Adipophilin expression in cutaneous malignant melanoma

The Warburg hypothesis and the emergence of the mitochondrial metabolic theory of cancer

Otto Warburg originally proposed that cancer arose from a two-step process. The first step involved a chronic insufficiency of mitochondrial oxidative phosphorylation (OxPhos), while the second step involved a protracted compensatory energy synthesis through lactic acid fermentation. His extensive findings showed that oxygen consumption was lower while lactate production was higher in cancerous tissues than in non-cancerous tissues. Warburg considered both oxygen consumption and extracellular lactate as accurate markers for ATP production through OxPhos and glycolysis, respectively. Warburg's hypothesis was challenged from findings showing that oxygen consumption remained high in some cancer cells despite the elevated production of lactate suggesting that OxPhos was largely unimpaired. New information indicates that neither oxygen consumption nor lactate production are accurate surrogates for quantification of ATP production in cancer cells. Warburg also did not know that a significant amount of ATP could come from glutamine-driven mitochondrial substrate level phosphorylation in the glutaminolysis pathway with succinate produced as end product, thus confounding the linkage of oxygen consumption to the origin of ATP production within mitochondria. Moreover, new information shows that cytoplasmic lipid droplets and elevated aerobic lactic acid fermentation are both biomarkers for OxPhos insufficiency. Warburg's original hypothesis can now be linked to a more complete understanding of how OxPhos insufficiency underlies dysregulated cancer cell growth. These findings can also address several questionable assumptions regarding the origin of cancer thus allowing the field to advance with more effective therapeutic strategies for a less toxic metabolic management and prevention of cancer.

Omics Approaches to Study Perilipins and Their Significant Biological Role in Cardiometabolic Disorders

Lipid droplets (LDs), highly dynamic cellular organelles specialized in lipid storage and maintenance of lipid homeostasis, contain several proteins on their surface, among which the perilipin (Plin) family stands out as the most abundant group of LD-binding proteins. They play a pivotal role in influencing the behavior and functionality of LDs, regulating lipase activity, and preserving a balance between lipid synthesis and degradation, which is crucial in the development of obesity and abnormal accumulation of fat in non-adipose tissues, causing negative adverse biological effects, such as insulin resistance, mitochondrial dysfunction, and inflammation. The expression levels of Plins are often associated with various diseases, such as hepatic steatosis and atherosclerotic plaque formation. Thus, it becomes of interest to investigate the Plin roles by using appropriate "omics" approaches that may provide additional insight into the mechanisms through which these proteins contribute to cellular and tissue homeostasis. This review is intended to give an overview of the most significant omics studies focused on the characterization of Plin proteins and the identification of their potential targets involved in the development and progression of cardiovascular and cardiometabolic complications, as well as their interactors that could be useful for more efficient therapeutic and preventive approaches for patients.

Lipolysis-stimulated lipoprotein receptor promote lipid uptake and fatty acid oxidation in gastric cancer

BACKGROUND

Lipolysis-stimulated lipoprotein receptor (LSR), a lipid receptor, is associated with cancer progression. However, detailed effects on intracellular metabolism are unclear. We aimed to elucidate the mechanism of LSR-mediated lipid metabolism in gastric cancer.

METHODS

We investigated lipid metabolic changes induced by lipoprotein administration in gastric cancer cells and evaluated the significance of LSR expression and lipid droplets formation in gastric cancer patients. The efficacy of inhibiting β-oxidation in gastric cancer cells was also examined in vitro and vivo.

RESULTS

In gastric cancer cells, LSR promoted cellular uptake of lipoprotein and cell proliferation. Furthermore, the inhibition of LSR in gastric cancer cells expressing high levels of LSR counteracted both effects. Immunohistochemical analysis of human gastric cancer tissues showed that the increase in lipid droplets via LSR is a factor that influences prognosis. Lipidomics analysis of LSR-high-expressing gastric cancer cells revealed an increase in β-oxidation. Based on these results, we used etomoxir, a β-oxidation inhibitor, and found that it inhibited cell proliferation as well as the suppression of LSR. Similarly, in a mouse xenograft model of LSR-highly expressing gastric cancer cells, the tumor growth effect of high-fat diet feeding was counteracted by etomoxir, consistent with the Ki-67 labeling index.

