Unique metabolic features of pancreatic cancer stroma: relevance to the tumor compartment, prognosis, and invasive potential.

Pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis. The aggressiveness and therapeutic recalcitrance of this malignancy has been attributed to multiple factors including the influence of an active desmoplastic stroma. How the stromal microenvironment of PDAC contributes to the fatal nature of this disease is not well defined. In the analysis of clinical specimens, we observed diverse expression of the hypoxic marker carbonic anhydrase IX and the lactate transporter MCT4 in the stromal compartment. These stromal features were associated with the epithelial to mesenchymal phenotype in PDAC tumor cells, and with shorter patient survival. Cultured cancer-associated fibroblasts (CAFs) derived from primary PDAC exhibited a high basal level of hypoxia inducible factor 1a (HIF1α) that was both required and sufficient to modulate the expression of MCT4. This event was associated with increased transcription and protein synthesis of HIF1α in CAFs relative to PDAC cell lines, while surprisingly the protein turnover rate was equivalent. CAFs utilized glucose predominantly for glycolytic intermediates, whereas glutamine was the preferred metabolite for the TCA cycle. Unlike PDAC cell lines, CAFs were resistant to glucose withdrawal but sensitive to glutamine depletion. Consistent with the lack of reliance on glucose, CAFs could survive the acute depletion of MCT4. In co-culture and xenograft studies CAFs stimulated the invasive potential and metastatic spread of PDAC cell lines through a mechanism dependent on HIF1α and MCT4. Together, these data indicate that stromal metabolic features influence PDAC tumor cells to promote invasiveness and metastatic potential and associate with poor outcome in patients with PDAC

GLUT1 expression patterns in different Hodgkin lymphoma subtypes and progressively transformed germinal centers

Background: Increased glycolytic activity is a hallmark of cancer, allowing staging and restaging with 18F-fluorodeoxyglucose-positron-emission-tomography (PET). Since interim-PET is an important prognostic tool in Hodgkin lymphoma (HL), the aim of this study was to investigate the expression of proteins involved in the regulation of glucose metabolism in the different HL subtypes and their impact on clinical outcome. Methods: Lymph node biopsies from 54 HL cases and reactive lymphoid tissue were stained for glucose transporter 1 (GLUT1), lactate dehydrogenase A (LDHA) and lactate exporter proteins MCT1 and MCT4. In a second series, samples from additional 153 HL cases with available clinical data were stained for GLUT1 and LDHA. Results: Membrane bound GLUT1 expression was frequently observed in the tumor cells of HL (49% of all cases) but showed a broad variety between the different Hodgkin lymphoma subtypes: Nodular sclerosing HL subtype displayed a membrane bound GLUT1 expression in the Hodgkin-and Reed-Sternberg cells in 56% of the cases. However, membrane bound GLUT1 expression was more rarely observed in tumor cells of lymphocyte rich classical HL subtype (30%) or nodular lymphocyte predominant HL subtype (15%). Interestingly, in both of these lymphocyte rich HL subtypes as well as in progressively transformed germinal centers, reactive B cells displayed strong expression of GLUT1. LDHA, acting downstream of glycolysis, was also expressed in 44% of all cases. We evaluated the prognostic value of different GLUT1 and LDHA expression patterns; however, no significant differences in progression free or overall survival were found between patients exhibiting different GLUT1 or LDHA expression patterns. There was no correlation between GLUT1 expression in HRS cells and PET standard uptake values. Conclusions: In a large number of cases, HRS cells in classical HL express high levels of GLUT1 and LDHA indicating glycolytic activity in the tumor cells. Although interim-PET is an important prognostic tool, a predictive value of GLUT1 or LDHA staining of the primary diagnostic biopsy could not be demonstrated. However, we observed GLUT1 expression in progressively transformed germinal centers and hyperplastic follicles, explaining false positive results in PET. Therefore, PET findings suggestive of HL relapse should always be confirmed by histology

Elevated Tumor Lactate and Efflux in High-grade Prostate Cancer demonstrated by Hyperpolarized 13C Magnetic Resonance Spectroscopy of Prostate Tissue Slice Cultures.

