The kynurenine derivative 3-HAA sensitizes hepatocellular carcinoma to sorafenib by upregulating phosphatases

Expression of signal recognition particle 14 in hepatocellular carcinoma and its relationship with disease progression and patient survival

OBJECTIVES

To investigate the expression of signal recognition particle 14 (SRP14) in hepatocellular carcinoma (HCC) and its clinical significance.

METHODS

The data of SRP14 expression in HCC were obtained from bioinformatics study, and from investigation with quantitative reverse transcription polymerase chain reaction (qRT-PCR), immunohistochemical staining and Western blotting in clinical samples. The Kaplan-Meier analysis was used to determine the associations between SRP14 mRNA expression and the overall survival, progression-free survival, and disease-specific survival of HCC patients. The effect of SRP14 on the proliferation and migration of HCC cells were determined by EdU staining, MTS, Transwell and wound-healing assays. The potential mechanism for SRP14 regulating HCC was explored through Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analysis as well as qRT-PCR.

RESULTS

According to the data from GSE14520, TNMplot database and clinical samples, compared with paired tumor-adjacent tissues, non-paired tumor-adjacent tissues and normal tissues, the mRNA expression of SPR14 in HCC tissues was upregulated (all P<0.05). In clinical samples, compared with paired tumor-adjacent tissues, the protein expression of SPR14 in HCC tissues was increased (P<0.05). The increased mRNA expression of SRP14 was associated with good overall survival, progression-free survival, and disease-specific survival in HCC patients. SRP14 inhibited the proliferation and migration of HCC cells in vitro. According to the KEGG and GO enrichment analysis, in non-specific HCC, the genes co-expressed with SRP14 may predominantly regulate protein synthesis, processing, and transport, while in nonalcoholic fatty liver disease related HCC, the genes co-expressed with SRP14 could control multiple signaling pathways such as MAPK, cAMP, PI3K-Akt, and Wnt. Mechanistically, SRP14 up-regulated the mRNA expression of tumor suppressor gene GPRC5A inHCC cells (P<0.05).

CONCLUSIONS

SRP14 may regulate HCC progression and influence patient prognosis.

An optimal combination of four active components in Huangqin decoction for the synergistic sensitization of irinotecan against colorectal cancer

BACKGROUND

Irinotecan (CPT-11) is a first-line treatment for advanced colorectal cancer (CRC). Four components (baicalin, baicalein, wogonin, and glycyrrhizic acid) derived from Huangqin Decoction (HQD) have been proven to enhance the anticancer activity of CPT-11 in our previous study.

OBJECTIVE

This study aimed to determine the optimal combination of the four components for sensitizing CPT-11 as well as to explore the underlying mechanism.

METHODS

The orthogonal design method was applied to obtain candidate combinations (Cmb1-9) of the four components. The influence of different combinations on the anticancer effect of CPT-11 was first evaluated in vitro by cell viability, wound healing ability, cloning formation, apoptosis, and cell cycle arrest. Then, a CRC xenograft mice model was constructed to evaluate the anticancer effect of the optimal combination in vivo. Potential mechanisms of the optimal combination exerting a sensitization effect combined with CPT-11 against CRC were analyzed by targeted metabolomics.

RESULTS

In vitro experiments determined that Cmb8 comprised of baicalin, baicalein, wogonin, and glycyrrhizic acid at the concentrations of 17 μM, 47 μM, 46.5 μM and 9.8 μM respectively was the most effective combination. Importantly, the cell viability assay showed that Cmb8 exhibited synergistic anticancer activity in combination with CPT-11. In in vivo experiments, this combination (15 mg/kg of baicalin, 24 mg/kg of baicalein, 24 mg/kg of wogonin, and 15 mg/kg of glycyrrhizic acid) also showed a synergistic anticancer effect. Meanwhile, inflammatory factors and pathological examination of the colon showed that Cmb8 could alleviate the gastrointestinal damage induced by CPT-11. Metabolic profiling of the tumors suggested that the synergistic anticancer effect of Cmb8 might be related to the regulation of fatty acid metabolism.

