Expression of GLUT1 in primary renal tumors: morphologic and biologic implications

Identification of SLC2A1 as a predictive biomarker for survival and response to immunotherapy in lung squamous cell carcinoma

BACKGROUND

As one of the common subtypes of non-small lung cancer, lung squamous cell carcinoma (LUSC) patients with advanced stage have few choices of treatment strategies. Therefore, it is urgent to discover genes that are associated with the survival and efficacy of immunotherapies.

METHOD

Differential gene expression analyses were conducted using TCGA LUSC bulk-sequencing and single-cell RNA-sequencing data. Prognostic genes were identified from the TCGA LUSC cohort. Protein expression validation and survival analyses were performed. Experiments were conducted to explore the underlying mechanisms. In addition, the correlation between gene expression and pathological response to adjuvant immunochemotherapy was also investigated.

RESULTS

After a series of bioinformatic analyses, solute carrier family 2 member 1(SLC2A1), encoding glucose transporter-1 (GLUT1), was found to be differentially expressed between tumor and normal tissues. GLUT1 was subsequently identified as an independent prognostic factor for LUSC. GSEA analysis revealed the glycolysis metabolism pathway of KEGG enriched in SLC2A1high tumor tissues. LASSO analyses revealed that tumor tissues with high expression of SLC2A1 were associated with high levels of protein lactylation. We found that SLC2A1 was preferentially expressed by SPP1+ macrophages in the tumor microenvironment, and the expression of SLC2A1 was associated with the abundance of SPP1+ macrophages. Immunofluorescence demonstrated GLUT1 and HIF1α colocalization in tumor-infiltrating macrophages. In vitro experiments showed HIF-1α-induced macrophage polarization under hypoxia, and GLUT1 inhibition blocked this polarization. In addition, SLC2A1 was negatively associated with the common immune checkpoint molecules, such as programmed cell death 1(PD-1), T cell immunoreceptor with Ig and ITIM domains (TIGIT), cytotoxic T-lymphocyte associated protein 4 (CTLA4) and lymphocyte activating 3 (LAG3), while showed a positive association with CD44. Finally, we observed that there was a significant correlation between pre-adjuvant-treatment GLUT1 expression and the pathological response.

CONCLUSION

SLC2A1 expression was differentially upregulated in tumor tissues, and elevated GLUT1 expression was associated with worse survival and poor pathological response to adjuvant immunochemotherapy. Upregulation of GLUT1 promoted macrophage polarization into the M2 phenotype. The findings will contribute to guiding the treatment selection for LUSC patients and providing personalized immunotherapy strategies.

Renal Cell Carcinoma as a Metabolic Disease: An Update on Main Pathways, Potential Biomarkers, and Therapeutic Targets

Clear cell renal cell carcinoma (ccRCC) is the most frequent histological kidney cancer subtype. Over the last decade, significant progress has been made in identifying the genetic and metabolic alterations driving ccRCC development. In particular, an integrated approach using transcriptomics, metabolomics, and lipidomics has led to a better understanding of ccRCC as a metabolic disease. The metabolic profiling of this cancer could help define and predict its behavior in terms of aggressiveness, prognosis, and therapeutic responsiveness, and would be an innovative strategy for choosing the optimal therapy for a specific patient. This review article describes the current state-of-the-art in research on ccRCC metabolic pathways and potential therapeutic applications. In addition, the clinical implication of pharmacometabolomic intervention is analyzed, which represents a new field for novel stage-related and patient-tailored strategies according to the specific susceptibility to new classes of drugs.

Mitochondrial metabolic reprogramming by SIRT3 regulation ameliorates drug resistance in renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) alters metabolic signals frequently, leading to mitochondrial dysfunction, such as increase of glycolysis and accumulation of lipid. Sirtuin3 (SIRT3) is a key factor for the regulation of both mitochondrial integrity and function. SIRT3 is downregulated and contributes in both cancer development and progression in ccRCC. The aim of this study is to investigate SIRT3-regulated mitochondrial biogenesis in ccRCC. SIRT3 overexpression alone reduced glucose uptake rate and enhanced membrane potential in mitochondria. ccRCC with overexpressed SIRT3 further improved the lethal effects when combined with anticancer drugs (Resveratrol, Everolimus and Temsirolimus). Cell viability was markedly decreased in a dose-dependent manner when treated with resveratrol or mTOR inhibitors in SIRT3 overexpressing ccRCC. In conclusion, SIRT3 improved mitochondrial functions in ccRCC through metabolic reprogramming. Mitochondrial reprogramming by SIRT3 regulation improves the sensitivity to anticancer drugs. The combination of SIRT3 and resveratrol functioned synergistically lethal effect in ccRCC.

