Tumors and mitochondrial respiration: a neglected connection

Enhanced mitochondrial biogenesis facilitates the development of cutaneous squamous cell carcinoma

Mitochondrial malfunction is traditionally viewed as a major factor in tumor growth and malignancy, while recent studies have introduced conflicting views suggesting the necessity of functional mitochondria for tumor growth. Despite these differing perspectives, the specific role of mitochondria in cutaneous squamous cell carcinoma (cSCC) remains poorly understood. In this study, we observed increased mitochondrial abundance and function during the development of cSCC. We also identified retinoic acid receptor response 1 (RARRES1), which is dramatically decreased in human cSCC samples, as a key regulator of mitochondrial homeostasis. Mechanistically, RARRES1 can translocate into mitochondria and facilitate the degradation of TFAM by binding to LONP1, thereby regulating mitochondrial biogenesis. While RARRES1 suppression unleashed TFAM to promote mitochondrial biogenesis, leading to the progression of cSCC. Targeting RARRES1-LONP1/TFAM axis shows significant potential for inhibiting cSCC development. This study reveals a unique network for regulating mitochondrial homeostasis and emphasizes the crucial role of mitochondria in cSCC development, positioning the RARRES1-LONP1/TFAM axis as promising therapeutic target for future clinical applications.

NADH:ubiquinone oxidoreductase core subunit S8 expression and functional significance in non-small cell lung cancer

Hyperfunctional mitochondria provide a growth advantage by supporting the energy-intensive processes essential for non-small cell lung cancer (NSCLC). NADH:ubiquinone oxidoreductase core subunit S8 (NDUFS8) is a key subunit of mitochondrial complex I involved in oxidative phosphorylation (OXPHOS) and cellular energy production. Bioinformatics and local tissue examinations show that NDUFS8 expression is elevated in NSCLC compared to normal lung tissue. Both immortalized and primary human NSCLC cells exhibit higher NDUFS8 levels. Single-cell RNA sequencing confirmed NDUFS8 upregulation in cancerous cells of NSCLC tumor. Silencing NDUFS8 via shRNA or Cas9/sgRNA-mediated knockout (KO) disrupted mitochondrial functions, leading to decreased complex I activity, ATP depletion, mitochondrial depolarization, increased reactive oxygen species (ROS) production, and heightened lipid peroxidation. Furthermore, NDUFS8 silencing/KO triggered apoptosis and significantly reduced Akt-mTOR activation, cell viability, proliferation, and motility in various NSCLC cells. In contrast, ectopic overexpression of NDUFS8 boosted mitochondrial complex I activity and ATP levels, promoting Akt-mTOR activation, and enhancing NSCLC cell proliferation and motility. NDUFS8 also contributes to radioresistance in NSCLC; silencing or KO enhanced ionizing radiation (IR)-induced cytotoxicity, while overexpression mitigated it. Intratumoral injection of NDUFS8 shRNA-expressing adeno-associated virus significantly inhibited growth of primary NSCLC xenografts in nude mice, with observed NDUFS8 silencing, ATP reduction, oxidative damage, proliferation inhibition, Akt-mTOR inactivation and apoptosis in treated tissues. These findings highlight the pivotal pro-tumorigenic role of NDUFS8 in NSCLC.

Phosphorylation of POU3F3 Mediated Nuclear Translocation Promotes Proliferation in Non-Small Cell Lung Cancer through Accelerating ATP5PF Transcription and ATP Production

Targeting oxidative phosphorylation (OXPHOS) through inhibiting the electron transport chain (ETC) has shown promising pre-clinical efficacy in cancer therapy. Although aerobic glycolysis is a hallmark of cancer, emerging evidence suggest OXPHOS is frequently enhanced, providing metabolic advantages for cell proliferation, metastasis, and drug resistance in a variety of aggressive cancer types including non-small cell lung cancer (NSCLC), yet the underlying molecular mechanisms remain elusive. Here it is reported that POU-domain containing family protein POU3F3 is translocated into the nuclei of NSCLC cell lines harboring mutant RAS, where it activates transcription of ATP5PF, an essential component of mitochondrial ATP synthase and consequent ATP production, leading to enhanced NSCLC proliferation and migration. Moreover, it is further found out that ERK1 phosphorylates POU3F3 at the S393 site in the cytoplasm and promotes the nuclear translocation of POU3F3 via receptor importin β1 in RAS mutant NSCLC cells. Mechanistically, RNA sequencing analysis combined with chromatin immunoprecipitation (ChIP) assay revealed that POU3F3 binds to the promoter of ATP5PF, leading to enhanced ATP5PF transcription and ATP production. Together, this study uncovers a novel RAS-POU3F3-ATP5PF axis in facilitating NSCLC progression, providing a new perspective on the understanding of molecular mechanisms for NSCLC progression.

TIMM23 overexpression drives NSCLC cell growth and survival by enhancing mitochondrial function

Mitochondrial hyperfunction is implicated in promoting non-small cell lung cancer (NSCLC) cell growth. TIMM23 (translocase of inner mitochondrial membrane 23) is a core component of the mitochondrial import machinery, facilitating the translocation of proteins across the inner mitochondrial membrane into the matrix. Its expression and potential functions in NSCLC were tested. Comprehensive bioinformatic analysis revealed a strong correlation between TIMM23 overexpression and adverse clinical outcomes in NSCLC patients. Single-cell RNA sequencing data further corroborated these findings, demonstrating elevated TIMM23 expression within the cancer cells of NSCLC mass. Subsequent experimental validation confirmed significantly increased TIMM23 mRNA and protein levels in locally-treated NSCLC tissues compared to matched normal lung tissues. Moreover, TIMM23 expression was consistently elevated across multiple primary/established NSCLC cells. Silencing or ablation of TIMM23 via shRNA or CRISPR/Cas9 in NSCLC cells resulted in impaired mitochondrial function, characterized by reduced complex I activity, ATP depletion, mitochondrial membrane potential dissipation, oxidative stress, and lipid peroxidation. These mitochondrial perturbations coincided with attenuated cell viability, proliferation, and migratory capacity, and concomitant induction of apoptosis. Conversely, ectopic overexpression of TIMM23 significantly enhanced mitochondrial complex I activity and ATP production, promoting NSCLC cell proliferation and motility. In vivo, intratumoral delivery of a TIMM23 shRNA-expressing adeno-associated virus significantly suppressed the growth of subcutaneous NSCLC xenografts in nude mice. Subsequent analysis of tumor tissues revealed depleted TIMM23 expression, ATP reduction, oxidative damage, proliferative arrest, and apoptotic induction. Collectively, these findings establish TIMM23 as a critical pro-tumorigenic factor in NSCLC, highlighting its potential as a prognostic biomarker and therapeutic target.

Targeting TRAP1-dependent metabolic reprogramming to overcome doxorubicin resistance in quiescent breast cancer

AIMS

TRAP1 is involved in metabolic reprogramming and promotes drug resistance. We aimed to explore whether a novel HSP90 inhibitor, C210, overcomes doxorubicin (DOX) resistance of quiescent breast cancer cells by targeting TRAP1.

METHODS

Breast cancer cells were induced to quiescence by hypoxia and low glucose. The relationship of cell metabolism with HSP90 and TRAP1 was investigated by Western blotting, ECAR, OCR, mitochondrial complex activity, and proteomic analysis. The targets of C210 and their functions were analyzed by SPR and immunoprecipitation. The antitumor effect in vivo was investigated with mouse tumor model.

RESULTS

In hypoxia and glucose deprivation, breast cancer cells exhibited elevated TRAP1 and an OXPHOS-enhanced quiescent phenotype. These cells were highly resistant to DOX but more sensitive to C210. C210 disrupted TRAP1's interaction with OXPHOS-associated client proteins, prompting proteasome-dependent degradation of these proteins, thereby reducing OCR, mitochondrial ATP production and resulting in selective elimination of the quiescent cancer cells by inducing mitochondrial apoptosis which could be reversed by exogenous ATP. Moreover, C210 targeted glycolytic, amino acid, and β-oxidation-associated proteome. C210 demonstrated promising in vivo anticancer efficacy which was particularly related to OXPHOS inhibition.

CONCLUSIONS

C210 eliminates DOX-resistant quiescent breast cancer cells by targeting TRAP1-dependent bioenergetics.

Mitochondrial carrier homolog 2 is important for mitochondrial functionality and non-small cell lung cancer cell growth

Discovering new molecular targets for non-small cell lung cancer (NSCLC) is critically important. Enhanced mitochondrial function can promote NSCLC progression by enabling metabolic reprogramming, resistance to apoptosis, and increased cell proliferation. Mitochondrial carrier homolog 2 (MTCH2), located in the outer mitochondrial membrane, is pivotal in regulating mitochondrial activities. This study examines MTCH2 expression and its functional role in NSCLC. Bioinformatic analysis showed that MTCH2 is overexpressed in NSCLC tissues, correlating with poor prognosis and other key clinical parameters of the patients. In addition, single-cell sequencing data revealed higher MTCH2 expression levels in cancer cells of NSCLC tumor mass. Moreover, MTCH2 is also upregulated in locally-treated NSCLC tissues and multiple primary/established human NSCLC cells. In various NSCLC cells, silencing MTCH2 via targeted shRNA or knockout (KO) using the CRISPR/Cas9 method significantly hindered cell proliferation, migration and invasion, while inducing apoptosis. MTCH2 knockdown or KO robustly impaired mitochondrial function, as indicated by reduced mitochondrial respiration, decreased complex I activity, lower ATP levels, lower mitochondrial membrane potential (mitochondrial depolarization), and increased reactive oxygen species (ROS) production. Conversely, ectopic overexpression of MTCH2 in primary NSCLC cells enhanced mitochondrial complex I activity and ATP production, promoting cell proliferation and migration. In vivo, the intratumoral injection of MTCH2 shRNA adeno-associated virus (aav) impeded the growth of subcutaneous xenografts of primary NSCLC cells in nude mice. In MTCH2 shRNA aav-injected NSCLC xenograft tissues, there was decreases in MTCH2 expression, mitochondrial complex I activity, ATP content, and the glutathione (GSH)/glutathione disulfide (GSSG) ratio, but increase in thiobarbituric acid reactive substances (TBAR) activity. Additionally, MTCH2 silencing led to reduced Ki-67 staining but increased apoptosis in NSCLC xenografts. Collectively, these findings demonstrate that overexpressed MTCH2 promotes NSCLC cell growth potentially through the maintenance of mitochondrial hyper-function, highlighting MTCH2 as a novel and promising therapeutic target for treating this disease.