CONCLUSION

The optimal combination of four components derived from HQD for the synergistic sensitization of CPT-11 against CRC was identified.

PPP1R15A-expressing monocytic MDSCs promote immunosuppressive liver microenvironment in fibrosis-associated hepatocellular carcinoma

Background & Aims

Recent studies demonstrated the importance of fibrosis in promoting an immunosuppressive liver microenvironment and thereby aggressive hepatocellular carcinoma (HCC) growth and resistance to immune checkpoint blockade (ICB), particularly via monocyte-to-monocytic myeloid-derived suppressor cell (M-MDSC) differentiation triggered by hepatic stellate cells (HSCs). We thus aimed to identify druggable targets in these immunosuppressive myeloid cells for HCC therapy.

Methods

M-MDSC signature genes were identified by integrated transcriptomic analysis of a human HSC-monocyte culture system and tumor-surrounding fibrotic livers of patients with HCC. Mechanistic and functional studies were conducted using in vitro-generated and patient-derived M-MDSCs. The therapeutic efficacy of a M-MDSC targeting approach was determined in fibrosis-associated HCC mouse models.

Results

We uncovered over-expression of protein phosphatase 1 regulatory subunit 15A (PPP1R15A), a myeloid cell-enriched endoplasmic reticulum stress modulator, in human M-MDSCs that correlated with poor prognosis and ICB non-responsiveness in patients with HCC. Blocking TGF-β signaling reduced PPP1R15A expression in HSC-induced M-MDSCs, whereas treatment of monocytes by TGF-β upregulated PPP1R15A, which in turn promoted ARG1 and S100A8/9 expression in M-MDSCs and reduced T-cell proliferation. Consistently, lentiviral-mediated knockdown of Ppp1r15a in vivo significantly reduced ARG1+S100A8/9+ M-MDSCs in fibrotic liver, leading to elevated intratumoral IFN-γ+GZMB+CD8+ T cells and enhanced anti-tumor efficacy of ICB. Notably, pharmacological inhibition of PPP1R15A by Sephin1 reduced the immunosuppressive potential but increased the maturation status of fibrotic HCC patient-derived M-MDSCs.

Conclusions

PPP1R15A+ M-MDSC cells are involved in immunosuppression in HCC development and represent a novel potential target for therapies.

Impact and implications

Our cross-species analysis has identified PPP1R15A as a therapeutic target governing the anti-T-cell activities of fibrosis-associated M-MDSCs (monocytic myeloid-derived suppressor cells). The results from the preclinical models show that specific inhibition of PPP1R15A can break the immunosuppressive barrier to restrict hepatocellular carcinoma growth and enhance the efficacy of immune checkpoint blockade. PPP1R15A may also function as a prognostic and/or predictive biomarker in patients with hepatocellular carcinoma.

Sorafenib and tetrakis (4-carboxyphenyl) porphyrin assembled nanoparticles for synergistic targeted chemotherapy and sonodynamic therapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is characterized by a high degree of malignancy and mortality. Sorafenib (SOR), a multi-kinase inhibitor, is clinically used in the treatment of HCC. However, SOR suffers from serious side effects and drug resistance. The development of novel therapeutic strategies for HCC therapy is urgently needed. Sonodynamic therapy (SDT) has unique advantages in treating deep tumors due to the merits of deep tissue penetration, low side effects, and the absence of drug resistance. Here, we developed multifunctional nanoparticles (NPs) termed SOR-TCPP@PEG-FA by assembling SOR, tetrakis (4-carboxyphenyl) porphyrin (TCPP), and folic acid (FA)-modified DSPE-PEG. The FA group enhances the tumor targeting capability of these NPs, while TCPP generates ROS under ultrasound (US) irradiation, which are toxic to tumor cells, and SOR with chemotherapeutic effects is released, thus realizing the synergistic SDT and chemotherapy of tumors.

