Pathway to Approval of Innovative Radiopharmaceuticals in China.

Since the late 1950s, radiopharmaceuticals have been used for diagnosis and treatment in clinical nuclear medicine in China. Over the decades, China has successfully established a relatively sophisticated system for radiopharmaceutical production and management, supported by state-of-the-art facilities. With the rapid growth of the national economy, the radiopharmaceutical market in China is expanding at a remarkable pace. This burgeoning market has led to an escalating demand for clinical-stage radiopharmaceuticals, either produced domestically or imported. Despite this positive trajectory, the development and application of radiopharmaceuticals in China have been hindered by several challenges that persist, such as inadequate research, insufficient investment, limited availability of radionuclides, shortage of trained personnel in related fields, and imperfections in policies and regulations. In an exciting development, the regulation reforms implemented since 2015 have positively affected China's drug regulatory system. The introduction of the "Mid- and Long-Term Development Plan (2021-2035) for Medical Isotopes" created concurrently an opportune environment for the advancement of innovative radiopharmaceuticals. In this review, we aim to provide an overview of the approval process for novel radiopharmaceuticals by the National Medical Products Administration and the status of radiopharmaceuticals in research and development in China. Preclinical development and clinical translation of radiopharmaceuticals are undergoing rapid evolution in China. As practitioners in the field in China, we provide several practical suggestions to stimulate open discussions and thoughtful consideration.

PFKFB3 regulates breast cancer tumorigenesis and Fulvestrant sensitivity by affecting ERα stability.

Estrogen receptor alpha (ERα) is expressed in approximately 70% of breast cancer cases and determines the sensitivity and effectiveness of endocrine therapy. 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase3 (PFKFB3) is a glycolytic enzyme that is highly expressed in a great many human tumors, and recent studies have shown that it plays a significant role in improving drug sensitivity. However, the role of PFKFB3 in regulating ERα expression and the underlying mechanism remains unclear. Here, we find by using immunohistochemistry (IHC) that PFKFB3 is elevated in ER-positive breast cancer and high expression of PFKFB3 resulted in a worse prognosis. In vitro and in vivo experiments verify that PFKFB3 promotes ER-positive breast cancer cell proliferation. The overexpression of PFKFB3 promotes the estrogen-independent ER-positive breast cancer growth. In an estrogen-free condition, RNA-sequencing data from MCF7 cells treated with siPFKFB3 showed enrichment of the estrogen signaling pathway, and a luciferase assay demonstrated that knockdown of PFKFB3 inhibited the ERα transcriptional activity. Mechanistically, down-regulation of PFKFB3 promotes STUB1 binding to ERα, which accelerates ERα degradation by K48-based ubiquitin linkage. Finally, growth of ER-positive breast cancer cells in vivo was more potently inhibited by fulvestrant combined with the PFKFB3 inhibitor PFK158 than for each drug alone. In conclusion, these data suggest that PFKFB3 is identified as an adverse prognosis factor for ER-positive breast cancer and plays a previously unrecognized role in the regulation of ERα stability and activity. Our results further explores an effective approach to improve fulvestrant sensitivity through the early combination with a PFKFB3 inhibitor.

The added diagnostic value of 18 F-FDG PET/CT radiomic analysis in multiple myeloma patients with negative visual analysis.

