Triterpenoids display single agent anti-tumor activity in a transgenic mouse model of chronic lymphocytic leukemia and small B cell lymphoma

The synthetic oleanane triterpenoid CDDO-2P-Im binds GRP78/BiP to induce unfolded protein response-mediated apoptosis in myeloma

Synthetic oleanane triterpenoids (SOTs) are small molecules with broad anticancer properties. A recently developed SOT, 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]-4(-pyridin-2-yl)-1H-imidazole (CDDO-2P-Im or '2P-Im'), exhibits enhanced activity and improved pharmacokinetics over CDDO-Im, a previous generation SOT. However, the mechanisms leading to these properties are not defined. Here, we show the synergy of 2P-Im and the proteasome inhibitor ixazomib in human multiple myeloma (MM) cells and 2P-Im activity in a murine model of plasmacytoma. RNA sequencing and quantitative reverse transcription PCR revealed the upregulation of the unfolded protein response (UPR) in MM cells upon 2P-lm treatment, implicating the activation of the UPR as a key step in 2P-Im-induced apoptosis. Supporting this hypothesis, the deletion of genes encoding either protein kinase R-like endoplasmic reticulum kinase (PERK) or DNA damage-inducible transcript 3 protein (DDIT3; also known as CHOP) impaired the MM response to 2P-Im, as did treatment with ISRIB, integrated stress response inhibitor, which inhibits UPR signaling downstream of PERK. Finally, both drug affinity responsive target stability and thermal shift assays demonstrated direct binding of 2P-Im to endoplasmic reticulum chaperone BiP (GRP78/BiP), a stress-inducible key signaling molecule of the UPR. These data reveal GRP78/BiP as a novel target of SOTs, and specifically of 2P-Im, and suggest the potential broader utility of this class of small molecules as modulators of the UPR.

Polyphenolics, antioxidant characterization and DNA barcoding of Kala zeera [Bunium persicum (Boiss.) Fedtsch] through multiple barcode analysis to unravel best barcode combination

BACKGROUND

Kala zeera [Bunium persicum (Boiss.) Fedtsch] is one of the important spice crops of North Western Himalayas with lot of medicinal and culinary values. In spite of having great importance, this crop is under the threat of extinction due to loss of habitat and lack of awareness. The limited availability of the seeds has ultimately increased the economic value of this spice. The upmarket of Kala zeera leads to its adulteration with other black seeds and cumin seeds. The present investigation was undertaken to evaluate polyphenolics and antioxidant properties of Kala zeera genotypes collected from North Western Himalayas and to develop DNA barcodes that can ensure their purity and can also guide in conservation of selected Kala zeera germplasm lines.

METHODS AND RESULTS

Various locations of North Western Himalayas were explored for collecting 31 diverse germplasm lines of Kala zeera. The collected germplasm was maintained at our experimental stations during 2019-2020 and 2020-2021. These genotypes were evaluated for different seed traits and the methanolic extract from Kala zeera seeds was examined for total phenolic content, total flavonoid content, antioxidant activities by DPPH and FRAP. The results revealed significant variation in seed traits, polyphenolic content and antioxidant properties. 100 seed weight ranged from 0.05 to 0.35 g, TPC ranged from 7.5 to 22.56 mg/g, TFC ranged from 0.58 to 4.15 mg/g, antioxidant properties DPPH ranged from 168 to 624.4 μg/ml and FRAP ranged from 0.72 to 6.91 mg/g. Further, three different barcodes (ITS, rbcL and psbA-trnH) were used to reveal the authenticity of selected Kala zeera. MEGA 5 software was used for clustering and the barcodes did clustering based on geographical distribution of Kala zeera germplasm.

CONCLUSION

Based on molecular barcoding, best barcode combination was identified that may discriminate the Kala zeera germplasm vis-a-vis can authenticate their purity. Moreover, the identified DNA barcodes will have significant role in studying the evolutionary biology of Bunium species and will be important for designing a strategy to conserve the selected Kala zeera germplasm lines. The identified genotypes with high phenolic content and antioxidant activity can further be utilized in Kala zeera breeding programmes.