On the benefits of the tryptophan metabolite 3-hydroxyanthranilic acid in Caenorhabditis elegans and mouse aging

Tryptophan metabolism through the kynurenine pathway influences molecular processes critical to healthy aging including immune signaling, redox homeostasis, and energy production. Aberrant kynurenine metabolism occurs during normal aging and is implicated in many age-associated pathologies including chronic inflammation, atherosclerosis, neurodegeneration, and cancer. We and others previously identified three kynurenine pathway genes-tdo-2, kynu-1, and acsd-1-for which decreasing expression extends lifespan in invertebrates. Here we report that knockdown of haao-1, a fourth gene encoding the enzyme 3-hydroxyanthranilic acid (3HAA) dioxygenase (HAAO), extends lifespan by ~30% and delays age-associated health decline in Caenorhabditis elegans. Lifespan extension is mediated by increased physiological levels of the HAAO substrate 3HAA. 3HAA increases oxidative stress resistance and activates the Nrf2/SKN-1 oxidative stress response. In pilot studies, female Haao knockout mice or aging wild type male mice fed 3HAA supplemented diet were also long-lived. HAAO and 3HAA represent potential therapeutic targets for aging and age-associated disease.

Modulation of T cells by tryptophan metabolites in the kynurenine pathway

Lymphocytes maturing in the thymus (T cells) are key factors in adaptive immunity and the regulation of inflammation. The kynurenine pathway of tryptophan metabolism includes several enzymes and compounds that can modulate T cell function, but manipulating these pharmacologically has not achieved the expected therapeutic activity for the treatment of autoimmune disorders and cancer. With increasing knowledge of other pathways interacting with kynurenines, the expansion of screening methods, and the application of virtual techniques to understanding enzyme structures and mechanisms, details of interactions between kynurenines and other pathways are being revealed. This review surveys some of these alternative approaches to influence T cell function indirectly via the kynurenine pathway and summarizes the most recent work on the development of compounds acting directly on the kynurenine pathway.

Effects of 3-HAA on HCC by Regulating the Heterogeneous Macrophages-A scRNA-Seq Analysis

Kynurenine derivative 3-hydroxyanthranilic acid (3-HAA) is known to regulate the immune system and exhibit anti-inflammatory activity by inhibiting T-cell cytokine secretion and influencing macrophage activity. However, the definite role of 3-HAA in the immunomodulation of hepatocellular carcinoma (HCC) is largely unexplored. An orthotopic HCC model and treated with 3-HAA by intraperitoneal injection is developed. Furthermore, cytometry by time-of-flight (CyTOF) and single-cell RNA sequencing (scRNA-seq) analyses are carried out to define the immune landscape of HCC. It is found that 3-HAA treatment can significantly suppress tumor growth in the HCC model and alter the level of various cytokines in plasma. CyTOF data shows that 3-HAA significantly increases the percentage of F4/80hi CX3CR1lo Ki67lo MHCIIhi macrophages and decreases the percentage of F4/80lo CD64+ PD-L1lo macrophages. scRNA-seq analyses demonstrate that 3-HAA treatment is proved to regulate the function of M1 macrophages, M2 macrophages, and proliferating macrophages. Notably, 3-HAA inhibits the proinflammatory factors TNF and IL-6 in multiple cell subsets, including resident macrophages, proliferating macrophages, and pDCs. This study reveals the landscape of immune cell subsets in HCC in response to 3-HAA, indicating that 3-HAA may be a promising therapeutic target for HCC.