CONCLUSIONS

We demonstrated that lipids are taken up into gastric cancer cells via LSR and cause an increase in β-oxidation, resulting in the promotion of cancer progression. Controlling LSR-mediated lipid metabolism may be a novel therapeutic strategy for gastric cancer.

Plin2 inhibits autophagy via activating AKT/mTOR pathway in non-small cell lung cancer

Perilipin 2 (Plin2) is known to be dysregulated in several human malignancies, which facilitates cancer progression. Recent studies have found that the abnormal expression of Plin2 is associated with poor prognosis of non-small cell lung cancer (NSCLC). However, the specific role of Plin2 and its underlying mechanism remain unclear. This study revealed that Plin2 expression was low in NSCLC tissues, and its relatively higher expression indicated larger tumor size and poorer prognosis. In vitro experiments proved that Plin2 promoted NSCLC cellular proliferation and inhibited autophagy by activating the AKT/mTOR pathway. Meanwhile, treatment with the AKT phosphorylation promoter or inhibitor neutralized the influence of Plin2 depletion or over-expression on proliferation and autophagy, respectively. In vivo study showed that Plin2 stimulated subcutaneous tumorigenesis of NSCLC cells in nude mice. Collectively, this study clarified the carcinogenic role of Plin2 and its molecular mechanism in NSCLC progression, which may facilitate a targeted therapy in the future.

Challenges in Pharmacological Intervention in Perilipins (PLINs) to Modulate Lipid Droplet Dynamics in Obesity and Cancer

Perilipins (PLINs) are the most abundant proteins in lipid droplets (LD). These LD-associated proteins are responsible for upgrading LD from inert lipid storage structures to fully functional organelles, fundamentally integrated in the lipid metabolism. There are five distinct perilipins (PLIN1-5), each with specific expression patterns and metabolic activation, but all capable of regulating the activity of lipases on LD. This plurality creates a complex orchestrated mechanism that is directly related to the healthy balance between lipogenesis and lipolysis. Given the essential role of PLINs in the modulation of the lipid metabolism, these proteins can become interesting targets for the treatment of lipid-associated diseases. Since reprogrammed lipid metabolism is a recognized cancer hallmark, and obesity is a known risk factor for cancer and other comorbidities, the modulation of PLINs could either improve existing treatments or create new opportunities for the treatment of these diseases. Even though PLINs have not been, so far, directly considered for pharmacological interventions, there are many established drugs that can modulate PLINs activity. Therefore, the aim of this study is to assess the involvement of PLINs in diseases related to lipid metabolism dysregulation and whether PLINs can be viewed as potential therapeutic targets for cancer and obesity.

Ocular and extraocular sebaceous carcinomas: A retrospective study with emphasis on the presence of in situ lesion and discussion and review of the histogenesis of extraocular sebaceous carcinoma

Sebaceous carcinoma (SC) is a rare carcinoma classified as ocular or extraocular. Ocular SC is believed to arise from the meibomian glands or the glands of Zeis. However, the origin of extraocular SC is controversial because there is no evidence of carcinoma arising from pre-existing sebaceous glands. Several hypotheses about the origin of extraocular SC have been proposed, including one suggesting an origin from intraepidermal neoplastic cells. Although extraocular SCs have been shown to occasionally comprise intraepidermal neoplastic cells, no study has investigated whether intraepidermal neoplastic cells possess sebaceous differentiation. The present study analyzed the clinicopathological features of ocular and extraocular SC, with an emphasis on the presence of in situ (intraepithelial) lesions. It retrospectively reviewed the clinicopathological features of eight patients with ocular and three patients with extraocular SC (eight women and three men; median age, 72 years), respectively. In situ (intraepithelial) lesions were observed in four of the eight ocular SC cases and one of the three extraocular SC cases and an apocrine component was noted in one patient with ocular SC (seboapocrine carcinoma). In addition, immunohistochemical analyses showed that the androgen receptor (AR) was expressed in all ocular SCs and two of the three extraocular SC cases. Adipophilin expression was observed in all ocular and extraocular SC. In situ lesions of extraocular SC showed positive immunoreactivity for both AR and adipophilin. The present study is the first to demonstrate sebaceous differentiation in in situ lesions of extraocular SC. The possible origin of extraocular SC is speculated to be the progenitor cells present in the sebaceous duct or interfollicular epidermis. The results of the present study and reported cases of SC in situ indicate that extraocular SC also arises from intraepidermal neoplastic cells.

