Posttranslational regulatory mechanism of PD-L1 in cancers and associated opportunities for novel small-molecule therapeutics.

Despite the tremendous progress in cancer research over the past few decades, effective therapeutic strategies are still urgently needed. Accumulating evidence suggests that immune checkpoints are the cause of tumor immune escape. PD-1/PD-L1 are among them. Posttranslational modification is the most critical step for protein function, and the regulation of PD-L1 by small molecules through posttranslational modification is highly valuable. In this review, we discuss the mechanisms of tumor cell immune escape and several posttranslational modifications associated with PD-L1 and describe examples in which small molecules can regulate PD-L1 through posttranslational modifications. Herein, we propose that the use of small molecule compounds that act by inhibiting PD-L1 through posttranslational modifications is a promising therapeutic approach with the potential to improve clinical outcomes for cancer patients.

Patients with endometriosis may experience worse clinical manifestations and therapeutic outcomes during COVID-19 in western China- a case series comparative analysis.

BACKGROUND: Endometriosis is a crippling, ongoing, chronic inflammatory condition. The management of these patients has been impacted by the current COVID-19 pandemic, which is still controversial. This study compared the clinical therapy outcomes and psychological scores between before and during- the epidemic. METHOD: The data of patients who were diagnosed with endometriosis in the Department of Gynecology, Chongqing Traditional Chinese Medicine Hospital from January 2018 to December 2022 were collected. The patients were divided into pre- and intra-COVID groups. The treatment results and psychological status of the two groups were compared. RESULTS: A total of 1022 patients with endometriosis were enrolled, with a mean age of 33.16 ± 9.81 years and a BMI of 23.90 ± 3.04 kg/m2, of which 434 cases (434/1022, 42.5%) were in the pre-COVID group and 588 cases (588/1022, 57.5%) in the intra-COVID group. Both groups were well balanced for age, BMI, history of abdominopelvic surgery, family relationships, education level, and duration between initial diagnosis and admission. Compared to the Pre-COVID group, the intra-COVID group had a higher proportion of patients with chronic pelvic pain (297/434, 68.4% vs. 447/588, 76.0%, p = 0.007) and dysmenorrhea (249/434, 62.8% vs. 402/588, 70.0%, p < 0.001), more patients requiring surgery (93/434, 21.4% vs. 178/588, 30.3%, p = 0.002) and longer hospital stays (5.82 ± 2.24 days vs. 7.71 ± 2.15 days, p < 0.001). A total of 830 questionnaires were completed. In the Intra-COVID group, PHQ-2 (2 (2, 3) vs. 3 (2,4), p < 0.001), GAD-2 (2 (1, 2) vs. 3 (2, 3), p < 0.001), PHQ-4 (4 (3, 5) vs. 5 (4, 7), EHP-5 (20.26 ± 6.05 vs. 28.08 ± 7.95, p < 0.001) scores were higher than that in the pre-COVID group, while BRS (3.0 (2.2, 4.0) vs. 2.4 (1.8, 3.8), p = 0.470) were not significantly different. CONCLUSION: During the COVID-19 epidemic, patients with endometriosis may have reduced visits to the hospital, more severe related symptoms, longer length of hospital stays, and worse quality of life, with the possible cause being a disturbance in hormone levels through increased anxiety and depression. This provides a valid clinical basis for optimizing the management of patients with endometriosis and for early psychological intervention during the epidemic.

Molecular mechanisms of ferroptosis and its antitumor applications in natural products.

Ferroptosis, an iron-dependent form of regulated cell death, results in lipid peroxidation of polyunsaturated fatty acids in the cell membrane, which is catalyzed by iron ions and accumulated to lethal levels. It is mechanistically distinct from other forms of cell death, such as apoptosis, pyroptosis, and necroptosis, so it may address the problem of cancer resistance to apoptosis and provide new therapeutic strategies for cancer treatment, which has been intensively studied over the past few years. Notably, considerable advances have been made in the antitumor research of natural products due to their multitargets and few side effects. According to research, natural products can also induce ferroptosis in cancer therapies. In this review we summarize the molecular mechanisms of ferroptosis, introduce the key regulatory genes of ferroptosis, and discuss the progress of natural product research in the field of ferroptosis to provide theoretical guidance for research on natural product-induced ferroptosis in tumors.

