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There is currently no consensus to determine which advanced melanoma patients will benefit from immunotherapy, highlighting the critical need to identify early-response biomarkers to immune checkpoint inhibitors. The aim of this work was to evaluate in vivo metabolic spectroscopy using hyperpolarized (HP) 13C-pyruvate and 13C-glucose to assess early response to anti-PD1 therapy in the YUMMER1.7 syngeneic melanoma model. The xenografts showed a significant tumor growth delay when treated with two cycles of an anti-PD1 antibody compared to an isotype control antibody. 13C-MRS was performed in vivo after the injection of hyperpolarized 13C-pyruvate, at baseline and after one cycle of immunotherapy, to evaluate early dynamic changes in 13C-pyruvate–13C-lactate exchange. Furthermore, ex vivo 13C-MRS metabolic tracing experiments were performed after U-13C-glucose injection following one cycle of immunotherapy. A significant decrease in the ratio of HP 13C-lactate to 13C-pyruvate was observed in vivo in comparison with the isotype control group, while there was a lack of change in the levels of 13C lactate and 13C alanine issued from 13C glucose infusion, following ex vivo assessment on resected tumors. Thus, these results suggest that hyperpolarized 13C-pyruvate could be used to assess early response to immune checkpoint inhibitors in melanoma patients.

Obesity is characterized by an excessive fat mass accumulation associated with multiple disorders, including impaired glucose homeostasis, altered adipokine levels, and hyperlipidemia. Despite clear associations between tumor progression and obesity, the effects of these disorders on tumor metabolism remain largely unknown. Thus, we studied the metabolic differences between tumors of obese and lean mice in murine models of triple-negative breast cancer (E0771 and PY8819). For this purpose, a real-time hyperpolarized 1-13C-pyruvate-to-lactate conversion was studied before and after glucose administration in fasting mice. This work was completed by U-13C glucose tracing experiments using nuclear magnetic resonance (NMR) spectroscopy, as well as mass spectrometry (MS). Ex vivo analyses included immunostainings of major lipid, glucose, and monocarboxylic acids transporters. On the one hand, we discovered that tumors of obese mice yield higher lactate/pyruvate ratios after glucose administration. On the other hand, we found that the same tumors produce higher levels of lactate and alanine from glucose than tumors from lean mice, while no differences on the expression of key transporters associated with glycolysis (i.e., GLUT1, MCT1, MCT4) have been observed. In conclusion, our data suggests that breast tumor metabolism is regulated by the host’s physiological status, such as obesity and diabetes.

In Oncology, chemoresistance is often responsible for therapeutic failure. In this work where we used human cancer models, we investigated whether precise metabolic changes could account for chemoresistance. Not only in cisplatin-resistant ovarian cancer but also in temozolomide-resistant glioblastoma, we evidenced highly oxidative chemoresistant phenotypes depending on mitophagy. Consequently, inhibiting either mitophagy by more largely blocking autophagy or cell respiration by targeting Complex I in the electron transport chain with olaparib allowed to resensitize cancer cells to cisplatin and/or to temozolomide. We propose that these two approaches used in combination therapies with selected forms of chemotherapy would be attractive for countering cancer chemoresistance., (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2022

Metabolic plasticity in cancer cells makes very challenging the use of metabolism-targeting agents as monotherapy due to resistance establishment. Moreover, the use of these drugs as anticancer treatments will not only affect cancer cells, but also immune cells in the tumor microenvironment and thereby might abrogate the beneficial effects of immunotherapy. In the first part of our work, we report that exposure to 3-bromopyruvate, a glycolysis inhibitor, renders cancer cells vulnerable to the blockade of monocarboxylate transporter 4 activity, which prevents resistant cells to growth. In the second part of this thesis, we show that acute treatment of activated T cells with fatty acid oxidation inhibitor leads to an increase of their proliferation in vitro, and to higher cytotoxic capacities towards melanoma cancer cells. Altogether our data offer metabolism-targeting therapeutic strategies to overcome resistance from plastic cancer cells and to potentiate benefits of immunotherapies., (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2022