Assessment of lipid and pigment content in suspicious melanocytic lesions to improve melanoma detection

Melanoma is a highly aggressive form of skin cancer and the most frequent lethal malignancy diagnosed by dermatologists. Although there have been advances for predicting melanoma prognosis, there are few highly sensitive and specific diagnostic tools for clinically evaluating suspicious melanocytic lesions prior to biopsy. We have recently determined that alterations in cellular lipid and pigment content are associated with tumor progression and melanoma metastasis. Here, we seek to determine if lipid droplet and pigment content assessments near the skin's surface are able to distinguish benign from malignant melanocytic lesions. We obtained 14 benign melanocytic lesions, classified as Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis (MPATH-Dx) class 1, and 22 malignant melanomas, classified as MPATH-Dx class 4 or 5, from Boston Medical Center. The malignant melanomas had an average greatest thickness of 1.8 ± 2.1 mm with 7/22 biopsies showing the presence of ulceration. Tissues were stained with the Fontana Masson stain to detect pigment or immunohistochemically stained for adipophilin, the main protein component of lipid droplets, to detect lipid droplets. Pigment and lipid droplets were quantified using ImageJ and CellProfiler, respectively. We found no significant difference in total pigment area between benign melanocytic lesions and malignant melanoma, and a 66% decrease in lipid content and 68% reduction in lipid/pigment content between benign melanocytic lesions and malignant melanoma ( P  < 0.05). Our results suggest that lipid content and lipid/pigment content ratios may distinguish benign and malignant melanocytic lesions, which may be useful as a diagnostic tool for histopathologically challenging pigmented lesions.

PLIN2 promotes HCC cells proliferation by inhibiting the degradation of HIF1α

PLIN2 has been found to be dysregulated in several human malignancies, which influences cancer progression. However, the roles of PLIN2 in regulating hepatocellular carcinoma (HCC) progression are still unclear. Here, we revealed that PLIN2 was frequently upregulated in HCC cells and tissues, and increased PLIN2 expression was associated with poor prognosis outcomes in HCC. In HCC cells, overexpressing PLIN2 promoted cell proliferation, PLIN2-deficiency inhibited cell vitality. Mechanistically, silencing of PLIN2 expression downregulated hypoxia inducible factor 1-α (HIF1α) expression and this downregulation in turn inhibited the targeting genes of HIF1α. Furthermore, we found that PLIN2 stabilized and retarded the degradation of the HIF1α through autophagy-lysosomal pathway by inhibiting AMPK/ULK1. Collectively, we clarified the carcinogenic role of PLIN2 in HCC and suggested a prognostic biomarker for diagnosis and clinical therapy in the future.

Lipid Droplet-Related PLIN2 in CD68+ Tumor-Associated Macrophage of Oral Squamous Cell Carcinoma: Implications for Cancer Prognosis and Immunotherapy

Background

PLIN2 (adipose differentiation-related protein) belongs to the perilipin family and is a marker of lipid droplets (LDs). Numerous types of tumor exhibit a high PLIN2 level, but its tumorigenic or tumor-suppressive role has been in debate. Recently, LDs serve as innate immune hubs and show antimicrobial capacity. We here aimed to investigate the heterogeneous functions of PLIN2 in the tumor microenvironment and immune regulation.

Methods

This retrospective study included 96 oral squamous cell carcinoma (OSCC) samples and analyzed the spatial distribution of PLIN2 by immunohistochemistry (IHC) and LD level by oil red O staining. A total of 21 serial sections were obtained to analyze the relationship between PLIN2 and immune cells by IHC and immunofluorescence (IF). Single-cell sequencing was used to analyze the cell locations of PLIN2. The values of diagnosis and prognosis of PLIN2 were also evaluated. Tumor Immune Estimation Resource (TIMER), cBioPortal databases, and IHC analysis were used to investigate the relationship between PLIN2 and OSCC immune microenvironment.