Deciphering novel mitochondrial signatures: multi-omics analysis uncovers cross-disease markers and oligodendrocyte pathways in Alzheimer's disease and glioblastoma

Introduction

Alzheimer's disease (AD) and glioblastoma (GBM) are severe neurological disorders that pose significant global healthcare challenges. Despite extensive research, the molecular mechanisms, particularly those involving mitochondrial dysfunction, remain poorly understood. A major limitation in current studies is the lack of cell-specific markers that effectively represent mitochondrial dynamics in AD and GBM.

Methods

In this study, we analyzed single-cell transcriptomic data using 10 machine learning algorithms to identify mitochondria-associated cell-specific markers. We validated these markers through the integration of gene expression and methylation data across diverse cell types. Our dataset comprised single-nucleus RNA sequencing (snRNA-seq) from AD patients, single-cell RNA sequencing (scRNA-seq) from GBM patients, and additional DNA methylation and transcriptomic data from the ROSMAP, ADNI, TCGA, and CGGA cohorts.

Results

Our analysis identified four significant cross-disease mitochondrial markers: EFHD1, SASH1, FAM110B, and SLC25A18. These markers showed both shared and unique expression profiles in AD and GBM, suggesting a common mitochondrial mechanism contributing to both diseases. Additionally, oligodendrocytes and their interactions with astrocytes were implicated in disease progression, particularly through the APP signaling pathway. Key hub genes, such as HS6ST3 and TUBB2B, were identified across different cellular subpopulations, highlighting a cell-specific co-expression network linked to mitochondrial function.

Lactate and lactylation in cancer

Accumulated evidence has implicated the diverse and substantial influence of lactate on cellular differentiation and fate regulation in physiological and pathological settings, particularly in intricate conditions such as cancer. Specifically, lactate has been demonstrated to be pivotal in molding the tumor microenvironment (TME) through its effects on different cell populations. Within tumor cells, lactate impacts cell signaling pathways, augments the lactate shuttle process, boosts resistance to oxidative stress, and contributes to lactylation. In various cellular populations, the interplay between lactate and immune cells governs processes such as cell differentiation, immune response, immune surveillance, and treatment effectiveness. Furthermore, communication between lactate and stromal/endothelial cells supports basal membrane (BM) remodeling, epithelial-mesenchymal transitions (EMT), metabolic reprogramming, angiogenesis, and drug resistance. Focusing on lactate production and transport, specifically through lactate dehydrogenase (LDH) and monocarboxylate transporters (MCT), has shown promise in the treatment of cancer. Inhibitors targeting LDH and MCT act as both tumor suppressors and enhancers of immunotherapy, leading to a synergistic therapeutic effect when combined with immunotherapy. The review underscores the importance of lactate in tumor progression and provides valuable perspectives on potential therapeutic approaches that target the vulnerability of lactate metabolism, highlighting the Heel of Achilles for cancer treatment.

Modification in Structures of Active Compounds in Anticancer Mitochondria-Targeted Therapy

Cancer is a multifaceted disease characterised by uncontrolled cellular proliferation and metastasis, resulting in significant global mortality. Current therapeutic strategies, including surgery, chemotherapy, and radiation therapy, face challenges such as systemic toxicity and tumour resistance. Recent advancements have shifted towards targeted therapies that act selectively on molecular structures within cancer cells, reducing off-target effects. Mitochondria have emerged as pivotal targets in this approach, given their roles in metabolic reprogramming, retrograde signalling, and oxidative stress, all of which drive the malignant phenotype. Targeting mitochondria offers a promising strategy to address these mechanisms at their origin. Synthetic derivatives of natural compounds hold particular promise in mitochondrial-targeted therapies. Innovations in drug design, including the use of conjugates and nanotechnology, focus on optimizing these compounds for mitochondrial specificity. Such advancements enhance therapeutic efficacy while minimizing systemic toxicity, presenting a significant step forward in modern anticancer strategies.

Inhibition of programmed cell death by melanoma cell subpopulations reveals mechanisms of melanoma metastasis and potential therapeutic targets

Melanoma is an aggressive type of skin cancer that arises from melanocytes, the cells responsible for producing skin pigment. In contrast to non-melanoma skin cancers like basal cell carcinoma and squamous cell carcinoma, melanoma is more invasive. Melanoma was distinguished by its rapid progression, high metastatic potential, and significant resistance to conventional therapies. Although it accounted for a small proportion of skin cancer cases, melanoma accounts for the majority of deaths caused by skin cancer due to its ability to invade deep tissues, adapt to diverse microenvironments, and evade immune responses. These unique features highlighted the challenges of treating melanoma and underscored the importance of advanced tools, such as single-cell sequencing, to unravel its biology and develop personalized therapeutic strategies. Thus, we conducted a single-cell analysis of the cellular composition within melanoma tumor tissues and further subdivided melanoma cells into subpopulations. Through analyzing metabolic pathways, stemness genes, and transcription factors (TFs) among cells in different phases (G1, G2/M, and S) as well as between primary and metastatic foci cells, we investigated the specific mechanisms underlying melanoma metastasis. We also revisited the cellular stemness and temporal trajectories of melanoma cell subpopulations, identifying the core subpopulation as C0 SOD3 + Melanoma cells. Our findings revealed a close relationship between the pivotal C0 SOD3 + Melanoma cells subpopulation and oxidative pathways in metastatic tumor tissues. Additionally, we analyzed prognostically relevant differentially expressed genes (DEGs) within the C0 SOD3 + Melanoma cells subpopulation and built a predictive model associated with melanoma outcomes. We selected the gene IGF1 with the highest coefficient (coef) value for further analysis, and experimentally validated its essential function in the proliferation and invasive metastasis of melanoma. In immune infiltration analysis, we discovered the critical roles played by M1/M2 macrophages in melanoma progression and immune evasion. Furthermore, the development and progression of malignant melanoma were closely associated with various forms of programmed cell death (PCD), including apoptosis, autophagic cell death, ferroptosis, and pyroptosis. Melanoma cells often resisted cell death mechanisms, maintaining their growth by inhibiting apoptosis and evading autophagic cell death. Meanwhile, the induction of ferroptosis and pyroptosis was thought to trigger immune responses that helped suppress melanoma dissemination. A deeper understanding of the relationship between melanoma and PCD pathways provided a critical foundation for developing novel targeted therapies, with the potential to enhance melanoma treatment efficacy. These findings contributed to the development of novel prognostic models for melanoma and shed light on research directions concerning melanoma metastasis mechanisms and therapeutic targets.

NAC regulates metabolism and cell fate in intestinal stem cells

Intestinal stem cells (ISCs) face the challenge of integrating metabolic demands with unique regenerative functions. Studies have shown an intricate interplay between metabolism and stem cell capacity; however, it is still not understood how this process is regulated. Combining ribosome profiling and CRISPR screening in intestinal organoids, we identify the nascent polypeptide-associated complex (NAC) as a key mediator of this process. Our findings suggest that NAC is responsible for relocalizing ribosomes to the mitochondria and regulating ISC metabolism. Upon NAC inhibition, intestinal cells show decreased import of mitochondrial proteins, which are needed for oxidative phosphorylation, and, consequently, enable the cell to maintain a stem cell identity. Furthermore, we show that overexpression of NACα is sufficient to drive mitochondrial respiration and promote ISC identity. Ultimately, our results reveal the pivotal role of NAC in regulating ribosome localization, mitochondrial metabolism, and ISC function, providing insights into the potential mechanism behind it.

Tumor-Targeted Metal-Organic Framework for Improved Photodynamic Therapy and Inhibited Tumor Metastasis in Melanoma

Tumor hypoxia and elevated intracellular glutathione (GSH) levels significantly compromise the effectiveness of photodynamic therapy (PDT) in treating melanoma. In this study, we synthesized positively charged nanoparticles through a self-assembly method, incorporating photosensitizer verteporfin (VER), mitochondrial respiratory inhibitor atovaquone (ATO), and Fe3+. Subsequently, the nanoparticles were modified with sodium hyaluronate (HA) to obtain HA-ATO-Fe3+-VER nanoparticles (HAFV NPs). The fabricated HAFV NPs demonstrated excellent stability and in vitro Fenton reaction activity. HA facilitated the cellular internalization of HAFV NPs by targeting CD44 receptors, hence relieving tumor hypoxia through the disruption of the mitochondrial respiratory chain and involvement in the Fenton reaction. Simultaneously, ATO directly impeded the biosynthesis of GSH by diminishing ATP levels, while Fe3+ was supposed to oxidate GSH to GSSG, thereby doubly depleting GSH. The integration of these multiple mechanisms markedly enhanced the PDT efficacy of VER. Following intravenous administration, HAFV NPs preferentially accumulated in tumor tissues with minimal accumulation in the skin, demonstrating favorable biocompatibility in vivo. Furthermore, HAFV NPs effectively inhibited tumor growth and lung metastasis, which presents a promising strategy for melanoma treatment.

