In vivo imaging of mitochondrial membrane potential in non-small-cell lung cancer

Precision Nanomedicines: Targeting Hot Mitochondria in Cancer Cells

Mitochondrion is a multifunctional organelle in a cell, and it is one of the important targets of antitumor therapy. Conventional mitochondrial targeting strategies can hardly distinguish the mitochondria in cancer cells from those in normal cells, which might raise a concern about the biosafety. Recent studies suggest that a relatively high temperature of mitochondria exists in cancer cells. We named it tumor intrinsic mitochondrial overheating (TIMO). By taking advantage of the difference in mitochondrial temperatures between cancer cells and normal cells, therapeutic agents can be specifically delivered to the mitochondria in cancer cells. Here we will briefly overview the mitochondria-targeted delivery strategies. In addition, the recent discovery of hot mitochondria in cancer cells and the development of mitochondrial temperature-responsive delivery systems for antitumor therapy will be reviewed.

Monitoring of Current Cancer Therapy by Positron Emission Tomography and Possible Role of Radiomics Assessment

Evaluation of cancer therapy with imaging is crucial as a surrogate marker of effectiveness and survival. The unique response patterns to therapy with immune-checkpoint inhibitors have facilitated the revision of response evaluation criteria using FDG-PET, because the immune response recalls reactive cells such as activated T-cells and macrophages, which show increased glucose metabolism and apparent progression on morphological imaging. Cellular metabolism and function are critical determinants of the viability of active cells in the tumor microenvironment, which would be novel targets of therapies, such as tumor immunity, metabolism, and genetic mutation. Considering tumor heterogeneity and variation in therapy response specific to the mechanisms of therapy, appropriate response evaluation is required. Radiomics approaches, which combine objective image features with a machine learning algorithm as well as pathologic and genetic data, have remarkably progressed over the past decade, and PET radiomics has increased quality and reliability based on the prosperous publications and standardization initiatives. PET and multimodal imaging will play a definitive role in personalized therapeutic strategies by the precise monitoring in future cancer therapy.

Bioinspired large Stokes shift small molecular dyes for biomedical fluorescence imaging

Long Stokes shift dyes that minimize cross-talk between the excitation source and fluorescent emission to improve the signal-to-background ratio are highly desired for fluorescence imaging. However, simple small molecular dyes with large Stokes shift (more than 120 nanometers) and near-infrared (NIR) emissions have been rarely reported so far. Here, inspired by the chromophore chemical structure of fluorescent proteins, we designed and synthesized a series of styrene oxazolone dyes (SODs) with simple synthetic methods, which show NIR emissions (>650 nanometers) with long Stokes shift (ranged from 136 to 198 nanometers) and small molecular weight (<450 daltons). The most promising SOD9 shows rapid renal excretion and blood-brain barrier passing properties. After functioning with the mitochondrial-targeted triphenylphosphonium (TPP) group, the resulting SOD9-TPP can be engineered for head-neck tumor imaging, fluorescence image-guided surgery, brain neuroimaging, and on-site pathologic analysis. In summary, our findings add an essential small molecular dye category to the classical dyes.

The decylTPP mitochondria-targeting moiety lowers electron transport chain supercomplex levels in primary human skin fibroblasts

Attachment of cargo molecules to lipophilic triphenylphosphonium (TPP⁺) cations is a widely applied strategy for mitochondrial targeting. We previously demonstrated that the vitamin E-derived antioxidant Trolox increases the levels of active mitochondrial complex I (CI), the first complex of the electron transport chain (ETC), in primary human skin fibroblasts (PHSFs) of Leigh Syndrome (LS) patients with isolated CI deficiency. Primed by this finding, we here studied the cellular effects of mitochondria-targeted Trolox (MitoE10), mitochondria-targeted ubiquinone (MitoQ10) and their mitochondria-targeting moiety decylTPP (C₁₀-TPP⁺). Chronic treatment (96 h) with these molecules of PHSFs from a healthy subject and an LS patient with isolated CI deficiency (NDUFS7-V122M mutation) did not greatly affect cell number. Unexpectedly, this treatment reduced CI levels/activity, lowered the amount of ETC supercomplexes, inhibited mitochondrial oxygen consumption, increased extracellular acidification, altered mitochondrial morphology and stimulated hydroethidine oxidation. We conclude that the mitochondria-targeting decylTPP moiety is responsible for the observed effects and advocate that every study employing alkylTPP-mediated mitochondrial targeting should routinely include control experiments with the corresponding alkylTPP moiety.

Exploring the Mechanism of Adjuvant Treatment of Glioblastoma Using Temozolomide and Metformin

Glioblastoma is the most frequent and lethal primary central nervous system tumor in adults, accounting for around 15% of intracranial neoplasms and 40–50% of all primary malignant brain tumors, with an annual incidence of 3–6 cases per 100,000 population. Despite maximum treatment, patients only have a median survival time of 15 months. Metformin is a biguanide drug utilized as the first-line medication in treating type 2 diabetes. Recently, researchers have noticed that metformin can contribute to antineoplastic activity. The objective of this study is to investigate the mechanism of metformin as a potential adjuvant treatment drug in glioblastoma. Glioblastoma cell lines U87MG, LNZ308, and LN229 were treated with metformin, and several cellular functions and metabolic states were evaluated. First, the proliferation capability was investigated using the MTS assay and BrdU assay, while cell apoptosis was evaluated using the annexin V assay. Next, a wound-healing assay and mesenchymal biomarkers (N-cadherin, vimentin, and Twist) were used to detect the cell migration ability and epithelial–mesenchymal transition (EMT) status of tumor cells. Gene set enrichment analysis (GSEA) was applied to the transcriptome of the metformin-treated glioblastoma cell line. Then, DCFH-DA and MitoSOX Red dyes were used to quantify reactive oxygen species (ROS) in the cytosol and mitochondria. JC-1 dye and Western blotting analysis were used to evaluate mitochondrial membrane potential and biogenesis. In addition, the combinatory effect of temozolomide (TMZ) with metformin treatment was assessed by combination index analysis. Metformin could decrease cell viability, proliferation, and migration, increase cell apoptosis, and disrupt EMT in all three glioblastoma cell lines. The GSEA study highlighted increased ROS and hypoxia in the metformin-treated glioblastoma cells. Metformin increased ROS production, impaired mitochondrial membrane potential, and reduced mitochondrial biogenesis. The combined treatment of metformin and TMZ had U87 as synergistic, LNZ308 as antagonistic, and LN229 as additive. Metformin alone or combined with TMZ could suppress mitochondrial transcription factor A, Twist, and O⁶-methylguanine-DNA methyltransferase (MGMT) proteins in TMZ-resistant LN229 cells. In conclusion, our study showed that metformin decreased metabolic activity, proliferation, migration, mitochondrial biogenesis, and mitochondrial membrane potential and increased apoptosis and ROS in some glioblastoma cells. The sensitivity of the TMZ-resistant glioblastoma cell line to metformin might be mediated via the suppression of mitochondrial biogenesis, EMT, and MGMT expression. Our work provides new insights into the choice of adjuvant agents in TMZ-resistant GBM therapy.

Assessment of mitochondrial dysfunction and implications in cardiovascular disorders

Mitochondria play a pivotal role in cellular function, not only acting as the powerhouse of the cell, but also regulating ATP synthesis, reactive oxygen species (ROS) production, intracellular Ca²⁺ cycling, and apoptosis. During the past decade, extensive progress has been made in the technology to assess mitochondrial functions and accumulating evidences have shown that mitochondrial dysfunction is a key pathophysiological mechanism for many diseases including cardiovascular disorders, such as ischemic heart disease, cardiomyopathy, hypertension, atherosclerosis, and hemorrhagic shock. The advances in methodology have been accelerating our understanding of mitochondrial molecular structure and function, biogenesis and ROS and energy production, which facilitates new drug target identification and therapeutic strategy development for mitochondrial dysfunction-related disorders. This review will focus on the assessment of methodologies currently used for mitochondrial research and discuss their advantages, limitations and the implications of mitochondrial dysfunction in cardiovascular disorders.