PIWIL1 promotes gastric cancer via a piRNA-independent mechanism.

Targeted cancer therapy aims to achieve specific elimination of cancerous but not normal cells. Recently, PIWI proteins, a subfamily of the PAZ-PIWI domain (PPD) protein family, have emerged as promising candidates for targeted cancer therapy. PPD proteins are essential for small noncoding RNA pathways. The Argonaute subfamily partners with microRNA and small interfering RNA, whereas the PIWI subfamily partners with PIWI-interacting RNA (piRNA). Both PIWI proteins and piRNA are mostly expressed in the germline and best known for their function in transposon silencing, with no detectable function in mammalian somatic tissues. However, PIWI proteins become aberrantly expressed in multiple types of somatic cancers, thus gaining interest in targeted therapy. Despite this, little is known about the regulatory mechanism of PIWI proteins in cancer. Here we report that one of the four PIWI proteins in humans, PIWIL1, is highly expressed in gastric cancer tissues and cell lines. Knocking out the PIWIL1 gene (PIWIL1-KO) drastically reduces gastric cancer cell proliferation, migration, metastasis, and tumorigenesis. RNA deep sequencing of gastric cancer cell line SNU-1 reveals that KO significantly changes the transcriptome, causing the up-regulation of most of its associated transcripts. Surprisingly, few bona fide piRNAs exist in gastric cancer cells. Furthermore, abolishing the piRNA-binding activity of PIWIL1 does not affect its oncogenic function. Thus, PIWIL1 function in gastric cancer cells is independent of piRNA. This piRNA-independent regulation involves interaction with the UPF1-mediated nonsense-mediated mRNA decay (NMD) mechanism. Altogether, our findings reveal a piRNA-independent function of PIWIL1 in promoting gastric cancer.

The Discovery and Anti-Colorectal Cancer Activities of Cembranolides from the South China Sea Soft Coral Sinularia pendunculata.

A new cembranolide, namely, sinupendunculide A (1), along with eight known related compounds (2-9), was isolated from the South China Sea Soft coral Sinularia pendunculata. The structure of sinupendunculide A (1) was established by extensive spectroscopic analysis and X-ray diffraction experiments. In a bioassay, anti-colorectal cancer (CRC) activity was performed, and the results showed that several compounds exhibited cytotoxicity against RKO cells, and a preliminary structure-activity relationship was analysed. Meanwhile, the most effective compound 7 was proven to increase reactive oxygen species levels, which promoted cell apoptosis and inhibited cell proliferation.

Consolidation radiographic morphology can be an indicator of the pathological basis and prognosis of partially solid nodules.

BACKGROUND: Part-solid nodules (PSNs) have gradually shifted to defining special clinical subtypes. Commonly, the solid portions of PSNs show various radiological morphologies, of which the corresponding pathological basis and prognosis are unclear. We conducted a radiological-pathological evaluation to determine the histopathologic basis of different consolidation radiographic morphologies related to prognosis. MATERIALS AND METHODS: A cohort of 275 patients with a surgical pathological diagnosis of lung adenocarcinoma were enrolled. Preoperative computed tomography (CT) images of the PSNs were recorded and assessed. A panel of 103 patients with complete pathological specimens was selected to examine the radiological-pathological associations, and follow-up was performed to identify the prognosis. RESULTS: Of the 275 patients, punctate consolidation was observed radiologically in 43/275 (15.7%), stripe consolidation in 68/275 (24.7%), and irregular consolidation in 164/275 (59.6%) patients. The radiological morphology of the solid components was significantly associated with the histopathological subtypes (P < 0.001). Visual punctate solid components on CT correlated with tertiary lymphoid structures, stripe solid components on CT correlated with fibrotic scar, and irregular solid components on CT correlated with invasion. PSNs with regular consolidation had a better prognosis than those with irregular consolidation. CONCLUSION: Radiological morphology of solid components in PSNs can indicate the pathological basis and is valuable for prognosis. In particular, irregular solid components in PSNs usually indicate serious invasive growth, which should be taken with caution during assessment.