Integrated analyses of multi-omic data derived from paired primary lung cancer and brain metastasis reveal the metabolic vulnerability as a novel therapeutic target

BACKGROUND

Lung cancer brain metastases (LC-BrMs) are frequently associated with dismal mortality rates in patients with lung cancer; however, standard of care therapies for LC-BrMs are still limited in their efficacy. A deep understanding of molecular mechanisms and tumor microenvironment of LC-BrMs will provide us with new insights into developing novel therapeutics for treating patients with LC-BrMs.

METHODS

Here, we performed integrated analyses of genomic, transcriptomic, proteomic, metabolomic, and single-cell RNA sequencing data which were derived from a total number of 154 patients with paired and unpaired primary lung cancer and LC-BrM, spanning four published and two newly generated patient cohorts on both bulk and single cell levels.

RESULTS

We uncovered that LC-BrMs exhibited a significantly greater intra-tumor heterogeneity. We also observed that mutations in a subset of genes were almost always shared by both primary lung cancers and LC-BrM lesions, including TTN, TP53, MUC16, LRP1B, RYR2, and EGFR. In addition, the genome-wide landscape of somatic copy number alterations was similar between primary lung cancers and LC-BrM lesions. Nevertheless, several regions of focal amplification were significantly enriched in LC-BrMs, including 5p15.33 and 20q13.33. Intriguingly, integrated analyses of transcriptomic, proteomic, and metabolomic data revealed mitochondrial-specific metabolism was activated but tumor immune microenvironment was suppressed in LC-BrMs. Subsequently, we validated our results by conducting real-time quantitative reverse transcription PCR experiments, immunohistochemistry, and multiplexed immunofluorescence staining of patients' paired tumor specimens. Therapeutically, targeting oxidative phosphorylation with gamitrinib in patient-derived organoids of LC-BrMs induced apoptosis and inhibited cell proliferation. The combination of gamitrinib plus anti-PD-1 immunotherapy significantly improved survival of mice bearing LC-BrMs. Patients with a higher expression of mitochondrial metabolism genes but a lower expression of immune genes in their LC-BrM lesions tended to have a worse survival outcome.

CONCLUSIONS

In conclusion, our findings not only provide comprehensive and integrated perspectives of molecular underpinnings of LC-BrMs but also contribute to the development of a potential, rationale-based combinatorial therapeutic strategy with the goal of translating it into clinical trials for patients with LC-BrMs.

Selective metabolic regulations by p53 mutant variants in pancreatic cancer

BACKGROUND

Approximately half of all human cancers harbour mutations in the p53 gene, leading to the generation of neomorphic p53 mutant proteins. These mutants can exert gain-of-function (GOF) effects, potentially promoting tumour progression. However, the clinical significance of p53 GOF mutations, as well as the selectivity of individual variants, remains controversial and unclear.

METHODS

To elucidate the metabolic regulations and molecular underpinnings associated with the specific p53R270H and p53R172H mutant variants (the mouse equivalents of human p53R273H and p53R175H, respectively), we employed a comprehensive approach. This included integrating global metabolomic analysis with epigenomic and transcriptomic profiling in mouse pancreatic cancer cells. Additionally, we assessed metabolic parameters such as oxygen consumption rate and conducted analyses of proliferation and cell-cell competition to validate the biological impact of metabolic changes on pancreatic ductal adenocarcinoma (PDAC) phenotype. Our findings were further corroborated through analysis of clinical datasets from human cancer cohorts.

RESULTS

Our investigation revealed that the p53R270H variant, but not p53R172H, sustains mitochondrial function and energy production while also influencing cellular antioxidant capacity. Conversely, p53R172H, while not affecting mitochondrial metabolism, attenuates the activation of pro-tumorigenic metabolic pathways such as the urea cycle. Thus, the two variants selectively control different metabolic pathways in pancreatic cancer cells. Mechanistically, p53R270H induces alterations in the expression of genes associated with oxidative stress and reduction in mitochondrial respiration. In contrast, p53R172H specifically impacts the expression levels of enzymes involved in the urea metabolism. However, our analysis of cell proliferation and cell competition suggested that the expression of either p53R270H or p53R172H does not influence confer any selective advantage to this cellular model in vitro. Furthermore, assessment of mitochondrial priming indicated that the p53R270H-driven mitochondrial effect does not alter cytochrome c release or the apoptotic propensity of pancreatic cancer cells.

CONCLUSIONS

Our study elucidates the mutant-specific impact of p53R270H and p53R172H on metabolism of PDAC cancer cells, highlighting the need to shift from viewing p53 mutant variants as a homogeneous group of entities to a systematic assessment of each specific p53 mutant protein. Moreover, our finding underscores the importance of further exploring the significance of p53 mutant proteins using models that more accurately reflect tumor ecology.

Curcumin: A Potential Weapon in the Prevention and Treatment of Head and Neck Cancer

Head and neck cancers (HNC) are aggressive, difficult-to-treat tumors that can be caused by genetic factors but mainly by lifestyle or infection caused by the human papillomavirus. As the sixth most common malignancy, it presents a formidable therapeutic challenge with limited therapeutic modalities. Curcumin, a natural polyphenol, is appearing as a promising multitarget anticancer and antimetastatic agent. Numerous studies have shown that curcumin and its derivatives have the potential to affect signaling pathways (NF-κB, JAK/STAT, and EGFR) and molecular mechanisms that are crucial for the growth and migration of head and neck tumors. Furthermore, its ability to interact with the tumor microenvironment and trigger the immune system may significantly influence the organism's immune response to the tumor. Combining curcumin with conventional therapies such as chemotherapy or radiotherapy may improve the efficacy of treatment and reduce the side effects of treatment, thereby increasing its therapeutic potential. This review is a comprehensive overview that discusses both the benefits and limitations of curcumin and its therapeutic effects in the context of tumor biology, with an emphasis on molecular mechanisms in the context of HNC. This review also includes possibilities to improve the limiting properties of curcumin both in terms of the development of new derivatives, formulations, or combinations with conventional therapies that have potential as a new type of therapy for the treatment of HNC and subsequent use in clinical practice.

Hyaluronic acid-coated porphyrin nanoplatform with oxygen sustained supplying and glutathione depletion for enhancing photodynamic/ion/chemo synergistic cancer treatment

Hypoxia and high concentration of glutathione (GSH) in tumor seriously hinder the role of reactive oxygen species (ROS) and oxygen-dependence strategy in tumor treatment. In this work, a self-generating oxygen and self-consuming GSH hyaluronic acid (HA)-coated porphyrin nanoplatform (TAPPP@CaO2/Pt(IV)/HA) is established for enhancing photodynamic/ion/chemo targeting synergistic therapy of tumor. During the efforts of ROS production by nanosystems, a GSH consuming strategy is implemented for augmenting ROS-induced oxidative damage for synergetic cancer therapy. CaO2 in the nanosystems is decomposed into O2 and H2O2 in an acidic environment, which alleviates hypoxia and enhances the photodynamic therapy (PDT) effect. Calcium overload causes mitochondria dysfunction and induces apoptosis. Pt (IV) reacts with GSH to produce Pt (II) for chemotherapy and reduce the concentration of GSH, protecting ROS from scavenging for augmenting ROS-induced oxidative damage. In vitro and in vivo results demonstrated the self-generating oxygen and self-consuming GSH strategy can enhance ROS-dependent PDT coupled with ion/chemo synergistic therapy. The proposed strategy not only solves the long-term problem that hypoxia limits therapeutic effect of PDT, but also ameliorates the highly reducing environment of tumors. Thus the preparation of TAPPP@CaO2/Pt(IV)/HA provided a novel strategy for the effective combined therapy of cancers.

Targeting glioblastoma tumor hyaluronan to enhance therapeutic interventions that regulate metabolic cell properties

Despite extensive advances in cancer research, glioblastoma (GBM) still remains a very locally invasive and thus challenging tumor to treat, with a poor median survival. Tumor cells remodel their microenvironment and utilize extracellular matrix to promote invasion and therapeutic resistance. We aim here to determine how GBM cells exploit hyaluronan (HA) to maintain proliferation using ligand-receptor dependent and ligand-receptor independent signaling. We use tissue engineering approaches to recreate the three-dimensional tumor microenvironment in vitro, then analyze shifts in metabolism, hyaluronan secretion, HA molecular weight distribution, as well as hyaluronan synthetic enzymes (HAS) and hyaluronidases (HYAL) activity in an array of patient derived xenograft GBM cells. We reveal that endogenous HA plays a role in mitochondrial respiration and cell proliferation in a tumor subtype dependent manner. We propose a tumor specific combination treatment of HYAL and HAS inhibitors to disrupt the HA stabilizing role in GBM cells. Taken together, these data shed light on the dual metabolic and ligand - dependent signaling roles of hyaluronan in glioblastoma.

PARP-1 negatively regulates nucleolar protein pool and mitochondrial activity: a cell protective mechanism

BACKGROUND

Poly(ADP-ribose) polymerase-1 (PARP-1) is a pan nuclear protein that utilizes NAD+ as a substrate for poly(ADP-ribosyl)ation reaction (PARylation), resulting in both auto-modification and the modification of its accepter proteins. Earlier reports suggested that several nucleolar proteins interact and colocalize with PARP-1, leading to their PARylation. However, whether PARP-1 has any role in nucleolar biogenesis and the functional relevance of such a role is still obscure.

