 suppresses K-RasV12-mediated transformation of NIH3T3 mouse fibroblasts in culture and in athymic mice

In many tumor cells, the activation and activity of extracellular signal-regulated kinases (ERK1/2) are very high because of the constitutive activation of the Ras-mediated signaling pathway. Here, we ectopically expressed the human homologue of rat eukaryotic initiation factor 2-associated glycoprotein, p67/MetAP2, in EGF-treated mouse embryonic NIH3T3 fibroblasts and C2C12 myoblasts and NIH3T3 cell lines expressing the constitutively active form of MAP kinase kinase (MEK) to inhibit the activation and activity of ERK1/2 MAP kinases. In addition, we also ectopically expressed rat p67/MetAP2 in oncogenic Ras-induced transformed NIH3T3 fibroblasts and inhibited their transformed phenotype both in culture and in athymic nude mice possibly by inhibiting angiogenesis. This inhibition of ERK1/2 MAP kinases is due to the direct binding with rat p67/MetAP2, and this leads to the inhibition of activity of ERK1/2 MAP kinases both in vitro and in vivo. Furthermore, expression of p67/MetAP2 siRNA in both NIH3T3 fibroblasts and C2C12 myoblasts causes activation and activity of ERK1/2 MAP kinases. Our results thus suggest that ectopic expression of rat p67/MetAP2 in transformed cells can inhibit the tumorigenic phenotype by inhibiting the activation and activity of ERK1/2 MAP kinases and, thus, that p67/MetAP2 has tumor suppression activity.

ABL fusion oncogene transformation and inhibitor sensitivity are mediated by the cellular regulator RIN1

ABL gene translocations create constitutively active tyrosine kinases that are causative in chronic myeloid leukemia, acute lymphocytic leukemia and other hematopoietic malignancies. Consistent retention of ABL SH3/SH2 autoinhibitory domains, however, suggests that these leukemogenic tyrosine kinase fusion proteins remain subject to regulation. We resolve this paradox, demonstrating that BCR-ABL1 kinase activity is regulated by RIN1, an ABL SH3/SH2 binding protein. BCR-ABL1 activity was increased by RIN1 overexpression and decreased by RIN1 silencing. Moreover, Rin1(-/-) bone marrow cells were not transformed by BCR-ABL1, ETV6-ABL1 or BCR-ABL1(T315I), a patient-derived drug-resistant mutant, as judged by growth factor independence. Rescue by ectopic RIN1 verified a cell autonomous mechanism of collaboration with BCR-ABL1 during transformation. Sensitivity to the ABL kinase inhibitor imatinib was increased by RIN1 silencing, consistent with RIN1 stabilization of an activated BCR-ABL1 conformation having reduced drug affinity. The dependence on activation by RIN1 to unleash full catalytic and cell transformation potential reveals a previously unknown vulnerability that could be exploited for treatment of leukemic cases driven by ABL translocations. The findings suggest that RIN1 targeting could be efficacious for imatinib-resistant disease and might complement ABL kinase inhibitors in first-line therapy.

Genetic analysis of Ras signalling pathways in cell proliferation, migration and survival

We have used mouse embryonic fibroblasts (MEFs) devoid of Ras proteins to illustrate that they are essential for proliferation and migration, but not for survival, at least in these cells. These properties are unique to the Ras subfamily of proteins because ectopic expression of other Ras-like small GTPases, even when constitutively active, could not compensate for the absence of Ras proteins. Only constitutive activation of components of the Raf/Mek/Erk pathway was sufficient to sustain normal proliferation and migration of MEFs devoid of Ras proteins. Activation of the phosphatidylinositol 3-kinase (PI3K)/PTEN/Akt and Ral guanine exchange factor (RalGEF)/Ral pathways, either alone or in combination, failed to induce proliferation or migration of Rasless cells, although they cooperated with Raf/Mek/Erk signalling to reproduce the full response mediated by Ras signalling. In contrast to current hypotheses, Ras signalling did not induce proliferation by inducing expression of D-type Cyclins. Rasless MEFs had normal levels of Cyclin D1/Cdk4 and Cyclin E/Cdk2. However, these complexes were inactive. Inactivation of the pocket proteins or knock down of pRb relieved MEFs from their dependence on Ras signalling to proliferate.