Triterpenoid CDDO-IM protects against lipopolysaccharide-induced inflammatory response and cytotoxicity in macrophages: The involvement of the NF-κB signaling pathway

Lipopolysaccharide (LPS), also known as endotoxin, can trigger septic shock, a severe form of inflammation-mediated sepsis with a very high mortality rate. However, the precise mechanisms underlying this endotoxin remain to be defined and detoxification of LPS is yet to be established. Macrophages, a type of immune cells, initiate a key response responsible for the cascade of events leading to the surge in inflammatory cytokines and immunopathology of septic shock. This study was undertaken to determine whether the LPS-induced inflammation in macrophage cells could be ameliorated via CDDO-IM (2-cyano-3,12 dioxooleana-1,9 dien-28-oyl imidazoline), a novel triterpenoid compound. Data from this study show that gene expression levels of inflammatory cytokine genes such as interleukin-1 beta (IL-1β), interleukin-8 (IL-8), tumor necrosis factor alpha (TNF-α), and monocyte chemoattractant protein-1 (MCP-1) were considerably increased by treatment with LPS in macrophages differentiated from ML-1 monocytes. Interestingly, LPS-induced increase in expression of pro-inflammatory cytokine levels is reduced by CDDO-IM. In addition, endogenous upregulation of a series of antioxidant molecules by CDDO-IM provided protection against LPS-induced cytotoxicity in macrophages. LPS-mediated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) transcriptional activity was also noted to decrease upon treatment with CDDO-IM in macrophages suggesting the involvement of the NF-κB signaling. This study would contribute to improve our understanding of the detoxification of endotoxin LPS by the triterpenoid CDDO-IM.

The Traf2DNxBCL2-tg Mouse Model of Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma Recapitulates the Biased IGHV Gene Usage, Stereotypy, and Antigen-Specific HCDR3 Selection of Its Human Counterpart

Chronic lymphocytic leukemia (CLL)/Small lymphocytic lymphoma (SLL) is a heterogeneous disease consisting of at least two separate subtypes, based on the mutation status of the immunoglobulin heavy chain variable gene (IGHV) sequence. Exposure to antigens seems to play a role in malignant transformation and in the selection and expansion of more aggressive CLL clones. Furthermore, a biased usage of particular IGHV gene subgroups and the existence of stereotyped B-cell receptors (BCRs) are distinctive characteristics of human CLL. We have previously described that Traf2DN/BCL2 double-transgenic (tg, ^+/+) mice develop CLL/SLL with high incidence with aging. In this model, TNF-Receptor Associated Factor (TRAF)-2 deficiency cooperates with B cell lymphoma (BCL)-2 in promoting CLL/SLL in mice by specifically enforcing marginal zone (MZ) B cell differentiation and rendering B cells independent of BAFF for survival. In this report, we have performed the sequencing of the IGHV-D-J rearrangements of B cell clones from the Traf2DN/BCL2-tg^+/+ mice with CLL/SLL. The results indicate that these mice develop oligoclonal and monoclonal B cell expansions. Allotransplantation of the oligoclonal populations into immunodeficient mice resulted in the preferential expansion of one of the parental clones. The analysis of the IGHV sequences indicated that 15% were mutated (M) and 85% unmutated (UM). Furthermore, while the Traf2DN/BCL2-tg^-/- (wild-type), ^-/+ (BCL2 single-tg) and ^+/- (Traf2DNDN single-tg) littermates showed the expression of various IGHV gene subgroups, the CLL/SLL expanded clones from the Traf2DN/BCL2-tg^+/+ (double-transgenic) mice showed a more restricted IGHV gene subgroup usage and an overrepresentation of particular IGHV genes. In addition, the HCDR3-encoded protein sequence indicates the existence of stereotyped immunoglobulin (Ig) in the BCRs and strong similarities with BCR recognizing autoantigens and pathogen-associated antigens. Altogether, these results highlight the remarkable similarities between the CLL/SLL developed by the Traf2DN/BCL2-tg^+/+ mice and its human counterpart.

The role of natural products in revealing NRF2 function

Covering: up to 2020The transcription factor NRF2 is one of the body's major defense mechanisms, driving transcription of >300 antioxidant response element (ARE)-regulated genes that are involved in many critical cellular processes including redox regulation, proteostasis, xenobiotic detoxification, and primary metabolism. The transcription factor NRF2 and natural products have an intimately entwined history, as the discovery of NRF2 and much of its rich biology were revealed using natural products both intentionally and unintentionally. In addition, in the last decade a more sinister aspect of NRF2 biology has been revealed. NRF2 is normally present at very low cellular levels and only activated when needed, however, it has been recently revealed that chronic, high levels of NRF2 can lead to diseases such as diabetes and cancer, and may play a role in other diseases. Again, this "dark side" of NRF2 was revealed and studied largely using a natural product, the quassinoid, brusatol. In the present review, we provide an overview of NRF2 structure and function to orient the general reader, we will discuss the history of NRF2 and NRF2-activating compounds and the biology these have revealed, and we will delve into the dark side of NRF2 and contemporary issues related to the dark side biology and the role of natural products in dissecting this biology.

