Rottlerin potentiates camptothecin-induced cytotoxicity in human hormone refractory prostate cancers through increased formation and stabilization of topoisomerase I-DNA cleavage complexes in a PKCδ-independent pathway

Construction of Bone Metastasis-Specific Regulation Network Based on Prognostic Stemness-Related Signatures in Prostate Cancer

Background

We planned to uncover the cancer stemness-related genes (SRGs) in prostate cancer (PCa) and its underlying mechanism in PCa metastasis.

Methods

We acquired the RNA-seq data of 406 patients with PCa from the TCGA database. Based on the mRNA stemness index (mRNAsi) calculated by one-class logistic regression (OCLR) algorithm, SRGs in PCa were extracted by WGCNA. Univariate and multivariate regression analyses were applied to uncover OS-associated SRGs. Gene Set Variation Analysis (GSVA), Gene Set Enrichment Analysis (GSEA), and Pearson's correlation analysis were performed to discover the possible mechanism of PCa metastasis. The significantly correlated transcription factors of OS-associated SRGs were also identified by Pearson's correlation analysis. ChIP-seq was applied to validate the binding relationship of TFs and OS-associated SRGs and spatial transcriptome and single-cell sequencing were performed to uncover the location of key biomarkers expression. Lastly, we explored the specific inhibitors for SRGs using CMap algorithm.

Results

We identified 538 differentially expressed genes (DEGs) between non-metastatic and metastatic PCa. Furthermore, OS-associated SRGs were identified. The Pearson correlation analysis revealed that FOXM1 was significantly correlated with NEIL3 (correlation efficient =0.89, p < 0.001) and identified hallmark_E2F_targets as the potential pathway mechanism of NEIL3 promoting PCa metastasis (correlation efficient =0.58, p < 0.001). Single-cell sequencing results indicated that FOXM1 regulating NEIL3 may get involved in the antiandrogen resistance of PCa. Rottlerin was discovered to be a potential target drug for PCa.

Conclusion

We constructed a regulatory network based on SRGs associated with PCa metastasis and explored possible mechanism.

Co-administration of tyrosine kinase inhibitors with rottlerin in metastatic prostate cancer cells

After prostatectomy due to prostate carcinoma, patients often develop metastases. Although prostate cancer is susceptible to hormonal manipulation, many patients become castration-resistant. Therefore, new therapies are the focus of investigations. We analyzed the effect of the tyrosine kinase inhibitors (TKIs), sorafenib and sunitinib, in combination with rottlerin, a PKCδ inhibitor, on metastatic mechanisms in prostate carcinoma cells. LNCaP and PC-3 prostate carcinoma cells were treated with sorafenib or sunitinib alone at various concentrations (1-20 µM) or in combination with rottlerin (10 µM) for 24 h. Then, cell toxicity (MTT test) and cell proliferation (BrdU incorporation assay) were quantified. The study demonstrated a dose-dependent inhibitory effect of sorafenib and sunitinib on PC-3 and LNCaP cell activity and proliferation. Both agents showed significantly stronger cytotoxic effects in LNCaP cells. At the highest concentrations, sorafenib and sunitinib inhibited the viability of LNCaP cells up to 2 % and 31 %, respectively, and the viability of PC-3 cell line up to 20 % and 43 %, respectively. The proliferation of both cell lines was significantly stronger inhibited by sorafenib than by sunitinib. In LNCaP cells, sorafenib and sunitinib at the highest concentrations inhibited cell proliferation up to 46 % and 49 %, respectively, and the proliferation of PC-3 line up to 40 % and 47 %, respectively. Rottlerin reduced the viability and proliferation of PC3 cells to 81 % and 42 %, whereas the viability and proliferation of LNCaP cells were reduced to 25 % and 57 %, respectively. Sorafenib and sunitinib at low concentrations partly neutralized the inhibitory effect of rottlerin on cell viability and proliferation. On the other hand, in PC-3 cells, rottlerin reduced the inhibitory effects of sorafenib and sunitinib at the highest concentrations on cell viability from 20 % to 30 % and from 43 % to 61 %, respectively. An additive effect on cell activity was observed after treating LNCaP cells with both sunitinib at high concentrations and rottlerin. This combination increased the cytotoxic effect from 31 % to 13 % at the highest sunitinib concentration. Our results showed that monotherapy with sorafenib was the most efficient in both PCa cell lines. A marginally additive effect of rottlerin was only observed in LNCaP cells treated with sunitinib at a high concentration. Sorafenib and sunitinib reduced cell migration in PC-3 cells to 10 % and 32 % of untreated cells, respectively. Co-treatment with sorafenib/sunitinib and rottlerin did not result in a significantly stronger anti-migratory effect than the treatment with each TKI alone. Given the strong cytotoxic effect of TKIs, especially sorafenib, on LNCaP cells, the results of the migration assay in this line were severely biased and not considered in the analysis. Unlike in other malignancies, combination therapy with TKI and rottlerin seems not beneficial in prostate cancer. More promising seems to be monotherapy with rottlerin, but further studies are needed to confirm this observation.