Microphysiological model of the renal cell carcinoma to inform anti-angiogenic therapy

Renal cell carcinomas are common genitourinary tumors characterized by high vascularization and strong reliance on glycolysis. Despite the many available therapies for renal cell carcinomas, first-line targeted therapies, such as cabozantinib, and durable reaponses are seen in only a small percentage of patients. Yet, little is known about the mechanisms that drive response (or lack thereof). This dearth of knowledge can be explained by the dynamic and complex microenvironment of renal carcinoma, which remains challenging to recapitulate in vitro. Here, we present a microphysiological model of renal cell carcinoma, including a tubular blood vessel model of induced pluripotent stem cell-derived endothelial cells and an adjacent 3D carcinoma model. Our model recapitulated hypoxia, glycolic metabolism, and sprouting angiogenesis. Using our model, we showed that cabozantinib altered cancer cell metabolism and decreased sprouting angiogenesis but did not restore barrier function. This microphysiological model could be helpful to elucidate, through multiple endpoints, the contributions of the relevant environmental components in eliciting a functional response or resistance to therapy in renal cell carcinoma.

Glucose transporters as markers of diagnosis and prognosis in cancer diseases

The primary metabolic substrate for cells is glucose, which acts as both a source of energy and a substrate in several processes. However, being lipophilic, the cell membrane is impermeable to glucose and specific carrier proteins are needed to allow transport. In contrast to normal cells, cancer cells are more likely to generate energy by glycolysis; as this process generates fewer molecules of adenosine triphosphate (ATP) than complete oxidative breakdown, more glucose molecules are needed. The increased demand for glucose in cancer cells is satisfied by overexpression of a number of glucose transporters, and decreased levels of others. As specific correlations have been observed between the occurrence of cancer and the expression of glucose carrier proteins, the presence of changes in expression of glucose transporters may be treated as a marker of diagnosis and/or prognosis for cancer patients.

Human Glucose Transporters in Renal Glucose Homeostasis

The kidney plays an important role in glucose homeostasis by releasing glucose into the blood stream to prevent hypoglycemia. It is also responsible for the filtration and subsequent reabsorption or excretion of glucose. As glucose is hydrophilic and soluble in water, it is unable to pass through the lipid bilayer on its own; therefore, transport takes place using carrier proteins localized to the plasma membrane. Both sodium-independent glucose transporters (GLUT proteins) and sodium-dependent glucose transporters (SGLT proteins) are expressed in kidney tissue, and mutations of the genes coding for these glucose transporters lead to renal disorders and diseases, including renal cancers. In addition, several diseases may disturb the expression and/or function of renal glucose transporters. The aim of this review is to describe the role of the kidney in glucose homeostasis and the contribution of glucose transporters in renal physiology and renal diseases.

Determining the immunohistochemical expression of GLUT1 in renal cell carcinoma using the HSCORE method

The aim of the present study was to compare the immunohistochemical expression of glucose transporter 1 (GLUT1) between the most common histological types of renal cell carcinoma (RCC), and to determine whether a correlation between GLUT1 expression and nuclear grade or tumor size exists. A total of 19 RCC samples were selected for the study, consisting of 8 clear cell (cc)RCC and 11 non-ccRCC tissues. Immunohistochemistry for GLUT1 was performed on formalin-fixed and paraffin-embedded sections using GLUT1 antibodies. All data analyses were performed using the MedCalc software. There was a higher immunohistochemical expression of GLUT1 in the ccRCC group compared with the non-cc group, but there was no difference in GLUT1 expression between groups of RCCs with differing nuclear grades. No significant correlation between GLUT1 expression and tumor size was found. The higher immunohistochemical expression of GLUT1 in ccRCC may be a contributing factor to the clinical characteristics and behavior of that group of carcinomas. These results suggest that GLUT1 expression cannot be used as a prognostic factor for RCC, but it may be used as a predictive factor in the future.

Metabolic reprogramming in renal cancer: Events of a metabolic disease

Recent studies have established that tumors can reprogram the pathways involved in nutrient uptake and metabolism to withstand the altered biosynthetic, bioenergetics and redox requirements of cancer cells. This phenomenon is called metabolic reprogramming, which is promoted by the loss of tumor suppressor genes and activation of oncogenes. Because of alterations and perturbations in multiple metabolic pathways, renal cell carcinoma (RCC) is sometimes termed as a "metabolic disease". The majority of metabolic reprogramming in renal cancer is caused by the inactivation of von Hippel-Lindau (VHL) gene and activation of the Ras-PI3K-AKT-mTOR pathway. Hypoxia-inducible factor (HIF) and Myc are other important players in the metabolic reprogramming of RCC. All types of RCCs are associated with reprogramming of glucose and fatty acid metabolism and the tricarboxylic acid (TCA) cycle. Metabolism of glutamine, tryptophan and arginine is also reprogrammed in renal cancer to favor tumor growth and oncogenesis. Together, understanding these modifications or reprogramming of the metabolic pathways in detail offer ample opportunities for the development of new therapeutic targets and strategies, discovery of biomarkers and identification of effective tumor detection methods.