PURPOSE: A small number of patients diagnosed with multiple myeloma (MM) by bone marrow aspiration reported as being disease-free on 18 F-FDG PET/CT. We aim to evaluate the diagnostic value of radiomics approach in patients with MM who were negative by visual analysis. MATERIALS AND METHODS: Thirty-three patients judged negative by visual analysis were assigned to the MM group. Contemporaneous 31 disease-free patients served as the control group. 70% of the whole data set was used as training set (23 from MM group and 22 from control group) and 30% as testing set (10 from MM group and 9 from control group). Axial skeleton volumes were automatically segmented and high-dimensional imaging features were extracted from PET and CT. The unsupervised machine learning method was used to filter and reduce the dimensions of the extracted features. Random forest was used to construct the prediction model and then validated with 10-fold cross-validation and evaluated on the independent testing set. RESULTS: One thousand seven hundred two quantitative features were extracted from PET and CT. Of those, three first-order and one high-order imaging features were uncorrelated. With the cross-validation on the training group, the sensitivity, specificity, accuracy and area under the curve of random forest were 0.850, 0.792, 0.818 and 0.894, respectively. On the independent testing set, the accuracy of the model was 0.850 and the area under the curve was 0.909. CONCLUSION: Radiomic analysis based on 18 F-FDG PET/CT using machine learning model provides a quantitative, objective and efficient mechanism for diagnosing patients with MM who were negative by visual analysis.

ImmunoPET imaging of Trop2 expression in solid tumors with nanobody tracers.

PURPOSE: The high expression of the transmembrane glycoprotein trophoblast cell-surface antigen 2 (Trop2) was strongly associated with the progression of solid tumors, including pancreatic and gastric cancers. Our study aimed to construct Trop2-specific immuno-positron emission tomography (immunoPET) probes and assess the diagnostic abilities in preclinical pancreatic and gastric cancer models. METHODS: The expression of Trop2 in pancreatic cancer was determined by single-cell sequencing and immunohistochemistry on tissue microarray (TMA). Flow cytometry was used to screen the expression of Trop2 in pancreatic cancer cell lines. Two nanobodies (i.e., RTD98 and RTD01) targeting Trop2 were developed and labeled with gallium-68 (68Ga, T1/2 = 1.1 h) to construct immunoPET imaging probes. The agents were researched in cell-derived pancreatic and patient-derived gastric cancer models expressing varying Trop2. RESULTS: Single-cell sequencing results showed high expression of Trop2 in pancreatic ductal cells as well as acinar cells and immunohistochemical staining of TMA from pancreatic cancers showed significantly higher expression of Trop2 in cancerous than in paracancerous tissues. ImmunoPET utilizing [68Ga]Ga-NOTA-RTD98 could clearly delineate subcutaneous tumors, both in cell-derived pancreatic cancer models and patient-derived gastric cancer models, superior to imaging using [18F]-FDG or a non-specific probe [68Ga]Ga-NOTA-RTD161. Another probe with improved pharmacokinetics targeting Trop2, [68Ga]Ga-NOTA-RTD01, was further prepared and showed advantageous diagnostic capabilities in preclinical pancreatic cancer models. CONCLUSION: In the work, we reported two nanobody tracers targeting human Trop2 which may facilitate better use of Trop2-targeted therapeutics by noninvasively displaying expression dynamics of the target.

ImmunoPET Imaging of CD47 with VHH-Derived Tracers in Pancreatic Cancers.

Pancreatic ductal adenocarcinoma (PDAC) is a malignant tumor with insidious onset, rapid progression, and a very poor prognosis. CD47 is a transmembrane protein associated with the development and poor prognosis of pancreatic cancer. The aim of this study was to evaluate the diagnostic value of novel immunoPET tracers targeting CD47 in preclinical pancreatic cancer models. The association of CD47 expression with pancreatic cancer was analyzed using the Gene Expression Profiling Interactive Analysis platform. Immunohistochemical analysis of tissue microarrays was performed to detect CD47 expression in PDAC. CD47 expression levels on BxPC-3 and AsPC-1 cell membranes were compared using flow cytometry. A VHH (C2)-targeting human CD47 and its albumin-binding derivative (ABDC2) were labeled with 68Ga or 89Zr, respectively. The developed tracers were evaluated by immuno-positron emission tomography (immunoPET) imaging in tumor-bearing nude and CD47-humanized mice. [68Ga]Ga-NOTA-C2 effectively detected tumor lesions in nude mice models and further showed confirmative imaging capacity in CD47-humanized PDAC models. Compared with [68Ga]Ga-NOTA-C2, [89Zr]Zr-DFO-ABDC2 had a significantly prolonged circulation time, increased tumor uptake, and reduced accumulation in the kidneys. Finally, biodistribution and histological staining confirmed the results of the immunoPET imaging studies. In this study, we validated that two novel VHH-derived molecular imaging tracers for immunoPET imaging ([68Ga]Ga-NOTA-C2 and [89Zr]Zr-DFO-ABDC2) can effectively annotate CD47 expression and diagnose PDAC in a target-specific manner. Clinical application of the imaging strategies may help select patients for CD47-targeted therapies and assess the response thereafter.