Protease Nexin I is a feedback regulator of EGF/PKC/MAPK/EGR1 signaling in breast cancer cells metastasis and stemness

Breast cancer is the most prevalent cancer in women worldwide, which remains incurable once metastatic. Breast cancer stem cells (BCSCs) are a small subset of breast cancer cells, which are the radical cause of drug resistance, tumor relapse, and metastasis in breast cancer. The extracellular serine protease inhibitor serpinE2, also named protease nexin-1 (PN-1), contributes to enhanced metastasis of cancer cells mainly by remodeling the tumor matrix. In this study, we found that PN-1 was up-regulated in breast cancer, which promoted cell invasion, migration and stemness. Furthermore, by using specific inhibitors, we discovered that epidermal growth factor (EGF) up-regulated PN-1 in breast cancer cells through cascade activation of epidermal growth factor receptor (EGFR) to the activation of protein kinase Cδ (PKCδ), mitogen-activated protein kinase (MEK) and extracellular signal-related kinase (ERK), which finally led to the up-regulation of early growth response protein 1 (EGR1). Moreover, EGF signaling was further activated as a feedback of PN-1 up-regulation through PN-1 blocking HtrA1. Taken together, our findings revealed a novel signaling axis that up-regulated PN-1 expression in breast cancer cells, and the new mechanism of PN-1-promoted breast cancer metastasis, which may provide new insights into identifying novel therapeutic targets for breast cancer.

Enhanced Liver Targeting of Camptothecin via Conjugation with Deoxycholic Acid

Camptothecin (CPT) shows potent anticancer activity through inhibition of topoisomerase I. However, its water insolubility and severe toxicity limit its clinical application. Coupling with bile acid moieties is a promising method for liver-targeted drug delivery, which takes advantage of the bile acid receptors on hepatocytes. In this study, we evaluated the potential liver targeting and stability of a deoxycholic acid-CPT conjugate (G2). The competitive inhibition of antitumor activity experiment based on bile acid transporters was performed using the MTT method. The effects of deoxycholic acid on uptake of G2 and CPT were assessed in 2D and 3D HepG2 cell models. The stability of G2 and CPT was evaluated in vitro (in simulated gastric fluid, simulated intestinal fluid, and fresh rat plasma). Finally, biodistribution of G2 and CPT was investigated in Kunming mice following oral administration. The results showed that deoxycholic acid pretreatment could significantly reduce the antitumor activity and cellular uptake of G2 in HepG2 cells, but had no distinct effects on CPT. Meanwhile, G2 exhibited better stability compared with CPT. More importantly, biodistribution study in mice demonstrated that the liver targeting index of G2 increased 1.67-fold than that of CPT. Overall, the study suggests that conjugation with deoxycholic acid is a feasible method to achieve liver targeting delivery of CPT.

Tumor suppressive role of rottlerin in cancer therapy

Cancer as a major public health problem is a big trouble to be cured at present in the world. Thus, it is essential to discover better anticancer drugs to treat cancer patients. It has been reported that rottlerin, a natural polyphenolic compound from the mature fruits of Mallotus philippinensis, possesses multiple anti-cancer biological activities. Rottlerin exhibited its antitumor property in a variety of human cancers, suggesting that rottlerin could be a potential agent for treating cancers. In this review we discuss the recent literature regarding the biological functions and tumor suppressive mechanisms of rottlerin in cancers. We hope rottlerin will be further exploited for potential treatment of human cancers.