GLUT1 biological function and inhibition: research advances

The GLUT is a key regulator of glucose metabolism and is widely expressed on the surface of most cells of the body. GLUT provides a variety of nutrients for the growth, proliferation and differentiation of cells. In recent years, the development of drugs affecting the energy intake of tumor cells has become a research hotspot. GLUT inhibitors are gaining increased attention because they can block the energy supply of malignant tumors. Herein, we elaborate on the structure and function of GLUT1, the structural and functional differences among GLUT1-4 transporters and the relationship between GLUT1 and tumor development, as well as GLUT1 transporter inhibitors, to provide a reference for the development of new GLUT1 inhibitors.

Reprogramming of Metabolism in Kidney Cancer

Metabolic reprogramming is one of the major steps that tumor cells take during cancer progression. This process allows the cells to survive in a nutrient- and oxygen-deprived environment, to become stress tolerant, and to metastasize to different sites. Recent studies have shown that reprogramming happens in stromal cells and involves the cross-talk of the cancer cell/tumor microenvironment. There are similarities between the metabolic reprogramming that occurs in both noncancerous kidney diseases and renal cell carcinoma (RCC), suggesting that such reprogramming is a means by which renal epithelial cells survive injury and repair the tissue, and that RCC cells hijack this system. This article reviews reprogramming of major metabolism pathways in RCC, highlighting similarities and differences from kidney diseases and potential therapeutic strategies against it.

Metabolic imaging with hyperpolarized 13 C pyruvate magnetic resonance imaging in patients with renal tumors-Initial experience

BACKGROUND

Optimal treatment selection for localized renal tumors is challenging because of their variable biologic behavior and limitations in the preoperative assessment of tumor aggressiveness. The authors investigated the emerging hyperpolarized (HP) ¹³ C magnetic resonance imaging (MRI) technique to noninvasively assess tumor lactate production, which is strongly associated with tumor aggressiveness.

METHODS

Eleven patients with renal tumors underwent HP ¹³ C pyruvate MRI before surgical resection. Tumor ¹³ C pyruvate and ¹³ C lactate images were acquired dynamically. Five patients underwent 2 scans on the same day to assess the intrapatient reproducibility of HP ¹³ C pyruvate MRI. Tumor metabolic data were compared with histopathology findings.

RESULTS

Eight patients had tumors with a sufficient metabolite signal-to-noise ratio for analysis; an insufficient tumor signal-to-noise ratio was noted in 2 patients, likely caused by poor tumor perfusion and, in 1 patient, because of technical errors. Of the 8 patients, 3 had high-grade clear cell renal cell carcinoma (ccRCC), 3 had low-grade ccRCC, and 2 had chromophobe RCC. There was a trend toward a higher lactate-to-pyruvate ratio in high-grade ccRCCs compared with low-grade ccRCCs. Both chromophobe RCCs had relatively high lactate-to-pyruvate ratios. Good reproducibility was noted across the 5 patients who underwent 2 HP ¹³ C pyruvate MRI scans on the same day.

CONCLUSIONS

The current results demonstrate the feasibility of HP ¹³ C pyruvate MRI for investigating the metabolic phenotype of localized renal tumors. The initial data indicate good reproducibility of metabolite measurements. In addition, the metabolic data indicate a trend toward differentiating low-grade and high-grade ccRCCs, the most common subtype of renal cancer.

LAY SUMMARY

Renal tumors are frequently discovered incidentally because of the increased use of medical imaging, but it is challenging to identify which aggressive tumors should be treated. A new metabolic imaging technique was applied to noninvasively predict renal tumor aggressiveness. The imaging results were compared with tumor samples taken during surgery and showed a trend toward differentiating between low-grade and high-grade clear cell renal cell carcinomas, which are the most common type of renal cancers.