RESULTS

Using PARP-1 depleted cells, we investigated the function of PARP-1 in maintaining the nucleolar morphology and protein levels under normal physiological conditions. Our results revealed that several nucleolar proteins like nucleolin, fibrillarin, and nucleophosmin get up-regulated when PARP-1 is depleted. Additionally, in line with the higher accumulation of nucleolin, stably depleted PARP-1 cells show lower activation of caspase-3, lesser annexin-V staining, and reduced accumulation of AIF in the nucleus upon induction of oxidative stress. Concurrently, PARP-1 silenced cells showed higher mitochondrial oxidative phosphorylation and more fragmented and intermediate mitochondria than the parental counterpart, suggesting higher metabolic activity for better survival.

CONCLUSION

Based on our findings, we demonstrate that PARP-1 may have a role in regulating nucleolar protein levels and mitochondrial activity, thus maintaining the homeostasis between cell protective and cell death pathways, and such cell-protective mechanism could be implicated as the priming state of a pre-cancerous condition or tumour dormancy.

Cytotoxic properties, glycolytic effects and high-resolution respirometry mitochondrial activities of Eriocephalus racemosus against MDA-MB 231 triple-negative breast cancer

INTRODUCTION

Triple-negative breast cancer (TNBC) represents a significant global health crisis due to its resistance to conventional therapies and lack of specific molecular targets. This study explored the potential of Eriocephalus racemosus (E. racemosus) as an alternative treatment for TNBC. The cytotoxic properties and high-resolution respirometry mitochondrial activities of E. racemosus against the MDA-MB 231 TNBC cell line were evaluated.

METHODS

Hexane solvent and bioactive fraction extractions of E. racemosus were performed, while mass spectrometry-based metabolite profiling was used to identify the phytochemical constituents of the extracts. The extracts were further tested against MDA-MB 231 TNBC cells to determine their cytotoxicity. The mode of cell death was determined using flow cytometry. The activities of caspases 3, 8, and 9 were assessed using a multiplex activity assay kit. Glycolytic activity and High-resolution respirometry measurements of mitochondrial function in the MDA-MB 231 cell line were conducted using the Seahorse XFp and Oroboros O2K.

RESULTS

Metabolite profiling of E. racemosus plant crude extracts identified the presence of coumarins, flavonoids, sesquiterpenoids, triterpenoids, and unknown compounds. The extracts demonstrated promising cytotoxic activities, with a half maximal inhibitory concentration (IC50) of 12.84 µg/mL for the crude hexane extract and 15.49 µg/mL for the bioactive fraction. Further, the crude hexane and bioactive fraction extracts induced apoptosis in the MDA-MB-231 TNBC cells, like the reference drug cisplatin (17.44%, 17.26% and 20.25%, respectively) compared to untreated cells. Caspase 3 activities confirmed the induction of apoptosis in both cisplatin and the plant crude extracts, while caspase 8 and 9 activities confirmed the activation of both the intrinsic and extrinsic apoptosis pathways. Increased levels of glycolytic activity were observed in the hexane crude extract. High-resolution respiratory measurements showed elevated mitochondrial activities in all mitochondrial states except for complex-IV activity.

CONCLUSION

These findings support further exploration of E. racemosus as a potential therapeutic agent for TNBC, offering a promising avenue for the development of targeted treatments with minimal adverse effects.

Mitochondria: a new intervention target for tumor invasion and metastasis

Mitochondria, responsible for cellular energy synthesis and signal transduction, intricately regulate diverse metabolic processes, mediating fundamental biological phenomena such as cell growth, aging, and apoptosis. Tumor invasion and metastasis, key characteristics of malignancies, significantly impact patient prognosis. Tumor cells frequently exhibit metabolic abnormalities in mitochondria, including alterations in metabolic dynamics and changes in the expression of relevant metabolic genes and associated signal transduction pathways. Recent investigations unveil further insights into mitochondrial metabolic abnormalities, revealing their active involvement in tumor cell proliferation, resistance to chemotherapy, and a crucial role in tumor cell invasion and metastasis. This paper comprehensively outlines the latest research advancements in mitochondrial structure and metabolic function. Emphasis is placed on summarizing the role of mitochondrial metabolic abnormalities in tumor invasion and metastasis, including alterations in the mitochondrial genome (mutations), activation of mitochondrial-to-nuclear signaling, and dynamics within the mitochondria, all intricately linked to the processes of tumor invasion and metastasis. In conclusion, the paper discusses unresolved scientific questions in this field, aiming to provide a theoretical foundation and novel perspectives for developing innovative strategies targeting tumor invasion and metastasis based on mitochondrial biology.

Cyanine dyes in the mitochondria-targeting photodynamic and photothermal therapy

Mitochondrial dysregulation plays a significant role in the carcinogenesis. On the other hand, its destabilization strongly represses the viability and metastatic potential of cancer cells. Photodynamic and photothermal therapies (PDT and PTT) target mitochondria effectively, providing innovative and non-invasive anticancer therapeutic modalities. Cyanine dyes, with strong mitochondrial selectivity, show significant potential in enhancing PDT and PTT. The potential and limitations of cyanine dyes for mitochondrial PDT and PTT are discussed, along with their applications in combination therapies, theranostic techniques, and optimal delivery systems. Additionally, novel approaches for sonodynamic therapy using photoactive cyanine dyes are presented, highlighting advances in cancer treatment.

Stilbenoid derivatives as potent inhibitors of HIF-1α-centric cancer metabolism under hypoxia

Hypoxia-inducible factor (HIF)-1α is a crucial transcription factor associated with cancer metabolism and is regarded as a potent anticancer therapeutic strategy within the hypoxic microenvironment of cancer. In this study, stilbenoid derivatives were designed, synthesized, and assessed for their capacity to inhibit HIF-1α-associated cancer metabolism and evaluated for inhibition of cancer cell viability and HIF activation. Through the structure-activity relationship studies, compound 28e was identified as the most potent derivative. Specifically, under the hypoxic condition, 28e reduced the accumulation of HIF-1α protein and the expression of its target genes related to glucose metabolism without affecting the expression of HIF-1α mRNA. Furthermore, 28e inhibited glucose uptake, glycolytic metabolism, and mitochondrial respiration, decreasing cellular ATP production under hypoxic conditions. In addition, 28e displayed significant anti-tumor effects and effectively suppressed the accumulation of HIF-1α protein in tumor tissue in vivo xenograft model. These findings suggest that our stilbenoid derivatives exert their anticancer effects by targeting HIF-1α-centered cancer metabolism under hypoxic conditions.

Tumor Dormancy and Reactivation: The Role of Heat Shock Proteins

Tumors are a heterogeneous group of cell masses originating in various organs or tissues. The cellular composition of the tumor cell mass interacts in an intricate manner, influenced by humoral, genetic, molecular, and tumor microenvironment cues that dictate tumor growth or suppression. As a result, tumors undergo a period of a dormant state before their clinically discernible stage, which surpasses the clinical dormancy threshold. Moreover, as a genetically imprinted strategy, early-seeder cells, a distinct population of tumor cells, break off to dock nearby or extravasate into blood vessels to secondary tissues, where they form disseminated solitary dormant tumor cells with reversible capacity. Among the various mechanisms underlying the dormant tumor mass and dormant tumor cell formation, heat shock proteins (HSPs) might play one of the most important roles in how the dormancy program plays out. It is known that numerous aberrant cellular processes, such as malignant transformation, cancer cell stemness, tumor invasion, metastasis, angiogenesis, and signaling pathway maintenance, are influenced by the HSPs. An accumulating body of knowledge suggests that HSPs may be involved in the angiogenic switch, immune editing, and extracellular matrix (ECM) remodeling cascades, crucial genetically imprinted strategies important to the tumor dormancy initiation and dormancy maintenance program. In this review, we highlight the biological events that orchestrate the dormancy state and the body of work that has been conducted on the dynamics of HSPs in a tumor mass, as well as tumor cell dormancy and reactivation. Additionally, we propose a conceptual framework that could possibly underlie dormant tumor reactivation in metastatic relapse.

Nanomedicine Targeting Cuproplasia in Cancer: Labile Copper Sequestration Using Polydopamine Particles Blocks Tumor Growth In Vivo through Altering Metabolism and Redox Homeostasis

Copper plays critical roles as a metal active site cofactor and metalloallosteric signal for enzymes involved in cell proliferation and metabolism, making it an attractive target for cancer therapy. In this study, we investigated the efficacy of polydopamine nanoparticles (PDA NPs), classically applied for metal removal from water, as a therapeutic strategy for depleting intracellular labile copper pools in triple-negative breast cancer models through the metal-chelating groups present on the PDA surface. By using the activity-based sensing probe FCP-1, we could track the PDA-induced labile copper depletion while leaving total copper levels unchanged and link it to the selective MDA-MB-231 cell death. Further mechanistic investigations revealed that PDA NPs increased reactive oxygen species (ROS) levels, potentially through the inactivation of superoxide dismutase 1 (SOD1), a copper-dependent antioxidant enzyme. Additionally, PDA NPs were found to interact with the mitochondrial membrane, resulting in an increase in the mitochondrial membrane potential, which may contribute to enhanced ROS production. We employed an in vivo tumor model to validate the therapeutic efficacy of PDA NPs. Remarkably, in the absence of any additional treatment, the presence of PDA NPs alone led to a significant reduction in tumor volume by a factor of 1.66 after 22 days of tumor growth. Our findings highlight the potential of PDA NPs as a promising therapeutic approach for selectively targeting cancer by modulating copper levels and inducing oxidative stress, leading to tumor growth inhibition as shown in these triple-negative breast cancer models.