Interactions of IDO and the Kynurenine Pathway with Cell Transduction Systems and Metabolism at the Inflammation-Cancer Interface

The mechanisms underlying a relationship between inflammation and cancer are unclear, but much emphasis has been placed on the role of tryptophan metabolism to kynurenine and downstream metabolites, as these make a substantial contribution to the regulation of immune tolerance and susceptibility to cancer. The proposed link is supported by the induction of tryptophan metabolism by indoleamine-2,3-dioxygenase (IDO) or tryptophan-2,3-dioxygenase (TDO), in response to injury, infection or stress. This review will summarize the kynurenine pathway and will then focus on the bi-directional interactions with other transduction pathways and cancer-related factors. The kynurenine pathway can interact with and modify activity in many other transduction systems, potentially generating an extended web of effects other than the direct effects of kynurenine and its metabolites. Conversely, the pharmacological targeting of those other systems could greatly enhance the efficacy of changes in the kynurenine pathway. Indeed, manipulating those interacting pathways could affect inflammatory status and tumor development indirectly via the kynurenine pathway, while pharmacological modulation of the kynurenine pathway could indirectly influence anti-cancer protection. While current efforts are progressing to account for the failure of selective IDO1 inhibitors to inhibit tumor growth and to devise means of circumventing the issue, it is clear that there are wider factors involving the relationship between kynurenines and cancer that merit detailed consideration as alternative drug targets.

PPARs and the Kynurenine Pathway in Melanoma-Potential Biological Interactions

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors involved in various physiological and pathological processes within the skin. PPARs regulate several processes in one of the most aggressive skin cancers, melanoma, including proliferation, cell cycle, metabolic homeostasis, cell death, and metastasis. In this review, we focused not only on the biological activity of PPAR isoforms in melanoma initiation, progression, and metastasis but also on potential biological interactions between the PPAR signaling and the kynurenine pathways. The kynurenine pathway is a major pathway of tryptophan metabolism leading to nicotinamide adenine dinucleotide (NAD+) production. Importantly, various tryptophan metabolites exert biological activity toward cancer cells, including melanoma. Previous studies confirmed the functional relationship between PPAR and the kynurenine pathway in skeletal muscles. Despite the fact this interaction has not been reported in melanoma to date, some bioinformatics data and biological activity of PPAR ligands and tryptophan metabolites may suggest a potential involvement of these metabolic and signaling pathways in melanoma initiation, progression, and metastasis. Importantly, the possible relationship between the PPAR signaling pathway and the kynurenine pathway may relate not only to the direct biological effect on melanoma cells but also to the tumor microenvironment and the immune system.

Deciphering the molecular mechanism of tetrandrine in inhibiting hepatocellular carcinoma and increasing sorafenib sensitivity by combining network pharmacology and experimental evaluation

CONTEXT

The mechanism of tetrandrine (TET) in hepatocellular carcinoma (HCC) progression and sorafenib (Sora) chemosensitivity deserves investigation.

OBJECTIVE

Using network pharmacology approaches to elucidate the mechanisms of TET in HCC.

MATERIALS AND METHODS

CCK-8, colony formation, and flow cytometry assays were used to measure cell phenotypes. BALB/c nude mice were divided into Control, Sora (10 mg/kg), TET (50 mg/kg), and TET + Sora (10 mg/kg Sora plus 50 mg/kg TET) groups to evaluate the antitumor effects of TET for 21 days. Sora and TET were given by intraperitoneal injection or oral gavage.

RESULTS

For SMMC7721 (IC₅₀ = 22.5 μM) and PLC8024 (IC₅₀ = 18.4 μM), TET (10, 20 μM) reduced colony number (0.68 ± 0.04- and 0.50 ± 0.04-fold, 0.56 ± 0.04- and 0.42 ± 0.02-fold), induced cell cycle arrest at G0/G1 stage (1.22 ± 0.03- and 1.39 ± 0.07-fold, 1.37 ± 0.06- and 1.55 ± 0.05-fold), promoted apoptosis (2.49 ± 0.26- and 3.63 ± 0.33-fold, 2.74 ± 0.42- and 3.73 ± 0.61-fold), and inactivated PI3K/AKT/mTOR signalling. Sora (10 μM) decreased cell proliferation, enhanced apoptosis, and inhibited PI3K/AKT/mTOR signalling, and these effects were further aggravated in the combination group. Activating PI3K/AKT/mTOR reversed the effects of TET on cell proliferation and Sora sensitivity. In the combination group, tumour volumes and weights were decreased to 202.3 ± 17.4 mm³ and 151.5 ± 25.8 mg compared with Sora (510.6 ± 48.2 mm³ and 396.7 ± 33.5 mg).