The First-in-Human Whole-Body Dynamic Pharmacokinetics Study of Aptamer.

Serving as targeting ligands, aptamers have shown promise in precision medicine. However, the lack of knowledge of the biosafety and metabolism patterns in the human body largely impeded aptamers' clinical translation. To bridge this gap, here we report the first-in-human pharmacokinetics study of protein tyrosine kinase 7 targeted SGC8 aptamer via in vivo PET tracking of gallium-68 (68Ga) radiolabeled aptamers. The specificity and binding affinity of a radiolabeled aptamer, named 68Ga[Ga]-NOTA-SGC8, were maintained as proven in vitro. Further preclinical biosafety and biodistribution evaluation confirmed that aptamers have no biotoxicity, potential mutation risks, or genotoxicity at high dosage (40 mg/kg). Based on this result, a first-in-human clinical trial was approved and carried out to evaluate the circulation and metabolism profiles, as well as biosafety, of the radiolabeled SGC8 aptamer in the human body. Taking advantage of the cutting-edge total-body PET, the aptamers' distribution pattern in the human body was acquired in a dynamic fashion. This study revealed that radiolabeled aptamers are harmless to normal organs and most of them are accumulated in the kidney and cleared from the bladder via urine, which agrees with preclinical studies. Meanwhile, a physiologically based pharmacokinetic model of aptamer was developed, which could potentially predict therapeutic responses and plan personalized treatment strategies. This research studied the biosafety and dynamic pharmacokinetics of aptamers in the human body for the first time, as well as demonstrated the capability of novel molecular imaging fashion in drug development.

Development and Characterization of Nanobody-Derived CD47 Theranostic Pairs in Solid Tumors.

Overexpression of CD47 is frequently observed in various types of human malignancies, inhibiting myeloid-mediated elimination of tumor cells and affecting the prognosis of cancer patients. By mapping biomarker expression, immuno-positron emission tomography has been increasingly used for patient screening and response monitoring. By immunization alpacas with recombinant human CD47, we prepared a CD47-targeting nanobody C2 and developed [68Ga]Ga-NOTA-C2, followed by an exploration of the diagnostic value in CD47-expressing tumor models including gastric-cancer patient-derived xenograft models. By fusing C2 to an albumin binding domain (ABD), we synthesized ABDC2, which had increased in vivo half-life and improved targeting properties. We further labeled ABDC2 with 68Ga/89Zr/177Lu to develop radionuclide theranostic pairs and evaluated the pharmacokinetics and theranostic efficacies of the agents in cell- and patient-derived models. Both C2 and ABDC2 specifically reacted with human CD47 with a high K D value of 23.50 and 84.57 pM, respectively. [68Ga]Ga-NOTA-C2 was developed with high radiochemical purity (99 >%, n = 4) and visualized CD47 expression in the tumors. In comparison to the rapid renal clearance and short half-life of [68Ga]Ga-NOTA-C2, both [68Ga]Ga-NOTA-ABDC2 and [89Zr]Zr-DFO-ABDC2 showed prolonged circulation and increased tumor uptake, with the highest uptake of [89Zr]Zr-DFO-ABDC2 occurring at 72 h post-injection. Moreover, [177Lu]Lu-DOTA-ABDC2 radioimmunotherapy suppressed the tumor growth but was associated with toxicity, warranting further optimization of the treatment schedules. Taken together, we reported a series of nanobody-derived CD47-targeted agents, of which [68Ga]Ga-NOTA-C2 and [89Zr]Zr-DFO-ABDC2 are readily translatable. Optimization and translation of CD47-targeted theranostic pair may provide new prospects for CD47-targeted management of solid tumors.