Acyl-CoA synthetase 4 modulates mitochondrial function in breast cancer cells

Mitochondria are dynamic organelles that respond to cellular stress through changes in global mass, interconnection, and subcellular location. As mitochondria play an important role in tumor development and progression, alterations in energy metabolism allow tumor cells to survive and spread even in challenging conditions. Alterations in mitochondrial bioenergetics have been recently proposed as a hallmark of cancer, and positive regulation of lipid metabolism constitutes one of the most common metabolic changes observed in tumor cells. Acyl-CoA synthetase 4 (ACSL4) is an enzyme catalyzing the activation of long chain polyunsaturated fatty acids with a strong substrate preference for arachidonic acid (AA). High ACSL4 expression has been related to aggressive cancer phenotypes, including breast cancer, and its overexpression has been shown to positively regulate the mammalian Target of Rapamycin (mTOR) pathway, involved in the regulation of mitochondrial metabolism genes. However, little is known about the role of ACSL4 in the regulation of mitochondrial function and metabolism in cancer cells. In this context, our objective was to study whether mitochondrial function and metabolism, processes usually altered in tumors, are modulated by ACSL4 in breast cancer cells. Using ACSL4 overexpression in MCF-7 cells, we demonstrate that this enzyme can increase the mRNA and protein levels of essential mitochondrial regulatory proteins such as nuclear respiratory factor 1 (NRF-1), voltage-dependent anion channel 1 (VDAC1) and respiratory chain Complex III. Furthermore, respiratory parameters analysis revealed an increase in oxygen consumption rate (OCR) and in spare respiratory capacity (SRC), among others. ACSL4 knockdown in MDA-MB-231 cells led to the decrease in OCR and in SCR, supporting the role of ACSL4 in the regulation of mitochondrial bioenergetics. Moreover, ACSL4 overexpression induced an increase in glycolytic function, in keeping with an increase in mitochondrial respiratory activity. Finally, there was a decrease in mitochondrial mass detected in cells that overexpressed ACSL4, while the knockdown of ACSL4 expression in MDA-MB-231 cells showed the opposite effect. Altogether, these results unveil the role of ACSL4 in mitochondrial function and metabolism and expand the knowledge of ACSL4 participation in pathological processes such as breast cancer.

Unraveling the intricacies of glioblastoma progression and recurrence: insights into the role of NFYB and oxidative phosphorylation at the single-cell level

Background

Glioblastoma (GBM), with its high recurrence and mortality rates, makes it the deadliest neurological malignancy. Oxidative phosphorylation is a highly active cellular pathway in GBM, and NFYB is a tumor-associated transcription factor. Both are related to mitochondrial function, but studies on their relationship with GBM at the single-cell level are still scarce.

Methods

We re-analyzed the single-cell profiles of GBM from patients with different subtypes by single-cell transcriptomic analysis and further subdivided the large population of Glioma cells into different subpopulations, explored the interrelationships and active pathways among cell stages and clinical subtypes of the populations, and investigated the relationship between the transcription factor NFYB of the key subpopulations and GBM, searching for the prognostic genes of GBM related to NFYB, and verified by experiments.

Results

Glioma cells and their C5 subpopulation had the highest percentage of G2M staging and rGBM, which we hypothesized might be related to the higher dividing and proliferating ability of both Glioma and C5 subpopulations. Oxidative phosphorylation pathway activity is elevated in both the Glioma and C5 subgroup, and NFYB is a key transcription factor for the C5 subgroup, suggesting its possible involvement in GBM proliferation and recurrence, and its close association with mitochondrial function. We also identified 13 prognostic genes associated with NFYB, of which MEM60 may cause GBM patients to have a poor prognosis by promoting GBM proliferation and drug resistance. Knockdown of the NFYB was found to contribute to the inhibition of proliferation, invasion, and migration of GBM cells.

Conclusion

These findings help to elucidate the key mechanisms of mitochondrial function in GBM progression and recurrence, and to establish a new prognostic model and therapeutic target based on NFYB.

Pancreatic ductal adenocarcinoma chemoresistance: From metabolism reprogramming to novel treatment

ABSTRACT

As pancreatic cancer (PC) is highly malignant, its patients tend to develop metastasis at an early stage and show a poor response to conventional chemotherapies. First-line chemotherapies for PC, according to current guidelines, include fluoropyrimidine- and gemcitabine-based regimens. Accumulating research on drug resistance has shown that biochemical metabolic aberrations in PC, especially those involving glycolysis and glutamine metabolism, are highly associated with chemoresistance. Additionally, lipid metabolism is a major factor in chemoresistance. However, emerging compounds that target these key metabolic pathways have the potential to overcome chemoresistance. This review summarizes how PC develops chemoresistance through aberrations in biochemical metabolism and discusses novel critical targets and pathways within cancer metabolism for new drug research.

Targeting the Metabolic Paradigms in Cancer and Diabetes

Dysregulated metabolic dynamics are evident in both cancer and diabetes, with metabolic alterations representing a facet of the myriad changes observed in these conditions. This review delves into the commonalities in metabolism between cancer and type 2 diabetes (T2D), focusing specifically on the contrasting roles of oxidative phosphorylation (OXPHOS) and glycolysis as primary energy-generating pathways within cells. Building on earlier research, we explore how a shift towards one pathway over the other serves as a foundational aspect in the development of cancer and T2D. Unlike previous reviews, we posit that this shift may occur in seemingly opposing yet complementary directions, akin to the Yin and Yang concept. These metabolic fluctuations reveal an intricate network of underlying defective signaling pathways, orchestrating the pathogenesis and progression of each disease. The Warburg phenomenon, characterized by the prevalence of aerobic glycolysis over minimal to no OXPHOS, emerges as the predominant metabolic phenotype in cancer. Conversely, in T2D, the prevailing metabolic paradigm has traditionally been perceived in terms of discrete irregularities rather than an OXPHOS-to-glycolysis shift. Throughout T2D pathogenesis, OXPHOS remains consistently heightened due to chronic hyperglycemia or hyperinsulinemia. In advanced insulin resistance and T2D, the metabolic landscape becomes more complex, featuring differential tissue-specific alterations that affect OXPHOS. Recent findings suggest that addressing the metabolic imbalance in both cancer and diabetes could offer an effective treatment strategy. Numerous pharmaceutical and nutritional modalities exhibiting therapeutic effects in both conditions ultimately modulate the OXPHOS-glycolysis axis. Noteworthy nutritional adjuncts, such as alpha-lipoic acid, flavonoids, and glutamine, demonstrate the ability to reprogram metabolism, exerting anti-tumor and anti-diabetic effects. Similarly, pharmacological agents like metformin exhibit therapeutic efficacy in both T2D and cancer. This review discusses the molecular mechanisms underlying these metabolic shifts and explores promising therapeutic strategies aimed at reversing the metabolic imbalance in both disease scenarios.

Natural Product-Based Glycolysis Inhibitors as a Therapeutic Strategy for Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitor-Resistant Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) is a leading cause of cancer-related deaths worldwide. Targeted therapy against the epidermal growth factor receptor (EGFR) is a promising treatment approach for NSCLC. However, resistance to EGFR tyrosine kinase inhibitors (TKIs) remains a major challenge in its clinical management. EGFR mutation elevates the expression of hypoxia-inducible factor-1 alpha to upregulate the production of glycolytic enzymes, increasing glycolysis and tumor resistance. The inhibition of glycolysis can be a potential strategy for overcoming EGFR-TKI resistance and enhancing the effectiveness of EGFR-TKIs. In this review, we specifically explored the effectiveness of pyruvate dehydrogenase kinase inhibitors and lactate dehydrogenase A inhibitors in combating EGFR-TKI resistance. The aim was to summarize the effects of these natural products in preclinical NSCLC models to provide a comprehensive understanding of the potential therapeutic effects. The study findings suggest that natural products can be promising inhibitors of glycolytic enzymes for the treatment of EGFR-TKI-resistant NSCLC. Further investigations through preclinical and clinical studies are required to validate the efficacy of natural product-based glycolytic inhibitors as innovative therapeutic modalities for NSCLC.

Targeting glioblastoma tumor hyaluronan to enhance therapeutic interventions that regulate metabolic cell properties

Despite extensive advances in cancer research, glioblastoma (GBM) still remains a very locally invasive and thus challenging tumor to treat, with a poor median survival. Tumor cells remodel their microenvironment and utilize extracellular matrix to promote invasion and therapeutic resistance. We aim here to determine how GBM cells exploit hyaluronan (HA) to maintain proliferation using ligand-receptor dependent and ligand-receptor independent signaling. We use tissue engineering approaches to recreate the three-dimensional tumor microenvironment in vitro, then analyze shifts in metabolism, hyaluronan secretion, HA molecular weight distribution, as well as hyaluronan synthetic enzymes (HAS) and hyaluronidases (HYAL) activity in an array of patient derived xenograft GBM cells. We reveal that endogenous HA plays a role in mitochondrial respiration and cell proliferation in a tumor subtype dependent manner. We propose a tumor specific combination treatment of HYAL and HAS inhibitors to disrupt the HA stabilizing role in GBM cells. Taken together, these data shed light on the dual metabolic and ligand - dependent signaling roles of hyaluronan in glioblastoma.