Results

PLIN2 was mainly expressed in tumor-infiltrating immunocytes (TIIs) of OSCC. Patients with high PLIN2 harbored more cytoplastic LDs. CD68⁺ tumor-associated macrophages (TAMs), instead of T cells and B cells, were found to be the main resource of PLIN2 in OSCC stroma and lung, pancreas, prostate, and testis. However, CD56⁺ NK cells also showed less extent of PLIN2 staining in OSCC. Moreover, patients with a high PLIN2 level in immune cells had a higher TNM stage and were susceptible to postoperative metastasis, but the escalated PLIN2 level in invasive tumor front independently predicted shorter metastasis-free survival. Furthermore, a high PLIN2 presentation in the microenvironment induced immune suppression which was featured as less infiltration of CD8⁺ T cells and more CD68⁺ TAMs and Foxp3⁺ Tregs, accompanied by more immune checkpoint molecules such as CSF1R, LGALS9, IL-10, CTLA-4, and TIGIT.

Conclusion

CD68⁺ TAM-derived PLIN2 might participate in regulating immune balance of OSCC patients, which provides new insight into immune checkpoint therapy.

Lipid Droplet Accumulation Independently Predicts Poor Clinical Prognosis in High-Grade Serous Ovarian Carcinoma

Simple Summary

High-grade serous carcinoma (HGSOC) is the most aggressive subtype of ovarian cancer and accounts for the vast majority of advanced stage cases. Intracellular accumulation of lipids as lipid droplets has been recognized as one of the characteristics of cancers and implicated in poor prognosis of several cancers, such as human melanomas. Here, we investigated the relationship between prognosis and lipid accumulation in HGSOC, and found that enhanced lipid accumulation in HGSOC tissues significantly correlated with poor prognosis. In cell-based assays with human ovarian cancer cells, we provide evidence that aerobic glycolysis, which is one of the characteristic metabolic abnormalities in cancer, induced lipid accumulation within cancer cells and targeting the lipid accumulation could suppress cancer cell proliferation. Thus, our results propose abnormal lipid accumulation as a negative indicator of HGSOC prognosis and a novel therapeutic target.

Abstract

High-grade serous ovarian carcinoma (HGSOC) is an epithelial cancer that accounts for most ovarian cancer deaths. Metabolic abnormalities such as extensive aerobic glycolysis and aberrant lipid metabolism are well-known characteristics of cancer cells. Indeed, accumulation of lipid droplets (LDs) in certain types of malignant tumors has been known for more than 50 years. Here, we investigated the correlation between LD accumulation and clinical prognosis. In 96 HGSOC patients, we found that high expression of the LD marker adipophilin was associated with poor progression-free and overall survival (p = 0.0022 and p = 0.014, respectively). OVCAR-3 ovarian carcinoma cells accumulated LDs in a glucose-dependent manner, which suggested the involvement of aerobic glycolysis and subsequently enhanced lipogenesis, with a result being LD accumulation. The acyl-CoA: cholesterol acyltransferase 1 inhibitor K604 and the hydroxymethylglutaryl-CoA reductase inhibitor pitavastatin blocked LD accumulation in OVCAR-3 cells and reduced phosphorylation of the survival-related kinases Akt and ERK1/2, both of which have been implicated in malignancy. Our cell-based assays thus suggested that enhanced aerobic glycolysis resulted in LD accumulation and activation of survival-related kinases. Overall, our results support the idea that cancers with lipogenic phenotypes are associated with poor clinical prognosis, and we suggest that adipophilin may serve as an independent indicator of a poor prognosis in HGSOC.

Adipophilin expression in skin lesions with clear cell histology

AIMS

Clear cells formed due to depositions of glycogen or lipids in the cytoplasm commonly occur in various tissues. Adipophilin (ADP), a lipid regulatory protein, is closely related to lipid droplets. This study aims to examine adipophilin expression in clear cells of various skin lesions.