Nutraceuticals and "Repurposed" Drugs of Phytochemical Origin in Prevention and Interception of Chronic Degenerative Diseases and Cancer

BACKGROUND

Chronic, degenerative diseases are often characterized by inflammation and aberrant angiogenesis. For these pathologies, including rheumatoid arthritis, cardiovascular and autoimmune diseases, cancer, diabetes, and obesity, current therapies have limited efficacy.

OBJECTIVES

The validation of novel (chemo)preventive and interceptive approaches, and the use of new or repurposed agents, alone or in combination with registered drugs, are urgently required.

RESULTS

Phytochemicals (triterpenoids, flavonoids, retinoids) and their derivatives, nonsteroidal anti-inflammatory drugs (aspirin) as well as biguanides (metformin and phenformin) originally developed from phytochemical backbones, are multi-target agents showing antiangiogenic and anti-anti-inflammatory proprieties. Many of them target AMPK and metabolic pathways such as the mTOR axis. We summarize the beneficial effects of several compounds in conferring protection and supporting therapy, and as a paradigm, we present data on terpenoids & biquanides on beer hop xanthohumol and hydroxytryrosol from olive mill waste waters.

CONCLUSIONS

These molecules could be employed for combinatorial chemoprevention and interception approaches or chemoprevention/therapy regimens for cancer and other chronic complex diseases.

Apoptosis inducers in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is characterized by a typical defect in apoptosis and is still an incurable disease. Numerous apoptosis inducers have been described. These synthetic compounds and natural products (mainly derived from plants) display antileukemic properties in vitro and in vivo and some have even been tested in the clinic in CLL. They act through several different mechanisms. Most of them involve proteins of the Bcl-2 family, which are the key regulators in triggering the mitochondrial pathway of caspase-dependent apoptosis. Thus, the Mcl-1/Noxa axis appeared as a target. Here I overview natural and synthetic apoptosis inducers and their mechanisms of action in CLL cells. Opportunities for developing novel, apoptosis-based therapeutics are presented.

Oleanolic acid and its synthetic derivatives for the prevention and therapy of cancer: preclinical and clinical evidence

Oleanolic acid (OA, 3β-hydroxyolean-12-en-28-oic acid) is a ubiquitous pentacyclic multifunctional triterpenoid, widely found in several dietary and medicinal plants. Natural and synthetic OA derivatives can modulate multiple signaling pathways including nuclear factor-κB, AKT, signal transducer and activator of transcription 3, mammalian target of rapamycin, caspases, intercellular adhesion molecule 1, vascular endothelial growth factor, and poly (ADP-ribose) polymerase in a variety of tumor cells. Importantly, synthetic derivative of OA, 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO), and its C-28 methyl ester (CDDO-Me) and C28 imidazole (CDDO-Im) have demonstrated potent antiangiogenic and antitumor activities in rodent cancer models. These agents are presently under evaluation in phase I studies in cancer patients. This review summarizes the diverse molecular targets of OA and its derivatives and also provides clear evidence on their promising potential in preclinical and clinical situations.

Synthetic oleanane triterpenoids: multifunctional drugs with a broad range of applications for prevention and treatment of chronic disease