Monocarboxylate transporter 1 promotes proliferation and invasion of renal cancer cells by mediating acetate transport

One hallmark of renal cell carcinoma (RCC) is metabolic reprogramming, which involves elevation of glycolysis and upregulation of lipid metabolism. However, the mechanism of metabolic reprogramming is incompletely understood. Monocarboxylate transporter 1 (MCT1) promotes transport for lactate and pyruvate, which are crucial for cell metabolism. The aim of present study was to investigate the function of MCT1 on RCC development and its mechanism on metabolic reprogramming. The results showed that MCT1 messenger RNA and protein levels significantly increased in cancer tissues of ccRCC compared to normal tissue. MCT1 was further found to mainly located in the cell membrane of RCC. The knockdown of MCT1 by RNAi significantly inhibited proliferation and migration of 786-O and ACHN cells. MCT1 also induced the expressions of proliferation marker Ki-67 and invasion marker SNAI1. Moreover, we also showed that acetate treatment could upregulate the expression of MCT1, but not other MCT isoforms. On the other hand, MCT1 was involved in acetate transport and intracellular histone acetylation. In summary, this study revealed that MCT1 is abnormally high in ccRCC and promotes cancer development. The regulatory effect of MCT1 on cell proliferation and invasion maybe mediated by acetate transport.

An eleven metabolic gene signature-based prognostic model for clear cell renal cell carcinoma

In this study, we performed bioinformatics and statistical analyses to investigate the prognostic significance of metabolic genes in clear cell renal cell carcinoma (ccRCC) using the transcriptome data of 539 ccRCC and 72 normal renal tissues from TCGA database. We identified 79 upregulated and 45 downregulated (n=124) metabolic genes in ccRCC tissues. Eleven prognostic metabolic genes (NOS1, ALAD, ALDH3B2, ACADM, ITPKA, IMPDH1, SCD5, FADS2, ACHE, CA4, and HK3) were identified by further analysis. We then constructed an 11-metabolic gene signature-based prognostic risk score model and classified ccRCC patients into high- and low-risk groups. Overall survival (OS) among the high-risk ccRCC patients was significantly shorter than among the low-risk ccRCC patients. Receiver operating characteristic (ROC) curve analysis of the prognostic risk score model showed that the areas under the ROC curve for the 1-, 3-, and 5-year OS were 0.810, 0.738, and 0.771, respectively. Thus, our prognostic model showed favorable predictive power in the TCGA and E-MTAB-1980 ccRCC patient cohorts. We also established a nomogram based on these eleven metabolic genes and validated internally in the TCGA cohort, showing an accurate prediction for prognosis in ccRCC.

Immunohistochemical expressionof sodium-dependent glucose transporter - 2 (SGLT-2) in clear cell renal carcinoma: possible prognostic implications

Purpose:

Glucose is a major energy resource for tumor cell survival and growth, and its influx into cells is mainly carried out by facilitative glucose transporters (GLUTs). Sodium - dependent glucose transporters (SGLTs) have been highlighted as playing important roles in diabetic treatment. However, their potential roles in cancer remain unclear. We examined expression patterns of SGLTs in tumor tissues together with conventional pathological variables to determine prognostic significance in patients with renal cell carcinoma (RCC).

Materials and Methods:

Nephrectomy specimens were obtained from 68 patients. GLUT - 1, - 2 and SGLT - 1, - 2 expression in tumor and adjacent normal tissues were analyzed by immunohistochemical staining, and intensity was quantified using an image analyzer.

Results:

The four glucose transporters evaluated were broadly distributed in tumor tissues as well as throughout the normal parenchyma. There was no significant correlation between transporter expression and conventional pathological variables. However, increased SGLT - 2 expression was significantly associated with shorter overall survival (p < 0.01), regardless of metastatic status.

Conclusions:

We propose possible prognostic significance of SGLT - 2 expression in human RCC. Given that glucose is a major energy resource for tumor cells and that glucose transport is largely mediated by SGLT, SGLT - 2 may serve as a possible therapeutic target in RCC.

Glucose transporter 1 in health and disease

Glucose, a major source of energy for all cells, is transported into cells with the help of glucose transporters (GLUTs). These transporters are of two types, namely sodium-dependent GLUTs and facilitative GLUTs. These transporters are present in a tissue-specific pattern and have substrate specificity. Among these transporters, GLUT1 (facilitative GLUT) is present ubiquitously on all tissues of the body and helps in the basal uptake of glucose. GLUT1 is known to have many physiological functions in the body from the time of implantation of an embryo and is also seen associated with pathologies, including cancers. This review mainly focuses on GLUT1 in physiological and pathological conditions and the recent advances related to its role in cancer development and applications in cancer therapeutics.

The two glycolytic markers GLUT1 and MCT1 correlate with tumor grade and survival in clear-cell renal cell carcinoma

Background

Clear-cell renal cell carcinoma (ccRCC) is the most common type of kidney cancer. Although ccRCC is characterized by common recurrent genetic abnormalities, including inactivation of the von Hippel-Lindau (vhl) tumor suppressor gene resulting in stabilization of hypoxia-inducible factors (HIFs), the tumor aggressiveness and outcome of ccRCC is variable. New biomarkers are thus required to improve ccRCC diagnosis, prognosis and therapeutic options. This work aims to investigate the expression of HIF and proteins involved in metabolism and pH regulation. Their correlation to histoprognostic parameters and survival was analyzed.