DISCUSSION AND CONCLUSIONS

TET enhances Sora sensitivity by inactivating PI3K/AKT/mTOR, suggesting the potential of TET as a chemosensitizer in HCC.

Dual Effect of Tryptamine on Prostate Cancer Cell Growth Regulation: A Pilot Study

Abnormal tryptophan metabolism is linked to cancer and neurodegenerative diseases, and tryptophan metabolites have been reported as potential prostate cancer (PCa) biomarkers. However, little is known about the bioactivities of tryptophan metabolites on PCa cell growth. In this study, MTT and transwell assays were used to study the cytotoxicities of 13 major tryptophan metabolites on PCa and normal prostate epithelial cell lines. Ultraperformance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) was used to analyze metabolic changes in cells treated with tryptamine. Flow cytometry, confocal imaging, and Western blot were used to test the apoptosis induced by tryptamine. It was shown that tryptamine had obvious inhibitory effects on PCa cell lines PC-3 and LNCaP, stronger than those on the normal prostate cell line RWPE-1. Tryptamine was further shown to induce apoptosis and inhibit PC-3 cell migration. Metabolic changes including amino acid metabolism related to cell proliferation and metastasis were found in PC-3 cells treated with tryptamine. Furthermore, a PC-3 xenograft mouse model was used to study the effect of tryptamine in vivo. The intratumoral injection of tryptamine was demonstrated to significantly reduce the tumor growth and tumor sizes in vivo; however, intraperitoneal treatment resulted in increased tumor growth. Such dual effects in vivo advanced our understanding of the bioactivity of tryptamine in regulating prostate tumor development, in addition to its major role as a neuromodulator.

Comparative Response of HCC Cells to TKIs: Modified in vitro Testing and Descriptive Expression Analysis

Introduction

Although the treatment paradigm for hepatocellular carcinoma (HCC) has recently shifted in favour of checkpoint inhibitor (CPI)-based treatment options, the tyrosine kinase inhibitors (TKI) currently approved for the treatment of HCC are expected to remain the cornerstone of HCC treatment alone or in combination with CPIs. Despite considerable research efforts, no biomarker capable of predicting the response to specific TKIs has been validated. Thus, personalized approaches to HCC may aid in determining optimal treatment lines for 2nd and 3rd lines. To identify new biomarkers, we examined differential sensitivity and investigated potential transcriptomic predictors.

Methods

To this aim, the sensitivity of nine HCC cell lines to sorafenib, lenvatinib, regorafenib, and cabozantinib was evaluated by a prolonged treatment scheme to determine their respective growth rate inhibition concentrations (GR50). Subgroups discriminated by GR50 values underwent differential expression and gene set enrichment analysis (GSEA).

Results

The nine cell lines showed broadly different sensitivities to different TKIs. GR50 values of sorafenib and regorafenib clustered closer in all cell lines, whereas treatments with lenvatinib and cabozantinib showed diversified GR50 values. GSEA showed the activation of specific pathways in sensitive vs non-sensitive cell lines. A signature consisting of 14 biomarkers (GAGE12H, GJB6, PTCHD3, PRH1-PRR4, C6orf222, HBB, C17orf99, GOLGA6A, CRYAA, CCL23, RP11-347C12.3, RP11-514O12.4, FAM180B, and TMPRSS4) discriminates the cell lines' response into three distinct treatment profiles: 1) equally sensible to sorafenib, regorafenib and cabozantinib, 2) sensible to lenvatinib, and 3) more sensible to regorafenib than sorafenib.

Conclusion

We observed diverse responses to either of the four TKIs. Subgroup analysis of TKI effectiveness showed distinct transcriptomic profiles and signaling pathways associated with responsiveness. This prompts more extensive studies to explore and validate pharmacogenomic and transcriptomic strategies for a personalized treatment approach, particularly after the failure of CPI treatment.

