Pseudolaric acid B induces caspase-dependent apoptosis and autophagic cell death in prostate cancer cells

Pseudolaric acid B triggers cell apoptosis by activating AMPK/JNK/DRP1/mitochondrial fission pathway in hepatocellular carcinoma

Pseudolaric acid B (PAB), a natural product isolated from the root bark of Pseudolarix kaempferi, has been reported to exert inhibitory effects in various cancers. However, the underlying mechanisms remain largely unclear. In the present study, we investigated the mechanism through which PAB exert its anticancer effects in hepatocellular carcinoma (HCC). PAB inhibited the viability of and induced apoptosis in Hepa1-6 cells in a dose-dependent manner. It disrupted mitochondrial membrane potential (MMP) and impaired ATP production. Furthermore, PAB induced phosphorylation of DRP1 at Ser616 and mitochondrial fission. Blocking DRP1 phosphorylation by Mdivi-1 inhibited mitochondrial fission and PAB-induced apoptosis. Moreover, c-Jun N-terminal kinase (JNK) was activated by PAB, and blocking JNK activity using SP600125 inhibited PAB-induced mitochondrial fission and cell apoptosis. Furthermore, PAB activated AMP-activated protein kinase (AMPK), and inhibiting AMPK by compound C attenuated PAB-stimulated JNK activation and blocked DRP1-dependent mitochondrial fission and apoptosis. Our in vivo data confirmed that PAB inhibited tumor growth and induced apoptosis in an HCC syngeneic mouse model by inducing the AMPK/JNK/DRP1/mitochondrial fission signaling pathway. Furthermore, a combination of PAB and sorafenib showed a synergistic effect in inhibiting tumor growth in vivo. Taken together, our findings highlight a potential therapeutic strategy for HCC.

Co-loaded lapatinib/PAB by ferritin nanoparticles eliminated ECM-detached cluster cells via modulating EGFR in triple-negative breast cancer

Cancer stem cell (CSC) cluster of triple-negative breast cancer (TNBC) is suggested to be responsible for therapy resistance, metastatic process and cancer recurrence, yet the sensitivity of CSC clusters of TNBC to ferroptosis remains elusive in a great measure. Current research revealed that epidermal growth factor receptor (EGFR) reinforced CD44-mediated TNBC cell clustering, whether blockade of EGFR has synergistic effects on erastin-induced tumor inhibition of CSC clusters is still poorly understood. Here, we found that fraction of CD24^lowCD44^high cells and size of tumor spheres clearly decreased following EGFR inhibition in TNBC cells. Inhibition of EGFR promoted expression of LC3B-II via YAP/mTOR signaling pathway, indicating that EGFR-mediated autophagy which contributed to ferroptosis. In order to further verify the protective effects of EGFR on ferroptosis induced by small molecules in TNBC cells, pseudolaric acid B (PAB) which led to ferroptosis of malignant cells was selected. In our experiment, lapatinib and PAB cotreatment inhibited TNBC cells viability and restrained formation of tumor spheres, accompanied with a high level of intracellular ROS. To target delivery lapatinib and PAB to TNBC cells, lapatinib/PAB@Ferritin (L/P@Ferritin) nanoparticles were prepared; results of in vitro and in vivo showed a higher tumor suppression efficiency of L/P@Ferritin, highlighting that it might provide a new perspective for treatment of CSC clusters of TNBC.

ABT-737 and erufosine combination against castration-resistant prostate cancer: a promising but cell-type specific response associated with the modulation of anti-apoptotic signaling

A deeper understanding of the molecular basis of castration-resistant prostate cancer (CRPC) paved the way for the rational design and development of targeted therapies, which yielded promising preclinical results. However, translation of these potentially promising agents into clinics has usually failed, partly because of tumor heterogeneity. In this study, anticancer activities of the Bcl-2 inhibitor ABT-737 and the Akt-inhibitor erufosine (ErPC3) alone and in combination were compared between CRPC (PC-3 and DU-145) and healthy (PNT-1A) cell lines. The combination of ABT-737 and ErPC3 showed synergistic antiproliferative, antimigratory, and apoptotic effects in PC-3 cells. In DU-145 cells, ErPC3 showed a resistant profile, with half-maximal inhibitory concentration (IC50) values more than two-fold of PC-3, and combining ErPC3 with ABT-737 yielded no added benefit for all the incubation periods compared with ErPC3 alone. In PNT-1A cells, ABT-737 and ErPC3 alone and in combination reduced cell survival slightly and only at the highest concentrations. Apoptosis analysis showed that ABT-737 induced increased Akt expression and ErPC3 induced increased Mcl-1 expression in DU-145 cells. In conclusion, the ABT-737 and ErPC3 combination seems to be promising against CRPC, with a favorable safety profile in healthy cells. However, CRPC cell-type-specific resistance may be induced by enhancement of antiapoptotic signaling.

