Lipoprotein lipase in chronic lymphocytic leukaemia - strong biomarker with lack of functional significance

Identification of a 9-gene prognostic signature for breast cancer

Breast cancer (BRCA) is the most common cancer among women and is the second leading cause of cancer death in women. In this study, we developed a 9‐gene prognostic signature to predict the prognosis of patients with BRCA. GSE20685, GSE42568, GSE20711, and GSE88770 were used as training sets. The Kaplan–Meier plot was constructed to assess survival differences and log‐rank test was performed to evaluate the statistical significance. The overall survival (OS) of patients in the low‐risk group was significantly higher than that in the high‐risk group. ROC analysis indicated that this 9‐gene signature shows good diagnostic efficiency both in OS and disease‐free survival (DFS). The 9‐gene signature was further validated through GSE16446, GSE7390, and TCGA‐BRCA datasets. We also established a nomogram that integrates clinicopathological features and 9‐gene signature. The analysis of the calibration plot showed that the nomogram has good prognostic performance. More convincingly, real‐time reverse transcription‐polymerase chain reaction (RT‐PCR) results indicated that the protective prognostic factors in BRCA patients were downregulated, whereas the dangerous prognostic factors were upregulated. The innovation of this article is not only constructing a prognostic gene signature, but also combining with clinical information to further establish a nomogram to better predict the survival probability of patients. It is worth mentioning that this signature also does not depend on other clinical factors or variables.

Altered expression of metabolic pathways in CLL detected by unlabelled quantitative mass spectrometry analysis

Chronic lymphocytic leukaemia (CLL) remains the most common incurable malignancy of B cells in the western world. Patient outcomes are heterogeneous and can be difficult to predict with current prognostic markers. Here, we used a quantitative label-free proteomic technique to ascertain differences in the B-cell proteome from healthy donors and CLL patients with either mutated (M-CLL) or unmutated (UM-CLL) IGHV to identify new prognostic markers. In peripheral B-CLL cells, 349 (22%) proteins were differentially expressed between normal B cells and B-CLL cells and 189 (12%) were differentially expressed between M-CLL and UM-CLL. We also examined the proteome of proliferating CLL cells in the lymph nodes, and identified 76 (~8%) differentially expressed proteins between healthy and CLL lymph nodes. B-CLL cells show over-expression of proteins involved in lipid and cholesterol metabolism. A comprehensive lipidomic analysis highlighted large differences in glycolipids and sphingolipids. A shift was observed from the pro-apoptotic lipid ceramide towards the anti-apoptotic/chemoresistant lipid, glucosylceramide, which was more evident in patients with aggressive disease (UM-CLL). This study details a novel quantitative proteomic technique applied for the first time to primary patient samples in CLL and highlights that primary CLL lymphocytes display markers of a metabolic shift towards lipid synthesis and breakdown.

LPL protein in Chronic Lymphocytic Leukaemia have different origins in Mutated and Unmutated patients. Advances for a new prognostic marker in CLL

Lipoprotein lipase (LPL) mRNA expression in chronic lymphocytic leukaemia (CLL) is associated with an unmutated immunoglobulin profile and poor clinical outcome. We evaluated the subcellular localization of LPL protein in CLL cells that did or did not express LPL mRNA. Our results show that LPL protein is differently located in CLL cells depending on whether it is incorporated from the extracellular medium in mutated CLL or generated de novo by leukaemic cells of unmutated patients. The specific quantification of endogenous LPL protein correlates with mRNA expression levels and mutational IGHV status, suggesting LPL protein as a possible reliable prognostic marker in CLL.