Spautin-1 inhibits mitochondrial complex I and leads to suppression of the unfolded protein response and cell survival during glucose starvation

The unfolded protein response (UPR) is an adaptive stress response pathway that is essential for cancer cell survival under endoplasmic reticulum stress such as during glucose starvation. In this study, we identified spautin-1, an autophagy inhibitor that suppresses ubiquitin-specific peptidase 10 (USP10) and USP13, as a novel UPR inhibitor under glucose starvation conditions. Spautin-1 prevented the induction of UPR-associated proteins, including glucose-regulated protein 78, activating transcription factor 4, and a splicing variant of x-box-binding protein-1, and showed preferential cytotoxicity in glucose-starved cancer cells. However, USP10 and USP13 silencing and treatment with other autophagy inhibitors failed to result in UPR inhibition and preferential cytotoxicity during glucose starvation. Using transcriptome and chemosensitivity-based COMPARE analyses, we identified a similarity between spautin-1 and mitochondrial complex I inhibitors and found that spautin-1 suppressed the activity of complex I extracted from isolated mitochondria. Our results indicated that spautin-1 may represent an attractive mitochondria-targeted seed compound that inhibits the UPR and cancer cell survival during glucose starvation.

Mitochondrial temperature-responsive drug delivery reverses drug resistance in lung cancer

Reversal of cancer drug resistance remains a critical challenge in chemotherapy. Mitochondria-targeted drug delivery has been suggested to mitigate drug resistance in cancer. To overcome the intrinsic limitations in conventional mitochondrial targeting strategies, we develop mitochondrial temperature-responsive drug delivery to reverse doxorubicin (DOX) resistance in lung cancer. Results demonstrate that the thermoresponsive nanocarrier can prevent DOX efflux and facilitate DOX accumulation and mitochondrial targeting in DOX-resistant tumors. As a consequence, thermoresponsive nanocarrier enhances the cytotoxicity of DOX and reverses the drug resistance in tumor-bearing mice. This work represents the first example of mitochondrial temperature-responsive drug delivery for reversing cancer drug resistance.

The Mechanism of Action of Biguanides: New Answers to a Complex Question

Biguanides are a family of antidiabetic drugs with documented anticancer properties in preclinical and clinical settings. Despite intensive investigation, how they exert their therapeutic effects is still debated. Many studies support the hypothesis that biguanides inhibit mitochondrial complex I, inducing energy stress and activating compensatory responses mediated by energy sensors. However, a major concern related to this “complex” model is that the therapeutic concentrations of biguanides found in the blood and tissues are much lower than the doses required to inhibit complex I, suggesting the involvement of additional mechanisms. This comprehensive review illustrates the current knowledge of pharmacokinetics, receptors, sensors, intracellular alterations, and the mechanism of action of biguanides in diabetes and cancer. The conditions of usage and variables affecting the response to these drugs, the effect on the immune system and microbiota, as well as the results from the most relevant clinical trials in cancer are also discussed.

Plasmodium infection suppresses colon cancer growth by inhibiting proliferation and promoting apoptosis associated with disrupting mitochondrial biogenesis and mitophagy in mice

BACKGROUND

Colon cancer is a common gastrointestinal tumor with a poor prognosis, and thus new therapeutic strategies are urgently needed. The antitumor effect of Plasmodium infection has been reported in some murine models, but it is not clear whether it has an anti-colon cancer effect. In this study, we investigated the anti-colon cancer effect of Plasmodium infection and its related mechanisms using a mouse model of colon cancer.

METHODS

An experimental model was established by intraperitoneal injection of Plasmodium yoelii 17XNL-infected erythrocytes into mice with colon cancer. The size of tumors was observed dynamically in mice, and the expression of Ki67 detected by immunohistochemistry was used to analyze tumor cell proliferation. Apoptosis was assessed by terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) staining, and the expression of apoptosis-related proteins including Bax, Bcl-2, caspase-9, and cleaved caspase-3 was detected by western blot and immunohistochemistry, respectively. Transmission electron microscopy (TEM) was used to observe the ultrastructural change in colon cancer cells, and the expression of mitochondrial biogenesis correlative central protein, PGC-1α, and mitophagy relevant crucial proteins, PINK1/Parkin, were detected by western blot.

RESULTS

We found that Plasmodium infection reduced the weight and size of tumors and decreased the expression of Ki67 in colon cancer-bearing mice. Furthermore, Plasmodium infection promoted mitochondria-mediated apoptosis in colon cancer cells, as evidenced by the increased proportion of TUNEL-positive cells, the upregulated expression of Bax, caspase-9, and cleaved caspase-3 proteins, and the downregulated expression of Bcl-2 protein. In colon cancer cells, we found destroyed cell nuclei, swollen mitochondria, missing cristae, and a decreased number of autolysosomes. In addition, Plasmodium infection disturbed mitochondrial biogenesis and mitophagy through the reduced expression of PGC-1α, PINK1, and Parkin proteins in colon cancer cells.

CONCLUSIONS

Plasmodium infection can play an anti-colon cancer role in mice by inhibiting proliferation and promoting mitochondria-mediated apoptosis in colon cancer cells, which may relate to mitochondrial biogenesis and mitophagy.

Analysis of the metabolic proteome of lung adenocarcinomas by reverse-phase protein arrays (RPPA) emphasizes mitochondria as targets for therapy

Lung cancer is the leading cause of cancer-related death worldwide despite the success of therapies targeting oncogenic drivers and immune-checkpoint inhibitors. Although metabolic enzymes offer additional targets for therapy, the precise metabolic proteome of lung adenocarcinomas is unknown, hampering its clinical translation. Herein, we used Reverse Phase Protein Arrays to quantify the changes in enzymes of glycolysis, oxidation of pyruvate, fatty acid metabolism, oxidative phosphorylation, antioxidant response and protein oxidative damage in 128 tumors and paired non-tumor adjacent tissue of lung adenocarcinomas to profile the proteome of metabolism. Steady-state levels of mitochondrial proteins of fatty acid oxidation, oxidative phosphorylation and of the antioxidant response are independent predictors of survival and/or of disease recurrence in lung adenocarcinoma patients. Next, we addressed the mechanisms by which the overexpression of ATPase Inhibitory Factor 1, the physiological inhibitor of oxidative phosphorylation, which is an independent predictor of disease recurrence, prevents metastatic disease. We highlight that IF1 overexpression promotes a more vulnerable and less invasive phenotype in lung adenocarcinoma cells. Finally, and as proof of concept, the therapeutic potential of targeting fatty acid assimilation or oxidation in combination with an inhibitor of oxidative phosphorylation was studied in mice bearing lung adenocarcinomas. The results revealed that this therapeutic approach significantly extended the lifespan and provided better welfare to mice than cisplatin treatments, supporting mitochondrial activities as targets of therapy in lung adenocarcinoma patients.

In vivo three-dimensional multispectral photoacoustic imaging of dual enzyme-driven cyclic cascade reaction for tumor catalytic therapy

Non-invasive visualization of dynamic molecular events in real-time via molecular imaging may enable the monitoring of cascade catalytic reactions in living systems, however effective imaging modalities and a robust catalytic reaction system are lacking. Here we utilize three-dimensional (3D) multispectral photoacoustic (PA) molecular imaging to monitor in vivo cascade catalytic therapy based on a dual enzyme-driven cyclic reaction platform. The system consists of a two-dimensional (2D) Pd-based nanozyme conjugated with glucose oxidase (GOx). The combination of nanozyme and GOx can induce the PA signal variation of endogenous molecules. Combined with the PA response of the nanozyme, we can simultaneously map the 3D PA signals of dynamic endogenous and exogenous molecules associated with the catalytic process, thus providing a real-time non-invasive visualization. We can also treat tumors under the navigation of the PA imaging. Therefore, our study demonstrates the imaging-guided potential of 3D multispectral PA imaging in feedback-looped cascade catalytic therapy.