METHODS

ADP expression was examined using immunohistochemistry in 108 sections from 15 skin lesion types with clear cell histology, namely, sebaceoma (n=16), sebaceous adenoma (n=3), sebaceous carcinoma (n=12), xanthomata cutis (n=10), xanthogranuloma (n=8), Paget's disease (n=10), Bowen disease (n=10), hidradenoma (n=9), atypical lipoma (n=5), superficial lipomatous nevus (n=5), metastatic renal cell carcinoma (n=5), squamous cell carcinoma (n=4), seborrheic keratosis (n=4), dermatofibroma (n=4) and clear cell sarcoma (n=3).

RESULTS

ADP was not expressed in Bowen disease, hidradenoma or seborrheic keratosis. Four expression patterns, foamy, reticular, granular and punctate, were summarised based on their expression in clear cells. Different expression patterns were related to tissue origin and differentiation degree. Foamy expression was commonly observed in lesions with mature sebaceous glands and xanthomas; reticular expression in adipocytes; granular expression in xanthoma, xanthogranuloma and metastatic renal carcinoma and punctate expression in sebaceoma, sebaceous carcinoma, Paget's disease, squamous cell carcinoma and clear cell sarcoma. Furthermore, stronger staining with focal vesicular labelling was noted in sebaceoma than in sebaceous carcinoma. Characteristic labelling was noted, including the circular distribution in Touton giant cells of xanthogranulomas and focal distribution in the clear cells along the edge of necrotic tissue in clear cell sarcoma.

CONCLUSIONS

ADP is useful in identifying intracytoplasmic lipids and can be used to diagnose skin lesions with clear cell histology, especially in some lesions with characteristic labelling.

Adipophilin expression is an independent marker for poor prognosis of patients with triple-negative breast cancer: An immunohistochemical study

Adipophilin is a lipid droplet-associated protein whose expression can act as a prognostic marker for specific cancers. Using immunohistochemical staining and tissue microarrays, we assayed the expression of adipophilin in 61 patients with triple-negative breast cancer (TNBC) who underwent surgery from January 2006-December 2018. Relapse-free survival (RFS) and its risk factors were analyzed based on adipophilin expression. Fourteen (23.0%) patients expressed adipophilin. As compared to the adipophilin-negative TNBC patients, adipophilin-positive patients exhibited poor RFS (p = 0.032). Among the TNBC patients with a high Ki-67 labeling index, patients negative for adipophilin exhibited better RFS than patients positive for adipophilin (p = 0.032). Moreover, among patients who did not undergo adjuvant chemotherapy, patients negative for adipophilin expression exhibited better RFS than adipophilin-positive patients (p = 0.080). Multivariate analysis showed that adipophilin expression correlated with a high rate of relapse (hazard ratio, 4.89; 95% confidence interval, 1.04-23.0; p = 0.044). Taken together, these results indicate that adipophilin is a novel marker for the poor prognosis of patients with TNBC.

Lipid-Producing Ciliochoroidal Melanoma with Expression of HMG-CoA Reductase

Uveal melanoma (UM) is the commonest primary intraocular malignancy in adults. There is limited published data on lipid production in UM. Here, we describe the clinical, histological, immunohistochemical, and molecular findings in a ciliochoroidal melanoma with lipid production and expression of the enzyme HMG-CoA reductase. This case highlights an unusual UM tumour phenotype with a high-risk molecular metastatic profile and discusses tumour lipogenesis and activation of the mevalonate pathway as a potential therapeutic target in managing lipidised ciliochoroidal UM.

Gene and immunohistochemical expression of HIF-1α, GLUT-1, FASN, and adipophilin in carcinoma ex pleomorphic adenoma development

OBJECTIVE

To analyze the gene and immunohistochemical expression of HIF-1α, GLUT-1, FASN, and adipophilin in normal salivary gland (NSG), pleomorphic adenoma (PA), and carcinoma ex pleomorphic adenoma (CXPA) samples.