Ibrutinib inhibits free fatty acid metabolism in chronic lymphocytic leukemia

Unlike normal B-cells, and similar to fat cells, chronic lymphocytic leukemia (CLL) cells aberrantly express lipoprotein lipase (LPL), which contributes to free fatty acids (FFAs) metabolism. Here we show that, in CLL cells, the B-cell receptor (BCR) inhibitor ibrutinib reduced LPL mRNA and protein levels and inhibited FFA metabolism in vitro. Likewise, in CLL cells from ibrutinib-treated patients, FFA metabolism was reduced and eventually stopped. Because ibrutinib disrupts CLL cells' ability to use FFAs for energy production, and because various BCR-dependent cellular functions rely on a continuous supply of chemical energy, ibrutinib interrupts several pathways imperative for cellular function in CLL cells.

SUOX is negatively associated with multistep carcinogenesis and proliferation in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the most common malignant tumor in the head and neck region. The aim of this study was to identify the key molecules and to elucidate the molecular mechanisms of OSCC carcinogenesis through a microarray analysis of RNA extracted from normal epithelium, dysplasia, and squamous cell carcinoma components. Out of molecules that showed changes in gene expression in the microarray analysis, we focused on Sulfite oxidase (SUOX), which correlated significantly with carcinogenic process and exhibited a stepwise decrease in expression. The expression of SUOX was evaluated in detail at the protein level using samples from 58 patients with cancer of the tongue, and correlating clinicopathological factors were also comprehensively examined. SUOX expression declined significantly from normal epithelium to dysplasia to squamous cell carcinoma components in line with carcinogenic process. With regard to squamous cell carcinoma, SUOX expression was significantly lower when T classification was high. Our findings indicated that SUOX is negatively associated with the progression and proliferation of tongue cancer, and suggest that SUOX may be a key molecule in tongue tumors.

Lipoprotein Lipase Expression in Chronic Lymphocytic Leukemia: New Insights into Leukemic Progression

Lipoprotein lipase (LPL) is a central enzyme in lipid metabolism. Due to its catalytic activity, LPL is involved in metabolic pathways exploited by various solid and hematologic malignancies to provide an extra energy source to the tumor cell. We and others described a link between the expression of LPL in the tumor cell and a poor clinical outcome of patients suffering Chronic Lymphocytic Leukemia (CLL). This leukemia is characterized by a slow accumulation of mainly quiescent clonal CD5 positive B cells that infiltrates secondary lymphoid organs, bone marrow and peripheral blood. Despite LPL being found to be a reliable molecular marker for CLL prognosis, its functional role and the molecular mechanisms regulating its expression are still matter of debate. Herein we address some of these questions reviewing the current state of the art of LPL research in CLL and providing some insights into where currently unexplored questions may lead to.

To treat or not to treat: metabolomics reveals biomarkers for treatment indication in chronic lymphocytic leukaemia patients

In chronic lymphocytic leukaemia (CLL), the clinical course of patients is heterogeneous. Some present an aggressive disease onset and require immediate therapy, while others remain without treatment for years. Current disease staging systems developed by Rai and Binet may be useful in forecasting patient survival time, but do not discriminate between stable and progressive forms of the disease in the early stages. Recently ample attention has been directed towards identifying new disease prognostic markers capable of predicting clinical aggressiveness at diagnosis. In the present study serum samples from stable (n = 51) and progressive (n = 42) CLL patients and controls (n = 45) were used with aim to discover metabolic indicators of disease status. First an LC-MS based metabolic fingerprinting method was used to analyse selected samples in order to find a potential markers discriminating aggressive from indolent patients. Ten of these discovered markers were validated on the whole set of samples with an independent analytical technique. Linoleamide (p = 0.002) in addition to various acylcarnitines (p = 0.001-0.000001) showed to be significant markers of CLL in its aggressive form. Acetylcarnitine (p = 0.05) and hexannoylcarnitine (p = 0.005) were also distinguishable markers of indolent subjects. Forming a panel of selected acylcarnitines and fatty acid amides, it was possible to reach a potentially highly specific and sensitive diagnostic approach (AUC = 0.766).