Photoacoustic imaging can be used to monitor chemical reaction in cells and tissues. Here, the authors develop a Pd based nanozyme conjugated with glucose oxidase that can induce the change of photoacoustic signals during the catalytic cascade process, the system can also be used to treat tumor-bearing mice.

LKB1 drives stasis and C/EBP-mediated reprogramming to an alveolar type II fate in lung cancer

LKB1 is among the most frequently altered tumor suppressors in lung adenocarcinoma. Inactivation of Lkb1 accelerates the growth and progression of oncogenic KRAS-driven lung tumors in mouse models. However, the molecular mechanisms by which LKB1 constrains lung tumorigenesis and whether the cancer state that stems from Lkb1 deficiency can be reverted remains unknown. To identify the processes governed by LKB1 in vivo, we generated an allele which enables Lkb1 inactivation at tumor initiation and subsequent Lkb1 restoration in established tumors. Restoration of Lkb1 in oncogenic KRAS-driven lung tumors suppressed proliferation and led to tumor stasis. Lkb1 restoration activated targets of C/EBP transcription factors and drove neoplastic cells from a progenitor-like state to a less proliferative alveolar type II cell-like state. We show that C/EBP transcription factors govern a subset of genes that are induced by LKB1 and depend upon NKX2-1. We also demonstrate that a defining factor of the alveolar type II lineage, C/EBPα, constrains oncogenic KRAS-driven lung tumor growth in vivo. Thus, this key tumor suppressor regulates lineage-specific transcription factors, thereby constraining lung tumor development through enforced differentiation.

Towards an integrative understanding of cancer mechanobiology: calcium, YAP, and microRNA under biophysical forces

An increasing number of studies have demonstrated the significant roles of the interplay between microenvironmental mechanics in tissues and biochemical-genetic activities in resident tumor cells at different stages of tumor progression. Mediated by molecular mechano-sensors or -transducers, biomechanical cues in tissue microenvironments are transmitted into the tumor cells and regulate biochemical responses and gene expression through mechanotransduction processes. However, the molecular interplay between the mechanotransduction processes and intracellular biochemical signaling pathways remains elusive. This paper reviews the recent advances in understanding the crosstalk between biomechanical cues and three critical biochemical effectors during tumor progression: calcium ions (Ca²⁺), yes-associated protein (YAP), and microRNAs (miRNAs). We address the molecular mechanisms underpinning the interplay between the mechanotransduction pathways and each of the three effectors. Furthermore, we discuss the functional interactions among the three effectors in the context of soft matter and mechanobiology. We conclude by proposing future directions on studying the tumor mechanobiology that can employ Ca²⁺, YAP, and miRNAs as novel strategies for cancer mechanotheraputics. This framework has the potential to bring insights into the development of novel next-generation cancer therapies to suppress and treat tumors.

Pathophysiological Integration of Metabolic Reprogramming in Breast Cancer

Simple Summary

Tumors exhibit metabolic changes that differentiate them from the normal tissues from which they derive. These metabolic changes favor tumor growth, are primarily induced by cancer cells, and produce metabolic and functional changes in the surrounding stromal cells. There is a close functional connection between the metabolic changes in tumor cells and those that appear in the surrounding stroma. A better understanding of intratumoral metabolic interactions may help identify new vulnerabilities that will facilitate new, more individualized treatment strategies against cancer. We review the metabolic changes described in tumor and stromal cells and their functional changes and then consider, in depth, the metabolic interactions between the cells of the two compartments. Although these changes are generic, we illustrate them mainly with reference to examples in breast cancer.

Abstract

Metabolic changes that facilitate tumor growth are one of the hallmarks of cancer. The triggers of these metabolic changes are located in the tumor parenchymal cells, where oncogenic mutations induce an imperative need to proliferate and cause tumor initiation and progression. Cancer cells undergo significant metabolic reorganization during disease progression that is tailored to their energy demands and fluctuating environmental conditions. Oxidative stress plays an essential role as a trigger under such conditions. These metabolic changes are the consequence of the interaction between tumor cells and stromal myofibroblasts. The metabolic changes in tumor cells include protein anabolism and the synthesis of cell membranes and nucleic acids, which all facilitate cell proliferation. They are linked to catabolism and autophagy in stromal myofibroblasts, causing the release of nutrients for the cells of the tumor parenchyma. Metabolic changes lead to an interstitium deficient in nutrients, such as glucose and amino acids, and acidification by lactic acid. Together with hypoxia, they produce functional changes in other cells of the tumor stroma, such as many immune subpopulations and endothelial cells, which lead to tumor growth. Thus, immune cells favor tissue growth through changes in immunosuppression. This review considers some of the metabolic changes described in breast cancer.

Discovery of a cinnamyl piperidine derivative as new neddylation inhibitor for gastric cancer treatment

Targeting neddylation pathway has been recognized as an attractive anticancer therapeutic strategy, thus discovering potent and selective neddylation inhibitors is highly desirable. Our work reported the discovery of novel cinnamyl piperidine compounds and their antitumor activity in vitro and in vivo. Among these compounds, compound 4g was identified as a novel neddylation inhibitor and decreased the neddylation levels of cullin 1, cullin 3 and cullin 5. Mechanistic studies demonstrated that compound 4g could inhibit the migration ability of gastric cancer cells and induce apoptosis partly mediated by the Nrf2-Keap1 pathway. Furthermore, in vivo anti-tumor studies showed that 4g effectively inhibited tumor growth without obvious toxicity. Collectively, the cinnamyl piperidine derivatives could serve as new lead compounds for developing highly effective neddylation inhibitors for gastric cancer therapy.

Mitochondrial matrix protein C14orf159 attenuates colorectal cancer metastasis by suppressing Wnt/β-catenin signalling

BACKGROUND

The mechanisms underlying metastasis of colorectal cancer (CRC) remain unclear. C14orf159 is a mitochondrial matrix protein converting D-glutamate to 5-oxo-D-proline. Other metabolic functions of C14orf159, especially on mitochondrial metabolism, and its contribution to CRC metastasis, are not elucidated.

METHODS

Metabolome analysis by gas chromatography-mass spectrometry, RNA-sequencing analysis, flow cytometry, migration and invasion assay, sphere-formation assay using C14orf159-knockout and -stable expressing cells, immunohistochemistry of C14orf159 in human CRC specimens, and xenograft experiments using Balb/c nude mice were conducted.

RESULTS

C14orf159 maintained the mitochondrial membrane potential of human CRC cells, and its involvement in amino acid and glutathione metabolism was demonstrated. In human CRC specimens, a decrease in C14orf159 expression at the invasive front of the tumour and in metastasis was determined. C14orf159 was also shown to attenuate the migration, invasion, and spheroid growth of CRC cells in vitro and colorectal tumour growth and metastasis in vivo. Mechanistically, C14orf159 reduced the expression of genes involved in CRC metastasis, including members of the Wnt and MMP family, by maintaining the mitochondrial membrane potential.

CONCLUSIONS

Our findings link mitochondrial membrane potential to Wnt/β-catenin signalling and reveal a previously unrecognised function of the mitochondrial matrix protein C14orf159 as a suppressor of CRC metastasis.