Targeting Autophagic Pathways by Plant Natural Compounds in Cancer Treatment

Nowadays, natural compounds of plant origin with anticancer effects have gained more attention because of their clinical safety and broad efficacy profiles. Autophagy is a multistep lysosomal degradation pathway that may have a unique potential for clinical benefit in the setting of cancer treatment. To retrieve articles related to the study, the databases of Google Scholar, Web of sciences, Medline and Scopus, using the following keywords: Autophagic pathways; herbal medicine, oncogenic autophagic pathways, tumor-suppressive autophagic pathways, and cancer were searched. Although natural plant compounds such as resveratrol, curcumin, oridonin, gossypol, and paclitaxel have proven anticancer potential via autophagic signaling pathways, there is still a great need to find new natural compounds and investigate the underlying mechanisms, to facilitate their clinical use as potential anticancer agents through autophagic induction.

Pseudolaric Acid B Induces Growth Inhibition and Caspase-Dependent Apoptosis on Head and Neck Cancer Cell lines through Death Receptor 5

Pseudolaric Acid B (PAB), diterpenoid isolated from the root bark of Pseudolarix kaempferi Gordon tree (Pinaceae), exhibits an anti-proliferative and apoptotic activity in various cancer cell lines but to date, the effects of PAB on head and neck cancer (HNC) cell lines remain to be elucidated. In this study, we showed that PAB significantly inhibited the viability and caspase-dependent apoptosis in HN22 cell line. PAB-induced apoptosis is through inducing death receptor 5 (DR5) together with the increase in the expression of cleaved caspase-8. It also inhibited the proliferations and induced apoptosis through DR5 in other three HNC cell lines (HSC3, Ca9.22, and HSC4). Extending our in vitro findings, we found that ethanol extract of Pseudolarix kaempferi (2.5 mg/kg/day) reduced tumor growth in a xenograft model bearing HN22 cell line without any change in body weight. DR5 were also found to be increased in tumors tissue of PAB-treated mice without any apparent histopathological changes in liver or kidney tissues. Taken together, PAB may be a potential lead compound for chemotherapeutic agents against head and neck cancer.

BH3 Mimetics for the Treatment of Prostate Cancer

Despite improved diagnostic and therapeutic intervention, advanced prostate cancer (PC) remains incurable. The acquired resistance of PC cells to current treatment protocols has been traced to apoptosis resistance based on the upregulation of anti-apoptotic proteins of the Bcl-2 family. The use of BH3 mimetics, mimicking pro-apoptotic activator or sensitizer proteins of the intrinsic apoptotic pathway, is therefore a promising treatment strategy. The present review gives an overview of preclinical and clinical studies with pan- and specific BH3 mimetics as sensitizers for cell death and gives an outlook how they could be effectively used for the therapy of advanced PC in future.

A Systematic Review of the Immune-Regulating and Anticancer Activities of Pseudolaric Acid B

Cortex pseudolaricis, the root bark of Pseudolarix kaempferi Gord, has been used to treat tinea and other skin diseases for the antimicrobial activities in Traditional Chinese Medicine (TCM). Pseudolaric acid B (PAB) has been identified as the major component responsible for the action of C. pseudolaricis. Recently, PAB has been demonstrated to be used as novel treatments for cancer, immune disorders, inflammatory diseases, and immunosuppression. However, the mechanisms through which PAB exerts its properties are not understood well, and little attention in the literature has been given to review its pharmacological activities before. In this review, we performed a systematic summary of the literature with respect to the anticancer, immunosuppressive and anti-inflammatory properties of PAB and its derivatives. Currently available data suggest that PAB is a promising immunosuppressive and anti-inflammatory agent candidate and should be explored further in cancer treatment and prevention.