Development and Characterization of Novel FAP-Targeted Theranostic Pairs: A Bench-to-Bedside Study.

Fibroblast activation protein (FAP) is among the most popular targets in nuclear medicine imaging and cancer theranostics. Several small-molecule moieties (FAPI-04, FAPI-46, etc.) are used for developing FAP-targeted theranostic agents. Nonetheless, the circulation time of FAP inhibitors is relatively short, resulting in rapid clearance via kidneys, low tumor uptake, and associated unsatisfactory treatment efficacy. To address the existing drawbacks, we engineered 3 peptides named FD1, FD2, and FD3 with different circulation times through solid-phase peptide synthesis. All the 3 reported peptides bind to human and murine FAP with single-digit nanomolar affinity measured by surface plasmon resonance. The diagnostic and therapeutic potential of the agents labeled with 68Ga and 177Lu was assessed in several tumor models exhibiting different levels of FAP expression. While radiolabeled FD1 was rapidly excreted from kidneys, radiolabeled FD2/FD3 have significantly prolonged circulation, increased tumor uptake, and decreased kidney accumulation. Our findings indicated that [68Ga]Ga-DOTA-FD1 positron emission tomography (PET) effectively detected FAP dynamics, whereas [177Lu]Lu-DOTA-FD2 and [177Lu]Lu-DOTA-FD3 exhibited remarkable therapeutic efficacy in FAP-overexpressing tumor models, including pancreatic cancer cell models characterized by abundant stroma. Moreover, a pilot translational investigation demonstrated that [68Ga]Ga-DOTA-FD1 had the capability to identify both primary and metastatic tumors with precision and distinction. In summary, we developed [68Ga]Ga-DOTA-FD1 for same-day PET imaging of FAP dynamics and [177Lu]Lu-DOTA-FD2 and [177Lu]Lu-DOTA-FD3 for effective radioligand therapy of FAP-overexpressing tumors.

Development and comparison of 68Ga/18F/64Cu-labeled nanobody tracers probing Claudin18.2.

Claudin 18.2 (CLDN18.2) is an emerging target for the treatment of gastric cancers. We aim to develop tracers to image the expression of CLDN18.2. A humanized nanobody targeting CLDN18.2 (clone hu19V3) was produced and labeled with 68Ga, 64Cu, and 18F. The tracers were investigated in subcutaneous and metastatic models established using two different mouse types (nude and Balb/c mice) and two different cell lines (CHO-CLDN18.2 and CT26-CLDN18.2). Gastric cancer patient-derived xenograft (PDX) models were further established for validation experiments. Three novel CLDN18.2-targeted tracers (i.e., [68Ga]Ga-NOTA-hu19V3, [64Cu]Cu-NOTA-hu19V3, and [18F]F-hu19V3) were developed with good radiochemical yields and excellent radiochemical purities. [68Ga]Ga-NOTA-hu19V3 immuno-positron emission tomography (immunoPET) rapidly delineated subcutaneous CHO-CLDN18.2 lesions and CT26-CLDN18.2 tumors, as well as showing excellent diagnostic value in PDX models naturally expressing CLDN18.2. While [68Ga]Ga-NOTA-hu19V3 had high kidney accumulation, [64Cu]Cu-NOTA-hu19V3 showed reduced kidney accumulation and improved image contrast at late time points. Moreover, [18F]F-hu19V3 was developed via click chemistry reaction under mild conditions and precisely disseminated CHO-CLDN18.2 lesions in the lungs. Furthermore, region of interest analysis, biodistribution study, and histopathological staining results correlated well with the in vivo imaging results. Taken together, immunoPET imaging with the three tracers can reliably visualize CLDN18.2 expression.