Metabolic targeting of cancer by a ubiquinone uncompetitive inhibitor of mitochondrial complex I

SMIP004-7 is a small molecule inhibitor of mitochondrial respiration with selective in vivo anti-cancer activity through an as-yet unknown molecular target. We demonstrate here that SMIP004-7 targets drug-resistant cancer cells with stem-like features by inhibiting mitochondrial respiration complex I (NADH:ubiquinone oxidoreductase, complex I [CI]). Instead of affecting the quinone-binding site targeted by most CI inhibitors, SMIP004-7 and its cytochrome P450-dependent activated metabolite(s) have an uncompetitive mechanism of inhibition involving a distinct N-terminal region of catalytic subunit NDUFS2 that leads to rapid disassembly of CI. SMIP004-7 and an improved chemical analog selectively engage NDUFS2 in vivo to inhibit the growth of triple-negative breast cancer transplants, a response mediated at least in part by boosting CD4⁺ and CD8⁺ T cell-mediated immune surveillance. Thus, SMIP004-7 defines an emerging class of ubiquinone uncompetitive CI inhibitors for cell autonomous and microenvironmental metabolic targeting of mitochondrial respiration in cancer.

Metabolic Phenotypes, Dependencies, and Adaptation in Lung Cancer

Lung cancer is a heterogeneous disease that is subdivided into histopathological subtypes with distinct behaviors. Each subtype is characterized by distinct features and molecular alterations that influence tumor metabolism. Alterations in tumor metabolism can be exploited by imaging modalities that use metabolite tracers for the detection and characterization of tumors. Microenvironmental factors, including nutrient and oxygen availability and the presence of stromal cells, are a critical influence on tumor metabolism. Recent technological advances facilitate the direct evaluation of metabolic alterations in patient tumors in this complex microenvironment. In addition, molecular alterations directly influence tumor cell metabolism and metabolic dependencies that influence response to therapy. Current therapeutic approaches to target tumor metabolism are currently being developed and translated into the clinic for patient therapy.

One-Step and Facile Synthesis of Poly(phenylalanine) as a Robust Drug Carrier for Enhanced Cancer Therapy

In recent decades, many poly(amino acid)s have been successfully prepared for various biomedical applications. To date, the synthesis and purification procedures used to generate these poly(amino acid)s have generally been complicated and costly. Here, a one-step synthesis strategy was developed and optimized via direct polymerization using thionyl chloride to easily and economically obtain poly(amino acid)s. Phenylalanine (Phe) was selected as a model amino acid to construct a family of biodegradable and biocompatible poly(phenylalanine) (PPhe) molecules with a tunable molecular weight. The prepared PPhe can self-assemble into nanoparticles (PP-NPs) through nanoprecipitation with a particle size of approximately 100 nm. PP-NPs exhibit a high drug-loading capacity (>12 wt %) of paclitaxel (PTX, a commercial antitumor drug) and good therapeutic effects in CT26 cells. The in vivo evaluation of PTX@PP-NPs indicates that it has a prolonged blood circulation time and high tumor aggregation after intravenous injection, resulting in significant antitumor effects in CT26 tumor-bearing mice with minimal toxicity to normal organs. Overall, this study provides a facile and simple strategy for synthesizing poly(amino acids) and a PPhe-based nanoparticle platform for effectively delivering various small-molecule drugs.

Mitochondria govern histone acetylation in colorectal cancer

Cancer cells have an altered metabolic state that supports their growth, for example, aerobic glycolysis, known as the Warburg effect. Colorectal cancer cells have been reported to exhibit the Warburg effect and mainly rely on glycolysis for progression and have dysfunctional mitochondria. So far, how mitochondrial function influences the properties of colorectal cancer cells is unclear. Here, we demonstrated that mitochondria maintain histone acetylation, in particular acetylated histone H3 lysine 27 (H3K27ac), a surrogate epigenomic marker of active super-enhancers, in colorectal cancer cells. Immunohistochemistry was used on human colorectal adenocarcinoma specimens and showed that mitochondrial mass and H3K27ac marks were increased in adenocarcinoma lesions compared with adjacent non-neoplastic mucosa. Immunoblotting after using inhibitors of the mitochondrial respiratory complex or mitochondrial DNA-depleted human colorectal cancer cells revealed that mitochondria maintained pan-histone acetylation and H3K27ac marks. Notably, anchorage-independent growth, a feature of cancer, increased mitochondrial mass and H3K27ac marks in human colorectal cancer cells. These findings indicate that mitochondria in human colorectal cancer cells are not dysfunctional, as formerly believed, but function as inducers of histone acetylation. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Dissecting the single-cell transcriptome network in patients with esophageal squamous cell carcinoma receiving operative paclitaxel plus platinum chemotherapy

Esophageal squamous cell carcinoma (ESCC) accounts for 90% of all cases of esophageal cancers worldwide. Although neoadjuvant chemotherapy (NACT-ESCC) improves the survival of ESCC patients, the five-year survival rate of these patients is dismal. The tumor microenvironment (TME) and tumor heterogeneity decrease the efficacy of ESCC therapy. In our study, 113,581 cells obtained from five ESCC patients who underwent surgery alone (SA-ESCC) and five patients who underwent preoperative paclitaxel plus platinum chemotherapy (NACT-ESCC), were used for scRNA-seq analysis to explore molecular and cellular reprogramming patterns. The results showed samples from NACT-ESCC patients exhibited the characteristics of malignant cells and TME unlike samples from SA-ESCC patients. Cancer cells from NACT-ESCC samples were mainly at the ‘intermediate transient stage’. Stromal cell dynamics showed molecular and functional shifts that formed the immune-activation microenvironment. APOE, APOC1, and SPP1 were highly expressed in tumor-associated macrophages resulting in anti-inflammatory macrophage phenotypes. Levels of CD8+ T cells between SA-ESCC and NACT-ESCC tissues were significantly different. Immune checkpoints analysis revealed that LAG3 is a potential immunotherapeutic target for both NACT-ESCC and SA-ESCC patients. Cell–cell interactions analysis showed the complex cell-cell communication networks in the TME. In summary, our findings elucidate on the molecular and cellular reprogramming of NACT-ESCC and ESCC patients. These findings provide information on the potential diagnostic and therapeutic targets for ESCC patients.

Heme Sequestration Effectively Suppresses the Development and Progression of Both Lung Adenocarcinoma and Squamous Cell Carcinoma

Lung adenocarcinoma (ADC) and squamous cell carcinoma (SCC) are two most common subtypes of lung cancer. Here, to identify new, targetable molecular properties of both subtypes, we monitored changes in the levels of heme- and oxidative phosphorylation (OXPHOS)-related proteins during lung tumorigenesis. Heme is a central molecule for oxidative metabolism and ATP generation via OXPHOS. Notably, both lung ADC and SCC tumors can be induced in the genetically engineered KL_Luc mouse model harboring the G12D Kras mutation and a conditional Lkb1 knockout. We found that the levels of the rate-limiting heme synthesis enzyme ALAS1 and uptake protein SLC48A1, along with OXPHOS complex subunits, progressively increased as lung tumorigenesis advanced. Our data demonstrated that elevated levels of heme- and OXPHOS-related proteins were associated with both ADC and SCC. Importantly, treatment of KL_Luc mice with a heme-sequestering protein, HeSP2, that inhibits heme uptake in tumor cells effectively arrested lung tumor progression, and both ADC and SCC tumors were strongly suppressed. Additionally, HeSP2 effectively suppressed the growth of both SCC and ADC tumor xenografts in NOD/SCID mice. Further analyses indicated that HeSP2 effectively diminished OXPHOS in both ADC and SCC, reduced angiogenesis, alleviated tumor hypoxia, and suppressed cell proliferation. These results show that the advancing of lung tumorigenesis requires progressive increase in cellular heme synthesis and uptake, leading to intensified OXPHOS activity and ATP generation and promoting aggressive tumorigenic functions. IMPLICATIONS: Heme sequestration is an effective strategy for the suppression of both ADC and SCC tumor initiation and development.

