Regulation of Vinca alkaloid-induced apoptosis by NF-κB/IκB pathway in human tumor cells

Breast Tumor Microenvironment: Emerging target of therapeutic phytochemicals

Triple negative breast cancer (TNBC) is the most aggressive and challenging form of breast cancers. Tumor microenvironment (TME) of TNBC is associated with induction of metastasis, immune system suppression, escaping immune detection and drug resistance. TME is highly complex and heterogeneous, consists of tumor cells, stromal cells and immune cells. The rapid expansion of tumors induce hypoxia, which concerns the reprogramming of TME components. The reciprocal communication of tumor cells and TME cells predisposes cancer cells to metastasis by modulation of developmental pathways, Wnt, notch, hedgehog and their related mechanisms in TME. Dietary phytochemicals are non-toxic and associated with various human health benefits and remarkable spectrum of biological activities. The phytochemicals serve as vital resources for drug discovery and also as a source for breast cancer therapy. The novel properties of dietary phytochemicals propose platform for modulation of tumor signaling, overcoming drug resistance, and targeting TME. Therefore, TME could serve as promising target for the treatment of TNBC. This review presents current status and implications of experimentally evaluated therapeutic phytochemicals as potential targeting agents of TME, potential nanosystems for targeted delivery of phytochemicals and their current challenges and future implications in TNBC treatment. The dietary phytochemicals especially curcumin with significant delivery system could prevent TNBC development as it is considered safe and well tolerated in phase II clinical trials.

Novel genetic and epigenetic factors of importance for inter-individual differences in drug disposition, response and toxicity

Individuals differ substantially in their response to pharmacological treatment. Personalized medicine aspires to embrace these inter-individual differences and customize therapy by taking a wealth of patient-specific data into account. Pharmacogenomic constitutes a cornerstone of personalized medicine that provides therapeutic guidance based on the genomic profile of a given patient. Pharmacogenomics already has applications in the clinics, particularly in oncology, whereas future development in this area is needed in order to establish pharmacogenomic biomarkers as useful clinical tools. In this review we present an updated overview of current and emerging pharmacogenomic biomarkers in different therapeutic areas and critically discuss their potential to transform clinical care. Furthermore, we discuss opportunities of technological, methodological and institutional advances to improve biomarker discovery. We also summarize recent progress in our understanding of epigenetic effects on drug disposition and response, including a discussion of the only few pharmacogenomic biomarkers implemented into routine care. We anticipate, in part due to exciting rapid developments in Next Generation Sequencing technologies, machine learning methods and national biobanks, that the field will make great advances in the upcoming years towards unlocking the full potential of genomic data.

Induction of apoptosis in human leukemia cells through an intrinsic pathway by cathachunine, a unique alkaloid isolated from Catharanthus roseus

BACKGROUND

Catharanthus roseus (L.) G. Don consists of a range of dimeric indole alkaloids with significant antitumor activities. These alkaloids have been found to possess apoptosis-inducing activity against tumor cells in vitro and in vivo mediated by nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and c-Jun N-terminal kinase (JNK) pathways, in which DNA damage and mitochondrial dysfunction play important roles. In this study, a unique bisindole alkaloid named cathachunine, along with five known dimeric indole alkaloids, was obtained from C. roseus and investigated in vitro.

PURPOSE

The aim of this study was to investigate the antitumor activity of isolated alkaloids and the mechanism through which cathachunine exerts its antitumor effect.

STUDY DESIGN AND METHODS

Cell growth inhibition was assessed by WST-1 and lactate dehydrogenase (LDH) assays in HL60, K562 leukemia cells and EA.hy926 umbilical vein cells. Induction of apoptosis in HL60 cells was confirmed by observation of nuclear morphology, a caspase-3 activity assay and annexin V-fluorescein isothiocyanate/propidium iodide (FITC/PI) double staining. The intrinsic apoptotic pathway induced by cathachunine was evidenced by B-cell lymphoma 2/Bcl-2-associated X protein (Bcl-2/Bax) dysregulation, loss of mitochondrial membrane potential, translocation of cytochrome c, and cleavage of caspase-3 and poly-ADP ribose polymerase (PARP). Reactive oxygen species (ROS) production after cathachunine treatment was determined by 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) staining. Cell cycle arrest of the S phase was also observed in HL60 cells after cathachunine treatment.

RESULTS

The WST-1 and LDH assays showed that Catharanthus alkaloids were cytotoxic toward human leukemia cells to a greater extent than toward normal human endothelial cells, and the anti-proliferation and pro-apoptosis abilities of cathachunine were much more potent than other previously reported alkaloids. The induction of apoptosis by cathachunine occurred through an ROS-dependent mitochondria-mediated intrinsic pathway rather than an extrinsic pathway, and was regulated by the Bcl-2 protein family.

CONCLUSION

An unprecedented bisindole alkaloid cathachunine which lost C-18' and C-19' was isolated from C. roseus. It exerted a potent antitumor effect toward human leukemia cells through the induction of apoptosis via an intrinsic pathway. Thus, this study provides evidence for a new lead compound from a natural source for anti-cancer investigations.