GPC3-targeted immunoPET imaging of hepatocellular carcinomas.

PURPOSE: Early detection of hepatocellular carcinoma (HCC) remains a clinical challenge. Glypican 3 (GPC3) is a proteoglycan highly specific for HCC and is a potential diagnostic and therapeutic target for HCC. This work aims to develop GPC3-targeted immuno-positron emission tomography (immunoPET) imaging strategies and to assess the diagnostic values in preclinical HCC models. METHODS: Flow cytometry was used to screen GPC3-positive HCC cell lines. The expression of GPC3 in HCCs was detected by immunohistochemistry on tissue microarray. A novel GPC3-specific single domain antibody (sdAb) was produced and labeled with gallium-68 (68Ga, T1/2 = 1.1 h) and fluorine-18 (18F, T1/2 = 1.8 h) to develop radiotracers with different half-lives. The diagnostic efficacies of the developed probes (i.e., [68Ga]Ga-NOTA-G2, [18F]F-G2, and [68Ga]Ga-NOTA-ABDG2) were interrogated in preclinical HCC models bearing varying GPC3 levels. RESULTS: GPC3 was strongly expressed on HCC cell lines and patients with poorly differentiated HCC. [68Ga]Ga-NOTA-G2 immunoPET imaging specifically delineated the subcutaneous HCC lesions, outperforming the traditional 18F-fluorodeoxyglucose PET and the nonspecific [68Ga]Ga-NOTA-NbGFP immunoPET. ImmunoPET imaging with [18F]F-G2 also efficiently diagnosed the tumors with clarity. Moreover, the fusion of G2 to an albumin-binding domain (ABD) significantly increased the tumor uptake and decreased kidney accumulation of the radiotracer when compared to [68Ga]Ga-NOTA-G2. CONCLUSIONS: In the work, we successfully developed sdAb-derived GPC3-targeted immunoPET imaging strategies and characterized the superior diagnostic accuracies in preclinical HCC models. Furthermore, we synthesized a fusion protein ABDG2 with improved targeting and pharmacokinetic properties, serving as a promising candidate for developing radioimmunotherapy agents.

Annotating BCMA Expression in Multiple Myelomas.

B cell maturation antigen (BCMA) is a promising theranostic target for multiple myeloma (MM). BCMA-targeted therapeutics, such as antibody-drug conjugates and chimeric antigen receptor T-cell immunotherapies, are rapidly reshaping the treatment landscape of MM. Along with the progress, a critical challenge is to noninvasively visualize the dynamic change of BCMA for a better-personalized prescription of the above-mentioned therapeutics. We aim to develop immuno-positron emission tomography (immunoPET) imaging strategies to visualize BCMA expression and realize target-specific diagnosis of MM in the work. A series of BCMA-targeting nanobodies were produced and two of them were successfully labeled with gallium-68 (68Ga). MM models were established using MM.1S cell line and NOD-Prkdcem26Cd52Il2rgem26Cd22/Nju mice. The diagnostic efficacies of the developed probes (i.e., [68Ga]Ga-NOTA-MMBC2 and [68Ga]Ga-NOTA-MMBC3) were investigated in disseminated MM models by immunoPET imaging, region of interest analysis on PET images, biodistribution study, and histopathological staining study. [68Ga]Ga-NOTA-MMBC2 and [68Ga]Ga-NOTA-MMBC3 were developed with radiochemical purities of >99%. ImmunoPET imaging with either [68Ga]Ga-NOTA-MMBC2 or [68Ga]Ga-NOTA-MMBC3 precisely visualized BCMA expression and delineated MM lesions throughout the bone marrows. Moreover, [68Ga]Ga-NOTA-MMBC3 immunoPET successfully detected remnant MM after treatment with daratumumab, a prescription medicine used to treat MM. The immunoPET imaging data correlated well with the biodistribution and immunohistochemistry staining results. The work successfully developed two state-of-the-art BCMA-targeted radiotracers for annotating BCMA expression and diagnosing MM. Translational studies interpreting the diagnostic efficacies of the immunoPET radiotracers are warranted.