Significance

The control of aberrant hyaluronan metabolism in the tumor microenvironment can improve the efficacy of current treatments. Bioengineered preclinical models demonstrate potential to predict, stratify and accelerate the development of cancer treatments.

Rewiring of mitochondrial metabolism in therapy-resistant cancers: permanent and plastic adaptations

Deregulation of tumor cell metabolism is widely recognized as a "hallmark of cancer." Many of the selective pressures encountered by tumor cells, such as exposure to anticancer therapies, navigation of the metastatic cascade, and communication with the tumor microenvironment, can elicit further rewiring of tumor cell metabolism. Furthermore, phenotypic plasticity has been recently appreciated as an emerging "hallmark of cancer." Mitochondria are dynamic organelles and central hubs of metabolism whose roles in cancers have been a major focus of numerous studies. Importantly, therapeutic approaches targeting mitochondria are being developed. Interestingly, both plastic (i.e., reversible) and permanent (i.e., stable) metabolic adaptations have been observed following exposure to anticancer therapeutics. Understanding the plastic or permanent nature of these mechanisms is of crucial importance for devising the initiation, duration, and sequential nature of metabolism-targeting therapies. In this review, we compare permanent and plastic mitochondrial mechanisms driving therapy resistance. We also discuss experimental models of therapy-induced metabolic adaptation, therapeutic implications for targeting permanent and plastic metabolic states, and clinical implications of metabolic adaptations. While the plasticity of metabolic adaptations can make effective therapeutic treatment challenging, understanding the mechanisms behind these plastic phenotypes may lead to promising clinical interventions that will ultimately lead to better overall care for cancer patients.

Single-cell RNA-Seq and bulk RNA-Seq reveal reliable diagnostic and prognostic biomarkers for CRC

PURPOSE

The potential role of epithelium-specific genes through the adenoma-carcinoma sequence in the development of colorectal cancer (CRC) remains unknown. Therefore, we integrated single-cell RNA sequencing and bulk RNA sequencing data to select diagnosis and prognosis biomarkers for CRC.

METHODS

The CRC scRNA-seq dataset was used to describe the cellular landscape of normal intestinal mucosa, adenoma and CRC and to further select epithelium-specific clusters. Differentially expressed genes (DEGs) of epithelium-specific clusters were identified between intestinal lesion and normal mucosa in the scRNA-seq data throughout the adenoma-carcinoma sequence. Diagnostic biomarkers and prognostic biomarker (the risk score) for CRC were selected in the bulk RNA-seq dataset based on DEGs shared by the adenoma epithelium-specific cluster and the CRC epithelium-specific cluster (shared-DEGs).

RESULTS

Among the 1063 shared-DEGs, we selected 38 gene expression biomarkers and 3 methylation biomarkers that had promising diagnostic power in plasma. Multivariate Cox regression identified  174 shared-DEGs as prognostic genes for CRC. We combined 1000 times LASSO-Cox regression and two-way stepwise regression to select 10 prognostic shared-DEGs to construct the risk score in the CRC meta-dataset. In the external validation dataset, the 1- and 5-year AUCs of the risk score were higher than those of stage, the pyroptosis-related genes (PRG) score and the cuproptosis-related genes (CRG) score. In addition, the risk score was closely associated with the immune infiltration of CRC.

CONCLUSION

The combined analysis of the scRNA-seq dataset and the bulk RNA-seq dataset in this study provides reliable biomarkers for the diagnosis and prognosis of CRC.

Synthesis and biological evaluation of novel pyrazole amides as potent mitochondrial complex I inhibitors

Targeting mitochondrial complex I (CI) is emerging as an attractive anticancer strategy, and CI inhibitor IACS-010759 has achieved breakthrough success. However, the narrow therapeutic index of IACS-010759 seriously hinders its further application. In this study, a series of novel pyrazole amides were designed and optimized based on IACS-010759, and their potential CI inhibitory effects were biologically evaluated. Among them, the maximum tolerated dose (MTD) values of SCAL-255 (compound 5q) and SCAL-266 (compound 6f) were 68 mg/kg, which was nearly 10 times that of IACS-010759 (6 mg/kg), showing good safety. In addition, SCAL-255 and SCAL-266 significantly inhibited the proliferation of HCT116 and KG-1 cells in vitro and exerted satisfactory inhibitory activity against KG-1 cells in vivo. These results suggested that the optimized compounds might serve as promising CI inhibitors against oxidative phosphorylation (OXPHOS)-dependent cancer, which merits further study.

Combining the antianginal drug perhexiline with chemotherapy induces complete pancreatic cancer regression in vivo

Pancreatic ductal adenocarcinoma (PDAC) remains one of the human cancers with the poorest prognosis. Interestingly, we found that mitochondrial respiration in primary human PDAC cells depends mainly on the fatty acid oxidation (FAO) to meet basic energy requirements. Therefore, we treated PDAC cells with perhexiline, a well-recognized FAO inhibitor used in cardiac diseases. Some PDAC cells respond efficiently to perhexiline, which acts synergistically with chemotherapy (gemcitabine) in vitro and in two xenografts in vivo. Importantly, perhexiline in combination with gemcitabine induces complete tumor regression in one PDAC xenograft. Mechanistically, this co-treatment causes energy and oxidative stress promoting apoptosis but does not exert inhibition of FAO. Yet, our molecular analysis indicates that the carnitine palmitoyltransferase 1C (CPT1C) isoform is a key player in the response to perhexiline and that patients with high CPT1C expression have better prognosis. Our study reveals that repurposing perhexiline in combination with chemotherapy is a promising approach to treat PDAC.

Mitochondrial Metabolism Drives Low-density Lipoprotein-induced Breast Cancer Cell Migration

Most cancer-related deaths are due to metastases. Systemic factors, such as lipid-enriched environments [as low-density lipoprotein (LDL)-cholesterol], favor breast cancer, including triple-negative breast cancer (TNBC) metastasis formation. Mitochondria metabolism impacts TNBC invasive behavior but its involvement in a lipid-enriched setting is undisclosed. Here we show that LDL increases lipid droplets, induces CD36 and augments TNBC cells migration and invasion in vivo and in vitro. LDL induces higher mitochondrial mass and network spread in migrating cells, in an actin remodeling-dependent manner, and transcriptomic and energetic analyses revealed that LDL renders TNBC cells dependent on fatty acids (FA) usage for mitochondrial respiration. Indeed, engagement on FA transport into the mitochondria is required for LDL-induced migration and mitochondrial remodeling. Mechanistically, LDL treatment leads to mitochondrial long-chain fatty acid accumulation and increased reactive oxygen species (ROS) production. Importantly, CD36 or ROS blockade abolished LDL-induced cell migration and mitochondria metabolic adaptations. Our data suggest that LDL induces TNBC cells migration by reprogramming mitochondrial metabolism, revealing a new vulnerability in metastatic breast cancer.

Significance

LDL induces breast cancer cell migration that relies on CD36 for mitochondrial metabolism and network remodeling, providing an antimetastatic metabolic strategy.

Near Infrared-Activatable Methylene Blue Polypeptide Codelivery of the NO Prodrug via π-π Stacking for Cascade Reactive Oxygen Species Amplification-Mediated Photodynamic Therapy

The application of photodynamic therapy (PDT) has attracted remarkable interest in cancer treatment because of the advantages of noninvasiveness and spatiotemporal selectivity. However, the PDT efficiency is considerably limited by photosensitizer (PS) quenching and severe hypoxia in solid tumors. Herein, a kind of near infrared (NIR)-activatable methylene blue (MB) peptide nanocarrier was developed for codelivery of nitric oxide (NO) prodrug JSK, expecting a cascade of reactive oxygen species (ROS) amplification-mediated antitumor PDT. In detail, MB was conjugated to water-soluble polyethylene glycol-polylysine (PEG-PLL) through NIR-photocleavable 10-N-carbamoyl bonds, and the subsequent amphiphilic conjugates (mPEG-PLL-MB) self-assembled into nanoparticles (NPs), which allowed JSK codelivery via π-π stacking interactions. MB in quenched state in mPEG-PLL-MB/JSK NPs could be photoactivated by NIR light locoregionally in a controlled manner due to the photocleavage of carbamoyl bonds. Apart from ROS production, assembly disturbance and even disintegration of mPEG-PLL-MB/JSK occurred along with MB activation that subsequently freed JSK, which was further triggered by intracellularly overexpressed glutathione (GSH) and glutathione S-transferase (GST) to sustain the release of NO. NO then served as a hypoxia relief agent through inhibition of cellular respiration to economize O₂, cooperating with MB activation and GSH depletion, which synergistically enabled a cascade of ROS amplification to augment PDT for mitochondrial apoptosis-mediated tumor inhibition in vitro and in vivo. Therefore, this pioneering strategy of cascade amplification of ROS addressed the key issues of PS inactivation, hypoxia resistance, and ROS neutralization in a three-pronged approach, which hold great promise in efficient antitumor PDT.

Recent advances of mitochondrial complex I inhibitors for cancer therapy: Current status and future perspectives

Mitochondrial complex I (CI) as a critical multifunctional respiratory complex of electron transport chain (ETC) in mitochondrial oxidative phosphorylation has been identified as vital and essence in ATP production, biosynthesis and redox balance. Recent progress in targeting CI has provided both insight and inspiration for oncotherapy, highlighting that the development of CI-targeting inhibitors is a promising therapeutic approach to fight cancer. Natural products possessing of ample scaffold diversity and structural complexity are the majority source of CI inhibitors, although low specificity and safety hinder their extensive application. Along with the gradual deepening in understanding of CI structure and function, significant progress has been achieved in exploiting novel and selective small molecules targeting CI. Among them, IACS-010759 had been approved by FDA for phase I trial in advanced cancers. Moreover, drug repurposing represents an effective and prospective strategy for CI inhibitor discovery. In this review, we mainly elaborate the biological function of CI in tumor progression, summarize the CI inhibitors reported in recent years and discuss the further perspectives for CI inhibitor application, expecting this work may provide insights into innovative discovery of CI-targeting drugs for cancer treatment.