Pseudolaric acid B circumvents multidrug resistance phenotype in human gastric cancer SGC7901/ADR cells by downregulating Cox-2 and P-gp expression

Multidrug resistance (MDR) is a challenging issue in the treatment of gastric cancer. Pseudolaric acid B is a new diterpene acid compound isolated from pseudolarix, which has been found to have anti-tumor activities in recent studies. The purpose of the present study was to evaluate the effects of pseudolaric acid B in an MDR gastric cancer cell line and elucidate the possible underlying mechanisms of action. SGC7901/ADR, a P-glycoprotein (P-gp)-overexpressing cell line, was used to evaluate the efficacy of pseudolaric acid B against MDR phenotypes. The effects of pseudolaric acid B and chemotherapeutic agents on cell proliferation and apoptosis were assessed using the MTT assay and flow cytometry, respectively. Immunocytochemistry and Western blot were used to detect the possible relevant molecules in order to elucidate the underlying mechanism of action. The results showed that pseudolaric acid B inhibited cell proliferation and induced apoptosis in SGC7901/ADR cells. A low dose of pseudolaric acid B (0.5 µmol/L) augmented the inhibitory effects of chemotherapeutic agents on proliferation (p < 0.05). The expression of P-gp and cyclooxygenase 2 (Cox-2) was downregulated with pseudolaric acid B treatment. The present results showed that pseudolaric acid B inhibited cell proliferation, induced apoptosis, circumvented MDR, and increased the sensitivity of chemotherapeutic agents in vitro by downregulating the expression of P-gp and Cox-2.

The high-mobility group nucleosome-binding domain 5 is highly expressed in breast cancer and promotes the proliferation and invasion of breast cancer cells

The high-mobility group nucleosome-binding domain 5 (HMGN5) is a member of the high-mobility group proteins family. Previous study found that HMGN5 is required for tumorigenesis in vitro, and aberrations in the expression of HMGN5 were found in human osteosarcoma, prostate cancer, and squamous cell carcinoma. Nevertheless, the role of HMGN5 in breast cancer remains unclear. This study aimed to investigate the expression and clinical significance of HMGN5 in human breast cancer, confirm the oncogenic role of HMGN5, and explore the mechanism by which HMGN5 contributes to invasion and metastasis. HMGN5 expression was detected in breast cancer tissues and corresponding adjacent non-cancerous tissues from 43 patients by immunohistochemistry, and the clinicopathologic characteristics of all patients were also analyzed. Next, knockdown of HMGN5 protein in MDA-MB-231 cells was performed through a small interfering RNA (siRNA) technique, and cell viability, apoptosis, and invasion were detected by cell vitality test, flow cytometry, and transwell assay, respectively. Immunohistostaining showed that HMGN5 were highly expressed in the nucleus in all breast cancer tissues as compared with the adjacent non-cancerous tissues (ANCT;(73.5 ± 11 vs. 31.0 ± 5 %, P < 0.01). HMGN5 expression level was associated with the poorly differentiated tumor cells, lymph node involvement tumor, and T4 staging tumor. Knockdown of HMGN5 inhibited cell growth, suppressed invasion, and increased cell apoptosis in human breast cancer MDA-MB-231 cells. Western blot analysis demonstrated that the expressions of PCNA, connective tissue growth factor (CTGF), and MMP-9 were decreased in human breast MDA-MB-231 cells depleted of HMGN5. In addition, the apoptotic markers (cleaved PARP and cleaved caspase-3) were significantly increased by HMGN5 knockdown, but microtubule-associated protein 1 light chain 3-II/I (LC3-II/I) did not alter. HMGN5 plays an oncogenic role in human breast cancer by inhibiting cell proliferation and invasion, and activating apoptosis, which could be exploited as a target for therapy in human breast cancer.

Targeting apoptosis pathways in cancer and perspectives with natural compounds from mother nature

Although the incidences are increasing day after day, scientists and researchers taken individually or by research group are trying to fight against cancer by several ways and also by different approaches and techniques. Sesquiterpenes, flavonoids, alkaloids, diterpenoids, and polyphenolic represent a large and diverse group of naturally occurring compounds found in a variety of fruits, vegetables, and medicinal plants with various anticancer properties. In this review, our aim is to give our perspective on the current status of the natural compounds belonging to these groups and discuss their natural sources, their anticancer activity, their molecular targets, and their mechanism of actions with specific emphasis on apoptosis pathways, which may help the further design and conduct of preclinical and clinical trials. Unlike pharmaceutical drugs, the selected natural compounds induce apoptosis by targeting multiple cellular signaling pathways including transcription factors, growth factors, tumor cell survival factors, inflammatory cytokines, protein kinases, and angiogenesis that are frequently deregulated in cancers and suggest that their simultaneous targeting by these compounds could result in efficacious and selective killing of cancer cells. This review suggests that they provide a novel opportunity for treatment of cancer, but clinical trials are still required to further validate them in cancer chemotherapy.