Lipoprotein Lipase as a Prognostic Marker in Chronic Lymphocytic Leukemia

The marked clinical heterogeneity of CLL makes early prognosis assessment important. Lipoprotein lipase (LPL) has been shown to confer adverse prognosis in CLL, recent data indicating it might also contribute to CLL cell survival and metabolism. We determined LPL mRNA expression in unselected peripheral blood of 84 CLL patients by RT PCR. Results were correlated with other prognostic markers and outcome. 30/84 (40 %) of cases were LPL positive based on the cutoff established by ROC analysis. In LPL positive patients significantly shorter median survival (136 vs 258 months, p < 0.0001) and time to first treatment intervals (36 vs 144 months, p < 0.002) were documented. LPL values correlated with male gender, higher stages, more treatment requirement, CD38 positivity and unmutated IgVH genes. Among cases with 13q deletion, LPL positivity identified a subcohort with poor outcome (median survival 108 months vs NR, p < 0.0001). In multivariate analysis, cytogenetic aberrations and LPL had significant impact on survival. Our results confirm that LPL is a strong predictor of outcome in CLL, able to improve prognostic accuracy in good risk cytogenetic subgroups. The relationship between its prognostic and functional role in CLL needs to be explored further.

Lipoprotein lipase in chronic lymphocytic leukemia: function and prognostic implications

Chronic lymphocytic leukemia (CLL) is a clinically heterogeneous disease characterized by the accumulation of a clonal population of B cells in peripheral blood, bone marrow, and lymphoid organs. More than 10 years ago, lipoprotein lipase (LPL) mRNA was identified as being strongly expressed in patients experiencing a more aggressive phenotype, while CLL patients with an indolent disease course lack expression of this marker. Since then, several reports confirmed the capability of LPL to predict CLL disease evolution at the moment of diagnosis. In contrast, data on the functional implications of LPL in CLL are scarce. LPL exerts a central role in overall lipid metabolism and transport, but plays additional, non-catalytic roles as well. Which of those is more important in the pathogenesis of CLL remains largely unclear. Here, we review the current knowledge on the prognostic and biological relevance of LPL in CLL.

Elimination of chronic lymphocytic leukemia cells in stromal microenvironment by targeting CPT with an antiangina drug perhexiline

Chronic lymphocytic leukemia (CLL) is the most common adult leukemia in the western countries and is currently incurable due, in part, to difficulty in eliminating the leukemia cells protected by stromal microenvironment. Based on previous observations that CLL cells exhibit mitochondrial dysfunction and altered lipid metabolism and that carnitine palmitoyltransferases (CPT) have a major role in transporting fatty acid into mitochondria to support cancer cell metabolism, we tested several clinically relevant inhibitors of lipid metabolism for their ability to eliminate primary CLL cells. We discovered that perhexiline, an antiangina agent that inhibits CPT, was highly effective in killing CLL cells in stromal microenvironment at clinically achievable concentrations. These effective concentrations caused low toxicity to normal lymphocytes and normal stromal cells. Mechanistic study revealed that CLL cells expressed high levels of CPT1 and CPT2. Suppression of fatty acid transport into mitochondria by inhibiting CPT using perhexiline resulted in a depletion of cardiolipin, a key component of mitochondrial membranes, and compromised mitochondrial integrity, leading to rapid depolarization and massive CLL cell death. The therapeutic activity of perhexiline was further demonstrated in vivo using a CLL transgenic mouse model. Perhexiline significantly prolonged the overall animal survival by only four drug injections. Our study suggests that targeting CPT using an antiangina drug is able to effectively eliminate leukemia cells in vivo, and is a novel therapeutic strategy for potential clinical treatment of CLL.

LPL gene expression is associated with poor prognosis in CLL and closely related to NOTCH1 mutations

INTRODUCTION

Chronic lymphocytic leukemia is a heterogeneous yet incurable disease. Whole-genome and whole-exome sequencing studies have revealed recurrently occurring somatic mutations in some genes. Several other prognostic markers have previously been tested for their prognostic value in CLL. LPL is among these markers.