Cancer as a Model System for Testing Metabolic Scaling Theory

Biological allometries, such as the scaling of metabolism to mass, are hypothesized to result from natural selection to maximize how vascular networks fill space yet minimize internal transport distances and resistance to blood flow. Metabolic scaling theory argues two guiding principles—conservation of fluid flow and space-filling fractal distributions—describe a diversity of biological networks and predict how the geometry of these networks influences organismal metabolism. Yet, mostly absent from past efforts are studies that directly, and independently, measure metabolic rate from respiration and vascular architecture for the same organ, organism, or tissue. Lack of these measures may lead to inconsistent results and conclusions about metabolism, growth, and allometric scaling. We present simultaneous and consistent measurements of metabolic scaling exponents from clinical images of lung cancer, serving as a first-of-its-kind test of metabolic scaling theory, and identifying potential quantitative imaging biomarkers indicative of tumor growth. We analyze data for 535 clinical PET-CT scans of patients with non-small cell lung carcinoma to establish the presence of metabolic scaling between tumor metabolism and tumor volume. Furthermore, we use computer vision and mathematical modeling to examine predictions of metabolic scaling based on the branching geometry of the tumor-supplying blood vessel networks in a subset of 56 patients diagnosed with stage II-IV lung cancer. Examination of the scaling of maximum standard uptake value with metabolic tumor volume, and metabolic tumor volume with gross tumor volume, yield metabolic scaling exponents of 0.64 (0.20) and 0.70 (0.17), respectively. We compare these to the value of 0.85 (0.06) derived from the geometric scaling of the tumor-supplying vasculature. These results: (1) inform energetic models of growth and development for tumor forecasting; (2) identify imaging biomarkers in vascular geometry related to blood volume and flow; and (3) highlight unique opportunities to develop and test the metabolic scaling theory of ecology in tumors transitioning from avascular to vascular geometries.

Mitochondrial Metabolism Targeted Nanoplatform for Efficient Triple-Negative Breast Cancer Combination Therapy

Tumor reprogram pathway of mitochondrial metabolism is an emerging approach for malignant tumor treatment, such as triple-negative breast cancer. In this study, a tumor/mitochondria cascaded targeting, adenosine-triphosphate (ATP) responsive nanocarrier of zeolitic imidazolate framework-90 (ZIF-90) for breast cancer combination therapy is reported. Atovaquone (AVO) and hemin are loaded into ZIF-90, then a peptide iRGD with tumor-targeting ability is modified on the ZIF-90 nanoplatform. Hemin can specifically degrade BTB and CNC homology1 (BACH1), resulting in the changes of mitochondrial metabolism, and AVO acts as the inhibitor of the electron transport chain (ETC). The degradation of BACH1 using hemin can effectively improve the anti-tumor efficiency of mitochondrial metabolism inhibitor AVO, by increasing dependency on mitochondrial respiration. This nanoplatform displays both tumor-targeting and mitochondria-targeting capacity with high level of ATP responsive drug release behavior. The specific characteristic of mitochondria-targeting ability of this nanoplatform can increase the accumulation of AVO in the mitochondria, and in turn, can effectively improve the inhibition of the ETC. Both in vitro and in vivo results reveal that this composite nanocarrier has excellent tumor inhibition ability with limited side effects. Accordingly, this study provides an attractive strategy in the mitochondrial metabolism for cancer targeted therapy.

A Simple Route toward Next-Generation Thiobase-Based Photosensitizers for Cancer Theranostics

Sulfur-substituted biocompatible carbonyl fluorophores have been recognized as effective heavy-atom-free photosensitizers (PSs) for cancer therapy due to their remarkable phototherapeutic properties. However, guidelines on their molecular design are still a substantial challenge. Most of the existing thiocarbonyl-based PSs are nonemissive in both the solution and restricted states, which hinders their further biomedical applications. Herein, we report the interesting finding that sulfur-substituted coumarins exhibit an uncommon phenomenon, aggregation-induced emission. More intriguingly, we also found that the introduction of a strong electron-accepting trifluoromethyl group is crucial to facilitate the mitochondrial-targeting ability of neutral coumarin fluorophores. The resulting CMS-2 PS displayed selective imaging of mitochondria and exhibited much higher photodynamic therapy efficiency toward cancer cells than that of the commercial PS erythrosine B. This work provides deep insight into the molecular design of heavy-atom-free thiobase-based PSs and simultaneously offers a great opportunity to develop novel mitochondrial-targeting fluorescent indicators with neutral bioinspired platforms.

Exploring the therapeutic potential of mitochondrial uncouplers in cancer

BACKGROUND

Mitochondrial uncouplers are well-known for their ability to treat a myriad of metabolic diseases, including obesity and fatty liver diseases. However, for many years now, mitochondrial uncouplers have also been evaluated in diverse models of cancer in vitro and in vivo. Furthermore, some mitochondrial uncouplers are now in clinical trials for cancer, although none have yet been approved for the treatment of cancer.

SCOPE OF REVIEW

In this review we summarise published studies in which mitochondrial uncouplers have been investigated as an anti-cancer therapy in preclinical models. In many cases, mitochondrial uncouplers show strong anti-cancer effects both as single agents, and in combination therapies, and some are more toxic to cancer cells than normal cells. Furthermore, the mitochondrial uncoupling mechanism of action in cancer cells has been described in detail, with consistencies and inconsistencies between different structural classes of uncouplers. For example, many mitochondrial uncouplers decrease ATP levels and disrupt key metabolic signalling pathways such as AMPK/mTOR but have different effects on reactive oxygen species (ROS) production. Many of these effects oppose aberrant phenotypes common in cancer cells that ultimately result in cell death. We also highlight several gaps in knowledge that need to be addressed before we have a clear direction and strategy for applying mitochondrial uncouplers as anti-cancer agents.

MAJOR CONCLUSIONS

There is a large body of evidence supporting the therapeutic use of mitochondrial uncouplers to treat cancer. However, the long-term safety of some uncouplers remains in question and it will be critical to identify which patients and cancer types would benefit most from these agents.

Fluorescent probe for early mitochondrial voltage dynamics

Mitochondrial voltage dynamics plays a crucial role in cell healthy and disease. Here, a new fluorescent probe to monitor mitochondrial early voltage variations is described. The slowly permeant probe is retained in mitochondria during measurements to avoid interferences from natural membrane potential by incorporating an hydrolizable ester function. Voltage, local polarity, pH parameters and transmembrane dynamics were found to be deeply correlated opening a approach in mitochondrial sensing.

Failure to Guard: Mitochondrial Protein Quality Control in Cancer

Mitochondria are energetic and dynamic organelles with a crucial role in bioenergetics, metabolism, and signaling. Mitochondrial proteins, encoded by both nuclear and mitochondrial DNA, must be properly regulated to ensure proteostasis. Mitochondrial protein quality control (MPQC) serves as a critical surveillance system, employing different pathways and regulators as cellular guardians to ensure mitochondrial protein quality and quantity. In this review, we describe key pathways and players in MPQC, such as mitochondrial protein translocation-associated degradation, mitochondrial stress responses, chaperones, and proteases, and how they work together to safeguard mitochondrial health and integrity. Deregulated MPQC leads to proteotoxicity and dysfunctional mitochondria, which contributes to numerous human diseases, including cancer. We discuss how alterations in MPQC components are linked to tumorigenesis, whether they act as drivers, suppressors, or both. Finally, we summarize recent advances that seek to target these alterations for the development of anti-cancer drugs.