Methods

ccRCC of 45 patients were analyzed. HIF-1α, HIF-2α, HAF, GLUT1, MCT1, MCT4, CAIX and CAXII expression was assessed by immunohistochemistry in a semi-quantitative and qualitative manner. The GLUT1, MCT1, MCT4, CAIX and CAXII mRNA levels were analyzed in an independent cohort of 43 patients.

Results

A significant correlation was observed between increased GLUT1, MCT1, CAXII protein expression and a high Fuhrman grade in ccRCC patients. Moreover, while HIF-1α, HIF-2α and HAF expression was heterogenous within tumors, we observed and confirmed that HIF-2α co-localized with HAF.

We confirmed, in an independent cohort, that GLUT1, MCT1 and CAXII mRNA levels correlated with the Fuhrman grade. Moreover, we demonstrated that the high mRNA level of both MCT1 and GLUT1 correlated with poor prognosis.

Conclusions

This study demonstrates for the first time a link between the aggressiveness of high- Fuhrman grade ccRCC and metabolic reprogramming. It also confirms the role of HIF-2α and HAF in tumor invasiveness. Finally, these results demonstrate that MCT1 and GLUT1 are strong prognostic markers and promising therapeutic targets.

Distribution of glucose transporters in renal diseases

Kidneys play an important role in glucose homeostasis. Renal gluconeogenesis prevents hypoglycemia by releasing glucose into the blood stream. Glucose homeostasis is also due, in part, to reabsorption and excretion of hexose in the kidney.Lipid bilayer of plasma membrane is impermeable for glucose, which is hydrophilic and soluble in water. Therefore, transport of glucose across the plasma membrane depends on carrier proteins expressed in the plasma membrane. In humans, there are three families of glucose transporters: GLUT proteins, sodium-dependent glucose transporters (SGLTs) and SWEET. In kidney, only GLUTs and SGLTs protein are expressed. Mutations within genes that code these proteins lead to different renal disorders and diseases. However, diseases, not only renal, such as diabetes, may damage expression and function of renal glucose transporters.

Metabolic reprogramming in clear cell renal cell carcinoma

Research in many cancers has uncovered changes in metabolic pathways that control tumour energetics and biosynthesis, so-called metabolic reprogramming. Studies in clear cell renal cell carcinoma (ccRCC) have been particularly revealing, leading to the concept that ccRCC is a metabolic disease. ccRCC is generally accompanied by reprogramming of glucose and fatty acid metabolism and of the tricarboxylic acid cycle. Metabolism of tryptophan, arginine and glutamine is also reprogrammed in many ccRCCs, and these changes provide opportunities for new therapeutic strategies, biomarkers and imaging modalities. In particular, metabolic reprogramming facilitates the identification of novel and repurposed drugs that could potentially be used to treat ccRCC, which when metastatic has currently limited long-term treatment options. Further research and dissemination of these concepts to nephrologists and oncologists will lead to clinical trials of therapeutics specifically targeted to tumour metabolism, rather than generally toxic to all proliferating cells. Such novel agents are highly likely to be more effective and to have far fewer adverse effects than existing drugs.

Targeting glycogen metabolism in bladder cancer

Metabolism has been a heavily investigated topic in cancer research for the past decade. Although the role of aerobic glycolysis (the Warburg effect) in cancer has been extensively studied, abnormalities in other metabolic pathways are only just being understood in cancer. One such pathway is glycogen metabolism; its involvement in cancer development, particularly in urothelial malignancies, and possible ways of exploiting aberrations in this process for treatment are currently being studied. New research shows that the glycogen debranching enzyme amylo-α-1,6-glucosidase, 4-α-glucanotransferase (AGL) is a novel tumour suppressor in bladder cancer. Loss of AGL leads to rapid proliferation of bladder cancer cells. Another enzyme involved in glycogen debranching, glycogen phosphorylase, has been shown to be a tumour promoter in cancer, including in prostate cancer. Studies demonstrate that bladder cancer cells in which AGL expression is lost are more metabolically active than cells with intact AGL expression, and these cells are more sensitive to inhibition of both glycolysis and glycine synthesis--two targetable pathways. As a tumour promoter and enzyme, glycogen phosphorylase can be directly targeted, and preclinical inhibitor studies are promising. However, few of these glycogen phosphorylase inhibitors have been tested for cancer treatment in the clinical setting. Several possible limitations to the targeting of AGL and glycogen phosphorylase might also exist.