Annotating CD38 Expression in Multiple Myeloma with [18F]F-Nb1053.

Noninvasive diagnosis of multiple myeloma (MM) is a clinical challenge. CD38 is an established biomarker for MM, and the development of CD38-targeted radiotracers may improve the management of MM. By taking the advantages of bioorthogonal click chemistry, a nanobody (i.e., Nb1053-LLQS) specific for CD38 was successfully labeled with 18F. The diagnostic efficacy and specificity of the developed tracer (i.e., [18F]F-Nb1053) were evaluated by immuno-positron emission tomography (immunoPET) imaging in disseminated MM.1S-bearing models. [18F]F-Nb1053 was developed with high radiochemical purity (>98%) and excellent immunoreactivity. [18F]F-Nb1053 immunoPET successfully delineated disseminated MM lesions in preclinical MM models. The uptake in the humerus, femur, and tibia was 1.42 ± 0.50%ID/g, 1.35 ± 0.53%ID/g, and 1.48 ± 0.67%ID/g (n = 6), respectively. Tumor uptake of [18F]F-Nb1053 decreased after daratumumab premedication, indicating the superior specificity of the reported probe. This work successfully developed a novel CD38-specific probe [18F]F-Nb1053 that may potentially optimize the management of MM upon clinical translation.

PD-L1 correlated gene expression profiles and tumor infiltrating lymphocytes in pancreatic cancer.

Objective: To study the expression and clinical value of PD-L1 gene in pancreatic cancer, and to predict the role of PD-L1 gene in the development of pancreatic cancer. Methods: The pancreatic cancer datasets were downloaded from the Cancer Genome Atlas (TCGA) and the Oncomine to obtain the PD-L1 gene expression profile and clinical information. Bioinformatics methods were used to analyze the correlation between the expression level of PD-L1 gene in pancreatic cancer and clinicopathological indicators, as well as its influence on prognosis. GSEA and WGCNA analysis was performed to predict the possible pathways of PD-L1 gene regulation in pancreatic cancer. TIMER and MCP-counter were used for PD-L1 with immune infiltration. The genes interact with PD-L1 were also investigated by STING and immunoco-precipitation combined with mass spectrometry analysis (IP-MS). Results: In TCGA database, the overall survival of patients with high expression of PD-L1 gene was significantly lower than that of patients with low expression of PD-L1 gene (χ2 = 12.52, P < 0.001). The samples with high expression of PD-L1 gene showed enrichment of 8 pathways including toll-like receptor signaling pathway and NOD receptor signaling pathway (P < 0.01, FDR < 0.05). Immune infiltration analysis suggested that PD-L1 were associated with monocytic lineage (r = 0.5). The proteins interacting with PD-L1 are mainly concentrated in RNA binding, ribosome, spliceosome and other biological processes or pathways. Conclusion: PD-L1 gene may play an important role in the development of pancreatic cancer and is expected to be a prognostic indicator of pancreatic cancer.

ImmunoPET imaging of multiple myeloma with [68Ga]Ga-NOTA-Nb1053.