Non-invasive assessment of the biological aggressiveness of prostate cancer (PCa) is needed for men with localized disease. Hyperpolarized (HP) 13C magnetic resonance (MR) spectroscopy is a powerful approach to image metabolism, specifically the conversion of HP [1-13C]pyruvate to [1-13C]lactate, catalyzed by lactate dehydrogenase (LDH). Significant increase in tumor lactate was measured in high-grade PCa relative to benign and low-grade cancer, suggesting that HP 13C MR could distinguish low-risk (Gleason score ≤3 + 4) from high-risk (Gleason score ≥4 + 3) PCa. To test this and the ability of HP 13C MR to detect these metabolic changes, we cultured prostate tissues in an MR-compatible bioreactor under continuous perfusion. 31P spectra demonstrated good viability and dynamic HP 13C-pyruvate MR demonstrated that high-grade PCa had significantly increased lactate efflux compared to low-grade PCa and benign prostate tissue. These metabolic differences are attributed to significantly increased LDHA expression and LDH activity, as well as significantly increased monocarboxylate transporter 4 (MCT4) expression in high- versus low- grade PCa. Moreover, lactate efflux, LDH activity, and MCT4 expression were not different between low-grade PCa and benign prostate tissues, indicating that these metabolic alterations are specific for high-grade disease. These distinctive metabolic alterations can be used to differentiate high-grade PCa from low-grade PCa and benign prostate tissues using clinically translatable HP [1-13C]pyruvate MR

Astrocytes and neurons communicate via a monocarboxylic acid shuttle

Since formulation of the Astrocyte-Neuron Lactate Shuttle (ANLS) hypothesis in 1994, the hypothesis has provoked criticism and debate. Our review does not criticise, but rather integrates experimental data characterizing proton-linked monocarboxylate transporters (MCTs) into the ANLS. MCTs have wide substrate specificity and are discussed to be in protein complex with a proton donor (PD). We particularly focus on the proton-driven transfer of L-lactic acid (L-lacH) and pyruvic acid (pyrH), were PDs link MCTs to a flow of energy. The precise nature of the PD predicts the activity and catalytic direction of MCTs. By doing so, we postulate that the MCT4•phosphoglycerate kinase complex exports and at the same time in the same astrocyte, MCT1•carbonic anhydrase II complex imports monocarboxylic acids. Similarly, neuronal MCT2 preferentially imports pyrH. The repertoire of MCTs in astrocytes and neurons allows them to communicate via monocarboxylic acids. A change in imported pyrH/L-lacH ratio in favour of L-lacH encodes signals stabilizing the transit of glucose from astrocytes to neurons. The presented astrocyte neuron communication hypothesis has the potential to unite the community by suggesting that the exchange of monocarboxylic acids paves the path of glucose provision

Metabolic reprogramming identifies the most aggressive lesions at early phases of hepatic carcinogenesis

Metabolic changes are associated with cancer, but whether they are just bystander effects of deregulated oncogenic signaling pathways or characterize early phases of tumorigenesis remains unclear. Here we show in a rat model of hepatocarcinogenesis that early preneoplastic foci and nodules that progress towards hepatocellular carcinoma (HCC) are characterized both by inhibition of oxidative phosphorylation (OXPHOS) and by enhanced glucose utilization to fuel the pentose phosphate pathway (PPP). These changes respectively require increased expression of the mitochondrial chaperone TRAP1 and of the transcription factor NRF2 that induces the expression of the rate-limiting PPP enzyme glucose-6-phosphate dehydrogenase (G6PD), following miR-1 inhibition. Such metabolic rewiring exclusively identifies a subset of aggressive cytokeratin-19 positive preneoplastic hepatocytes and not slowly growing lesions. No such metabolic changes were observed during non-neoplastic liver regeneration occurring after two/third partial hepatectomy. TRAP1 silencing inhibited the colony forming ability of HCC cells while NRF2 silencing decreased G6PD expression and concomitantly increased miR-1; conversely, transfection with miR-1 mimic abolished G6PD expression. Finally, in human HCC patients increased G6PD expression levels correlates with grading, metastasis and poor prognosis. Our results demonstrate that the metabolic deregulation orchestrated by TRAP1 and NRF2 is an early event restricted to the more aggressive preneoplastic lesions

Metformin: a modulator of bevacizumab activity in cancer? A case report.

Recurrent type I endometrial cancer ((EC)) has poor prognosis and demands novel therapeutic approaches. Bevacizumab, a VEGF-A neutralizing monoclonal antibody, has shown clinical activity in this setting. To our knowledge, however, although some diabetic cancer patients treated with bevacizumab may also take metformin, whether metformin modulates response to anti-VEGF therapy has not yet been investigated. Here, we report the case of a patient with advanced (EC) treated, among other drugs, with bevacizumab in combination with metformin. The patient affected by relapsed (EC) G3 type 1, presented in march 2010 with liver, lungs and mediastinic metastases. After six cycles of paclitaxel and cisplatin she underwent partial response. Later on, she had disease progression notwithstanding administration of multiple lines of chemotherapy. In march 2013, due to brain metastases with coma, she began steroid therapy with development of secondary diabetes. At this time, administration of Bevacizumab plus Metformin improved her performance status. CT scans performed in this time window showed reduced radiologic density of the lung and mediastinic lesions and of liver disease, suggestive of increased tumor necrosis. Strong F-18-FDG uptake by PET imaging along with high levels of monocarboxylate transporter 4 and lack of liver kinase B1 expression in liver metastasis, highlighted metabolic features previously associated with response to anti-VEGF therapy and phenformin in preclinical models. However, clinical benefit was transitory and was followed by rapid and fatal disease progression. These findingsalbeit limited to a single casesuggest that tumors lacking LKB1 expression and/or endowed with an highly glycolytic phenotype might develop large necrotic areas following combined treatment with metformin plus bevacizumab. As metformin is widely used among diabetes patients as well as in ongoing clinical trials in cancer patients, these results deserve further clinical investigation