AIM

To evaluate LPL gene expression together with the well-established prognostic markers of CLL and investigate correlations with more recently identified prognostic markers, NOTCH1 and TP53 mutations.

METHODS

On 149 patients, LPL gene expression was analyzed by real-time RT-PCR. Exon 34 of NOTCH1 was PCR-amplified and directly sequenced.

RESULTS

LPL gene expression could be measured as a categorical variable (LPL+/LPL-) and was associated with time to treatment (P < 0.001) and overall survival (P = 0.007). In patients otherwise classified as having a good prognosis according to established and new prognostic markers, 3 of 4 patients, who received treatment within 24 months after diagnosis, were LPL+ (P = 0.03). There was a strong correlation between NOTCH1 mutation and LPL+ (P = 0.005). The unfavorable prognosis of LPL+ was maintained in CLL with wild-type NOTCH1.

CONCLUSIONS

NOTCH1 mutations are tightly associated with LPL gene expression. LPL expression is independently associated with poor outcome in CLL and can be measured as a categorical variable.

Developing Molecular Signatures for Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a clonal malignancy of mature B cells that displays a great clinical heterogeneity, with many patients having an indolent disease that will not require intervention for many years, while others present an aggressive and symptomatic leukemia requiring immediate treatment. Although there is no cure for CLL, the disease is treatable and current standard chemotherapy regimens have been shown to prolong survival. Recent advances in our understanding of the biology of CLL have led to the identification of numerous cellular and molecular markers with potential diagnostic, prognostic and therapeutic significance. We have used the recently developed digital multiplexed gene-expression technique (DMGE) to analyze a cohort of 30 CLL patients for the presence of specific genes with known diagnostic and prognostic potential. Starting from a set of 290 genes we were able to develop a molecular signature, based on the analysis of 13 genes, which allows distinguishing CLL from normal peripheral blood and from normal B cells, and a second signature based on 24 genes, which distinguishes mutated from unmutated cases (LymphCLL Mut). A third classifier (LymphCLL Diag), based on a 44-gene signature, distinguished CLL cases from a series of other B-cell chronic lymphoproliferative disorders (n = 51). While the methodology presented here has the potential to provide a "ready to use" classification tool in routine diagnostics and clinical trials, application to larger sample numbers are still needed and should provide further insights about its robustness and utility in clinical practice.

Aberrant LPL Expression, Driven by STAT3, Mediates Free Fatty Acid Metabolism in CLL Cells

While reviewing chronic lymphocytic leukemia (CLL) bone marrow slides, we identified cytoplasmic lipid vacuoles in CLL cells but not in normal B cells. Because lipoprotein lipase (LPL), which catalyzes hydrolysis of triglycerides into free fatty acids (FFA), is aberrantly expressed in CLL, we investigated whether LPL regulates the oxidative metabolic capacity of CLL cells. We found that unlike normal B cells, CLL cells metabolize FFAs. Because STAT3 is constitutively activated in CLL cells and because we identified putative STAT3 binding sites in the LPL promoter, we sought to determine whether STAT3 drives the aberrant expression of LPL. Transfection of luciferase reporter gene constructs driven by LPL promoter fragments into MM1 cells revealed that STAT3 activates the LPL promoter. In addition, chromatin immunoprecipitation confirmed that STAT3 binds to the LPL promoter. Furthermore, transfection of CLL cells with STAT3-shRNA downregulated LPL transcripts and protein levels, confirming that STAT3 activates the LPL gene. Finally, transfection of CLL cells with LPL-siRNAs decreased the capacity of CLL cells to oxidize FFAs and reduced cell viability.

IMPLICATIONS

Our study suggests that CLL cells adopt their metabolism to oxidize FFA. Activated STAT3 induces LPL, which catalyzes the hydrolysis of triglycerides into FFA. Therefore, inhibition of STAT3 is likely to prevent the capacity of CLL cells to utilize FFA.