PINK1-Mediated Mitophagy Promotes Oxidative Phosphorylation and Redox Homeostasis to Induce Drug-Tolerant Persister Cancer Cells

The drug-tolerant persister (DTP) state enables cancer cells to evade cytotoxic stress from anticancer therapy. However, the mechanisms governing DTP generation remain poorly understood. Here, we observed that lung adenocarcinoma (LUAD) cells and organoids entered a quiescent DTP state to survive MAPK inhibitor treatment. DTP cells following MAPK inhibition underwent a metabolic switch from glycolysis to oxidative phosphorylation (OXPHOS). PTEN-induced kinase 1 (PINK1), a serine/threonine kinase that initiates mitophagy, was upregulated to maintain mitochondrial homeostasis during DTP generation. PINK1-mediated mitophagy supported DTP cell survival and contributed to poor prognosis. Mechanistically, MAPK pathway inhibition resulted in MYC-dependent transcriptional upregulation of PINK1, leading to mitophagy activation. Mitophagy inhibition using either clinically applicable chloroquine or depletion of PINK1 eradicated drug tolerance and allowed complete response to MAPK inhibitors. This study uncovers PINK1-mediated mitophagy as a novel tumor protective mechanism for DTP generation, providing a therapeutic opportunity to eradicate DTP and achieve complete responses.

SIGNIFICANCE

DTP cancer cells that cause relapse after anticancer therapy critically depend on PINK1-mediated mitophagy and metabolic reprogramming, providing a therapeutic opportunity to eradicate persister cells to prolong treatment efficacy.

Phytochemicals and mitochondria: Therapeutic allies against gastric cancer

BACKGROUND

Mitochondria are the energy factories of cells with the ability to modulate the cell cycle, cellular differentiation, signal transduction, growth, and apoptosis. Existing drugs targeting mitochondria in cancer treatment have disadvantages of drug resistance and side effects. Phytochemicals, which are widely found in plants, are bioactive compounds that could facilitate the development of new drugs for gastric cancer. Studies have shown that some phytochemicals can suppress the development of gastric cancer.

METHODS

We searched for data from PubMed, China National Knowledge Infrastructure, Web of Science, and Embase databases from initial establishment to December 2021 to review the mechanism by which phytochemicals suppress gastric cancer cell growth by modulating mitochondrial function. Phytochemicals were classified and summarized by their mechanisms of action.

RESULTS

Phytochemicals can interfere with mitochondria through several mechanisms to reach the goal of promoting apoptosis in gastric cancer cells. Some phytochemicals, e.g., daidzein and tetrandrine promoted cytochrome c spillover into the cytoplasm by modulating the members of the B-cell lymphoma-2 protein family and induced apoptotic body activity by activating the caspase protein family. Phytochemicals (e.g., celastrol and shikonin) could promote the accumulation of reactive oxygen species and reduce the mitochondrial membrane potential. Several phytochemicals (e.g., berberine and oleanolic acid) activated mitochondrial apoptotic submission via the phosphatidylinositol-3-kinase/Akt signaling pathway, thereby triggering apoptosis in gastric cancer cells. Several well-known phytochemicals that target mitochondria, including berberine, ginsenoside, and baicalein, showed the advantages of multiple targets, high efficacy, and fewer side effects.

CONCLUSIONS

Phytochemicals could target the mitochondria in the treatment of gastric cancer, providing potential directions and evidence for clinical translation. Drug discovery focused on phytochemicals has great potential to break barriers in cancer treatment.

Comparative proteomic analysis of the mitochondria of menstrual stem cells and ovarian cancer cells

Mitochondrial transplantation is a popular field of research in cell-free therapy. Menstrual stem cells (MenSCs) are potential donor cells for provision of foreign mitochondria. The present study aimed to investigate the potential effects of MenSC-derived mitochondria on ovarian cancer from the perspective of protein expression profiling. MenSCs were harvested from menstrual blood. The mitochondria were isolated from MenSCs and ovarian cancer cell line SKOV3. A label-free mitochondria proteomics and analysis were performed by comparing the protein expression in mitochondria of MenSCs and SKOV3 cells. The differentially expressed proteins with fold-change >2 were analyzed by Gene Ontology, Kyoto Encyclopedia of Genes and Genomes pathway and protein domain enrichment, protein interaction networks and parallel reaction monitoring (PRM) analysis. In total, 592 proteins that were found to have increased expression in the mitochondria of MenSCs were analyzed. Functional enrichment analysis revealed these proteins were enriched in metabolism-associated pathway entries including 'oxidative phosphorylation' (OXPHOS) pathway. PRM analysis confirmed that four of 6 candidate proteins in the OXPHOS pathway showed similar increasing trends. The protein domain enrichment analysis showed that domains such as 'thioredoxin domain' were significantly enriched. Based on these findings, it was hypothesized that mitochondria from MenSCs have the potential to enhance progression of ovarian cancer likely mediated by the enrichment of OXPHOS-associated metabolic pathways.

Comprehensive analysis of the prognosis, tumor microenvironment, and immunotherapy response of SDHs in colon adenocarcinoma

Background

Succinate dehydrogenase (SDH), one of the key enzymes in the tricarboxylic acid cycle, is mainly found in the mitochondria. SDH consists of four subunits encoding SDHA, SDHB, SDHC, and SDHD. The biological function of SDH is significantly related to cancer progression. Colorectal cancer (CRC) is one of the most common malignant tumors globally, whose most common histological subtype is colon adenocarcinoma (COAD). However, the correlation between SDH factors and COAD remains unclear.

Methods

The data on pan-cancer was obtained from The Cancer Genome Atlas (TCGA) database. Kaplan-Meier survival analysis showed the prognostic ability of SDHs. The cBioPortal database reflected genetic variations of SDHs. The correlation analysis was conducted between SDHs and mitochondrial energy metabolism genes (MMGs) and the protein-protein interaction (PPI) network was built. Consequently, Univariate and Multivariate Cox Regression Analysis on SDHs and other clinical characteristics were conducted. A nomogram was established. The ssGSEA analysis visualized the association between SDHs and immune infiltration. Immunophenoscore (IPS) explored the correlation between SDHs and immunotherapy, and the correlation between SDHs and targeted therapy was investigated through Genomics of Drug Sensitivity in Cancer. Finally, qPCR and immunohistochemistry detected SDHs' expression.

Results

After assessing SDHs differential expression in pan-cancer, we found that SDHB, SDHC, and SDHD benefit COAD patients. The cBioPortal database demonstrated that SDHA was the top gene in mutation frequency rank. Correlation analysis mirrored a strong link between SDHs and MMGs. We formulated a nomogram and found that SDHB, SDHC, SDHD, and clinical characteristics correlated with COAD patients' survival. For T helper cells, Th2 cells, and Tem, SDHA, SDHB, SDHC, and SDHD were significantly enriched in the high expression group. Moreover, COAD patients with high SDHA expression were more suitable for immunotherapy. And COAD patients with different SDHs' expression have different sensitivity to targeted drugs. Further verifying the gene and protein expression levels of SDHs, we found that the tissues were consistent with the bioinformatics analysis.

Conclusions

Our study analyzed the expression and prognostic value of SDHs in COAD, explored the pathway mechanisms involved, and the immune cell correlations, indicating that SDHs might be biomarkers for COAD patients.

The Effect of Oxidative Phosphorylation on Cancer Drug Resistance

Recent studies have shown that oxidative phosphorylation (OXPHOS) is a target for the effective attenuation of cancer drug resistance. OXPHOS inhibitors can improve treatment responses to anticancer therapy in certain cancers, such as melanomas, lymphomas, colon cancers, leukemias and pancreatic ductal adenocarcinoma (PDAC). However, the effect of OXPHOS on cancer drug resistance is complex and associated with cell types in the tumor microenvironment (TME). Cancer cells universally promote OXPHOS activity through the activation of various signaling pathways, and this activity is required for resistance to cancer therapy. Resistant cancer cells are prevalent among cancer stem cells (CSCs), for which the main metabolic phenotype is increased OXPHOS. CSCs depend on OXPHOS to survive targeting by anticancer drugs and can be selectively eradicated by OXPHOS inhibitors. In contrast to that in cancer cells, mitochondrial OXPHOS is significantly downregulated in tumor-infiltrating T cells, impairing antitumor immunity. In this review, we summarize novel research showing the effect of OXPHOS on cancer drug resistance, thereby explaining how this metabolic process plays a dual role in cancer progression. We highlight the underlying mechanisms of metabolic reprogramming in cancer cells, as it is vital for discovering new drug targets.

