Metabolic reprogramming as a continuous changing behavior of tumor cells

Exploring metabolic reprogramming in melanoma via acquired resistance to the oxidative phosphorylation inhibitor phenformin

Therapeutic failures in cancer therapy are often associated with metabolic plasticity. The use of metabolic modulators as anti-cancer agents has been effective in correcting metabolic alterations; however, molecular events behind metabolic switch are still largely unexplored. Herein, we characterize the molecular and functional events that follow prolonged oxidative phosphorylation inhibition by phenformin in order to study how melanoma cells adapt to this specific metabolic pressure. We show that melanoma cells cultured up to 3 months with high doses of phenformin (R-cells) are less viable and migrate and invade less than parental (S-) cells. Microarray analysis of R-melanoma cells reveals a switch in the energy production strategy accompanied by the modulation of several immunological-associated genes. R-cells display low oxygen consumption rate and high basal extracellular acidification rate. When treated with vemurafenib, R-cell viability, growth and extracellular signal-regulated kinase activation decrease. Finally, phenformin withdrawal reverts R-cells phenotype. In summary, our study provides an in vitro model of on-off metabolic switch in melanoma and reveals interesting molecular signatures controlling metabolic reprogramming in this tumour.

A drug potency signature links progression of chronic lymphocytic leukemia to mitochondria-related stress responses and metabolic reprogramming under hypoxia

Chronic lymphocytic leukemia (CLL) cells change their metabolic program between normoxia and hypoxia, possibly affecting cytotoxic drug potency by altering mitochondria-related cell stress responses (MRCSR) including mitophagy, mitochondrial biogenesis, and mitochondrial proteostasis. We evaluated in CLL cells from nine patients, the single and multiple-combined drug potency of arsenic trioxide (ATO), valproic acid (VPA), vincristine (VCR) and MG132 as four pharmacological sensors influencing mitochondrial apoptosis, mitochondrial biogenesis, mitophagy, and mitochondrial proteostasis respectively, under normoxia and hypoxia to force hypoxia-induced metabolic reprogramming (HMR). Untreated cells from all patients remained viable under O₂ levels below 0.5% for 72 h. We obtained 21 measures of drug potency and interaction at 50% effect level that we denoted drug potency signature (DPS). Using the comparative DPS between normoxia and hypoxia, two non-supervised classification algorithms discriminated CLL patients with active disease (ADT) and stable disease (NAD) and showed complete consistency with their clinical characteristics. In ADT group under hypoxia, the potency of MG132 was increased, the interaction of ATO + VPA and ATO + VPA + VCR shifted towards antagonism, and ATO + VPA + VCR + MG132 shifted towards synergism, indicating a prominent role of mitochondrial proteostasis. Classification of patients based on DPS, depended on the contrasting response of drugs under hypoxia and normoxia, owing to HMR. Using these drugs as pharmacological sensors, we linked the metabolic arrangement of CLL cells under hypoxia, to potency of drugs targeting MRCSR, and to the clinical features of individual patients, therefore providing new sources of data on disease progression, drug response and risk prognosis.

Carbonic anhydrase IX inhibition affects viability of cancer cells adapted to extracellular acidosis

Among the players of the adaptive response of cancer cells able to promote a resistant and aggressive phenotype, carbonic anhydrase IX (CAIX) recently has emerged as one of the most relevant drug targets. Indeed, CAIX targeting has received a lot of interest, and selective inhibitors are currently under clinical trials. Hypoxia has been identified as the master inductor of CAIX, but, to date, very few is known about the influence that another important characteristic of tumor microenvironment, i.e., extracellular acidosis, exerts on CAIX expression and activity. In the last decades, acidic microenvironment has been associated with aggressive tumor phenotype endowed with epithelial-to-mesenchymal transition (EMT) profile, high invasive and migratory ability, apoptosis, and drug resistance. We demonstrated that melanoma, breast, and colorectal cancer cells transiently and chronically exposed to acidified medium (pH 6.7 ± 0.1) showed a significantly increased CAIX expression compared to those grown in standard conditions (pH 7.4 ± 0.1). Moreover, we observed that the CAIX inhibitor FC16-670A (also named SLC-0111, which just successfully ended phase I clinical trials) not only prevents such increased expression under acidosis but also promotes apoptotic and necrotic programs only in acidified cancer cells. Thus, CAIX could represent a selective target of acidic cancer cells and FC16-670A inhibitor as a useful tool to affect this aggressive subpopulation characterized by conventional therapy escape.

KEY MESSAGES

Cancer cells overexpress CAIX under transient and chronic extracellular acidosis. Acidosis-induced CAIX overexpression is NF-κB mediated and HIF-1α independent. FC16-670A prevents CAIX overexpression and induces acidified cancer cell death.

Prognostic value of preoperative serum lactate dehydrogenase in thymic carcinoma

BACKGROUND

The prognostic value of serum lactate dehydrogenase (LDH) has been demonstrated in various solid tumors. We attempted to determine whether serum LDH was predictive of survival in thymic carcinoma after surgical resection.

METHODS

Ninety-five patients with thymic carcinoma treated in our hospital between January 2005 and December 2015 were retrospectively enrolled. Serum LDH was measured before surgery and categorized as low or high relative to the upper limit of normal (ULN) (225 U/L). The relationships of serum LDH level and other clinical variables with survival were estimated by Cox regression and Kaplan-Meier survival analysis.

RESULTS

Serum LDH levels were found to be significantly associated with overall survival (OS) and progression-free survival (PFS) of these patients. The 1-, 3-, and 5-year PFS were 76%, 51%, and 38%, and the 1-, 3- and 5-year OS were 97%, 75%, and 46%, respectively. Univariate analysis found that high serum LDH (>225 U/L) was associated with both lower OS [hazard ratio (HR) =2.710; 95% confidence interval (CI): 1.363-1.5.391; P=0.004] and PFS (HR =3.365; 95% CI: 1.776-6.374; P<0.001). Multivariate analysis found that high serum LDH was associated with lower PFS (HR =2.122; 95% CI: 1.056-4.267; P=0.035). Moreover, high LDH was significantly associated with advanced Masaoka stage (P=0.001).

CONCLUSIONS

High serum LDH (>225 U/L) was an independent predictor of decreased PFS in thymic carcinoma patients. It was also significantly associated with reduced OS, but was not an independent predictor of death in those patients.