Invasive phenotype induced by low extracellular pH requires mitochondria dependent metabolic flexibility

CPT1B maintains redox homeostasis and inhibits ferroptosis to induce gemcitabine resistance via the KEAP1/NRF2 axis in pancreatic cancer

BACKGROUND

Although we have made progress in treatment and have increased the 5-year survival by ≤30% in pancreatic cancer, chemotherapy resistance remains a major obstacle. However, whether reprogrammed lipid metabolism contributes to chemoresistance still needs to be further studied.

METHODS

Gene expression was determined using Western blotting and quantitative reverse transcription polymerase chain reaction. Cell cloning formation assay, Cell Counting Kit-8, EdU assay, wound healing assay, transwell assay, and flow cytometry were used to detect apoptosis, cell proliferation capacity, migration capacity, and cytotoxicity of gemcitabine. Confocal fluorescence microscopy, transmission electron microscopy, etc., were used to detect the changes in intracellular reactive oxygen species, glutathione, lipid peroxidation level, and cell morphology. An animal study was performed to evaluate the effect of CPT1B knockdown on tumor growth and gemcitabine efficacy.

RESULTS

In our study, we observed that the CPT1B expression level was higher in pancreatic ductal adenocarcinoma tissues than in normal tissues and correlated with a low rate of survival. Moreover, silencing of CPT1B significantly suppressed the proliferative ability and metastasis of pancreatic cancer cells. Furthermore, we discovered that CPT1B interacts with Kelch-like ECH-associated protein 1, and CPT1B knockdown led to decreased NRF2 expression and ferroptosis induction. In addition, CPT1B expression increased after gemcitabine treatment, and it was highly expressed in gemcitabine-resistant pancreatic ductal adenocarcinoma cells. Finally, we discovered that ferroptosis induced by CPT1B knockdown enhanced the gemcitabine toxicity in pancreatic ductal adenocarcinoma.

CONCLUSION

CPT1B may act as a promising target in treating patients with gemcitabine-resistant pancreatic ductal adenocarcinoma .

Acidic Growth Conditions Promote Epithelial-to-Mesenchymal Transition to Select More Aggressive PDAC Cell Phenotypes In Vitro

Pancreatic Ductal Adenocarcinoma (PDAC) is characterized by an acidic microenvironment, which contributes to therapeutic failure. So far there is a lack of knowledge with respect to the role of the acidic microenvironment in the invasive process. This work aimed to study the phenotypic and genetic response of PDAC cells to acidic stress along the different stages of selection. To this end, we subjected the cells to short- and long-term acidic pressure and recovery to pH_e 7.4. This treatment aimed at mimicking PDAC edges and consequent cancer cell escape from the tumor. The impact of acidosis was assessed for cell morphology, proliferation, adhesion, migration, invasion, and epithelial-mesenchymal transition (EMT) via functional in vitro assays and RNA sequencing. Our results indicate that short acidic treatment limits growth, adhesion, invasion, and viability of PDAC cells. As the acid treatment progresses, it selects cancer cells with enhanced migration and invasion abilities induced by EMT, potentiating their metastatic potential when re-exposed to pH_e 7.4. The RNA-seq analysis of PANC-1 cells exposed to short-term acidosis and pH_e-selected recovered to pH_e 7.4 revealed distinct transcriptome rewiring. We describe an enrichment of genes relevant to proliferation, migration, EMT, and invasion in acid-selected cells. Our work clearly demonstrates that upon acidosis stress, PDAC cells acquire more invasive cell phenotypes by promoting EMT and thus paving the way for more aggressive cell phenotypes.

Acid Adaptation Promotes TRPC1 Plasma Membrane Localization Leading to Pancreatic Ductal Adenocarcinoma Cell Proliferation and Migration through Ca2+ Entry and Interaction with PI3K/CaM

Simple Summary

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers globally, with a 5-year overall survival of less than 10%. The development and progression of PDAC are linked to its fluctuating acidic tumor microenvironment. Ion channels act as important sensors of this acidic tumor microenvironment. They transduce extracellular signals and regulate signaling pathways involved in all hallmarks of cancer. In this study, we evaluated the interplay between a pH-sensitive ion channel, the calcium (Ca²⁺) channel transient receptor potential C1 (TRPC1), and three different stages of the tumor microenvironment, normal pH, acid adaptation, and acid recovery, and its impact on PDAC cell migration, proliferation, and cell cycle progression. In acid adaptation and recovery conditions, TRPC1 localizes to the plasma membrane, where it interacts with PI3K and calmodulin, and permits Ca²⁺ entry, which results in downstream signaling, leading to proliferation and migration. Thus, TRPC1 exerts a more aggressive role after adaptation to the acidic tumor microenvironment.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal malignancies, with a low overall survival rate of less than 10% and limited therapeutic options. Fluctuations in tumor microenvironment pH are a hallmark of PDAC development and progression. Many ion channels are bona fide cellular sensors of changes in pH. Yet, the interplay between the acidic tumor microenvironment and ion channel regulation in PDAC is poorly understood. In this study, we show that acid adaption increases PANC-1 cell migration but attenuates proliferation and spheroid growth, which are restored upon recovery. Moreover, acid adaptation and recovery conditions favor the plasma membrane localization of the pH-sensitive calcium (Ca²⁺) channel transient receptor potential C1 (TRPC1), TRPC1-mediated Ca²⁺ influx, channel interaction with the PI3K p85α subunit and calmodulin (CaM), and AKT and ERK1/2 activation. Knockdown (KD) of TRPC1 suppresses cell migration, proliferation, and spheroid growth, notably in acid-recovered cells. KD of TRPC1 causes the accumulation of cells in G0/G1 and G2/M phases, along with reduced expression of CDK6, −2, and −1, and cyclin A, and increased expression of p21^CIP1. TRPC1 silencing decreases the basal Ca²⁺ influx in acid-adapted and -recovered cells, but not in normal pH conditions, and Ca²⁺ chelation reduces cell migration and proliferation solely in acid adaptation and recovery conditions. In conclusion, acid adaptation and recovery reinforce the involvement of TRPC1 in migration, proliferation, and cell cycle progression by permitting Ca²⁺ entry and forming a complex with the PI3K p85α subunit and CaM.