Ovarian tissue cryopreservation and further transplantation has proved its effectiveness in restoring fertility after cancer, with over 200 live births worldwide to date. However, it is limited by massive ischemic damage that occurs shortly after transplantation, causing a significant decline in the ovarian reserve. This project aimed to develop a novel strategy using adipose tissue-derived stem cells (ASCs) for ovarian tissue transplantation, after our preliminary results revealed their impact on hypoxia and revascularization. ASCs are able to protect the ovarian reserve from hypoxic damage, thereby reducing follicle loss. Moreover, their secretome, rich in growth factors, is able to both enhance graft revascularization and reperfusion, and mitigate the primordial follicle burn-out due to abnormal activation soon after transplantation. The present work proved the effecicacy of ASC use in ovarian tissue transplantation, which is now one step closer to clinical application., (MED - Sciences médicales) -- UCL, 2022

A vast majority of BRAF V600E mutated melanoma patients will develop resistance to combined BRAF/MEK inhibition after initial clinical response. Resistance to targeted therapy is described to be accompanied by specific metabolic changes in melanoma. The aim of this work was to evaluate metabolic imaging using 13C-MRS (Magnetic Resonance Spectroscopy) as a marker of response to BRAF/MEK inhibition in a syngeneic melanoma model. Tumor growth was significantly delayed in mice bearing YUMM1.7 melanoma xenografts treated with the BRAF inhibitor vemurafenib, and/or with the MEK inhibitor trametinib, in comparison with the control group. 13C-MRS was performed in vivo after injection of hyperpolarized (HP) 13C-pyruvate, at baseline and 24 h after treatment, to evaluate dynamic changes in pyruvate-lactate exchange. Furthermore, ex vivo 13C-MRS steady state metabolic tracing experiments were performed after U-13C-glucose or 5-13C-glutamine injection, 24 h after treatment. The HP 13C-lactate-to-pyruvate ratio was not modified in response to BRAF/MEK inhibition, whereas the production of 13C-lactate from 13C-glucose was significantly reduced 24 h after treatment with vemurafenib, trametinib, or with the combined inhibitors. Conversely, 13C-glutamine metabolism was not modified in response to BRAF/MEK inhibition. In conclusion, we identified 13C-glucose fluxomic as a potential marker of response to BRAF/MEK inhibition in YUMM1.7 melanoma xenografts.

Cancer cachexia is a complex multi-organ syndrome characterised by body weight loss, weakness, muscle atrophy and fat depletion. The modulation of the gut microbiota, an important regulator of the host metabolism, has shown therapeutic potential. To evaluate the contribution of gut microbiota alterations to the metabolic dysfunctions observed in cancer cachexia, we first investigated the role of Klebsiella oxytoca. We found that this Enterobacteriaceae species acts as a gut pathobiont by altering the gut barrier function in cachectic mice. Then, a multi –omics strategy revealed multiple host metabolic alterations and a reduction of different beneficial intestinal bacterial activities in cachectic mice. Finally, we used a multi –omics approach to show that acute myeloid leukemic patients display gut microbiome alterations at diagnosis. Such alterations may contribute to metabolic and inflammatory dysregulations in those patients. By combining preclinical and clinical data, this thesis work pinpoints important metabolic and microbial alterations in cancer cachexia and shows the interest of this research field for future therapeutic applications., (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2022