Radiographic features and prognosis of early- and late-onset non-small cell lung cancer immune checkpoint inhibitor-related pneumonitis.

BACKGROUND: Immunotherapy is becoming a standard of care for non-small cell lung cancer (NSCLC). Checkpoint inhibitor-associated pneumonia (CIP) is a rare and potentially life-threatening event that can occur at any time during tumor immunotherapy. However, there may be differences in the radiological patterns and prognosis of CIP during different periods. This study aimed to investigate the radiographic features and prognosis of early- and late-onset immune-related pneumonitis. METHODS: We retrospectively analyzed the clinical data of 677 NSCLC patients receiving immunotherapy to identify 32 patients with CIP, analyzed the clinical and radiographic data, and summarized the radiological features and prognosis of early- and late-onset CIP. RESULTS: CIP had an incidence of 4.7%, a median onset time of 10 weeks, and a mortality of 28.1%. Among these, CIP included 14 early-onset cases, where grade ≥ 3 CIP accounted for 92.9%, main radiographic pattern was organizing pneumonia (OP)-like pattern, and mortality was 50.0%. We also identified 18 late-onset CIPs, where grade ≥ 3 CIP accounted for 50.0%, main radiographic pattern was nonspecific interstitial pneumonia (NSIP)-like pattern, and mortality was 11.1%. The overall survival rate of the early-onset group was significantly lower than that of the late-onset group (P < 0.05). CONCLUSION: Early-onset CIP cases were higher in the Common Terminology Criteria for Adverse Events (CTCAE v5.0) grade and mainly presented with an OP-like radiographic pattern; whereas, late-onset CIP cases were lower in CTCAE grade and mainly presented with an NSIP-like radiographic pattern. Finally, the prognosis of the early-onset CIP group was poorer than that of the late-onset CIP group. We believe that this study will be helpful for clinicians for making early diagnosis and deciding treatment modalities for patients with CIP.

Circulating miR-221/222 reduces CD4+ T cells by inhibiting CD4 expression in colorectal cancer.

Many patients with cancers have low levels of CD4+ in their peripheral blood. However, the molecular mechanism is still unclear. Here, we found that the blood levels of miR-221 and miR-222 were dramatically increased in patients with colorectal cancer (CRC), and both circulating miR-211 and miR-222 served as sensitive diagnostic markers with an area under the curve of 0.8790 and 0.9148, respectively. Transfection of either miR-221 or miR-222 resulted in the reduction of the surface CD4 antigen level but not the surface CD8 antigen level. The luciferase reporter assay showed that miR-221/222 directly regulated CD4 expression in human primary T cells. These data showed that miR-221/222 levels were upregulated in the blood of patients with CRC and that the expression of CD4 in human primary T cells was inhibited by miR-221/222. These findings provide a novel strategy for modulating the number of CD4+ T cells in the blood and further adjusting the microenvironment suitable for immunotherapy.

Exosomal piRNA profiling revealed unique circulating piRNA signatures of cholangiocarcinoma and gallbladder carcinoma.