Regulated expression of the Ras effector Rin1 in forebrain neurons

The Ras effector Rin1 is induced concomitant with synaptogenesis in forebrain neurons, where it inhibits fear conditioning and amygdala LTP. In epithelial cells, lower levels of Rin1 orchestrate receptor endocytosis. A 945 bp Rin1 promoter fragment was active in hippocampal neurons and directed accurate tissue-specific and temporal expression in transgenic mice. Regulated expression in neurons and epithelial cells was mediated in part by Snail transcriptional repressors: mutation of a conserved Snail site increased expression and endogenous Snai1 was detected at the Rin1 promoter. We also describe an element closely related to, but distinct from, the consensus site for REST, a master repressor of neuronal genes. Conversion to a consensus REST sequence reduced expression in both cell types. These results provide insight into regulated expression of a neuronal Ras effector, define a promoter useful in telencephalic neuron studies, and describe a novel REST site variant directing expression to mature neurons.

Cell proliferation and epidermal growth factor signaling in non-small cell lung adenocarcinoma cell lines are dependent on Rin1

Rin1 is a Rab5 guanine nucleotide exchange factor that plays an important role in Ras-activated endocytosis and growth factor receptor trafficking in fibroblasts. In this study, we show that Rin1 is expressed at high levels in a large number of non-small cell lung adenocarcinoma cell lines, including Hop62, H650, HCC4006, HCC827, EKVX, HCC2935, and A549. Rin1 depletion from A549 cells resulted in a decrease in cell proliferation that was correlated to a decrease in epidermal growth factor receptor (EGFR) signaling. Expression of wild type Rin1 but not the Rab5 guanine nucleotide exchange factor-deficient Rin1 (Rin1Delta) complemented the Rin1 depletion effects, and overexpression of Rin1Delta had a dominant negative effect on cell proliferation. Rin1 depletion stabilized the cell surface levels of EGFR, suggesting that internalization was necessary for robust signaling in A549 cells. In support of this conclusion, introduction of either dominant negative Rab5 or dominant negative dynamin decreased A549 proliferation and EGFR signaling. These data demonstrate that proper internalization and endocytic trafficking are critical for EGFR-mediated signaling in A549 cells and suggest that up-regulation of Rin1 in A549 cell lines may contribute to their proliferative nature.

Cell proliferation and epidermal growth factor signaling in non-small cell lung adenocarcinoma cell lines are dependent on Rin1

Rin1 is a Rab5 guanine nucleotide exchange factor that plays an important role in Ras-activated endocytosis and growth factor receptor trafficking in fibroblasts. In this study, we show that Rin1 is expressed at high levels in a large number of non-small cell lung adenocarcinoma cell lines, including Hop62, H650, HCC4006, HCC827, EKVX, HCC2935, and A549. Rin1 depletion from A549 cells resulted in a decrease in cell proliferation that was correlated to a decrease in epidermal growth factor receptor (EGFR) signaling. Expression of wild type Rin1 but not the Rab5 guanine nucleotide exchange factor-deficient Rin1 (Rin1Delta) complemented the Rin1 depletion effects, and overexpression of Rin1Delta had a dominant negative effect on cell proliferation. Rin1 depletion stabilized the cell surface levels of EGFR, suggesting that internalization was necessary for robust signaling in A549 cells. In support of this conclusion, introduction of either dominant negative Rab5 or dominant negative dynamin decreased A549 proliferation and EGFR signaling. These data demonstrate that proper internalization and endocytic trafficking are critical for EGFR-mediated signaling in A549 cells and suggest that up-regulation of Rin1 in A549 cell lines may contribute to their proliferative nature.

Caveolin-1 activates Rab5 and enhances endocytosis through direct interaction

Caveolin-1, a constitutive protein of the caveolae, is implicated in processes of vesicular transport during caveolae-mediated endocytosis. However, the molecular mechanisms of caveolae-mediated endocytosis are not yet clearly defined. Here, we show the physiological role of the Rab5-caveolin-1 interaction during caveolae-mediated endocytosis. Rab5 was found in caveolae-enriched fractions and Rab5 directly bound to caveolin-1. Furthermore, binding sites of Rab5 to caveolin-1 were identified in the scaffold (SD), transmembrane (TM), and C-terminus (CC) domains, and the Rab5 binding domain of caveolin-1 was required for CTXB uptake. Subsequently, we performed a GST-R5BD pull-down assay to determine whether the Rab5 binding domain of caveolin-1 is involved in Rab5 activity or not. The results showed that overexpression of the Rab5 binding domain of caveolin-1 increase the amount of Rab5-GTP in Cos-1 cells. These findings imply that caveolin-1 controls the Rab5 activity during the caveolae-mediated endocytosis.