Solid tumors are generally characterized by an acidic tumor microenvironment (TME) that favors cancer progression, therapy resistance, and immune evasion. By single-cell RNA-sequencing analysis in PDAC patients, we reveal hereby Solute Carrier Family 4 Member 4 (SLC4A4) as the most abundant bicarbonate transporter, predominantly expressed by epithelial ductal cells. Functionally, SLC4A4 inhibition in PDAC cancer cells mitigates the acidosis of the TME due to bicarbonate accumulation in the extracellular space and decrease in lactate production by cancer cells as the result of reduced glycolysis. In PDAC-bearing mice, genetic or pharmacological SLC4A4 targeting improves T cell-mediated immune response and breaches macrophage-mediated immunosuppression, thus inhibiting tumor growth and metastases. In addition, Slc4a4 targeting in combination with immune-checkpoint blockade is able to overcome immunotherapy resistance and prolong survival. Overall, our data propose SLC4A4 as a therapeutic target to unleash an anti-tumor immune response in PDAC.

Mito-metformin10 (MM10), synthesized by attaching a triphenylphosphonium cationic moiety via a 10-carbon aliphatic side chain to metformin, is a mitochondria-targeted analog of metformin that was recently demonstrated to alter mitochondrial function and proliferation in pancreatic ductal adenocarcinoma. Here, we hypothesized that this compound may decrease the oxygen consumption rate (OCR) in prostate cancer cells, increase the level of mitochondrial ROS, alleviate tumor hypoxia, and radiosensitize tumors. OCR and mitochondrial superoxide production were assessed by EPR (9 GHz) in vitro in PC-3 and DU-145 prostate cancer cells. Reduced and oxidized glutathione were assessed before and after MM10 exposure. Tumor oxygenation was measured in vivo using 1 GHz EPR oximetry in PC-3 tumor model. Tumors were irradiated at the time of maximal reoxygenation. 24-hours exposure to MM10 significantly decreased the OCR of PC-3 and DU-145 cancer cells. An increase in mitochondrial superoxide levels was observed in PC-3 but not in DU-145 cancer cells, an observation consistent with the differences observed in glutathione levels in both cancer cell lines. In vivo, the tumor oxygenation significantly increased in the PC-3 model (daily injection of 2 mg/kg MM10) 48 and 72 h after initiation of the treatment. Despite the significant effect on tumor hypoxia, MM10 combined to irradiation did not increase the tumor growth delay compared to the irradiation alone. MM10 altered the OCR in prostate cancer cells. The effect of MM10 on the superoxide level was dependent on the antioxidant capacity of cell line. In vivo, MM10 alleviated tumor hypoxia, yet without consequence in terms of response to irradiation.

(1) Background: Because statins were found to decrease the oxygen consumption rate (OCR) of a variety of normal cells, our hypothesis was that statins may also decrease the OCR of cancer cells, alleviate tumor hypoxia and radiosensitize tumors. (2) Methods: OCR was assessed using the Seahorse XF96 technology and EPR respirometry in PC-3 prostate cancer cells. Mitochondrial superoxide production was measured by EPR with mitoTEMPO-H as a sensing probe. Tumor pO2 was measured in vivo using low-frequency EPR oximetry to define the optimal window of reoxygenation, the time at which tumors were irradiated with a single 6 Gy dose with a Cesium-137 irradiator. (3) Results: 24-h exposure to simvastatin and fluvastatin significantly decreased the OCR of PC-3 cancer cells. An increase in mitochondrial superoxide levels was also observed after fluvastatin exposure. The PC-3 prostate cancer model was found highly hypoxic at the basal level. When mice were treated with simvastatin or fluvastatin (daily injection of 20 mg/kg), tumor oxygenation increased 48 and 72 h after initiation of the treatment. However, despite reoxygenation, simvastatin did not sensitize the PC-3 tumor model to RT. (4) Conclusions: exposure to statins affect tumor metabolism and tumor oxygenation, however, with limited impact on tumor growth with or without irradiation.