Cholangiocarcinoma (CCA) and gallbladder carcinoma (GBC) are biliary tract cancers with poor five-year survival and high recurrence rates. Both CCA and GBC patients suffer from lack of circulating diagnostic biomarkers at the early stage. Extracellular vesicles, especially exosomes, have been emerged as promising diagnostic sources for cancers due to easy and quick accessibility. Hence, identification of exosomal biomarkers provides a novel strategy for CCA and GBC diagnosis. Here, five CCA patients and four GBC patients were enrolled for exosomal small RNA sequencing. Our data showed that exosomal piwi-interacting RNA (piRNA) populations were altered in the plasma of CCA and GBC patients. In comparison to healthy individuals, 694 and 323 piRNAs were upregulated in CCA and GBC, respectively, while 36 and 191 piRNAs were downregulated. Interestingly, sequencing results predicted that piR-2660989, piR-10506469, piR-20548188, piR-10822895, piR-hsa-23209, and piR-18044111 were upregulated in both CCA and GBC plasma. Importantly, we further included blood samples from 50 health individuals, 40 CCA patients, and 25 GBC patients and found that piR-10506469 were significantly increased in the exosomes of plasma from both CCA and GBC patients. Moreover, we analyzed the expression levels of differentially expressed exosomal piRNAs in the plasma of CCA and GBC patient before and after surgeries and found that piR-10506469 and piR-20548188 were significantly decreased in patients underwent surgeries. Taken together, our data revealed that exosomal piRNAs those are differentially expressed in CCA and GBC plasma may serve as potential biomarkers for the diagnosis of CCA and GBC.

Exosomal miRNA profiling before and after surgery revealed potential diagnostic and prognostic markers for lung adenocarcinoma.

Exosome is a crucial manner for cancer cell to cell communication and circulating exosomes sever as promising diagnostic and prognostic markers for various types of diseases. A predominant type of cargo of exosome is small RNAs, especially miRNAs. Here, we profiled plasma exosomal miRNAs of six lung adenocarcinoma patients before and after surgery, as well as six healthy individuals as normal control. Our profiling revealed 38 upregulated and 37 downregulated exosomal miRNAs in the plasma of lung adenocarcinoma patients. Additionally, we found that most upregulated miRNAs were increased in the lung adenocarcinoma samples of TCGA database. We further evaluated the correlation between the upregulated exosomal miRNAs and overall survival with Kaplan-Meier survival analysis using online databases. Our results suggested that exosomal miR-151a-5p, miR-10b-5p, miR-192-5p, miR-106b-3p, and miR-484 are potential prognostic markers for lung adenocarcinoma. Importantly, we validated candidate miRNAs in lung adenocarcinoma patients before and after surgery as well as in healthy controls and found that miR-484 was significantly increased in the plasma of lung adenocarcinoma patients and strikingly decreased post-surgery. Hence, we provided novel information on lung adenocarcinoma-derived exosomal miRNA and potential non-invasive diagnostic and prognostic markers for lung adenocarcinoma.

Bcl-3 promotes proliferation and chemosensitivity in BL1 subtype of TNBC cells.

Bcl-3 is an established oncogene in diverse malignant tumors. In this study, we investigated a dual role of Bcl-3 in BL1-subtype triple-negative breast cancer (TNBC). The BL1-subtype TNBC is featured by increasing cell cycle gene expression and the highest sensitivity to chemotherapy among all subtypes. Bcl-3 is associated with a better prognosis in BL1 patients. Bcl-3 knockdown in BL1 cell MDA-MB-468 induces the inhibition of cell proliferation and the G1/S transition arrest by promoting p27 and reducing the expressions of c-Myc and skp2 at mRNA and protein levels. Meanwhile, Bcl-3 enhances the sensitivity of MDA-MB-468 to chemotherapeutics ABX and PTX. Furthermore, the regulation mechanisms are restricted to BL1 cell and do not occur in SUM159PT, a typical MSL subtype of TNBC cell. These data suggest that Bcl-3 may be a potential clinical biomarker for diagnosis, treatment, and prognosis of patients with BL1-subtype TNBC.

The Role of PIWIL4, an Argonaute Family Protein, in Breast Cancer.