Metabolic reprogramming in cancer: mechanistic insights from Drosophila

Cancer cells constantly reprogram their metabolism as the disease progresses. However, our understanding of the metabolic complexity of cancer remains incomplete. Extensive research in the fruit fly Drosophila has established numerous tumor models ranging from hyperplasia to neoplasia. These fly tumor models exhibit a broad range of metabolic profiles and varying nutrient sensitivity. Genetic studies show that fly tumors can use various alternative strategies, such as feedback circuits and nutrient-sensing machinery, to acquire and consolidate distinct metabolic profiles. These studies not only provide fresh insights into the causes and functional relevance of metabolic reprogramming but also identify metabolic vulnerabilities as potential targets for cancer therapy. Here, we review the conceptual advances in cancer metabolism derived from comparing and contrasting the metabolic profiles of fly tumor models, with a particular focus on the Warburg effect, mitochondrial metabolism, and the links between diet and cancer.

Summary: Recent research in fruit flies has demonstrated that tumors rewire their metabolism by using diverse strategies that involve feedback regulation, nutrient sensing, intercellular or even inter-organ interactions, yielding new molecules as potential cancer markers or drug targets.

The fungal-specific subunit i/j of F1FO-ATP synthase stimulates the pathogenicity of Candida albicans independent of oxidative phosphorylation

Invasive fungal infections are a major cause of human mortality due in part to a very limited antifungal drug arsenal. The identification of fungal-specific pathogenic mechanisms is considered a crucial step to current antifungal drug development and represents a significant goal to increase the efficacy and reduce host toxicity. Although the overall architecture of F1FO-ATP synthase is largely conserved in both fungi and mammals, the subunit i/j (Su i/j, Atp18) and subunit k (Su k, Atp19) are proteins not found in mammals and specific to fungi. Here, the role of Su i/j and Su k in Candida albicans was characterized by an in vivo assessment of the virulence and in vitro growth and mitochondrial function. Strikingly, the atp18Δ/Δ mutant showed significantly reduced pathogenicity in systemic murine model. However, this substantial defect in infectivity exists without associated defects in mitochondrial oxidative phosphorylation or proliferation in vitro. Analysis of virulence-related traits reveals normal in both mutants, but shows cell wall defects in composition and architecture in the case of atp18Δ/Δ. We also find that the atp18Δ/Δ mutant is more susceptible to attack by macrophages than wild type, which may correlate well with the abnormal cell wall function and increased sensitivity to oxidative stress. In contrast, no significant changes were observed in any of these studies for the atp19Δ/Δ. These results demonstrate that the fungal-specific Su i/j, but not Su k of F1FO-ATP synthase may play a critical role in C. albicans infectivity and represent another opportunity for new therapeutic target investigation.

LAY ABSTRACT

This study aims to investigate biological functions of fungal-specific subunit i/j and subunit k of ATP synthase in C. albicans oxidative phosphorylation and virulence potential. Our results revealed that subunit i/j, and not subunit k, is critical for C. albicans pathogenicity.

Dissecting the single-cell transcriptome network underlying esophagus non-malignant tissues and esophageal squamous cell carcinoma

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is among the most prevalent causes of cancer-related death in adults. Tumor microenvironment (TME) has been associated with therapeutic failure and lethal outcomes for patients. However, published reports on the heterogeneity and TME in ESCC are scanty.

METHODS

Five tumor samples and five corresponding non-malignant samples were subjected to scRNA-seq analysis. Bulk RNA sequencing data were retrieved in publicly available databases.

FINDINGS

From the scRNA-seq data, a total of 128,688 cells were enrolled for subsequent analyses. Gene expression and CNV status exhibited high heterogeneity of tumor cells. We further identified a list of tumor-specific genes and four malignant signatures, which are potential new markers for ESCC. Metabolic analysis revealed that energy supply-related pathways are pivotal in cancer metabolic reprogramming. Moreover, significant differences were found in stromal and immune cells between the esophagus normal and tumor tissues, which promoted carcinogenesis at both cellular and molecular levels in ESCC. Immune checkpoints, regarded as potential targets for immunotherapy in ESCC were significantly highly expressed in ESCC, including LAG3 and HAVCR2. Eventually, we constructed a cell-to-cell communication atlas based on cancer cells and immune cells and performed the flow cytometry, qRT-PCR, immunofluorescence, and immunohistochemistry analyses to validate the results.

INTERPRETATION

This study demonstrates a widespread reprogramming across multiple cellular elements within the TME in ESCC, particularly in transcriptional states, cellular functions, and cell-to-cell interactions. The findings offer an insight into the exploration of TME and heterogeneity in the ESCC and provide new therapeutic targets for its clinical management in the future.

FUNDING

The work was supported by the Shanghai Pujiang Program (2020PJD009) and Research Development Fund of Zhongshan Hospital, Fudan University (2019ZSFZ002 and 2019ZSFZ19).

Preparation and biological evaluation of radioiodine-labeled triphenylphosphine derivatives as mitochondrial targeting probes

The positive-charged lipophilic triphenylphosphonium cations (TPPs+ ) have been served as mitochondrial targeting vehicles for the delivery of various probes. In this study, we developed a new method for the preparation of radioiodine-labeled TPPs+ . Four 125 I-labeled TPPs+ , [125 I] 9-[125 I] 12, were prepared from the corresponding triphenylphosphine phenylborate precursors of B 5-B 8 via an optimized copper-catalyzed one-step procedure in high radiochemical yield (>95%). After radio-HPLC purification, the final products could be obtained with high specific activity. Their physicochemical properties, in vitro cellular uptake, and ex vivo mice biodistribution were investigated. The results suggested the 125 I-labeled TPPs+ were lipophilic and could specifically accumulate in the mitochondrial-rich myocardial cells through the mitochondrial membrane potential.

Quantification of Myocardial Mitochondrial Membrane Potential Using PET

PURPOSE OF REVIEW

To present a method enabling in vivo quantification of tissue membrane potential (ΔΨ_T), a proxy of mitochondrial membrane potential (ΔΨ_m), to review the origin and role of ΔΨ_m, and to highlight potential applications of myocardial ΔΨ_T imaging.

RECENT FINDINGS

Radiolabelled lipophilic cations have been used for decades to measure ΔΨ_m in vitro. Using similar compounds labeled with positron emitters and appropriate compartment modeling, this technique now allows in vivo quantification of ΔΨ_T with positron emission tomography. Studies have confirmed the feasibility of measuring myocardial ΔΨ_T in both animals and humans. In addition, ΔΨ_T showed very low variability among healthy subjects, suggesting that this method could allow detection of relatively small pathological changes. In vivo assessment of myocardial ΔΨ_T provides a new tool to study the pathophysiology of cardiovascular diseases and has the potential to serve as a new biomarker to assess disease stage, prognosis, and response to therapy.

A protet-based, protonic charge transfer model of energy coupling in oxidative and photosynthetic phosphorylation

Textbooks of biochemistry will explain that the otherwise endergonic reactions of ATP synthesis can be driven by the exergonic reactions of respiratory electron transport, and that these two half-reactions are catalyzed by protein complexes embedded in the same, closed membrane. These views are correct. The textbooks also state that, according to the chemiosmotic coupling hypothesis, a (or the) kinetically and thermodynamically competent intermediate linking the two half-reactions is the electrochemical difference of protons that is in equilibrium with that between the two bulk phases that the coupling membrane serves to separate. This gradient consists of a membrane potential term Δψ and a pH gradient term ΔpH, and is known colloquially as the protonmotive force or pmf. Artificial imposition of a pmf can drive phosphorylation, but only if the pmf exceeds some 150-170mV; to achieve in vivo rates the imposed pmf must reach 200mV. The key question then is 'does the pmf generated by electron transport exceed 200mV, or even 170mV?' The possibly surprising answer, from a great many kinds of experiment and sources of evidence, including direct measurements with microelectrodes, indicates it that it does not. Observable pH changes driven by electron transport are real, and they control various processes; however, compensating ion movements restrict the Δψ component to low values. A protet-based model, that I outline here, can account for all the necessary observations, including all of those inconsistent with chemiosmotic coupling, and provides for a variety of testable hypotheses by which it might be refined.