Obesity is a known factor increasing the risk of developing breast cancer and reducing disease free survival. In addition to these well-documented effects, recent studies have shown that obesity is also affecting response to chemotherapy. Among the multiple dysregulations associated with obesity, increased level of the apelin adipokine has been recently shown to be directly involved in the association between obesity and increased breast cancer progression. In this study, we analyzed in a retrospective cohort of 62 breast cancer patients the impact of obesity and tumoral apelin expression on response to neoadjuvant chemotherapy. In the multivariate logistic regression, obesity and high tumoral apelin expression were associated with a reduced response to NAC in our cohort. However, obesity and high tumoral apelin expression were not correlated, suggesting that those two parameters could be independently associated with reduced NAC response. These findings should be confirmed in independent cohorts.

A growing body of evidence indicates that mitochondria play a key role in many disorders as well as in cancer progression and response to treatment. Next to being the main cellular energy generator through respiration, mitochondria are also the major producer of superoxide and other downstream reactive oxygen species in the cell. In this thesis, we aimed to develop an integrated electron paramagnetic resonance (EPR) toolbox enabling the assessment of mitochondrial (dys)function by measuring the oxygen consumption rate and superoxide production in a same cellular or mitochondrial preparation. This EPR toolbox was used for the benefit of two different projects: discovering potential radiosensitizers in anticancer therapy (like statins) and assessing the impact of agents such as Boscalid and Bixafen, which are succinate dehydrogenase inhibitors (SDHI), on the mitochondrial function of human cells., (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2021

In this paper, we describe an assay to analyze simultaneously the oxygen consumption rate (OCR) and superoxide production in a biological system. The analytical set-up uses electron paramagnetic resonance (EPR) spectroscopy with two different isotopically-labelled sensors: N-PDT (4-oxo-2,2,6,6-tetramethylpiperidine-d-N-1-oxyl) as oxygen-sensing probe and N-CMH (1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine, a cyclic hydroxylamine, as sensor of reactive oxygen species (ROS). The superoxide contribution to CMH oxidation is assessed using SOD or PEGSOD as controls. Because the EPR spectra are not superimposable, the variation of EPR linewidth of N-PDT (linked to OCR) and the formation of the nitroxide from N-CMH (linked to superoxide production) can be recorded simultaneously over time on a single preparation. The EPR toolbox was qualified in biological systems of increasing complexity. First, we used an enzymatic assay based on the hypoxanthine (HX)/xanthine oxidase (XO) which is a well described model of oxygen consumption and superoxide production. Second, we used a cellular model of superoxide production using macrophages exposed to phorbol 12-myristate 13-acetate (PMA) which stimulates the NADPH oxidase (NOX) to consume oxygen and produce superoxide. Finally, we exposed isolated mitochondria to established inhibitors of the electron transport chain (rotenone and metformin) in order to assess their impact on OCR and superoxide production. This EPR toolbox has the potential to screen the effect of intoxicants or drugs targeting the mitochondrial function.

Fungicides are used to suppress the growth of fungi for crop protection. The most widely used fungicides are succinate dehydrogenase inhibitors (SDHIs) that act by blocking succinate dehydrogenase, the complex II of the mitochondrial electron transport chain. As recent reports suggested that SDHI-fungicides could not be selective for their fungi targets, we tested the mitochondrial function of human cells (Peripheral Blood Mononuclear Cells or PBMCs, HepG2 liver cells, and BJ-fibroblasts) after exposure for a short time to Boscalid and Bixafen, the two most used SDHIs. Electron Paramagnetic Resonance (EPR) spectroscopy was used to assess the oxygen consumption rate (OCR) and the level of mitochondrial superoxide radical. The OCR was significantly decreased in the three cell lines after exposure to both SDHIs. The level of mitochondrial superoxide increased in HepG2 after Boscalid and Bixafen exposure. In BJ-fibroblasts, mitochondrial superoxide was increased after Bixafen exposure, but not after Boscalid. No significant increase in mitochondrial superoxide was observed in PBMCs. Flow cytometry revealed an increase in the number of early apoptotic cells in HepG2 exposed to both SDHIs, but not in PBMCs and BJ-fibroblasts, results consistent with the high level of mitochondrial superoxide found in HepG2 cells after exposure. In conclusion, short-term exposure to Boscalid and Bixafen induces a mitochondrial dysfunction in human cells.