Analysis and interpretation of transcriptomic data obtained from extended Warburg effect genes in patients with clear cell renal cell carcinoma

Background

Many cancers adopt a metabolism that is characterized by the well-known Warburg effect (aerobic glycolysis). Recently, numerous attempts have been made to treat cancer by targeting one or more gene products involved in this pathway without notable success. This work outlines a transcriptomic approach to identify genes that are highly perturbed in clear cell renal cell carcinoma (CCRCC).

Methods

We developed a model of the extended Warburg effect and outlined the model using Cytoscape. Following this, gene expression fold changes (FCs) for tumor and adjacent normal tissue from patients with CCRCC (GSE6344) were mapped on to the network. Gene expression values with FCs of greater than two were considered as potential targets for treatment of CCRCC.

Results

The Cytoscape network includes glycolysis, gluconeogenesis, the pentose phosphate pathway (PPP), the TCA cycle, the serine/glycine pathway, and partial glutaminolysis and fatty acid synthesis pathways. Gene expression FCs for nine of the 10 CCRCC patients in the GSE6344 data set were consistent with a shift to aerobic glycolysis. Genes involved in glycolysis and the synthesis and transport of lactate were over-expressed, as was the gene that codes for the kinase that inhibits the conversion of pyruvate to acetyl-CoA. Interestingly, genes that code for unique proteins involved in gluconeogenesis were strongly under-expressed as was also the case for the serine/glycine pathway. These latter two results suggest that the role attributed to the M2 isoform of pyruvate kinase (PKM2), frequently the principal isoform of PK present in cancer: i.e. causing a buildup of glucose metabolites that are shunted into branch pathways for synthesis of key biomolecules, may not be operative in CCRCC. The fact that there was no increase in the expression FC of any gene in the PPP is consistent with this hypothesis. Literature protein data generally support the transcriptomic findings.

Conclusions

A number of key genes have been identified that could serve as valid targets for anti-cancer pharmaceutical agents. Genes that are highly over-expressed include ENO2, HK2, PFKP, SLC2A3, PDK1, and SLC16A1. Genes that are highly under-expressed include ALDOB, PKLR, PFKFB2, G6PC, PCK1, FBP1, PC, and SUCLG1.

Molecular imaging of urogenital diseases

There is an expanding and exciting repertoire of PET imaging radiotracers for urogenital diseases, particularly in prostate cancer, renal cell cancer, and renal function. Prostate cancer is the most commonly diagnosed cancer in men. With growing therapeutic options for the treatment of metastatic and advanced prostate cancer, improved functional imaging of prostate cancer beyond the limitations of conventional CT and bone scan is becoming increasingly important for both clinical management and drug development. PET radiotracers, apart from ¹⁸F-FDG, for prostate cancer are ¹⁸F-sodium fluoride, ¹¹C-choline, and ¹⁸F-fluorocholine, and (¹¹C-acetate. Other emerging and promising PET radiotracers include a synthetic l-leucine amino acid analogue (anti-¹⁸F-fluorocyclobutane-1-carboxylic acid), dihydrotestosterone analogue (¹⁸F-fluoro-5α-dihydrotestosterone), and prostate-specific membrane antigen-based PET radiotracers (eg, N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-4-¹⁸F-fluorobenzyl-l-cysteine, ⁸⁹Zr-DFO-J591, and ⁶⁸Ga [HBED-CC]). Larger prospective and comparison trials of these PET radiotracers are needed to establish the role of PET/CT in prostate cancer. Although renal cell cancer imaging with FDG-PET/CT is available, it can be limited, especially for detection of the primary tumor. Improved renal cell cancer detection with carbonic anhydrase IX (CAIX)-based antibody (¹²⁴I-girentuximab) and radioimmunotherapy targeting with ¹⁷⁷Lu-cG250 appear promising. Evaluation of renal injury by imaging renal perfusion and function with novel PET radiotracers include p-¹⁸F-fluorohippurate, hippurate m-cyano-p-¹⁸F-fluorohippurate, and rubidium-82 chloride (typically used for myocardial perfusion imaging). Renal receptor imaging of the renal renin-angiotensin system with a variety of selective PET radioligands is also becoming available for clinical translation.