Non-canonical phosphoglycerate dehydrogenase activity promotes liver cancer growth via mitochondrial translation and respiratory metabolism

Phosphoglycerate dehydrogenase (PHGDH) is a key serine biosynthesis enzyme whose aberrant expression promotes various types of tumors. Recently, PHGDH has been found to have some non-canonical functions beyond serine biosynthesis, but its specific mechanisms in tumorigenesis remain unclear. Here, we show that PHGDH localizes to the inner mitochondrial membrane and promotes the translation of mitochondrial DNA (mtDNA)-encoded proteins in liver cancer cells. Mechanistically, we demonstrate that mitochondrial PHGDH directly interacts with adenine nucleotide translocase 2 (ANT2) and then recruits mitochondrial elongation factor G2 (mtEFG2) to promote mitochondrial ribosome recycling efficiency, thereby promoting mtDNA-encoded protein expression and subsequent mitochondrial respiration. Moreover, we show that treatment with a mitochondrial translation inhibitor or depletion of mtEFG2 diminishes PHGDH-mediated tumor growth. Collectively, our findings uncover a previously unappreciated function of PHGDH in tumorigenesis acting via promotion of mitochondrial translation and bioenergetics.

Respiratory Complex I dysfunction in cancer: from a maze of cellular adaptive responses to potential therapeutic strategies

Mitochondria act as key organelles in cellular bioenergetics and biosynthetic processes producing signals that regulate different molecular networks for proliferation and cell death. This ability is also preserved in pathologic contexts such as tumorigenesis, during which bioenergetic changes and metabolic reprogramming confer flexibility favoring cancer cell survival in a hostile microenvironment. Although different studies epitomize mitochondrial dysfunction as a protumorigenic hit, genetic ablation or pharmacological inhibition of respiratory complex I causing a severe impairment is associated with a low-proliferative phenotype. In this scenario, it must be considered that despite the initial delay in growth, cancer cells may become able to resume proliferation exploiting molecular mechanisms to overcome growth arrest. Here, we highlight the current knowledge on molecular responses activated by complex I-defective cancer cells to bypass physiological control systems and to re-adapt their fitness during microenvironment changes. Such adaptive mechanisms could reveal possible novel molecular players in synthetic lethality with complex I impairment, thus providing new synergistic strategies for mitochondrial-based anticancer therapy.

The promising therapeutic effects of metformin on metabolic reprogramming of cancer-associated fibroblasts in solid tumors

Tumor-infiltrated lymphocytes are exposed to many toxic metabolites and molecules in the tumor microenvironment (TME) that suppress their anti-tumor activity. Toxic metabolites, such as lactate and ketone bodies, are produced mainly by catabolic cancer-associated fibroblasts (CAFs) to feed anabolic cancer cells. These catabolic and anabolic cells make a metabolic compartment through which high-energy metabolites like lactate can be transferred via the monocarboxylate transporter channel 4. Moreover, a decrease in molecules, including caveolin-1, has been reported to cause deep metabolic changes in normal fibroblasts toward myofibroblast differentiation. In this context, metformin is a promising drug in cancer therapy due to its effect on oncogenic signal transduction pathways, leading to the inhibition of tumor proliferation and downregulation of key oncometabolites like lactate and succinate. The cross-feeding and metabolic coupling of CAFs and tumor cells are also affected by metformin. Therefore, the importance of metabolic reprogramming of stromal cells and also the pivotal effects of metformin on TME and oncometabolites signaling pathways have been reviewed in this study.

The Role of IL-6 in Cancer Cell Invasiveness and Metastasis-Overview and Therapeutic Opportunities

Interleukin 6 (IL-6) belongs to a broad class of cytokines involved in the regulation of various homeostatic and pathological processes. These activities range from regulating embryonic development, wound healing and ageing, inflammation, and immunity, including COVID-19. In this review, we summarise the role of IL-6 signalling pathways in cancer biology, with particular emphasis on cancer cell invasiveness and metastasis formation. Targeting principal components of IL-6 signalling (e.g., IL-6Rs, gp130, STAT3, NF-κB) is an intensively studied approach in preclinical cancer research. It is of significant translational potential; numerous studies strongly imply the remarkable potential of IL-6 signalling inhibitors, especially in metastasis suppression.

From Low to No O2-Dependent Hypoxia Photodynamic Therapy (hPDT): A New Perspective

The advent of photochemical techniques has revolutionized the landscape of biology and medical sciences. Especially appealing in this context is photodynamic therapy (PDT), which is a photon-initiated treatment modality that uses cytotoxic reactive oxygen species (ROS) to kill malignant cells. In the past decade, PDT has risen to the forefront of cancer therapy. Its optical control enables noninvasive and spatiotemporal manipulation of the treatment process, and its photoactive nature allows unique patterns to avoid drug resistance to conventional chemotherapeutics. However, despite the impressive advances in this field, achieving widespread clinical adoption of PDT remains difficult. A major concern is that in the hostile tumor microenvironment, tumor cells are hypoxic, which hinders ROS generation during PDT action. To overcome this "Achilles' heel", current strategies focus primarily on the improvement of the intratumoral O₂ perfusion, while clinical trials suggest that O₂ enrichment may promote cancer cell proliferation and metastasis, thereby making FDA approval and clinical transformation of these paradigms challenging.In an effort to improve hypoxia photodynamic therapy (hPDT) in the clinic, we have explored "low to no O₂-dependent" photochemical approaches over the years to combat hypoxia-induced resistance. In this Account, we present our contributions to this theme during the past 5 years, beginning with low O₂-dependent approaches (e.g., type I superoxide radical (O₂^•-) generator, photodynamic O₂-economizer, mitochondrial respiration inhibition, cellular self-protective pathway modulation, etc.) and progressing to O₂-independent strategies (e.g., autoadaptive PDT/PTT complementary therapy, O₂-independent artificial photoredox catalysis in cells). These studies have attracted tremendous attention. Particularly in the pioneering work of 2018, we presented the first demonstration that the O₂^•--mediated partial O₂-recyclability mechanism can overcome PDT resistance ( J. Am. Chem. Soc. 2018, 140, 14851-14859). This launched an era of renewed interest in type I PDT, resulting in a plethora of new O₂^•- photogenerators developed by many groups around the world. Moreover, with the discovery of O₂-independent photoredox reactions in living cells, artificial photoredox catalysis has emerged as a new field connecting photochemistry and biomedicine, stimulating the development of next-generation phototherapeutic tools ( J. Am. Chem. Soc. 2022, 144, 163-173). Our recent work also disclosed that "photoredox catalysis in cells" might be a general mechanism of action of PDT ( Proc. Natl. Acad. Sci. U.S.A. 2022, 119, e2210504119). These emergent concepts, molecular designs, photochemical mechanisms, and applications in cancer diagnosis and therapeutics, as well as pros and cons, are discussed in depth in this Account. It is expected that our contributions to date will be of general use to researchers and inspire future efforts to identify more promising hPDT approaches that better meet the clinical needs of cancer therapy.

Glioblastoma cell motility depends on enhanced oxidative stress coupled with mobilization of a sulfurtransferase

Cell motility is critical for tumor malignancy. Metabolism being an obligatory step in shaping cell behavior, we looked for metabolic weaknesses shared by motile cells across the diverse genetic contexts of patients' glioblastoma. Computational analyses of single-cell transcriptomes from thirty patients' tumors isolated cells with high motile potential and highlighted their metabolic specificities. These cells were characterized by enhanced mitochondrial load and oxidative stress coupled with mobilization of the cysteine metabolism enzyme 3-Mercaptopyruvate sulfurtransferase (MPST). Functional assays with patients' tumor-derived cells and -tissue organoids, and genetic and pharmacological manipulations confirmed that the cells depend on enhanced ROS production and MPST activity for their motility. MPST action involved protection of protein cysteine residues from damaging hyperoxidation. Its knockdown translated in reduced tumor burden, and a robust increase in mice survival. Starting from cell-by-cell analyses of the patients' tumors, our work unravels metabolic dependencies of cell malignancy maintained across heterogeneous genomic landscapes.

Glioblastoma cell motility depends on enhanced oxidative stress coupled with mobilization of a sulfurtransferase

Cell motility is critical for tumor malignancy. Metabolism being an obligatory step in shaping cell behavior, we looked for metabolic weaknesses shared by motile cells across the diverse genetic contexts of patients' glioblastoma. Computational analyses of single-cell transcriptomes from thirty patients' tumors isolated cells with high motile potential and highlighted their metabolic specificities. These cells were characterized by enhanced mitochondrial load and oxidative stress coupled with mobilization of the cysteine metabolism enzyme 3-Mercaptopyruvate sulfurtransferase (MPST). Functional assays with patients' tumor-derived cells and -tissue organoids, and genetic and pharmacological manipulations confirmed that the cells depend on enhanced ROS production and MPST activity for their motility. MPST action involved protection of protein cysteine residues from damaging hyperoxidation. Its knockdown translated in reduced tumor burden, and a robust increase in mice survival. Starting from cell-by-cell analyses of the patients' tumors, our work unravels metabolic dependencies of cell malignancy maintained across heterogeneous genomic landscapes.

The roles of intratumour heterogeneity in the biology and treatment of pancreatic ductal adenocarcinoma

Intratumour heterogeneity (ITH) has become an important focus of cancer research in recent years. ITH describes the cellular variation that enables tumour evolution, including tumour progression, metastasis and resistance to treatment. The selection and expansion of genetically distinct treatment-resistant cancer cell clones provides one explanation for treatment failure. However, tumour cell variation need not be genetically encoded. In pancreatic ductal adenocarcinoma (PDAC) in particular, the complex tumour microenvironment as well as crosstalk between tumour and stromal cells result in exceptionally variable tumour cell phenotypes that are also highly adaptable. In this review we discuss four different types of phenotypic heterogeneity within PDAC, from morphological to metabolic heterogeneity. We suggest that these different types of ITH are not independent, but, rather, can inform one another. Lastly, we highlight recent findings that suggest how therapeutic efforts may halt PDAC progression by constraining cellular heterogeneity.