Stromal Monocarboxylate Transporter MCT4 is a Poor Prognostic Factor in Squamous Cell Carcinoma

ABSTRACT Introduction: Monocarboxylate transporter 4 (MCT4) is the main exporter of lactate out of cells. It is also a critical component in the glycolytic metabolism of cancer cells. In this study, stromal MCT4 in oral SCC was correlated with risk of recurrence (ROR), extent of primary tumor (pT) and nodal metastasis (pN), perineural invasion (PNI), lymphovascular invasion (LVI), HPV status, extracapsular extension (ECE) and positive margin. Methods: Clinical data were collected for 86 consecutive patients with oral HNSCC. Tissue microarrays (TMA) were constructed from paraffin blocks of resection specimens and stained for MCT4. Immunohistochemistry (IHC) staining was assessed and quantified by digital image analysis with Aperio software. Using a co-localization algorithm we assessed the intensity of staining and the percentage of positive cells in the tumoral stromal cells. Correlations of MCT4 expression with clinicopathological features and survival were studied. Results: Increased IHC staining for MCT4 was strongly associated with an increased risk of recurrence, OR 1.96 (95%CI: 1.17-3.40), presence of PNI, OR 2.25 (95%CI: 1.33-3.95), higher pT, OR 1.68 (95%CI: 0.99-2.89), higher pN, OR 2.07 (95%CI: 1.25-3.57) and presence of LVI, OR 2.21 (95%CI: 1.11-4.67). We didn’t find any significant association between stromal MCT4 expression and HPV status, presence of ECE or positive margin. Conclusions: This study demonstrates that MCT4, a marker of glycolysis in cancer-associated stroma, is highly expressed in oral SCC. The IHC staining pattern of stromal MCT4 suggests that high MCT4 expression appears to be a useful marker for tumor progression and prognosis. We propose MCT4 serves as a new prognostic factor in oral SCC and can act as a potential therapeutic target marker considering pharmacological development of MCT4 inhibitors

Tumor Metabolism in the Microenvironment of Nodal Metastasis in Head and Neck Squamous Cell Carcinoma

ABSTRACT Introduction: Monocarboxylate transporter 4 (MCT4) is a cell membrane transporter of lactate. MCT4 is a tumor-specific marker of oxidative stress, glycolysis and hypoxia in tumor stromal cells. We investigated HPV positive and negative tumors with regional metastases to cervical lymph nodes (LN) to study how the metastatic tumor cells interact with their microenvironment. By selecting cancers with extracapsular extension (ECE), we intended to evaluate the interaction between metastases and the surrounding extranodal tissue. Methods: Clinical data were collected from 24 advanced stage oropharyngeal squamous cell carcinoma (OPSCC) patients with neck LN metastasis. All patients presented with at least N1 disease and had ECE. Sixteen cases were negative for HPV and eight were positive. Ten patients (42%) had ECE \u3c 1 mm, and 14 (58%) had ECE \u3e than 1 mm. The extent of ECE was quantified on H&E stains by distance from the edge of capsule. The paraffin-embedded metastatic LN sections were stained with MCT4 and quantification was accomplished using the Aperio Co-localization algorithm. Results: High stromal MCT4 expression was strongly associated with the extent of ECE regardless of HPV status (p=0.031). The stromal MCT4 expression in ECE area was significantly higher as opposed to the surrounding extranodal tissue adjacent to intact capsule (p\u3c0.001). We also found a borderline difference in expression of MCT4 in HPV- LN with ECE \u3e1mm vs. \u3c1mm(p=0.06). Conclusions: MCT4 is a marker of oxidative stress and higher expression of stromal MCT4 in ECE area is significantly correlated with the extent of ECE. The stromal cells separating nests of cancer cells in ECE area have apparent expression of the MCT4. Together these findings provide new insight into the critical role of stromal MCT4 in nodal metastasis and ECE in OPSCC and it may be useful to develop a novel prognostic marker and new anti-cancer agents