P-element-induced wimpy testis (PIWI) proteins bind to PIWI-interacting RNAs and play key roles in the biogenesis and functions of PIWI-interacting RNAs. It has been reported that PIWI proteins are essential for stem cell self-renewal and germline development in diverse organisms and that they are ectopically expressed in multiple forms of cancer. However, the role of PIWI in cancer remains elusive. Here we report that one of the four PIWI proteins in humans, PIWIL4, is highly expressed in both breast cancer tissues and the cytoplasm of MDA-MB-231 cells derived from breast cancer. Reducing PIWIL4 expression drastically impairs the migration ability of MDA-MB-231 cells, significantly increases their apoptosis, and mildly affects their proliferation. Our transcriptome and proteome analysis reveal that these functions are at least partially achieved via the PIWIL4 regulation of TGF-ß and FGF signaling pathways and MHC class II proteins. These findings suggest that PIWIL4 may serve as a potential therapeutic target for breast cancer.

A microRNA 221- and 222-mediated feedback loop maintains constitutive activation of NFκB and STAT3 in colorectal cancer cells.

BACKGROUND & AIMS: Constitutive activation of the transcription factors nuclear factor κB (NF-κB) and STAT3 is involved in the development and progression of human colorectal cancer (CRC). Little is known about how these factors become activated in cancer cells. We investigated whether microRNA miR-221 and miR-222 regulate NF-κB and signal transducer and activator of transcription 3 (STAT3) activation in human CRC cell lines. METHODS: CRC cell lines (HCT116 and RKO) were transfected with miR-221 or miR-222 mimics or inhibitors. The activity levels of NF-κB and STAT3 were measured in dual luciferase reporter assays. We used immunoblot and real-time polymerase chain reaction analyses to measure protein and messenger RNA (mRNA) levels. Cells were analyzed by proliferation, viability, and flow cytometry analyses. Mice were given injections of azoxymethane, followed by dextran sodium sulfate, along with control lentivirus or those expressing mRNAs that bind miR-221 and miR-222 (miR-221/miR-222 sponge). The levels of miR-221 and miR-222 as well as RelA, STAT3, and PDLIM2 mRNAs were measured in 57 paired CRC and adjacent nontumor tissues from patients. RESULTS: In CRC cell lines, mimics of miR-221 and miR-222 activated NF-κB and STAT3, further increasing expression of miR-221 and miR-222. miR-221 and miR-222 bound directly to the coding region of RelA mRNA, increasing its stability. miR-221 and miR-222 also reduced the ubiquitination and degradation of the RelA and STAT3 proteins by binding to the 3' untranslated region of PDLIM2 mRNA (PDLIM2 is a nuclear ubiquitin E3 ligase for RelA and STAT3). Incubation of CRC cells with miR-221 and miR-222 inhibitors reduced their proliferation and colony formation compared with control cells. In mice with colitis, injection of lentiviruses expressing miR-221/miR-222 sponges led to formation of fewer tumors than injection of control lentiviruses. Human CRC tissues had higher levels of miR-221 and miR-222 than nontumor colon tissues; increases correlated with increased levels of RelA and STAT3 mRNAs. Levels of PDLIM2 mRNA were lower in CRC than nontumor tissues. CONCLUSIONS: In human CRC cells, miR-221 and miR-222 act in a positive feedback loop to increase expression levels of RelA and STAT3. Antagonism of miR-221 and miR-222 reduces growth of colon tumors in mice with colitis.

miR-27 inhibits adipocyte differentiation via suppressing CREB expression.

miR-27 plays a negative role in the regulation of adipogenesis. However, the molecular mechanism still remains to be clarified. In the present study, we found that miR-27 inhibits adipogenesis partially by repressing the early adipogenic transcription factor cAMP response element-binding protein by directly targeting its 3' untranslated region. In addition, we demonstrated that tumor necrosis factor-α (TNF-α) treatment up-regulates miR-27 through the NF-κB pathway. Furthermore, anti-miR-27 reduces the TNF-α-induced inhibition of adipogenesis. Simultaneously, the levels of miR-27 expression were decreased in mature adipocytes of obese mice when compared with lean mice. Our data revealed a novel mechanism of miR-27 in the regulation of adipogenesis.