PURPOSE: Multiple myeloma (MM) remains incurable and its diagnosis relies heavily on bone marrow aspiration and biopsy. CD38 is a glycoprotein highly specific for MM. Antibody therapeutics (e.g., daratumumab) targeting CD38 have shown encouraging efficacy in treating MM, either as a monotherapy agent or in combination with other regimens. However, efficient stratification of patients who might benefit from daratumumab therapy and timely monitoring of the therapeutic responses are still clinical challenges. This work aims to devise a CD38-targeted imaging strategy and assess its value in diagnosing MMs. METHODS: By labeling a CD38-specific single domain antibody (Nb1053) with 68Ga (t1/2 = 1.1 h), we developed a CD38-targeted immuno-positron emission tomography (immunoPET) imaging probe [68Ga]Ga-NOTA-Nb1053. The probe was developed with good radiochemical yield (> 50%), excellent radiochemical purity (> 99%), and immunoreactivity (> 95%). The diagnostic accuracy of the probe was thoroughly investigated in preclinical MM models. RESULTS: ImmunoPET imaging with [68Ga]Ga-NOTA-Nb1053 specifically depicted all the subcutaneous and orthotopic MM lesions, outperforming the traditional 18F-fluorodeoxyglucose PET and the nonspecific [68Ga]Ga-NOTA-NbGFP immunoPET. More importantly, daratumumab preloading significantly reduced [68Ga]Ga-NOTA-Nb1053 uptake in the disseminated bone lesions, indicating the overlapping targeting epitopes of [68Ga]Ga-NOTA-Nb1053 with that of daratumumab. Furthermore, premedication with sodium maleate or fructose significantly decreased kidney retention of [68Ga]Ga-NOTA-Nb1053 and improved the diagnostic value of the probe in lymphoma models. CONCLUSION: This work successfully developed a novel CD38-targeted immunoPET imaging approach that enabled precise visualization of CD38 and diagnosis of MMs. Upon clinical translation, [68Ga]Ga-NOTA-Nb1053 immunoPET may serve as a valuable CD38-targeted molecular imaging toolbox, facilitating early diagnosis of MM and precise assessment of the therapeutic responses.

PCK1 Regulates Glycolysis and Tumor Progression in Clear Cell Renal Cell Carcinoma Through LDHA.

BACKGROUND: Suppressed gluconeogenesis and increased glycolysis are common in clear cell renal cell carcinoma (ccRCC). Phosphoenolpyruvate carboxykinase 1 (PCK1) is a rate-limiting gluconeogenesis enzyme. However, the role of PCK1 in tumor metabolism and progression remains unclear. METHODS: Artificial modulation of PCK1 (down- and upregulation) in two ccRCC cell lines was performed to explore the role of PCK1 in the glycolytic phenotype and in tumor growth and metastasis in vitro and in vivo. Sixty-two patients with ccRCC underwent 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography. The levels of PCK1 and lactate dehydrogenase A (LDHA) in ccRCC tissues and peritumor tissues were investigated with immunohistochemistry. The relationships between 18F-FDG accumulation and the expression of PCK1 and LDHA were analyzed. The mechanisms underlying the regulation of LDHA by PCK1 were analyzed using in vitro molecular techniques. RESULTS: PCK1 suppressed ccRCC cell growth and metastasis in vitro and inhibited tumorigenesis in nude mice by blocking the aerobic glycolysis pathway. Clinically, low levels of PCK1 expression were associated with poor prognosis in patients with ccRCC. The expression level of PCK1 was negatively correlated with tumor progression, the LDHA expression level and 18F-FDG accumulation in primary ccRCC tissue. We also demonstrated that PCK1 reduces the stability of LDHA through posttranslational regulation. Finally, we showed that the effects of PCK1 on glucose metabolism, cell proliferation and metastasis are mediated via the inhibition of LDHA. CONCLUSION: Our study identified a novel molecular mechanism underlying the Warburg effect. PCK1 may serve as a candidate prognostic biomarker, and targeting the PCK1/LDHA pathway might be a new strategy to selectively inhibit tumor metabolism in human ccRCC.

SIRT5-mediated deacetylation of LDHB promotes autophagy and tumorigenesis in colorectal cancer.