Mitochondria-targeting graphene oxide nanocomposites for fluorescence imaging-guided synergistic phototherapy of drug-resistant osteosarcoma

BACKGROUND

Osteosarcoma (OS) is the most common primary malignant bone tumor occurring in children and young adults. Drug-resistant osteosarcoma often results in chemotherapy failure. Therefore, new treatments aimed at novel therapeutic targets are urgently needed for the treatment of drug-resistant osteosarcoma. Mitochondria-targeted phototherapy, i.e., synergistic photodynamic/photothermal therapy, has emerged as a highly promising strategy for treating drug-resistant tumors. This study proposed a new nano-drug delivery system based on near-infrared imaging and multifunctional graphene, which can target mitochondria and show synergistic phototherapy, with preferential accumulation in tumors.

METHODS AND RESULTS

Based on our previous study, (4-carboxybutyl) triphenyl phosphonium bromide (TPP), a mitochondria-targeting ligand, was conjugated to indocyanine green (ICG)-loaded, polyethylenimine-modified PEGylated nanographene oxide sheets (TPP-PPG@ICG) to promote mitochondrial accumulation after cellular internalization. Thereafter, exposure to a single dose of near-infrared irradiation enabled synergistic photodynamic and photothermal therapy, which simultaneously inhibited adenosine triphosphate synthesis and mitochondrial function. Induction of intrinsic apoptosis assisted in surmounting drug resistance and caused tumor cell death. After fluorescence imaging-guided synergistic phototherapy, the mitochondria-targeting, multifunctional graphene-based, drug-delivery system showed highly selective anticancer efficiency in vitro and in vivo, resulting in marked inhibition of tumor progression without noticeable toxicity in mice bearing doxorubicin-resistant MG63 tumor cells.

CONCLUSION

The mitochondria-targeting TPP-PPG@ICG nanocomposite constitutes a new class of nanomedicine for fluorescence imaging-guided synergistic phototherapy and shows promise for treating drug-resistant osteosarcoma.

Phenformin Inhibits Hedgehog-Dependent Tumor Growth through a Complex I-Independent Redox/Corepressor Module

The antidiabetic drug phenformin displays potent anticancer activity in different tumors, but its mechanism of action remains elusive. Using Shh medulloblastoma as model, we show here that at clinically relevant concentrations, phenformin elicits a significant therapeutic effect through a redox-dependent but complex I-independent mechanism. Phenformin inhibits mitochondrial glycerophosphate dehydrogenase (mGPD), a component of the glycerophosphate shuttle, and causes elevations of intracellular NADH content. Inhibition of mGPD mimics phenformin action and promotes an association between corepressor CtBP2 and Gli1, thereby inhibiting Hh transcriptional output and tumor growth. Because ablation of CtBP2 abrogates the therapeutic effect of phenformin in mice, these data illustrate a biguanide-mediated redox/corepressor interplay, which may represent a relevant target for tumor therapy.

Imaging Beyond Seeing: Early Prognosis of Cancer Treatment

Assessing cancer response to therapeutic interventions has been realized as an important course to early predict curative efficacy and treatment outcomes due to tumor heterogeneity. Compared to the traditional invasive tissue biopsy method, molecular imaging techniques have fundamentally revolutionized the ability to evaluate cancer response in a spatiotemporal manner. The past few years has witnessed a paradigm shift on the efforts from manufacturing functional molecular imaging probes for seeing a tumor to a vantage stage of interpreting the tumor response during different treatments. This review is to stand by the current development of advanced imaging technologies aiming to predict the treatment response in cancer therapy. Special interest is placed on the systems that are able to provide rapid and noninvasive assessment of pharmacokinetic drug fates (e.g., drug distribution, release, and activation) and tumor microenvironment heterogeneity (e.g., tumor cells, macrophages, dendritic cells (DCs), T cells, and inflammatory cells). The current status, practical significance, and future challenges of the emerging artificial intelligence (AI) technology and machine learning in the applications of medical imaging fields is overviewed. Ultimately, the authors hope that this review is timely to spur research interest in molecular imaging and precision medicine.

The crosstalk between HIFs and mitochondrial dysfunctions in cancer development

Mitochondria are essential cellular organelles that are involved in regulating cellular energy, metabolism, survival, and proliferation. To some extent, cancer is a genetic and metabolic disease that is closely associated with mitochondrial dysfunction. Hypoxia-inducible factors (HIFs), which are major molecules that respond to hypoxia, play important roles in cancer development by participating in multiple processes, such as metabolism, proliferation, and angiogenesis. The Warburg phenomenon reflects a pseudo-hypoxic state that activates HIF-1α. In addition, a product of the Warburg effect, lactate, also induces HIF-1α. However, Warburg proposed that aerobic glycolysis occurs due to a defect in mitochondria. Moreover, both HIFs and mitochondrial dysfunction can lead to complex reprogramming of energy metabolism, including reduced mitochondrial oxidative metabolism, increased glucose uptake, and enhanced anaerobic glycolysis. Thus, there may be a connection between HIFs and mitochondrial dysfunction. In this review, we systematically discuss the crosstalk between HIFs and mitochondrial dysfunctions in cancer development. Above all, the stability and activity of HIFs are closely influenced by mitochondrial dysfunction related to tricarboxylic acid cycle, electron transport chain components, mitochondrial respiration, and mitochondrial-related proteins. Furthermore, activation of HIFs can lead to mitochondrial dysfunction by affecting multiple mitochondrial functions, including mitochondrial oxidative capacity, biogenesis, apoptosis, fission, and autophagy. In general, the regulation of tumorigenesis and development by HIFs and mitochondrial dysfunction are part of an extensive and cooperative network.

Vγ9Vδ2 T cells strengthen cisplatin inhibition activity against breast cancer MDA-MB-231 cells by disrupting mitochondrial function and cell ultrastructure

BACKGROUND

Breast cancer ranks second of new cases and fifth of death in 2018 worldwide. Cis-platinum (CDDP) has been used as a chemotherapy to treat breast cancer for years. However, CDDP can adversely disrupt immune function of host. Thus, development of new protocol that can minimize side effect and meanwhile elevate clinical efficacy of CDDP will eventually benefit cancer patients. Since Vγ9Vδ2 T cells can up-regulate immune function of cancer patients, therefore, our hypothesis is that introduction of Vγ9Vδ2 T cells could potentiate CDDP efficacy against breast cancer.

METHODS

We used breast cancer cell line MDA-MB-231 as model cell to test our hypothesis. The cancer cell viability in vitro in the context of different dose of CDDP was analyzed by flow cytometry. The cytoskeleton alteration was visualized by confocal microscopy, and the ultrastructure of cell membrane was observed by atomic force microscopy. The mitochondrial function of MDA-MB-231 cells was detected as well by flow cytometry.

RESULTS

Comparing to either Vγ9Vδ2 T cells or CDDP alone, Vγ9Vδ2 T cells plus CDDP could more strikingly induce MDA-MB-231 cell membrane ultrastructure disruption and cytoskeleton disorder, and more significantly enhance the inhibition of CDDP on proliferation of MDA-MB-231 cells. At the same time, Vγ9Vδ2 T cells strengthened CDDP-induced mitochondrial dysfunction of cancer cells.