We review the rationale for the use of synthetic oleanane triterpenoids (SOs) for prevention and treatment of disease, as well as extensive biological data on this topic resulting from both cell culture and in vivo studies. Emphasis is placed on understanding mechanisms of action. SOs are noncytotoxic drugs with an excellent safety profile. Several hundred SOs have now been synthesized and in vitro have been shown to: 1) suppress inflammation and oxidative stress and therefore be cytoprotective, especially at low nanomolar doses, 2) induce differentiation, and 3) block cell proliferation and induce apoptosis at higher micromolar doses. Animal data on the use of SOs in neurodegenerative diseases and in diseases of the eye, lung, cardiovascular system, liver, gastrointestinal tract, and kidney, as well as in cancer and in metabolic and inflammatory/autoimmune disorders, are reviewed. The importance of the cytoprotective Kelch-like erythroid cell-derived protein with CNC homology-associated protein 1/nuclear factor (erythroid-derived 2)-like 2/antioxidant response element (Keap1/Nrf2/ARE) pathway as a mechanism of action is explained, but interactions with peroxisome proliferator-activated receptor γ (PARPγ), inhibitor of nuclear factor-κB kinase complex (IKK), janus tyrosine kinase/signal transducer and activator of transcription (JAK/STAT), human epidermal growth factor receptor 2 (HER2)/ErbB2/neu, phosphatase and tensin homolog (PTEN), the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway, mammalian target of rapamycin (mTOR), and the thiol proteome are also described. In these interactions, Michael addition of SOs to reactive cysteine residues in specific molecular targets triggers biological activity. Ultimately, SOs are multifunctional drugs that regulate the activity of entire networks. Recent progress in the earliest clinical trials with 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO) methyl ester (bardoxolone methyl) is also summarized.

TNFR-associated factor 2 deficiency in B lymphocytes predisposes to chronic lymphocytic leukemia/small lymphocytic lymphoma in mice

We have previously shown that transgenic (tg) mice expressing in B lymphocytes both BCL-2 and a TNFR-associated factor 2 (TRAF2) mutant lacking the really interesting new gene and zinc finger domains (TRAF2DN) develop small lymphocytic lymphoma and chronic lymphocytic leukemia with high incidence (Zapata et al. 2004. Proc. Nat. Acad. Sci. USA 101: 16600-16605). Further analysis of the expression of TRAF2 and TRAF2DN in purified B cells demonstrated that expression of both endogenous TRAF2 and tg TRAF2DN was negligible in Traf2DN-tg B cells compared with wild-type mice. This was the result of proteasome-dependent degradation, and rendered TRAF2DN B cells as bona fide TRAF2-deficient B cells. Similar to B cells with targeted Traf2 deletion, Traf2DN-tg mice show expanded marginal zone B cell population and have constitutive p100 NF-κB2 processing. Also, TRAF3, X-linked inhibitor of apoptosis, and Bcl-X(L) expression levels were increased, whereas cellular inhibitors of apoptosis 1 and 2 levels were drastically reduced compared with those found in wild-type B cells. Moreover, consistent with previous results, we also show that TRAF2 was required for efficient JNK and ERK activation in response to CD40 engagement. However, TRAF2 was deleterious for BCR-mediated activation of these kinases. In contrast, TRAF2 deficiency had no effect on CD40-mediated p38 MAPK activation but significantly reduced BCR-mediated p38 activation. Finally, we further confirm that TRAF2 was required for CD40-mediated proliferation, but its absence relieved B cells of the need for B cell activating factor for survival. Altogether, our results suggest that TRAF2 deficiency cooperates with BCL-2 in promoting chronic lymphocytic leukemia/small lymphocytic lymphoma in mice, possibly by specifically enforcing marginal zone B cell accumulation, increasing X-linked inhibitor of apoptosis expression, and rendering B cells independent of B cell activating factor for survival.

Design of novel BH3 mimetics for the treatment of chronic lymphocytic leukemia

Impaired programmed cell death is an important factor in the pathogenesis of chronic lymphocytic leukemia (CLL) and in the development of resistance to chemoimmunotherapy. Hence, the reactivation of apoptotic processes is likely to be a pertinent strategy for circumventing this resistance. Proteins from the Bcl-2 family are critical elements in defective apoptosis. Some compounds induce the apoptosis of CLL cells ex vivo by downregulation of prosurvival members of this family (for example, Bcl-2 and Mcl-1), whereas others act by upregulation of proapoptotic Bcl-2 homology (BH) 3-only members (for example, Noxa and Bim). The concept of BH3 mimetics was prompted by the fact that BH3-only proteins are specific antagonistic ligands of prosurvival Bcl-2 family members. This led to the design of small molecules capable of inhibiting the activity of prosurvival Bcl-2 proteins and inducing apoptosis in leukemia cells in vitro and antileukemic effects in animal models. Several putative or actual BH3 mimetics are currently being trialed in the clinic. Two novel BH3 mimetics that can specifically bind to and antagonize Mcl-1 (a crucial antiapoptotic factor in CLL) have recently been discovered. The evaluation of this type of compound's clinical impact in CLL can now be considered.