Obesity is a known factor increasing the risk of developing breast cancer and reducing disease free survival. In addition to these well-documented effects, recent studies have shown that obesity is also affecting response to chemotherapy. Among the multiple dysregulations associated with obesity, increased level of the apelin adipokine has been recently shown to be directly involved in the association between obesity and increased breast cancer progression. In this study, we analyzed in a retrospective cohort of 62 breast cancer patients the impact of obesity and tumoral apelin expression on response to neoadjuvant chemotherapy. In the multivariate logistic regression, obesity and high tumoral apelin expression were associated with a reduced response to NAC in our cohort. However, obesity and high tumoral apelin expression were not correlated, suggesting that those two parameters could be independently associated with reduced NAC response. These findings should be confirmed in independent cohorts.

Hypoxia is a crucial factor in cancer therapy, determining prognosis and the effectiveness of treatment. Although efforts are being made to develop methods for assessing tumor hypoxia, no markers of hypoxia are currently used in routine clinical practice. Recently, we showed that the combined endogenous MR biomarkers, R and R *, which are sensitive to [dissolved O ] and [dHb], respectively, were able to detect changes in tumor oxygenation induced by a hyperoxic breathing challenge. In this study, we further validated the ability of the combined MR biomarkers to assess the change in tumor oxygenation induced by an allosteric effector of hemoglobin, myo-inositol trispyrophosphate (ITPP), on rat tumor models. ITPP induced an increase in tumor pO , as observed using L-band electron paramagnetic resonance oximetry, as well as an increase in both R and R * MR parameters. The increase in R indicated an increase in [O ], whereas the increase in R * resulted from an increase in O release from blood, inducing an increase in [dHb]. The impact of ITPP was then evaluated on factors that can influence tumor oxygenation, including tumor perfusion, saturation rate of hemoglobin, blood pH and oxygen consumption rate (OCR). ITPP decreased blood [HbO ] and significantly increased blood acidity, which is also a factor that right-shifts the oxygen dissociation curve. No change in tumor perfusion was observed after ITPP treatment. Interestingly, ITPP decreased OCR in both tumor cell lines. In conclusion, ITPP increased tumor pO via a combined mechanism involving a decrease in OCR and an allosteric effect on hemoglobin that was further enhanced by a decrease in blood pH. MR biomarkers could assess the change in tumor oxygenation induced by ITPP. At the intra-tumoral level, a majority of tumor voxels were responsive to ITPP treatment in both of the models studied.

Obesity is known to increase the risk of developing breast cancer, to promote mammary tumor progression and to reduce the response to chemotherapy. However, the mechanisms involved in the association between obesity and breast cancer are still not well understood. As the apelin adipokine is overexpressed in obesity, our project was designed to investigate the potential effects of apelin on breast cancer progression in the context of obesity. We showed in mice that reproducing obesity-relevant levels of apelin in lean mice promoted breast cancer growth and metastatization. In addition, the administration of an apelinergic antagonist in obese mice succeeded in reducing breast cancer progression. Finally, we showed in human breast cancer patients that high tumoral apelin expression was associated with a reduced response to neoadjuvant chemotherapy. These results highlighted that targeting the apelinergic system could be beneficial for obese breast cancer patients., (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2020

Hypoxia is the common feature of most solid tumors. The hypoxic environment is associated with the reduced efficacy of cancer treatments, especially radiation therapy. Although modification of tumor hypoxia improves the outcome of radiation therapy, screening for the presence of hypoxia has not been the entry criterion prior to hypoxia modification trials. To bridge the gap between the occurrence of tumor hypoxia and the routine clinical practice, there is an important need to have a method to robustly map tumor oxygenation for patient stratification and treatment adaptation. Among the methods that have been developed to measure hypoxia, MRI endogenous contrast markers, R1 and R2*, appear to be a relevant approach for this purpose. Since there is a lack of study comparing R1 and R2* in response to oxygen modifiers, the aim of this thesis is to address the value of R1 and R2* to assess tumor oxygenation and response to radiation therapy using different oxygen modifiers., (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2019