The human cell surfaceome of breast tumors

Introduction. Cell surface proteins are ideal targets for cancer therapy and diagnosis. We have identified a set of more than 3700 genes that code for transmembrane proteins believed to be at human cell surface. Methods. We used a high-throuput qPCR system for the analysis of 573 cell surface protein-coding genes in 12 primary breast tumors, 8 breast cell lines, and 21 normal human tissues including breast. To better understand the role of these genes in breast tumors, we used a series of bioinformatics strategies to integrates different type, of the datasets, such as KEGG, protein-protein interaction databases, ONCOMINE, and data from, literature. Results. We found that at least 77 genes are overexpressed in breast primary tumors while at least 2 of them have also a restricted expression pattern in normal tissues. We found common signaling pathways that may be regulated in breast tumors through the overexpression of these cell surface protein-coding genes. Furthermore, a comparison was made between the genes found in this report and other genes associated with features clinically relevant for breast tumorigenesis. Conclusions. The expression profiling generated in this study, together with an integrative bioinformatics analysis, allowed us to identify putative targets for breast tumors.

Tumor-suppressive microRNA-1291 directly regulates glucose transporter 1 in renal cell carcinoma

Our recent studies of microRNA (miRNA) expression signatures demonstrated that microRNA-1291 (miR-1291) was significantly downregulated in renal cell carcinoma (RCC) clinical specimens and was a putative tumor-suppressive miRNA in RCC. The aim of the present study was to investigate the functional significance of miR-1291 in cancer cells and to identify novel miR-1291-mediated cancer pathways and target genes in RCC. Expression of miR-1291 was significantly downregulated in RCC tissues compared with adjacent non-cancerous tissues. Restoration of mature miR-1291 in RCC cell lines (A498 and 786-O) revealed significant inhibition of cell proliferation, migration and invasion, suggesting that miR-1291 functioned as a tumor suppressor. To identify miR-1291-mediated molecular pathways and targets, we used gene expression analysis (expression of RCC clinical specimens and miR-1291-transfected A498 cells) and in silico database analysis. Our data demonstrated that 79 signaling pathways were significantly regulated by tumor-suppressive miR-1291 in RCC cells. Moreover, solute career family 2 member 1 (SLC2A1) was a candidate target of miR-1291 regulation. The SLC2A1 gene provides instructions for producing glucose transporter protein type 1 (GLUT1). Luciferase reporter assays showed that miR-1291 directly regulated SLC2A1/GLUT1. In RCC clinical specimens, the expression of SLC2A1/GLUT1 mRNA was significantly higher in cancer tissues than in non-cancerous tissues. A significant inverse correlation was recognized between SLC2A1/GLUT1 and miR-1291 expression (r = -0.55, P < 0.0001). Loss of tumor-suppressive miR-1291 enhanced RCC cell proliferation, migration and invasion through targeting SLC2A1/GLUT1. The identification of novel tumor-suppressive miR-1291-mediated molecular pathways and targets has provided new insights into RCC oncogenesis and metastasis.

Metabolic features of clear-cell renal cell carcinoma: mechanisms and clinical implications

Central to the malignant behaviour that endows cancer cells with growth advantage is their unique metabolism. Cancer cells can process nutrient molecules differently from normal cells and use it to overcome stress imposed on them by various therapies. This metabolic conversion is controlled by specific genetic mutations that are associated with activation of oncogenes and loss of tumour suppressor proteins. Understanding these processes is important as it can lead to the discovery of biomarkers that can predict the aggressiveness of the disease and its response to therapy, and even more importantly, to the development of novel therapeutics. A classic tumour in this respect is clear-cell renal cell carcinoma (RCC). In this review, we will begin with a brief summary of normal cellular bioenergetic pathways, which will be followed by a description of the characteristic metabolism of glucose and lipids in clear-cell RCC cells and its clinical implications. Data relating to the potential effect of dietary nutrients on RCC will also be reviewed along with potential therapies targeted at interrupting specific metabolic pathways in clear-cell RCC.

Von Hippel-Lindau gene product directs cytokinesis: a new tumor suppressor function

One of the mechanisms of tumorigenesis is that the failure of cell division results in genetically unstable, multinucleated cells. Here we show that pVHL, a tumor suppressor protein that has been implicated in the pathogenesis of renal cell carcinoma (RCC), plays an important role in regulation of cytokinesis. We found that pVHL-deficient RCC 786-O cells were multinucleated and polyploid. Reintroduction of wild-type pVHL into these cells rescued the diploid cell population, whereas the mutant pVHL-K171G failed to do so. We demonstrate that lysine 171 of pVHL is important for the final step of cytokinesis: the midbody abscission. The pVHL-K171G caused failure to localize the ESCRT-1 interacting protein Alix and the v-SNARE complex component Endobrevin to the midbody in 786-O cells, leading to defective cytokinesis. Moreover, SUMOylation of pVHL at lysine 171 might modulate its function as a cytokinesis regulator. pVHL tumor suppressor function was also disrupted by the K171G mutation, as evidenced by the xenograft tumor formation when 786-O clones expressing pVHL-K171G were injected into mice. Most RCC cell lines show a polyploid chromosome complement and consistent heterogeneity in chromosome number. Thus, this study offers a way to explain the chromosome instability in RCC and reveals a new direction for the tumor suppressor function of pVHL, which is independent of its E3 ubiquitin ligase activity.