Characterization and antitumor activity of camptothecin from endophytic fungus Fusarium solani isolated from Camptotheca acuminate

BACKGROUND

Camptothecin (CPT) is a potent drug against cancers, originally from plants. The endophytic fungi could produce the secondary metabolite same as the host and is used as medicine.

OBJECTIVES

The aim of this paper was to investigate an endophytic fungal CPT with anti-neoplastic activity.

METHODS

Endophytic fungi were isolated from Camptotheca acuminata in China. CPT from strain S-019 was characterized by TLC, HPLC and EI-MS analysis. Anti-tumor activity of fungal CPT was detected by MTT and fluorescent dye methods using Vero and PC-3 cells.

RESULTS

A total of 94 endophytic fungi strains were isolated from tissues of C. acuminata and 16 fungi strains displayed cytotoxic activity on Vero or PC3 cells. Of which, the fungal strain S-019, classified as Fusarium solani, displayed impressive cytotoxic activity on cancer cells and was found to produce CPT by analysis of TLC, HPLC and EI-MS methods. Bioassay studies confirmed that the fungi CPT had potent cytotoxicity on Vero cells and induced apoptosis of Vero cells.

CONCLUSION

The endophytic fungi from camptotheca trees are a reliable source for natural anticancer compounds. The endophytic fungi could produce CPT same as plant. The fungal CPT exhibited effective activity at inhibiting cell growth and inducing apoptosis on Vero cells.

Water-soluble oxoglaucine-Y(iii), Dy(iii) complexes: in vitro and in vivo anticancer activities by triggering DNA damage, leading to S phase arrest and apoptosis

The complexes exhibited considerable in vitro and in vivo anticancer activity, and higher safety than ciplatin.

Synthesis and evaluation of 3-salicyloylpyridine derivatives as cytotoxic mitochondrial apoptosis inducers

A series of novel 3-salicyloylpyridines (4a-h) were synthesized with good yield by modified Knoevenagel-Stobbel method; o-allylation with allyl bromide lead to formation of compounds (5a-h). The synthesized compounds were characterized by spectroscopic techniques and evaluated for cytotoxic activity against human cancer cell lines. Compounds bearing hydroxyl group displayed high cytotoxicity (4a-h) as compared to o-allylated molecules (5a-h). The most active compound 4b was selected for further investigation to look for mechanism of cell death in prostate cancer (PC-3) cells. The apoptotic bodies induced by 4b in PC-3 cells were scanned by confocal microscopy and confirmed by scanning electron microscopy (SEM). Further results obtained from spectrofluorimetric determination of mitochondrial membrane potential (ΔΨm) and intracellular reactive oxygen species (ROS) in treated PC-3 cells revealed that mitochondria dependent apoptosis was involved in the cell death.

Preparation of chondroitin sulfate-g-poly(ε-caprolactone) copolymers as a CD44-targeted vehicle for enhanced intracellular uptake

Chondroitin sulfate-g-poly(ε-caprolactone) (CP) copolymers were synthesized via atom transfer radical addition (ATRA). The CP copolymers self-assembled into micelles in water, and the micelles could be used to encapsulate a hydrophobic anticancer drug, camptothecin (CPT), in the core for tumor targeting delivery. The physicochemical properties of the micelles and CPT-loaded micelles were thoroughly characterized. For the in vitro test, the CPT release, the protection of the lactone ring of CPT from hydrolysis and the cellular uptake of CPT were studied. The cell-killing and apoptosis-inducing effects using the CPT-loaded micelles were significantly better than using free CPT against CRL-5802 cells. The micellar internalization into CRL-5802 cells was primarily via CD44 and clathrin dual-mediated endocytosis. For the in vivo test, the therapeutic efficacy of the CPT-loaded micelles was studied in a non-small-cell lung cancer xenograft animal model. The CPT-loaded micelles showed good inhibition in tumor growth as compared with a commercial product, CPT-11, in CRL-5802 tumor-bearing mice. The in vitro and in vivo data suggested the CP-based micelles are promising anticancer drug vehicles for lung cancer targeting.