Tumour hypoxia is a well-established factor of resistance in radiation therapy (RT). Myo-inositol trispyrophosphate (ITPP) is an allosteric effector that reduces the oxygen-binding affinity of haemoglobin and facilitates the release of oxygen by red blood cells. We investigated herein the oxygenation effect of ITPP in six tumour models and its radiosensitizing effect in two of these models. The evolution of tumour pO upon ITPP administration was monitored on six models using 1.2 GHz Electron Paramagnetic Resonance (EPR) oximetry. The effect of ITPP on tumour perfusion was assessed by Hoechst staining and the oxygen consumption rate (OCR) in vitro was measured using 9.5 GHz EPR. The therapeutic effect of ITPP with and without RT was evaluated on rhabdomyosarcoma and 9L-glioma rat models. ITPP enhanced tumour oxygenation in six models. The administration of 2 g/kg ITPP once daily for 2 days led to a tumour reoxygenation for at least 4 days. ITPP reduced the OCR in six cell lines but had no effect on tumour perfusion when tested on 9L-gliomas. ITPP plus RT did not improve the outcome in rhabdomyosarcomas. In 9L-gliomas, some of tumours receiving the combined treatment were cured while other tumours did not benefit from the treatment. ITPP increased oxygenation in six tumour models. A decrease in OCR could contribute to the decrease in tumour hypoxia. The association of RT with ITPP was beneficial for a few 9L-gliomas but was absent in the rhabdomyosarcomas.

Saponins, amphiphilic compounds widely found in plants, attract more and more attention based on their biological activities including anticancer properties. The activity for some saponins has been attributed to their interactions with membrane cholesterol. In this study, we focus on the saponin ginsenoside Rh2 found in Panax ginseng root. Our goal was to obtain detailed knowledge about the activity of Rh2 and to elucidate the respective importance of cholesterol and sphingomyelin for its activity. Results obtained in artificial and biological membranes clearly highlight the importance of membrane lipid nature for the Rh2 activity. We revealed the critical role of sphingomyelin in the activity of Rh2 while cholesterol seems to depress the sensitivity of the membrane to Rh2. At the end of th PhD thesis, we initiated a long-term study aiming at evaluating the potential interest of Rh2 to modulate tumor cell invasion. From a more global point-of-view, the favorable interaction of a molecule with a membrane lipid could provide a powerful tool to evidence this lipid or target the latter in a pathophysiological context such as tumor growth and metastasis., (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2019

The ability of certain cancer cells to maintain a highly reduced intracellular environment is correlated with aggressiveness and drug resistance. Since the gluthathione (GSH) and thioredoxin (TRX) systems cooperate to a tight regulation of ROS in cell physiology, and to a stimulation of tumor initiation and progression, modulation of the GSH and TRX pathways are emerging as new potential targets in cancer. In vivo methods to assess changes in tumor redox status are critically needed to assess the relevance of redox-targeted agents. The current study assesses in vitro and in vivo biomarkers of tumor redox status in response to treatments targeting the GSH and TRX pathways, by comparing cytosolic and mitochondrial redox nitroxide Electron Paramagnetic Resonance (EPR) probes, and cross-validation with redox dynamic fluorescent measurement. For that purpose, the effect of the GSH modulator buthionine sulfoximine (BSO) and of the TRX reductase inhibitor auranofin were measured in vitro using both cytosolic and mitochondrial EPR and roGFP probes in breast and cervical cancer cells. In vivo, mice bearing breast or cervical cancer xenografts were treated with the GSH or TRX modulators and monitored using the mito-TEMPO spin probe. Our data highlight the importance of using mitochondria targeted spin probes to assess changes in tumor redox status induced by redox modulators. Further in vivo validation of the mito-tempo spin probe with alternative in vivo methods should be considered, yet the spin probe used in vivo in xenografts demonstrated sensitivity to the redox status modulators.