The mitochondrial ATP-dependent Lon protease: a novel target in lymphoma death mediated by the synthetic triterpenoid CDDO and its derivatives

Synthetic triterpenoids are multitarget compounds exhibiting promise as preventative and therapeutic agents for cancer. Their proposed mechanism of action is by forming Michael adducts with reactive nucleophilic groups on target proteins. Our previous work demonstrates that the 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO) and its derivatives promote B-lymphoid cell apoptosis through a mitochondria-mediated pathway linked to mitochondrial protein aggregation. As one function of the Lon protease is to eliminate abnormal mitochondrial proteins, we hypothesized that CDDO-induced protein aggregation and lymphoma apoptosis occur by inactivating this enzyme. Here, we show that CDDO and its derivatives directly and selectively inhibit Lon. CDDO blocks Lon-mediated proteolysis in biochemical and cellular assays, but does not inhibit the 20S proteasome. Furthermore, a biotinylated-CDDO conjugate modifies mitochondrial Lon. A striking common phenotype of CDDO-treated lymphoma cells and Lon-knockdown cells is the accumulation of electron-dense aggregates within mitochondria. We also show that Lon protein levels are substantially elevated in malignant lymphoma cells, compared with resting or activated B cells. Finally, we demonstrate that Lon knockdown leads to lymphoma cell death. Together, these findings suggest that Lon inhibition plays a contributory role in CDDO-induced lymphoma cell death, and support the concept that mitochondrial Lon is a novel anticancer drug target.

Current evidence on the anticancer potential of Chios mastic gum

Chios mastic gum derived from the plant Pistacia lentiscus L. variation chia has been shown to exert beneficial effects on a wide range of human disorders. The most comprehensive data so far have indicated that mastic gum provides protection against gastrointestinal malfunctions and bacterial infections. Substantial evidence has also suggested that mastic gum exhibits hepatoprotective and cardioprotective, antiinflammatory/antioxidant, and antiatherogenic properties. In the last decade, an increasing number of studies further evaluated the potential antiproliferative properties of mastic gum against several types of human neoplasia. The present review aims to summarize the current data concerning the anticancer activities of mastic gum and their major constituents, highlighting also the molecular mechanisms through which they exert anticancer function. Mastic gum constituents that belong to the chemical class of triterpenoids appear to be mainly responsible for its anticancer potential. Thus, a brief discussion is dedicated to the anticancer activity of synthetic and naturally occurring triterpenoid analogues with similar chemical structure to mastic gum constituents. Taking into consideration the available data so far, Chios mastic gum could be considered as a conglomeration of effective anticancer drugs.

New synthetic triterpenoids: potent agents for prevention and treatment of tissue injury caused by inflammatory and oxidative stress

We review the original rationale for the development and the chemistry of a series of new synthetic oleanane triterpenoids (SO), based on oleanolic acid (1) as a starting material. Many of the new compounds that have been made, such as 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid ("CDDO", 8), are highly potent (activities found at levels below 1 nM) anti-inflammatory agents, as measured by their ability to block the cellular synthesis of the enzyme inducible nitric oxide synthase (iNOS) in activated macrophages. Details of the organic synthesis of new SO and their chemical mechanisms of biological activity are reviewed, as is formation of biotin conjugates for investigation of protein targets. Finally, we give a brief summary of important biological activities of SO in many organ systems in numerous animal models. Clinical investigation of a new SO (methyl 2-cyano-3,12-dioxooleana-1,9(11)dien-28-oate, "CDDO-Me", bardoxolone methyl, 13) is currently in progress.

Synthetic triterpenoids target the Arp2/3 complex and inhibit branched actin polymerization

Synthetic triterpenoids are anti-tumor agents that affect numerous cellular functions including apoptosis and growth inhibition. Here, we used mass spectrometric and protein array approaches and uncovered that triterpenoids associate with proteins of the actin cytoskeleton, including actin-related protein 3 (Arp3). Arp3, a subunit of the Arp2/3 complex, is involved in branched actin polymerization and the formation of lamellipodia. 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO)-Im and CDDO-Me were observed to 1) inhibit the localization of Arp3 and actin at the leading edge of cells, 2) abrogate cell polarity, and 3) inhibit Arp2/3-dependent branched actin polymerization. We confirmed our drug effects with siRNA targeting of Arp3 and observed a decrease in Rat2 cell migration. Taken together, our data suggest that synthetic triterpenoids target Arp3 and branched actin polymerization to inhibit cell migration.