CONCLUSION

This work revealed that Vγ9Vδ2 T cells could synergistically enhance the inhibition activity of CDDP against breast cancer cells. Meanwhile, this in vitro proof-of-concept study implied the clinical prospect of the combining application of Vγ9Vδ2 T cells and CDDP in breast cancer therapy.

Pathway-based classification of glioblastoma uncovers a mitochondrial subtype with therapeutic vulnerabilities

The transcriptomic classification of glioblastoma (GBM) has failed to predict survival and therapeutic vulnerabilities. A computational approach for unbiased identification of core biological traits of single cells and bulk tumors uncovered four tumor cell states and GBM subtypes distributed along neurodevelopmental and metabolic axes, classified as proliferative/progenitor, neuronal, mitochondrial and glycolytic/plurimetabolic. Each subtype was enriched with biologically coherent multiomic features. Mitochondrial GBM was associated with the most favorable clinical outcome. It relied exclusively on oxidative phosphorylation for energy production, whereas the glycolytic/plurimetabolic subtype was sustained by aerobic glycolysis and amino acid and lipid metabolism. Deletion of the glucose-proton symporter SLC45A1 was the truncal alteration most significantly associated with mitochondrial GBM, and the reintroduction of SLC45A1 in mitochondrial glioma cells induced acidification and loss of fitness. Mitochondrial, but not glycolytic/plurimetabolic, GBM exhibited marked vulnerability to inhibitors of oxidative phosphorylation. The pathway-based classification of GBM informs survival and enables precision targeting of cancer metabolism.

QuPath: The global impact of an open source digital pathology system

QuPath, originally created at the Centre for Cancer Research & Cell Biology at Queen's University Belfast as part of a research programme in digital pathology (DP) funded by Invest Northern Ireland and Cancer Research UK, is arguably the most wildly used image analysis software program in the world. On the back of the explosion of DP and a need to comprehensively visualise and analyse whole slides images (WSI), QuPath was developed to address the many needs associated with tissue based image analysis; these were several fold and, predominantly, translational in nature: from the requirement to visualise images containing billions of pixels from files several GBs in size, to the demand for high-throughput reproducible analysis, which the paradigm of routine visual pathological assessment continues to struggle to deliver. Resultantly, large-scale biomarker quantification must increasingly be augmented with DP. Here we highlight the impact of the open source Quantitative Pathology & Bioimage Analysis DP system since its inception, by discussing the scope of scientific research in which QuPath has been cited, as the system of choice for researchers.

Synthesis and Biological Evaluation of 99mTc(I) Tricarbonyl Complexes Dual-Targeted at Tumoral Mitochondria

For effective Auger therapy of cancer, the Auger-electron emitters must be delivered to the tumor cells in close proximity to a radiosensitive cellular target. Nuclear DNA is considered the most relevant target of Auger electrons to have augmented radiotoxic effects and significant cell death. However, there is a growing body of evidence that other targets, such as the mitochondria, could be relevant subcellular targets in Auger therapy. Thus, we developed dual-targeted 99mTc(I) tricarbonyl complexes containing a triphenylphosphonium (TPP) moiety to promote accumulation of 99mTc in the mitochondria, and a bombesin peptide to provide specificity towards the gastrin releasing peptide receptor (GRPr) overexpressed in prostate cancer cells. The designed dual-targeted complex, 99mTc-TPP-BBN, is efficiently internalized by human prostate cancer PC3 cells through a specific GRPr-mediated mechanism of uptake. Moreover, the radioconjugate provided an augmented accumulation of 99mTc in the mitochondria of the target tumor cells, most probably following its intracellular cleavage by cathepsin B. In addition, 99mTc-TPP-BBN showed an enhanced ability to reduce the survival of PC3 cells, in a dose-dependent manner.

Progression-Mediated Changes in Mitochondrial Morphology Promotes Adaptation to Hypoxic Peritoneal Conditions in Serous Ovarian Cancer

Ovarian cancer is the deadliest gynecological cancer in women, with a survival rate of less than 30% when the cancer has spread throughout the peritoneal cavity. Aggregation of cancer cells increases their viability and metastatic potential; however, there are limited studies that correlate these functional changes to specific phenotypic alterations. In this study, we investigated changes in mitochondrial morphology and dynamics during malignant transition using our MOSE cell model for progressive serous ovarian cancer. Mitochondrial morphology was changed with increasing malignancy from a filamentous network to single, enlarged organelles due to an imbalance of mitochondrial dynamic proteins (fusion: MFN1/OPA1, fission: DRP1/FIS1). These phenotypic alterations aided the adaptation to hypoxia through the promotion of autophagy and were accompanied by changes in the mitochondrial ultrastructure, mitochondrial membrane potential, and the regulation of reactive oxygen species (ROS) levels. The tumor-initiating cells increased mitochondrial fragmentation after aggregation and exposure to hypoxia that correlated well with our previously observed reduced growth and respiration in spheroids, suggesting that these alterations promote viability in non-permissive conditions. Our identification of such mitochondrial phenotypic changes in malignancy provides a model in which to identify targets for interventions aimed at suppressing metastases.

In Vivo Optical Metabolic Imaging of Long-Chain Fatty Acid Uptake in Orthotopic Models of Triple-Negative Breast Cancer

Simple Summary

A dysregulated metabolism is a hallmark of cancer. Once understood, tumor metabolic reprogramming can lead to targetable vulnerabilities, spurring the development of novel treatment strategies. Beyond the common observation that tumors rely heavily on glucose, building evidence indicates that a subset of tumors use lipids to maintain their proliferative or metastatic phenotype. This study developed an intra-vital microscopy method to quantify lipid uptake in breast cancer murine models using a fluorescently labeled palmitate molecule, Bodipy FL c16. This work highlights optical imaging’s ability to both measure metabolic endpoints non-destructively and repeatedly, as well as inform small animal metabolic phenotyping beyond in vivo optical imaging of breast cancer alone.

Abstract

Targeting a tumor’s metabolic dependencies is a clinically actionable therapeutic approach; however, identifying subtypes of tumors likely to respond remains difficult. The use of lipids as a nutrient source is of particular importance, especially in breast cancer. Imaging techniques offer the opportunity to quantify nutrient use in preclinical tumor models to guide development of new drugs that restrict uptake or utilization of these nutrients. We describe a fast and dynamic approach to image fatty acid uptake in vivo and demonstrate its relevance to study both tumor metabolic reprogramming directly, as well as the effectiveness of drugs targeting lipid metabolism. Specifically, we developed a quantitative optical approach to spatially and longitudinally map the kinetics of long-chain fatty acid uptake in in vivo murine models of breast cancer using a fluorescently labeled palmitate molecule, Bodipy FL c16. We chose intra-vital microscopy of mammary tumor windows to validate our approach in two orthotopic breast cancer models: a MYC-overexpressing, transgenic, triple-negative breast cancer (TNBC) model and a murine model of the 4T1 family. Following injection, Bodipy FL c16 fluorescence increased and reached its maximum after approximately 30 min, with the signal remaining stable during the 30–80 min post-injection period. We used the fluorescence at 60 min (Bodipy₆₀), the mid-point in the plateau region, as a summary parameter to quantify Bodipy FL c16 fluorescence in subsequent experiments. Using our imaging platform, we observed a two- to four-fold decrease in fatty acid uptake in response to the downregulation of the MYC oncogene, consistent with findings from in vitro metabolic assays. In contrast, our imaging studies report an increase in fatty acid uptake with tumor aggressiveness (6NR, 4T07, and 4T1), and uptake was significantly decreased after treatment with a fatty acid transport inhibitor, perphenazine, in both normal mammary pads and in the most aggressive 4T1 tumor model. Our approach fills an important gap between in vitro assays providing rich metabolic information at static time points and imaging approaches visualizing metabolism in whole organs at a reduced resolution.