The pro-tumorigenic activity of p38γ overexpression in nasopharyngeal carcinoma

It is urgent to identify and validate biomarkers for early diagnosis and efficient treatment of nasopharyngeal carcinoma (NPC). Recent studies have proposed p38 gamma (p38γ) as a cyclin-dependent kinase (CDK)-like kinase that phosphorylates retinoblastoma (Rb) to promote cyclins expression and tumorigenesis. Here the Gene Expression Profiling Interactive Analysis (GEPIA) database and results from the local NPC tissues demonstrate that p38γ is significantly upregulated in NPC tissues, correlating with poor overall survival. Furthermore, p38γ mRNA and protein expression is elevated in established NPC cell lines (CNE-1 HONE-1 and CNE-2) and primary human NPC cells, but low expression detected in human nasal epithelial cells. In established and primary NPC cells, p38γ depletion, using the shRNA strategy or the CRISPR/Cas9 gene-editing method, largely inhibited cell growth, proliferation and migration, and induced significant apoptosis activation. Contrarily, ectopic p38γ overexpression exerted opposite activity and promoted NPC cell proliferation and migration. Retinoblastoma (Rb) phosphorylation and cyclin E1/A expression were decreased in NPC cells with p38γ silencing or knockout, but increased after p38γ overexpression. Moreover, mitochondrial subcellular p38γ localization was detected in NPC cells. Significantly, p38γ depletion disrupted mitochondrial functions, causing mitochondrial depolarization, reactive oxygen species production, oxidative injury and ATP depletion in NPC cells. In vivo, intratumoral injection of adeno-associated virus-packed p38γ shRNA potently inhibited primary human NPC xenograft growth in nude mice. In p38γ shRNA virus-injected NPC xenograft tissues, p38γ expression, Rb phosphorylation, cyclin E1/A expression and ATP levels were dramatically decreased. Taken together, we conclude that p38γ overexpression is required for NPC cell growth, acting as a promising therapeutic target of NPC.

Emodin alleviates aortic valvular calcification by inhibiting the AKT/FOXO1 pathway

BACKGROUND

Valvular calcification commonly occurs in elderly individuals, and is increasingly considered an important economic and health burden. However, no efficient drugs against valvular calcification are available. The present work aimed to examine emodin's suppressive effect on high-calcium-dependent valve calcification and explore the underpinning mechanisms.

METHODS

Experiments were carried out in mice receiving vitamin D (Vit D) to induce valvular calcification.

RESULTS

Cell viability and apoptosis assays demonstrated celastrol suppressed proliferation and increased apoptosis in porcine aortic valve interstitial cells (PAVICs) at concentrations higher than 10 μM. Emodin (5 μM) attenuated the upregulation of osteogenic genes as well as calcium accumulation in PAVICs under high-calcium conditions. The elevations of calcium content in serum and valve, and calcium accumulation in valve and artery were suppressed by emodin in mice with valvular calcification after joint treatment with adenine and Vit D. In addition, p-AKT and p-FOXO1 were upregulated in PAVICs under high-calcium conditions, and this effect was reversed by emodin treatment. SC79, an AKT activator, reversed emodin's suppressive effects on increased calcium content, calcium deposition and osteogenic gene expression in PAVICs induced by calcific medium.

CONCLUSIONS

These data demonstrated emodin alleviates high-calcium-associated valvular calcification via AKT/FOXO1 signaling suppression, providing new insights into therapeutic strategies for clinical valvular calcification.