Mesenchymal stromal cells alone or expressing interferon-beta suppress pancreatic tumors in vivo, an effect countered by anti-inflammatory treatment

BACKGROUND AIMS

Because of the inflammatory nature and extensive stromal compartment in pancreatic tumors, we investigated the role of mesenchymal stromal cells (MSC) to engraft selectively in pancreatic carcinomas and serve as anti-tumor drug delivery vehicles to control pancreatic cancer progression.

METHODS

Human pancreatic carcinoma cells, PANC-1, expressing renilla luciferase were orthotopically implanted into SCID mice and allowed to develop for 10 days. Firefly luciferase-transduced MSC or MSC expressing interferon (IFN)-beta were then injected intraperitoneally weekly for 3 weeks. Mice were monitored by bioluminescent imaging for expression of renilla (PANC-1) and firefly (MSC) luciferase.

RESULTS

MSC selectively homed to sites of primary and metastatic pancreatic tumors and inhibited tumor growth (P=0.032). The production of IFN-beta within the tumor site by MSC-IFN-beta further suppressed tumor growth (P=0.0000083). Prior studies indicated that MSC home to sites of inflammation; therefore, we sought to alter the tumor microenvironment through treatment with a potent anti-inflammatory agent. After treatment, inflammation-associated mediators were effectively down-regulated, including NFkappaB, vascular endothelial growth factor (VEGF) and interleukin (IL)-6 as well as chemokines involved in MSC migration (CCL3 and CCL25). Treatment with the anti-inflammatory agent CDDO-Me before and after MSC-IFN-beta injections resulted in reduction of MSC in the tumors and reversed the positive effect of tumor inhibition by MSC-IFN-beta alone (P=0.041).

CONCLUSIONS

These results suggest that MSC exhibit innate anti-tumor effects against PANC-1 cells and can serve as delivery vehicles for IFN-beta for the treatment of pancreatic cancer. However, these beneficial effects may be lost in therapies combining MSC with anti-inflammatory agents.

Delivery of antiinflammatory nutraceuticals by nanoparticles for the prevention and treatment of cancer

Extensive research within the last two decades has revealed that most chronic illnesses, including cancer, diabetes, and cardiovascular and pulmonary diseases, are mediated through chronic inflammation. Thus, suppressing chronic inflammation has the potential to delay, prevent, and even treat various chronic diseases, including cancer. Various nutraceuticals from fruits, vegetables, vitamins, spices, legumes, and traditional Chinese and Ayurvedic medicine have been shown to safely suppress proinflammatory pathways; however, their low bioavailability in vivo limits their use in preventing and treating cancer. We describe here the potential of nanotechnology to fill this gap. Several nutraceuticals, including curcumin, green tea polyphenols, coenzyme Q, quercetin, thymoquinone and others, have been packaged as nanoparticles and proven to be useful in "nanochemoprevention" and "nano-chemotherapy".

Phosphatidylinositol 3-kinase-δ inhibitor CAL-101 shows promising preclinical activity in chronic lymphocytic leukemia by antagonizing intrinsic and extrinsic cellular survival signals

Targeted therapy with imatinib in chronic myeloid leukemia (CML) prompted a new treatment paradigm. Unlike CML, chronic lymphocytic leukemia (CLL) lacks an aberrant fusion protein kinase but instead displays increased phosphatidylinositol 3-kinase (PI3K) activity. To date, PI3K inhibitor development has been limited because of the requirement of this pathway for many essential cellular functions. Identification of the hematopoietic-selective isoform PI3K-δ unlocks a new therapeutic potential for B-cell malignancies. Herein, we demonstrate that PI3K has increased enzymatic activity and that PI3K-δ is expressed in CLL cells. A PI3K-δ selective inhibitor CAL-101 promoted apoptosis in primary CLL cells ex vivo in a dose- and time-dependent fashion that was independent of common prognostic markers. CAL-101-mediated cytotoxicity was caspase dependent and was not diminished by coculture on stromal cells. In addition, CAL-101 abrogated protection from spontaneous apoptosis induced by B cell-activating factors CD40L, TNF-α, and fibronectin. In contrast to malignant cells, CAL-101 does not promote apoptosis in normal T cells or natural killer cells, nor does it diminish antibody-dependent cellular cytotoxicity. However, CAL-101 did decrease activated T-cell production of various inflammatory and antiapoptotic cytokines. Collectively, these studies provide rationale for the clinical development of CAL-101 as a first-in-class targeted therapy for CLL and related B-cell lymphoproliferative disorders.