MATERIAL AND METHODS

The gene expression was investigated by the real-time PCR (qRT-PCR) method in 9 samples of frozen tissues of normal salivary gland, 13 PA, and 10 CXPA. We validated the reactions by immunohistochemistry on 20 samples from NSG, 85 PA, and 44 CXPA.

RESULTS

Our results showed that there was no statistically significant difference in HIF-1α gene and immunohistochemistry expression among the tissues studied while FASN gene and immunohistochemistry expression increased along the carcinogenesis of the PA. GLUT-1 was significantly more expressed in tumor tissues (PA and CXPA), although protein is mainly expressed in transformed cells than in PA and NSG. In contrast, adipophilin was significantly more expressed in NSG while the expression of the protein increased in PA and CXPA.

CONCLUSIONS

In summary, the data presented here suggest that neoplastic cells reprogram the expression of GLUT-1 and adipophilin to adapt to the tumor microenvironment and reinforce, through immunohistochemical results, a possible transcriptional and post-translational regulatory mechanisms that act on the expression of these genes.

Adipophilin expression in cutaneous malignant melanoma is associated with high proliferation and poor clinical prognosis

Adipophilin (ADP) is a primary protein component of lipid droplets (LDs). For more than half a century, certain types of cancer cells have been known to contain LDs in their cytoplasm. However, the pathological significance of ADP or LDs in cancer remains unclear. In the present study, we investigated the association between ADP and other pathological characteristics in cutaneous malignant melanomas to clarify the role of ADP in melanoma cells. We immunostained whole paraffin sections of primary cutaneous melanomas obtained from 90 cases for ADP, after which we analyzed the correlation between ADP immunohistochemistry (IHC) and patient survival data. We also studied the relationship between the ADP IHC score and in situ hybridization (ISH) score of ADP mRNA, and the Ki67-labeling index (Ki67-LI) by using tissue microarrays consisting of 74 primary cutaneous malignant melanomas, 19 metastasizing melanomas, and 29 melanocytic nevi. Finally, we analyzed the relationship between ADP expression and cell proliferation in cutaneous melanoma cell lines. We found that high ADP expression was associated with poor metastasis-free survival, disease-specific survival, and overall survival rates of patients with cutaneous melanomas (P < 0.05). By linear regression analysis, ADP IHC was correlated with increasing ADP mRNA ISH H-scores and Ki67-LI scores in melanocytic lesions (P < 0.01). ADP IHC and ADP ISH H-scores and Ki67-LI scores were greater in pT3-4 melanomas than in pT1-2 melanomas. In cell-based assays, cells with increased ADP expression showed higher proliferation rates compared with those of low-ADP cells. Thus, ADP expression in malignant melanoma was significantly associated with high cell proliferation and poor clinical prognosis. Our results thus indicate a significant association between ADP and melanoma progression, and we propose that ADP may be a novel marker of aggressive cutaneous melanoma with a lipogenic phenotype.

The Utility of Perilipin in Liposarcomas: PLIN1 Differentiates Round Cell Liposarcoma From Other Round Cell Sarcomas

Liposarcoma is the most common soft tissue sarcoma in adults; however, accurate diagnosis often depends on the use of ancillary molecular testing which can be time consuming and expensive. Myxoid/round cell liposarcoma may be a diagnostic challenge due to the morphologic similarities with other nonadipocytic sarcomas with round cell morphology. Immunohistochemistry may be a helpful adjunct to appropriately triage cases for molecular testing. Perilipin 1 (PLIN1) and perilipin 2 (adipophilin) (PLIN2) are intracellular proteins involved in lipid droplet formation, which we hypothesized may be useful as immunohistochemical markers for liposarcoma. Using archival tumor tissue, we assessed pattern of PLIN1 and PLIN2 expression in 46 adipocytic tumors and 36 nonadipocytic sarcomas. PLIN1 was expressed in 88% of liposarcomas, including 100% of myxoid/round cell liposarcomas, and did not have any expression in nonadipocytic sarcomas. PLIN1 was not expressed in dedifferentiated liposarcoma. Although PLIN2 demonstrates increased sensitivity for liposarcoma, including expression in dedifferentiated liposarcoma, it is not specific for adipocytic differentiation and is expressed in other nonadipocytic sarcomas. Furthermore, PLIN2 is not expressed in lipoma-like well-differentiated liposarcoma, and as such has limited diagnostic utility.