Glucose transporter Glut-1 is detectable in peri-necrotic regions in many human tumor types but not normal tissues: Study using tissue microarrays

The hypoxic tumor microenvironment is associated with malignant progression and poor treatment response. The glucose transporter Glut-1 is a prognostic factor and putative hypoxia marker. So far, studies of Glut-1 in cancer have utilized conventional immunohistochemical analysis in a series of individual biopsy or surgical specimens. Tissue microarrays, however, provide a rapid, inexpensive means of profiling biomarker expression. To evaluate hypoxia markers, tissue cores must show the architectural features of hypoxia; i.e. viable tissue surrounding necrotic regions. Glut-1 may be a useful biomarker to validate tissue microarrays for use in studies of hypoxia-regulated genes in cancer. In this study, we carried out immunohistochemical detection of Glut-1 protein in many tumor and normal tissue types in a range of tissue microarrays. Glut-1 was frequently found in peri-necrotic regions, occurring in 9/34 lymphomas, 6/12 melanomas, and 5/16 glioblastomas; and in 43/54 lung, 22/84 colon, and 23/60 ovarian tumors. Expression was rare in breast (6/40) and prostate (1/57) tumors, and in normal tissue, was restricted to spleen, tongue, and CNS endothelium. In conclusion, tissue microarrays enable the observation of Glut-1 expression in peri-necrotic regions, which may be linked to hypoxia, and reflect previous studies showing differential Glut-1 expression across tumor types and non-malignant tissue.

Potential role of sugar transporters in cancer and their relationship with anticancer therapy

Sugars, primarily glucose and fructose, are the main energy source of cells. Because of their hydrophilic nature, cells use a number of transporter proteins to introduce sugars through their plasma membrane. Cancer cells are well known to display an enhanced sugar uptake and consumption. In fact, sugar transporters are deregulated in cancer cells so they incorporate higher amounts of sugar than normal cells. In this paper, we compile the most significant data available about biochemical and biological properties of sugar transporters in normal tissues and we review the available information about sugar carrier expression in different types of cancer. Moreover, we describe the possible pharmacological interactions between drugs currently used in anticancer therapy and the expression or function of facilitative sugar transporters. Finally, we also go into the insights about the future design of drugs targeted against sugar utilization in cancer cells.

Expression of the GLUT1 glucose transporter and p53 in carcinomas of the pancreatobiliary tract

Only few studies have evaluated the usefulness of the GLUT1 and p53 status of pancreatobiliary tract carcinomas in revealing tumorigenesis. We studied GLUT1 and p53 immunoexpression in a total of 355 cases of the pancreatobiliary carcinoma to determine the biological significance of GLUT1 and p53 expression. Positive expression of GLUT1 was identified in 38 out of 67 (57.7%) ampulla of Vater (AV) carcinomas, in 27 out of 52 (51.8%) pancreatic (PA) carcinomas, in 38 out of 121 (31.4%) extrahepatic bile duct (EBD) carcinomas, and in 53 out of 115 (46.5%) gallbladder (GB) carcinomas. GLUT1 expression in pancreatobiliary carcinomas showed some positive correlation with histological grade, T stage, N stage, TNM stage, and lymphatic invasion. However, p53 expression showed no correlation with any prognostic factors. In the Kaplan-Meier test, positive GLUT1 expression was a poor prognostic factor in the pancreatobiliary tract cancers; however, only GB cancers were statistically significant (P=0.002). Our results suggest that GLUT1 expression in the AV, EBD, and GB carcinomas is associated with some prognostic factors, and GLUT1 expression is associated with a worse prognosis in the patients with GB carcinomas.

Molecular Pathology of the Genitourinary Tract: Molecular Pathology of Kidney and Testes

With the advent of newer molecular technologies, our knowledge of cellular mechanisms with tumors of the kidney and testis has grown exponentially. Molecular technologies have led to better understanding of interplay between the von Hippel-Lindau gene and angiogenic cytokines in renal cancer and isochromosome 12p in testicular neoplasms. The result has been development of antiangiogenic-targeted therapy within recent years that has become the mainstay treatment for metastatic renal cell cancer. In the near future, classification and diagnosis of renal and testicular tumors through morphologic analysis will be supplemented by molecular information correlating to prognosis and targeted therapy. This article outlines tumor molecular pathology of the kidney and testis encompassing current genomic, epigenomic, and proteonomic findings.