Lactate exchange between glycolytic and oxidative cancer cells is proposed to optimize tumor growth. Blocking lactate uptake through monocarboxylate transporter 1 (MCT1) represents an attractive therapeutic strategy but may stimulate glucose consumption by oxidative cancer cells. We report here that inhibition of mitochondrial pyruvate carrier (MPC) activity fulfils the tasks of blocking lactate use while preventing glucose oxidative metabolism. Using in vitroC-glucose and in vivo hyperpolarizedC-pyruvate, we identify 7ACC2 as a potent inhibitor of mitochondrial pyruvate transport which consecutively blocks extracellular lactate uptake by promoting intracellular pyruvate accumulation. Also, while in spheroids MCT1 inhibition leads to cytostatic effects, MPC activity inhibition induces cytotoxic effects together with glycolysis stimulation and uncompensated inhibition of mitochondrial respiration. Hypoxia reduction obtained with 7ACC2 is further shown to sensitize tumor xenografts to radiotherapy. This study positions MPC as a control point for lactate metabolism and expands on the anticancer potential of MPC inhibition.

A majority of patients with a V600x melanoma respond quickly to BRAF/MEK inhibition (BRAFi/MEKi) and have an obvious clinical benefit. Nearly all the patients after this initial phase will develop resistance. Therefore, non-invasive early markers of response/non-response are needed in order to identify those patients who, due to intrinsic or acquired resistance, do not respond to treatment and would be eligible for alternative treatments. The aim of this study was to investigate the value of magnetic resonance spectroscopy (H-MRS) of choline and diffusion-weighted magnetic resonance imaging (DW-MRI) as early markers of response to BRAF inhibition (BRAFi) with vemurafenib alone or in combination with MEK inhibition (MEKi) with trametinib, in BRAFi-sensitive and BRAFi-resistant melanoma xenografts. Tumor response was significantly improved by the combination of BRAFi and MEKi, compared to BRAFi alone, only in sensitive xenografts; thus indicating that vemurafenib-resistant A375R xenografts were cross-resistant to the inhibition of MEK, as confirmed by immunohistochemistry analysis for phosphorylated ERK. H-MRS showed that in sensitive melanoma xenografts, a significant blockage of ERK phosphorylation, but not a decrease in cell proliferation, was required to affect total choline (tCho) levels, thus suggesting that tCho could serve as a pharmacodynamic (PD) marker for agents targeting the MAPK cascade. In addition, early effects of the combination therapy on tumor cellularity could be detected via DW-MRI. In particular, skewness and kurtosis of the apparent diffusion coefficient (ADC) distribution may be useful to detect changes in the diffusional heterogeneity that might not affect the global ADC value.

Overweight and obesity are associated with increased risk of developing metabolic disorders such as diabetes and cardiovascular diseases. However, besides these metabolic diseases, excess body weight is also associated with different cancers, including gastrointestinal cancers, such as liver, pancreatic and colon cancers. Inflammation is a common feature of both obesity and cancer; however, the origin of this inflammation has been largely debated. Over the past decade, growing evidence has shown that the composition of the gut microbiota and its activity might be associated not only with the onset of inflammation but also with metabolic disorders and cancer. Here, we review the links between the gut microbiota, gut barrier function and the onset of low-grade inflammation in the development of gastrointestinal cancer. We also describe the mechanisms by which specific microorganism-associated molecular patterns crosstalk with the immune system and how the metabolic activity of bacteria induces specific signalling pathways beyond the gut that eventually trigger carcinogenesis.