Rottlerin induces Wnt co-receptor LRP6 degradation and suppresses both Wnt/β-catenin and mTORC1 signaling in prostate and breast cancer cells

Activation of Wnt/β-catenin signaling can result in up-regulation of mTORC1 signaling in cancer cells. The low density lipoprotein receptor-related protein-6 (LRP6) is an essential Wnt co-receptor for Wnt/β-catenin signaling. We found that rottlerin, a natural plant polyphenol, suppressed LRP6 expression and phosphorylation, and inhibited Wnt/β-catenin signaling in HEK293 cells. Furthermore, the inhibitory effects of rottlerin on LRP6 expression/phosphorylation and Wnt/β-catenin signaling were confirmed in human prostate cancer PC-3 and DU145 cells and breast cancer MDA-MB-231 and T-47D cells. Mechanistically, rottlerin promoted LRP6 degradation, but had no effects on LRP6 transcriptional activity. In addition, rottlerin-mediated LRP6 down-regulation was unrelated to activation of 5'-AMP-activated protein kinase (AMPK). Importantly, we also found that rottlerin inhibited mTORC1 signaling in prostate and breast cancer cells. Finally, we demonstrated that rottlerin was able to suppress the expression of cyclin D1 and survivin, two targets of both Wnt/β-catenin and mTORC1 signaling, in prostate and breast cancer cells, and displayed remarkable anticancer activity with IC(50) values between 0.7 and 1.7 μM for prostate cancer PC-3 and DU145 cells and breast cancer MDA-MB-231 and T-47D cells. The IC(50) values are comparable to those shown to suppress the activities of Wnt/β-catenin and mTORC1 signaling in prostate and breast cancer cells. Our data indicate that rottlerin is a novel LRP6 inhibitor and suppresses both Wnt/β-catenin and mTORC1 signaling in prostate and breast cancer cells, and that LRP6 represents a potential therapeutic target for cancers.

Synthesis and antitumor activity evaluation of a novel series of camptothecin analogs

A series of novel 10-substituted camptothecin analogs (3-10) with a carbamate linker were synthesized, and their biological activities were evaluated. The amino acid-linked carbamate derivatives (8-10) of the camptothecin-type natural product not only possessed good to excellent inhibitory activity against three human tumor cell lines K562, HepG2, and HT-29, but also showed significantly less cytotoxicity against normal human cell HEK293 (half maximal inhibiting concentration >10 μM). The selectivity of compound 9 toward tumor cells relative to normal cells is at least 250 times better than that of camptothecin. The preliminary testing result indicated that the solubility of these compounds was also improved compared to that of 10-hydroxy camptothecin.

3p21.3 tumor suppressor gene RBM5 inhibits growth of human prostate cancer PC-3 cells through apoptosis

Background

Recent studies have indicated that the nuclear RNA-binding protein RBM5 has the ability to modulate apoptosis and suppress tumor growth. The aim of this study is to investigate the expression of RBM5 in human prostate cancer and its mechanism of tumor suppression.

Methods

The expression of RBM5 protein in cancerous prostatic tissues and normal tissues was examined by IHC. PC-3 cell line was used to determine the apoptotic function of RBM5 in vitro. PC-3 cells were transiently transfected with pcDNA3.1-RBM5. Cell viability was determined by MTT assay. Rhodamine 123 staining and Annexin V analysis were performed to observe the apoptotic activity of PC-3 cells overexpressing RBM5. Expression of apoptosis-related genes was assessed by western blot.

Results

The expression of RBM5 protein was significantly decreased in cancerous prostatic tissues compared to the normal tissues. PC-3 cells overexpressing RBM5 showed not only significant growth inhibition compared with the vector controls, but also dysfunction of mitochondrial membrane potential and increased apoptotic activity. To further define RBM5 function in apoptotic pathways, we investigated differential expression profiles of various BH3-only proteins including Bid, Bad, and Bim, and apoptosis regulatory proteins include P53, cleaved caspase9, and cleaved caspase3. We found that the expression of both BH3-only proteins and apoptosis regulatory proteins was increased in RBM5 transfected cells.

Conclusion

The expression of RBM5 protein was significantly decreased in cancerous prostatic tissues, which suggests that RBM5 plays an important role in the pathogenesis of prostate cancer. RBM5 may induce the apoptosis of prostate cancer PC-3 cells by modulating the mitochondrial apoptotic pathway, and thus RBM5 might be a promising target for gene therapy on prostate cancer.