Characterization of morphological alterations in micropapillary adenocarcinoma of the lung using an established cell line

Micropapillary adenocarcinoma of the lung is a type of cancer associated with a poor prognosis and is characterized by the presence of tumor cells with a ring‑like glandular structure floating within alveolar spaces. In the present study, the association between its morphological, biochemical and immunohistochemical characteristics, and malignancy was investigated using the KU‑Lu‑MPPt3 cell line established from a patient with MIP adenocarcinoma. Two subpopulations of KU‑Lu‑MPPt3 cells, namely adhesive (AD) and clumpy and suspended (CS) cells, were prepared and subjected to DNA microarray, reverse transcription‑quantitative PCR, western blot and immunostaining analyses. Protein expression patterns were compared between the cell types and their derived tissues using immunostaining. The results revealed similar protein expression patterns between the tumor cells found in the alveolar spaces and CS cells, which exhibited morphological characteristic of MIP adenocarcinoma. Based on the results of DNA microarray analysis, the present study then focused on Akt and focal adhesion kinase (FAK), which were markedly activated in the KU‑Lu‑MPPt3 CS and AD cells, respectively. Following KU‑Lu‑MPPt3 CS cell plating onto collagen‑coated culture dishes, some cells exhibited a transformation of their morphology into KU‑Lu‑MPPt3 AD‑like cells within a few days, and their Akt and FAK activities were similar to those of the AD cells. Additionally, the inhibition of Akt and FAK activities with Akt and FAK inhibitors reduced KU‑Lu‑MPPt3 CS cell adhesion and proliferation. Thus, the aforementioned results indicated that the phosphorylation of FAK and Akt may play a crucial role in the regulation of KU‑Lu‑MPPt3 CS cell adhesion and proliferation, respectively. Furthermore, the malignant potential of MIP adenocarcinoma may be attributed to these morphological and biochemical alterations in the KU‑Lu‑MPPt3 cells.

Kynurenine derivative 3-HAA is an agonist ligand for transcription factor YY1

The 3-hydroxyanthranilic acid (3-HAA), a derivative of kynurenine, was reported to suppress tumor growth. However, the function of 3-HAA largely remains unclear. Here, we report that 3-hydroxyanthranilic acid (3-HAA) is lower in tumor cells, while adding exogenous 3-HAA induces apoptosis in hepatocellular carcinoma by binding YY1. This 3-HAA binding of YY1 leads to phosphorylation of YY1 at the Thr 398 by PKCζ, concomitantly enhances YY1 chromatin binding activity to increase expression of target genes. These findings demonstrate that 3-HAA is a ligand of YY1, suggesting it is a promising therapeutic candidate for HCC.

3-hydroxyanthranic acid increases the sensitivity of hepatocellular carcinoma to sorafenib by decreasing tumor cell stemness

Sorafenib is the FDA-approved first-line target drug for HCC patients. However, sorafenib only confers 3–5 months of survival benefit with <30% of HCC patients. Thus, it is necessary to develop a sensitizer for hepatocellular carcinoma (HCC) to sorafenib. Here, we report that in representative HCC cell lines (SMMC-7721 and PLC8024) that are insensitive to sorafenib, 3-HAA (50 μM) significantly enhances cell sensitivity to sorafenib to an extent that could not be explained by additive effects. In nude mice carrying HCC xenograft, tumor growth is inhibited by sorafenib (10 mg/kg/day) or 3-HAA (100 mg/kg/day) alone. When used in combination, the treatment effectively prevents the xenograft from growing. In a set of mechanistic experiments, we find enhanced AKT activation and increased proportion of CD44⁺CD133⁺ cells in sorafenib-resistant HCC cells and tissues. The proportion of CD44⁺CD133⁺ cells is reduced upon 3-HAA treatment in both cultured cells and mouse xenografts, suggesting that 3-HAA could decrease the stemness of HCC. We also detect decreased phosphorylation of AKT, a regulator of the GSK3β/β-catenin signaling upon 3-HAA treatment. The AKT activator SC79 activates GSK3 β/β-catenin signaling while the Wnt inhibitor XAV-939 abolishes 3-HAA inhibition of HCC growth in vitro and in mice. The current study demonstrates that 3-HAA sensitizes HCC cells to sorafenib by reducing tumor stemness, suggesting it is a promising molecule for HCC therapy.