Microtubule-depolymerizing agents used in antibody-drug conjugates induce antitumor immunity by stimulation of dendritic cells

Antibody-drug conjugates (ADC) are emerging as powerful treatment strategies with outstanding target-specificity and high therapeutic activity in patients with cancer. Brentuximab vedotin represents a first-in-class ADC directed against CD30(+) malignancies. We hypothesized that its sustained clinical responses could be related to the stimulation of an anticancer immune response. In this study, we demonstrate that the dolastatin family of microtubule inhibitors, from which the cytotoxic component of brentuximab vedotin is derived, comprises potent inducers of phenotypic and functional dendritic cell (DC) maturation. In addition to the direct cytotoxic effect on tumor cells, dolastatins efficiently promoted antigen uptake and migration of tumor-resident DCs to the tumor-draining lymph nodes. Exposure of murine and human DCs to dolastatins significantly increased their capacity to prime T cells. Underlining the requirement of an intact host immune system for the full therapeutic benefit of dolastatins, the antitumor effect was far less pronounced in immunocompromised mice. We observed substantial therapeutic synergies when combining dolastatins with tumor antigen-specific vaccination or blockade of the PD-1-PD-L1 and CTLA-4 coinhibitory pathways. Ultimately, treatment with ADCs using dolastatins induces DC homing and activates cellular antitumor immune responses in patients. Our data reveal a novel mechanism of action for dolastatins and provide a strong rationale for clinical treatment regimens combining dolastatin-based therapies, such as brentuximab vedotin, with immune-based therapies.

Chemotherapeutic drugs sensitize cancer cells to TRAIL-mediated apoptosis: up-regulation of DR5 and inhibition of Yin Yang 1

Several chemotherapeutic drugs in combination with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) result in reversal of resistance to TRAIL-mediated apoptosis through up-regulation of DR5 expression. The promoter of DR5 has one putative binding site for the transcription repressor Yin Yang 1 (YY1), and thus, we hypothesized that the sensitizing drugs may inhibit YY1. We have found that treatment of tumor cells with various chemotherapeutic drugs inhibited nuclear factor-kappaB. We examined whether drugs also inhibit YY1 activity and whether YY1 inhibition correlates with up-regulation of DR5 expression and sensitization of cells to TRAIL-induced apoptosis. The TRAIL- and drug-resistant prostate carcinoma PC-3 cell line was treated with CDDP, VP-16, ADR, and vincristine. DR5 luciferase reporter constructs and small interfering RNA against YY1 were used to determine the role of YY1 in DR5 transcription. Pretreatment of PC-3 cells and other tumor cell lines with various chemotherapeutic drugs sensitized the cells to TRAIL-induced apoptosis concurrently with up-regulation of DR5 expression and inhibition of YY1 expression and its DNA-binding activity. The baseline luciferase activity in PC-3 cells transfected with the wild-type DR5 reporter was significantly augmented in cells transfected with DR5 constructs carrying deletions or mutation in the YY1-binding site. Treatment with drug enhanced DR5 wild-type luciferase activity, with no increase in cells transfected with the YY1-deleted or YY1-mutated constructs. Cells transfected with YY1 small interfering RNA showed up-regulation of DR5 expression and sensitization to TRAIL-mediated apoptosis. The findings provide evidence that drug-induced sensitization of tumor cells to TRAIL is mediated, in part, by inhibition of the transcription repressor YY1 and up-regulation of DR5 expression. Hence, YY1 may be a potential therapeutic target to reverse resistance to TRAIL-induced apoptosis.

Apoptosis Induction by a Novel Retinoid-Related Molecule Requires Nuclear Factor-κB Activation

Nuclear factor-kappaB (NF-kappaB) activation has been shown to be both antiapoptotic and proapoptotic depending on the stimulus and the specific cell type involved. NF-kappaB activation has also been shown to be essential for apoptosis induction by a number of agents. The novel retinoid-related molecule 4-[3-Cl-(1-adamantyl)-4-hydroxyphenyl]-3-chlorocinnamic acid (3-Cl-AHPC) activates NF-kappaB with subsequent apoptosis in a number of cell types. We have found that NF-kappaB activation is essential for 3-Cl-AHPC-mediated apoptosis. 3-Cl-AHPC activates NF-kappaB through IKKalpha kinase activation and the subsequent degradation of IkappaB alpha. IKKalpha kinase activation is associated with IKKalpha-enhanced binding to HSP90. The HSP90 inhibitor geldanamycin enhances the degradation of IKKalpha and blocks 3-Cl-AHPC activation of NF-kappaB and 3-Cl-AHPC-mediated apoptosis. In addition, inhibition of IkappaB alpha degradation using a dominant-negative IkappaB alpha inhibits 3-Cl-AHPC-mediated apoptosis. NF-kappaB p65 activation is essential for 3-Cl-AHPC apoptosis induction as evidenced by the fact that inhibition of p65 activation utilizing the inhibitor helenalin or loss of p65 expression block 3-Cl-AHPC-mediated apoptosis. NF-kappaB has been shown to be antiapoptotic through its enhanced expression of a number of antiapoptotic proteins including X-linked inhibitor of apoptosis protein (XIAP), c-IAP1, and Bcl-X(L). Whereas exposure to 3-Cl-AHPC results in NF-kappaB activation, it inhibits the expression of XIAP, c-IAP1, and Bcl-X(L) and enhances the expression of proapoptotic molecules, including the death receptors DR4 and DR5 as well as Fas and Rip1. Thus, 3-Cl-AHPC, which is under preclinical development, has pleotrophic effects on malignant cells resulting in their apoptosis.