Tumor Microenvironment Features and Chemoresistance in Pancreatic Ductal Adenocarcinoma: Insights into Targeting Physicochemical Barriers and Metabolism as Therapeutic Approaches

Currently, the median overall survival of PDAC patients rarely exceeds 1 year and has an overall 5-year survival rate of about 9%. These numbers are anticipated to worsen in the future due to the lack of understanding of the factors involved in its strong chemoresistance. Chemotherapy remains the only treatment option for most PDAC patients; however, the available therapeutic strategies are insufficient. The factors involved in chemoresistance include the development of a desmoplastic stroma which reprograms cellular metabolism, and both contribute to an impaired response to therapy. PDAC stroma is composed of immune cells, endothelial cells, and cancer-associated fibroblasts embedded in a prominent, dense extracellular matrix associated with areas of hypoxia and acidic extracellular pH. While multiple gene mutations are involved in PDAC initiation, this desmoplastic stroma plays an important role in driving progression, metastasis, and chemoresistance. Elucidating the mechanisms underlying PDAC resistance are a prerequisite for designing novel approaches to increase patient survival. In this review, we provide an overview of the stromal features and how they contribute to the chemoresistance in PDAC treatment. By highlighting new paradigms in the role of the stromal compartment in PDAC therapy, we hope to stimulate new concepts aimed at improving patient outcomes.

Overcoming chemoresistance by targeting reprogrammed metabolism: the Achilles' heel of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer-related death due to its late diagnosis that removes the opportunity for surgery and metabolic plasticity that leads to resistance to chemotherapy. Metabolic reprogramming related to glucose, lipid, and amino acid metabolism in PDAC not only enables the cancer to thrive and survive under hypovascular, nutrient-poor and hypoxic microenvironments, but also confers chemoresistance, which contributes to the poor prognosis of PDAC. In this review, we systematically elucidate the mechanism of chemotherapy resistance and the relationship of metabolic programming features with resistance to anticancer drugs in PDAC. Targeting the critical enzymes and/or transporters involved in glucose, lipid, and amino acid metabolism may be a promising approach to overcome chemoresistance in PDAC. Consequently, regulating metabolism could be used as a strategy against PDAC and could improve the prognosis of PDAC.

pH variation impacts molecular pathways associated with somatic cell reprogramming and differentiation of pluripotent stem cells

RATIONALE

The study of somatic cell reprogramming and cell differentiation is essential for the application of recent techniques in regenerative medicine. It is, specifically, necessary to determine the appropriate conditions required for the induction of reprogramming and cell differentiation.

METHODS

Based on a comprehensive literature review, the effects of pH fluctuation on alternative splicing, mitochondria, plasma membrane, and phase separation, in several cell types are discussed. Additionally, the associated molecular pathways important for the induction of differentiation and reprogramming are reviewed.

RESULTS

While cells change their state, several factors such as cytokines and physical parameters affect cellular reprogramming and differentiation. As the extracellular and intracellular pH affects biophysical phenomena in a cell, the effects of pH fluctuation can ultimately decide the cell fate through molecular pathways. Though few studies have reported on the direct effects of culture pH on cell state, there is substantial information on the pathways related to stem cell differentiation and somatic cell reprogramming that can be stimulated by environmental pH.

CONCLUSION

Environmental pH fluctuations may decide cell fate through the molecular pathways associated with somatic cell reprogramming and cell differentiation.

Mitochondrial Metabolism in PDAC: From Better Knowledge to New Targeting Strategies

Cancer cells reprogram their metabolism to meet bioenergetics and biosynthetic demands. The first observation of metabolic reprogramming in cancer cells was made a century ago (“Warburg effect” or aerobic glycolysis), leading to the classical view that cancer metabolism relies on a glycolytic phenotype. There is now accumulating evidence that most cancers also rely on mitochondria to satisfy their metabolic needs. Indeed, the current view of cancer metabolism places mitochondria as key actors in all facets of cancer progression. Importantly, mitochondrial metabolism has become a very promising target in cancer therapy, including for refractory cancers such as Pancreatic Ductal AdenoCarcinoma (PDAC). In particular, mitochondrial oxidative phosphorylation (OXPHOS) is an important target in cancer therapy. Other therapeutic strategies include the targeting of glutamine and fatty acids metabolism, as well as the inhibition of the TriCarboxylic Acid (TCA) cycle intermediates. A better knowledge of how pancreatic cancer cells regulate mitochondrial metabolism will allow the identification of metabolic vulnerabilities and thus novel and more efficient therapeutic options for the benefit of each patient.