Apoptosis in leukemias: regulation and therapeutic targeting

Nearly 25 years after the seminal publication of John Foxton Kerr that first described apoptosis, the process of regulated cell death, our understanding of this basic physiological phenomenon is far from complete [39]. From cardiovascular disease to cancer, apoptosis has assumed a central role with broad ranging therapeutic implications that depend on a complete understanding of this process, yet have also identified an incredibly complex regulatory system that is critical for development and is at the core of many diseases, challenging scientist and clinicians to step into its molecular realm and modulate its circuitry for therapeutic purposes. This chapter will review our understanding of the molecular circuitry that controls apoptosis in leukemia and the pharmacological manipulations of this pathway that may yield therapeutic benefit.

Nuclear factor kappaB inhibitors alleviate and the proteasome inhibitor PS-341 exacerbates radiation toxicity in zebrafish embryos

Inflammatory changes are a major component of the normal tissue response to ionizing radiation, and increased nuclear factor kappaB (NF-kappaB) activity is an important mediator of inflammatory responses. Here, we used zebrafish embryos to assess the capacity of two different classes of pharmacologic agents known to target NF-kappaB to modify radiation toxicity in the vertebrate organism. These were proteasome inhibitors, including lactacystin, MG132, and PS-341 (Bortezomib/VELCADE), and direct inhibitors of NF-kappaB activity, including ethyl pyruvate (EP) and the synthetic triterpenoid CDDO-TFEA (RTA401), among others. The proteasome inhibitors either did not significantly affect radiation sensitivity of zebrafish embryos (MG132, lactacystin) or rendered zebrafish embryos more sensitive to the lethal effects of ionizing radiation (PS-341). Radiosensitization by PS-341 was reduced in fish with impaired p53 expression or function but not associated with enhanced expression of select p53 target genes. In contrast, the direct NF-kappaB inhibitors EP and CDDO-TFEA significantly improved overall survival of lethally irradiated zebrafish embryos. In addition, direct NF-kappaB inhibition reduced radiation-induced apoptosis in the central nervous system, abrogated aberrations in body axis development, restored metabolization and secretion of a reporter lipid through the gastrointestinal system, and improved renal clearance compromised by radiation. In contrast to amifostine, EP and CDDO-TFEA not only protected against but also mitigated radiation toxicity when given 1 to 2 hours postexposure. Finally, four additional IkappaB kinase inhibitors with distinct mechanisms of action similarly improved overall survival of lethally irradiated zebrafish embryos. In conclusion, inhibitors of canonical pathways to NF-kappaB activation may be useful in alleviating radiation toxicity in patients.

Identification of a potent natural triterpenoid inhibitor of proteosome chymotrypsin-like activity and NF-kappaB with antimyeloma activity in vitro and in vivo

As multiple myeloma tumors universally dysregulate cyclin D genes we conducted high-throughput chemical library screens for compounds that induce suppression of cyclin D2 promoter transcription. The top-ranked compound was a natural triterpenoid, pristimerin. Strikingly, the early transcriptional response of cells treated with pristimerin closely resembles cellular responses elicited by proteosome inhibitors, with rapid induction of heat shock proteins, activating transcription factor 3 (ATF3), and CHOP. Enzymatic assays and immunoblotting confirm that pristimerin rapidly (< 90 minutes) and specifically inhibits chymotrypsin-like proteosome activity at low concentrations (< 100 nM) and causes accumulation of cellular ubiquitinated proteins. Notably, cytotoxic triterpenoids including pristimerin inhibit NF-kappaB activation via inhibition of IKK alpha or IKK beta, whereas proteosome inhibitors instead suppress NF-kappaB function by impairing degradation of ubiquitinated I kappaB. By inhibiting both IKK and the proteosome, pristimerin causes overt suppression of constitutive NF-kappaB activity in myeloma cells that may mediate its suppression of cyclin D. Multiple myeloma is exquisitely sensitive to proteosome or NF-kappaB pathway inhibition. Consistent with this, pristimerin is potently and selectively lethal to primary myeloma cells (IC(50) < 100 nM), inhibits xenografted plasmacytoma tumors in mice, and is synergistically cytotoxic with bortezomib--providing the rationale for pharmaceutical development of triterpenoid dual-function proteosome/NF-kappaB inhibitors as therapeutics for human multiple myeloma and related malignancies.