Lipid droplets: platforms with multiple functions in cancer hallmarks

Lipid droplets (also known as lipid bodies) are lipid-rich, cytoplasmic organelles that play important roles in cell signaling, lipid metabolism, membrane trafficking, and the production of inflammatory mediators. Lipid droplet biogenesis is a regulated process, and accumulation of these organelles within leukocytes, epithelial cells, hepatocytes, and other nonadipocyte cells is a frequently observed phenotype in several physiologic or pathogenic situations and is thoroughly described during inflammatory conditions. Moreover, in recent years, several studies have described an increase in intracellular lipid accumulation in different neoplastic processes, although it is not clear whether lipid droplet accumulation is directly involved in the establishment of these different types of malignancies. This review discusses current evidence related to the biogenesis, composition and functions of lipid droplets related to the hallmarks of cancer: inflammation, cell metabolism, increased proliferation, escape from cell death, and hypoxia. Moreover, the potential of lipid droplets as markers of disease and targets for novel anti-inflammatory and antineoplastic therapies will be discussed.

Adipophilin expression is an indicator of poor prognosis in patients with pancreatic ductal adenocarcinoma: An immunohistochemical analysis

OBJECTIVE

Adipophilin is a lipid droplet-associated protein, and its expression has been correlated with aggressive clinical behavior in some types of carcinomas, though its role in pancreatic ductal adenocarcinoma (PDAC) has not been clarified. This study aimed to evaluate the role of adipophilin in PDAC.

METHODS

By immunohistochemical staining using tissue microarrays, we analyzed the expression profiles of adipophilin in 181 consecutive PDAC patients who underwent macroscopic margin-negative resection from January 2008 to December 2015. Overall survival (OS) and recurrence-free survival (RFS) were compared based on adipophilin expression, and the risk factors for OS, RFS, and early recurrence (within 6 months) were analyzed.

RESULTS

Of the 181 evaluated patients, 51 (28.2%) were positive for adipophilin expression. A histopathological grade of 3 (p = 0.0012), higher CA19-9 level (p = 0.0016), and R1 status (p = 0.028) were significantly associated with adipophilin-positive patients who had significantly poor OS and RFS compared to those associated with adipophilin-negative patients (p = 0.0007 and p = 0.0022, respectively). They also showed a significantly higher incidence of early recurrence (p = 0.030), based on multivariate analyses.

CONCLUSIONS

Adipophilin is a potential independent prognostic marker for PDAC.

Overexpression of PLIN2 is a prognostic marker and attenuates tumor progression in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most common renal malignancy in adults, the incidence of which continues to increase. The lipid droplet protein perilipin 2 (PLIN2), which was originally considered an RNA transcript, is markedly expressed during adipocyte differentiation. In addition, it has been observed to be elevated in numerous types of cancer, including ccRCC; however, its essential function remains unclear in ccRCC. The present study examined the expression of PLIN2 in ccRCC, and aimed to determine the association between PLIN2 expression and patient survival. The present study mined the transcriptional, clinicopathological and survival data of PLIN2 in patients with ccRCC through The Cancer Genome Atlas. The expression levels of PLIN2 were also detected in human ccRCC tissues and cell lines by western blotting and immunohistochemistry, and its biological role was identified by functional analysis. The results demonstrated that PLIN2 was predominantly elevated in RCC tissues and cells. In addition, the expression levels of PLIN2 were significantly associated with various clinicopathological factors, and high PLIN2 expression was associated with a good prognosis. The results of a multivariate analysis demonstrated that high PLIN2 expression was an independent prognostic indicator of overall survival (hazard ratio, 0.586; P=0.001). Furthermore, PLIN2 knockdown promoted proliferation of ccRCC cells, and enhanced cell invasion and migration. These results suggested that PLIN2 may be considered a novel prognostic factor in ccRCC and a specific diagnostic indicator for patients with ccRCC. Furthermore, it could be a potential novel target for the clinical treatment of ccRCC.