Integrating single-cell and spatial analysis reveals MUC1-mediated cellular crosstalk in mucinous colorectal adenocarcinoma.

BACKGROUND: Mucinous colorectal adenocarcinoma (MCA) is a distinct subtype of colorectal cancer (CRC) with the most aggressive pattern, but effective treatment of MCA remains a challenge due to its vague pathological characteristics. An in-depth understanding of transcriptional dynamics at the cellular level is critical for developing specialised MCA treatment strategies. METHODS: We integrated single-cell RNA sequencing and spatial transcriptomics data to systematically profile the MCA tumor microenvironment (TME), particularly the interactome of stromal and immune cells. In addition, a three-dimensional bioprinting technique, canonical ex vivo co-culture system, and immunofluorescence staining were further applied to validate the cellular communication networks within the TME. RESULTS: This study identified the crucial intercellular interactions that engaged in MCA pathogenesis. We found the increased infiltration of FGF7+/THBS1+ myofibroblasts in MCA tissues with decreased expression of genes associated with leukocyte-mediated immunity and T cell activation, suggesting a crucial role of these cells in regulating the immunosuppressive TME. In addition, MS4A4A+ macrophages that exhibit M2-phenotype were enriched in the tumoral niche and high expression of MS4A4A+ was associated with poor prognosis in the cohort data. The ligand-receptor-based intercellular communication analysis revealed the tight interaction of MUC1+ malignant cells and ZEB1+ endothelial cells, providing mechanistic information for MCA angiogenesis and molecular targets for subsequent translational applications. CONCLUSIONS: Our study provides novel insights into communications among tumour cells with stromal and immune cells that are significantly enriched in the TME during MCA progression, presenting potential prognostic biomarkers and therapeutic strategies for MCA. KEY POINTS: Tumour microenvironment profiling of MCA is developed. MUC1+ tumour cells interplay with FGF7+/THBS1+ myofibroblasts to promote MCA development. MS4A4A+ macrophages exhibit M2 phenotype in MCA. ZEB1+ endotheliocytes engage in EndMT process in MCA.

5,7,4'-Trimethoxyflavone triggers cancer cell PD-L1 ubiquitin-proteasome degradation and facilitates antitumor immunity by targeting HRD1.

Targeting the programmed cell death 1/programmed cell death ligand 1 (PD-1/PD-L1) pathway has been identified as a successful approach for tumor immunotherapy. Here, we identified that the small molecule 5,7,4'-trimethoxyflavone (TF) from Kaempferia parviflora Wall reduces PD-L1 expression in colorectal cancer cells and enhances the killing of tumor cells by T cells. Mechanistically, TF targets and stabilizes the ubiquitin ligase HMG-CoA reductase degradation protein 1 (HRD1), thereby increasing the ubiquitination of PD-L1 and promoting its degradation through the proteasome pathway. In mouse MC38 xenograft tumors, TF can activate tumor-infiltrating T-cell immunity and reduce the immunosuppressive infiltration of myeloid-derived suppressor cells and regulatory T cells, thus exerting antitumor effects. Moreover, TF synergistically exerts antitumor immunity with CTLA-4 antibody. This study provides new insights into the antitumor mechanism of TF and suggests that it may be a promising small molecule immune checkpoint modulator for cancer therapy.

Benzosceptrin C induces lysosomal degradation of PD-L1 and promotes antitumor immunity by targeting DHHC3.

Programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) blockade has become a mainstay of cancer immunotherapy. Targeting the PD-1/PD-L1 axis with small molecules is an attractive approach to enhance antitumor immunity. Here, we identified a natural marine product, benzosceptrin C (BC), that enhances the cytotoxicity of T cells to cancer cells by reducing the abundance of PD-L1. Furthermore, BC exerts its antitumor effect in mice bearing MC38 tumors by activating tumor-infiltrating T cell immunity. Mechanistic studies suggest that BC can prevent palmitoylation of PD-L1 by inhibiting DHHC3 enzymatic activity. Subsequently, PD-L1 is transferred from the membrane to the cytoplasm and cannot return to the membrane via recycling endosomes, triggering lysosome-mediated degradation of PD-L1. Moreover, the combination of BC and anti-CTLA4 effectively enhances antitumor T cell immunity. Our findings reveal a previously unrecognized antitumor mechanism of BC and represent an alternative immune checkpoint blockade (ICB) therapeutic strategy to enhance the efficacy of cancer immunotherapy.

The pathogenesis and potential therapeutic targets in sepsis.

Sepsis is defined as "a life-threatening organ dysfunction caused by dysregulated host systemic inflammatory and immune response to infection." At present, sepsis continues to pose a grave healthcare concern worldwide. Despite the use of supportive measures in treating traditional sepsis, such as intravenous fluids, vasoactive substances, and oxygen plus antibiotics to eradicate harmful pathogens, there is an ongoing increase in both the morbidity and mortality associated with sepsis during clinical interventions. Therefore, it is urgent to design specific pharmacologic agents for the treatment of sepsis and convert them into a novel targeted treatment strategy. Herein, we provide an overview of the molecular mechanisms that may be involved in sepsis, such as the inflammatory response, immune dysfunction, complement deactivation, mitochondrial damage, and endoplasmic reticulum stress. Additionally, we highlight important targets involved in sepsis-related regulatory mechanisms, including GSDMD, HMGB1, STING, and SQSTM1, among others. We summarize the latest advancements in potential therapeutic drugs that specifically target these signaling pathways and paramount targets, covering both preclinical studies and clinical trials. In addition, this review provides a detailed description of the crosstalk and function between signaling pathways and vital targets, which provides more opportunities for the clinical development of new treatments for sepsis.

Ainsliadimer A induces ROS-mediated apoptosis in colorectal cancer cells via directly targeting peroxiredoxin 1 and 2.

The peroxiredoxin (PRDX) family is a class of antioxidant enzymes with peroxidase activity. Human PRDXs currently have six members (PRDX1-6), which are gradually becoming potential therapeutic targets for major diseases such as cancer. In this study, we reported ainsliadimer A (AIN), a sesquiterpene lactone dimer with antitumor activity. We found that AIN directly targets Cys173 of PRDX1 and Cys172 of PRDX2 and then inhibits their peroxidase activities. As a result, the level of intracellular ROS increases, causing oxidative stress damage in mitochondria, inhibiting mitochondrial respiration, and significantly inhibiting ATP production. AIN inhibits the proliferation and induces apoptosis of colorectal cancer cells. Additionally, it inhibits tumor growth in mice and the growth of tumor organoid models. Therefore, AIN can be one of the natural compounds targeting PRDX1 and PRDX2 in the treatment of colorectal cancer.

Bioactivity-Driven Synthesis of the Marine Natural Product Naamidine J and Its Derivatives as Potential Tumor Immunological Agents by Inhibiting Programmed Death-Ligand 1.

The total synthesis of the marine natural product naamidine J and a rapid structure modification toward its derivatives were achieved on the basis of several rounds of structure-relationship analyses of their tumor immunological activities. These compounds were tested for programmed death-ligand 1 (PD-L1) protein expression in human colorectal adenocarcinoma RKO cells. Among them, compound 11c was found to efficiently suppress constitutive PD-L1 expression in RKO cells with low toxicity and further exerted its antitumor effect in MC38 tumor-bearing C57BL/6 mice by reducing PD-L1 expression and enhancing tumor-infiltrating T-cell immunity. This research work may provide insight for the discovery of new marine natural product-derived tumor immunological drug leads.