Lactate dehydrogenase B (LDHB) is a glycolytic enzyme that catalyses the conversion of lactate and NAD+ to pyruvate, NADH and H+ . Protons (H+ ) generated by LDHB promote lysosomal acidification and autophagy in cancer, but how this role is regulated has not been defined. In this study, we identified an important post-translational mechanism by which LDHB is regulated during autophagy in cancer cells. Mass spectrometry revealed that protein sirtuin 5 (SIRT5) is a binding partner of LDHB that deacetylated LDHB at lysine-329, thereby promoting its enzymatic activity. Deacetylated LDHB increased autophagy and accelerated the growth of colorectal cancer (CRC) cells. Notably, SIRT5 knockout or inhibition by GW5074 increased LDHB acetylation at K329 and inhibited LDHB activity, which downregulated autophagy and CRC cell growth in vitro and in vivo. Clinically, the LDHB-Ac-K329 staining score in CRC tissues was lower than that in corresponding peritumour tissues. Low LDHB-Ac-K329 status was associated with malignant progression of human CRC and served as a potential prognostic indicator for patients with CRC. Altogether, we conclude that SIRT5-induced deacetylation of LDHB triggers hyperactivation of autophagy, a key event in tumorigenesis. Thus, the SIRT5/LDHB pathway may represent a novel target for treating CRC.

Small ubiquitin-like modifier 1 modification of pyruvate kinase M2 promotes aerobic glycolysis and cell proliferation in A549 human lung cancer cells.

OBJECTIVE: Lung cancer is the leading cause of cancer-related death worldwide. Aerobic glycolysis is considered the seventh hallmark of cancer. The M2 isoform of pyruvate kinase (PKM2) is an important rate-limiting enzyme in glycolytic pathway, and is strongly expressed in several types of cancer. Thus, understanding the underlying mechanisms of regulation of PKM2 is of great value for targeted therapy for lung cancer. PATIENTS AND METHODS: Seventy-three lung adenocarcinoma patients were analyzed in our study. The expression levels of PKM2 were analyzed by immunohistochemistry on tissues. The effect of small ubiquitin-like modifier 1 (SUMO1) on PKM2 expression was investigated using Western blot assay and quantitative polymerase chain reaction. PKM2 SUMO1 modification was determined by in vitro and in vivo SUMOylation assays. 18F-deoxyglucose uptake and lactate production measurements were conducted to research the levels of glycolysis. The level of oxidative phosphorylation in cells was determined by cellular oxygen consumption rate measurements. Cell proliferation assays were carried out to confirm the growth ability of tumor cells. RESULTS: PKM2 was overexpressed in lung adenocarcinoma patients based on immunohistochemical staining. Patients with high PKM2 expression had reduced overall survival rate (P=0.017) and disease-free survival rate (P=0.027) compared with those with low PKM2 expression. SUMO1 promoted PKM2-dependent glycolysis. Western blotting analysis showed that SUMO1 knockdown in A549 cells led to a significant decrease in PKM2 protein expression. PKM2 could be covalently modified by SUMO1 at K336 (Lys336) site. SUMO1 modification of PKM2 at Lys-336 site increased glycolysis and promoted its cofactor functions. Moreover, PKM2 SUMO1 modification promoted the proliferation of A549 cells in vitro. CONCLUSION: This information is important in elucidating a new mechanism of regulation of PKM2, and suggested that SUMO1 modification of PKM2 could be a potential therapeutic target in lung cancer.

Met is involved in TIGAR-regulated metastasis of non-small-cell lung cancer.

TIGAR is a p53 target gene that is known to protect cells from ROS-induced apoptosis by promoting the pentose phosphate pathway. The role of TIGAR in tumor cell invasion and metastasis remains elusive. Here we found that downregulation of TIGAR reduced the invasion and metastasis of NSCLC cells in vitro and in vivo. Immunohistochemical analysis of 72 NSCLC patients showed that TIGAR and Met protein expression was positively correlated with late stages of lung cancer. Besides, patients with high co-expression of TIGAR and Met presented a significantly worse survival. In addition, we found that Met signaling pathway is involved in TIGAR-induced invasion and metastasis. Our study indicates that TIGAR/Met pathway may be a novel target for NSCLC therapy. It is necessary to evaluate the expression of TIGAR before Met inhibitors are used for NSCLC treatment.