Enhancement of ABL kinase catalytic efficiency by a direct binding regulator is independent of other regulatory mechanisms

ABL family tyrosine kinases are tightly regulated by autoinhibition and phosphorylation mechanisms. These kinases maintain an inactive conformation through intramolecular interactions involving SH3 and SH2 domains. RIN1, a downstream effector of RAS, binds to the ABL SH3 and SH2 domains and stimulates ABL tyrosine kinase activity. RIN1 binding to the ABL2 kinase resulted in a large decrease in Km and a small increase in Vmax toward an ABL consensus substrate peptide. The enzyme efficiency (k(cat)/Km) was increased more than 5-fold by RIN1. In addition, RIN1 strongly enhanced ABL-mediated phosphorylation of CRK, PSTPIP1, and DOK1, all established ABL substrates but with unique protein structures and distinct target sequences. Importantly RIN1-mediated stimulation of ABL kinase activity was independent of activation by SRC-mediated phosphorylation. RIN1 increased the kinase activity of both ABL1 and ABL2, and this occurred in the presence or absence of ABL regulatory domains outside the SH3-SH2-tyrosine kinase domain core. We further demonstrate that a catalytic site mutation associated with broad drug resistance, ABL1T315I, remains responsive to stimulation by RIN1. These findings are consistent with an allosteric kinase activation mechanism by which RIN1 binding promotes a more accessible ABL catalytic site through relief of autoinhibition. Direct disruption of RIN1 binding may therefore be a useful strategy to suppress the activity of normal and oncogenic ABL, including inhibitor-resistant mutants that confound current therapeutic strategies. Stimulation through derepression may be applicable to many other tyrosine kinases autoinhibited by coupled SH3 and SH2 domains.

Ras oncogenes: split personalities

Extensive research on the Ras proteins and their functions in cell physiology over the past 30 years has led to numerous insights that have revealed the involvement of Ras not only in tumorigenesis but also in many developmental disorders. Despite great strides in our understanding of the molecular and cellular mechanisms of action of the Ras proteins, the expanding roster of their downstream effectors and the complexity of the signalling cascades that they regulate indicate that much remains to be learnt.

Integration of transforming growth factor beta and RAS signaling silences a RAB5 guanine nucleotide exchange factor and enhances growth factor-directed cell migration

Transforming growth factor beta (TGF-beta) receptor (TbetaR) signaling contributes to normal development as well as tumorigenesis. Here we report that RIN1, a RAB5 guanine nucleotide exchange factor (GEF) and down regulator of receptor tyrosine kinases (RTKs), promotes TbetaR signaling through enhanced endocytosis. TbetaR activation induces SNAI1 (Snail), a transcription repressor that reduces RIN1 expression, providing a negative feedback mechanism to control TbetaR trafficking and downstream signaling. Persistent RAS signaling disrupts this equilibrium by stabilizing SNAI1 protein, resulting in strong silencing of RIN1 and stabilization of RTKs. TGF-beta-induced RIN1 silencing in breast cancer cells prolonged sensitivity to hepatocyte growth factor, a ligand for the MET-type RTK, and enhanced growth factor-directed cell motility. We conclude that in some tumor cells TbetaR and RAS signals are integrated through the silencing of RIN1, leading to a reduction in RAB5-mediated endocytosis. These findings shed new light on the basis for distinct interpretations of TGF-beta signaling by normal versus transformed cells.

Integration of transforming growth factor beta and RAS signaling silences a RAB5 guanine nucleotide exchange factor and enhances growth factor-directed cell migration

Transforming growth factor beta (TGF-beta) receptor (TbetaR) signaling contributes to normal development as well as tumorigenesis. Here we report that RIN1, a RAB5 guanine nucleotide exchange factor (GEF) and down regulator of receptor tyrosine kinases (RTKs), promotes TbetaR signaling through enhanced endocytosis. TbetaR activation induces SNAI1 (Snail), a transcription repressor that reduces RIN1 expression, providing a negative feedback mechanism to control TbetaR trafficking and downstream signaling. Persistent RAS signaling disrupts this equilibrium by stabilizing SNAI1 protein, resulting in strong silencing of RIN1 and stabilization of RTKs. TGF-beta-induced RIN1 silencing in breast cancer cells prolonged sensitivity to hepatocyte growth factor, a ligand for the MET-type RTK, and enhanced growth factor-directed cell motility. We conclude that in some tumor cells TbetaR and RAS signals are integrated through the silencing of RIN1, leading to a reduction in RAB5-mediated endocytosis. These findings shed new light on the basis for distinct interpretations of TGF-beta signaling by normal versus transformed cells.