Delivering integrated strategies from a mobile unit to address the intertwining epidemics of HIV and addiction in people who inject drugs: the HPTN 094 randomized controlled trial protocol (the INTEGRA Study).

BACKGROUND: Persons with opioid use disorders who inject drugs (PWID) in the United States (US) face multiple and intertwining health risks. These include interference with consistent access, linkage, and retention to health care including medication for opioid use disorder (MOUD), HIV prevention using pre-exposure prophylaxis (PrEP), and testing and treatment for sexually transmitted infections (STIs). Most services, when available, including those that address substance misuse, HIV prevention, and STIs, are often provided in multiple locations that may be difficult to access, which further challenges sustained health for PWID. HPTN 094 (INTEGRA) is a study designed to test the efficacy of an integrated, "whole-person" strategy that provides integrated HIV prevention including antiretroviral therapy (ART), PrEP, MOUD, and STI testing and treatment from a mobile health delivery unit ("mobile unit") with peer navigation compared to peer navigation alone to access these services at brick and mortar locations. METHODS: HPTN 094 (INTEGRA) is a two-arm, randomized controlled trial in 5 US cities where approximately 400 PWID without HIV are assigned either to an experimental condition that delivers 26 weeks of "one-stop" integrated health services combined with peer navigation and delivered in a mobile unit or to an active control condition using peer navigation only for 26 weeks to the same set of services delivered in community settings. The primary outcomes include being alive and retained in MOUD and PrEP at 26 weeks post-randomization. Secondary outcomes measure the durability of intervention effects at 52 weeks following randomization. DISCUSSION: This trial responds to a need for evidence on using a "whole-person" strategy for delivering integrated HIV prevention and substance use treatment, while testing the use of a mobile unit that meets out-of-treatment PWID wherever they might be and links them to care systems and/or harm reduction services. Findings will be important in guiding policy for engaging PWID in HIV prevention or care, substance use treatment, and STI testing and treatment by addressing the intertwined epidemics of addiction and HIV among those who have many physical and geographic barriers to access care. TRIAL REGISTRATION: ClinicalTrials.gov NCT04804072 . Registered on 18 March 2021.

Selinexor for the treatment of multiple myeloma.

Introduction: Despite unprecedented advances in the treatment of multiple myeloma (MM), almost all patients develop a disease that is resistant to the five most commonly used and active anti-MM agents. The prognosis for this patient population is particularly poor resulting in an unmet need for additional therapeutic options. Exportin-1 (XPO-1) is a major nuclear export protein of macromolecular cargo frequently overexpressed in MM. Selinexor is a first-in-class, oral Selective-Inhibitor-of-Nuclear-Export (SINE) compound that impedes XPO-1. Based on results of the STORM-trial, selinexor in combination with dexamethasone was granted accelerated FDA approval for patients with penta-refractory MM in July 2019.Areas covered: This article summarizes our up-to-date knowledge on the pathophysiologic role of XPO-1 in MM. Furthermore, it reviews the most recent clinical data on selinexor in combination with dexamethasone and other anti-MM agents; and discusses its safety profile, management strategies; and potential future developments.Expert opinion: Selinexor represents a next-generation-novel agent with an innovative mechanism of action that marks a significant advance in the treatment of heavily pretreated MM patients. Ongoing studies investigate its therapeutic potential also in earlier lines of therapy. Additional data is needed to confirm that selinexor and other SINE compounds are a valuable addition to our current therapeutic armamentarium.

Ixazomib maintenance therapy in newly diagnosed multiple myeloma: An integrated analysis of four phase I/II studies.

OBJECTIVES: To evaluate the safety and efficacy of maintenance therapy with the oral proteasome inhibitor ixazomib in patients with newly diagnosed multiple myeloma (NDMM) not undergoing transplantation. METHODS: Data were pooled from four NDMM phase I/II studies; patients received induction therapy with once- or twice-weekly ixazomib plus lenalidomide-dexamethasone (IRd), melphalan-prednisone (IMP), or cyclophosphamide-dexamethasone (ICd), followed by single-agent ixazomib maintenance, given at the last tolerated dose during induction, until disease progression, death, or unacceptable toxicity. RESULTS: A total of 121 patients achieved stable disease or better after induction (weekly IRd, n = 25; twice-weekly IRd, n = 18; weekly or twice-weekly IMP, n = 35; weekly ICd, n = 43) and received ≥ 1 dose of ixazomib maintenance. Grade ≥ 3 drug-related adverse events occurred in 24% of patients during maintenance; each event was reported in ≤2% of patients. Rates of complete response were 22% after induction and 35% after maintenance. A total of 28 patients (23%) improved their response during maintenance. CONCLUSIONS: Ixazomib maintenance following ixazomib-based induction is associated with deepening of responses and a positive safety profile with no cumulative toxicity in patients with NDMM not undergoing transplantation, suggesting that ixazomib is feasible for long-term administration. Phase III investigation of ixazomib maintenance is ongoing.

Maintenance and continuous therapy for multiple myeloma.

INTRODUCTION: In multiple myeloma (MM), maintenance therapy is a longer, less intensive treatment course than initial therapy that is administered postinduction to delay disease progression. Maintenance and continuous therapy have been shown to suppress minimal residual disease and deepen and prolong responses, with the goal of improving progression-free survival and overall survival. Areas covered: In this review, we have summarized current clinical trial data on maintenance and continuous therapy in newly diagnosed MM and relapsed/refractory MM (RRMM), focusing on lenalidomide and bortezomib. We have also analyzed the potential uses of newer agents, including carfilzomib, daratumumab, elotuzumab, pomalidomide, and ixazomib. Expert commentary: Although lenalidomide- and bortezomib-containing regimens have demonstrated safety and efficacy, only lenalidomide is approved for maintenance; it is the preferred agent in the National Comprehensive Cancer Network and European Society for Medical Oncology guidelines. Furthermore, results from the FIRST trial support lenalidomide plus low-dose dexamethasone (Rd) as a standard of care for continuous therapy. In RRMM, newer agents have been successfully added to Rd and data from additional trials are awaited. The vital roles of maintenance and continuous therapy and their benefits are now more clearly understood, but important questions remain regarding optimal duration of therapy and regimens.

Target Identification of Compounds from a Cell Viability Phenotypic Screen Using a Bead/Lysate-Based Affinity Capture Platform.

The pharmaceutical industry has been continually challenged by dwindling target diversity. To obviate this trend, phenotypic screens have been adopted, complementing target-centric screening approaches. Phenotypic screens identify drug leads using clinically relevant and translatable mechanisms, remaining agnostic to targets. While target anonymity is advantageous early in the drug discovery process, it poses challenges to hit progression, including the development of backup series, retaining desired pharmacology during optimization, discovery of markers, and understanding mechanism-driven toxicity. Consequently, significant effort has been expended to elaborate the targets and mechanisms at work for promising screening hits. Affinity capture is commonly leveraged, where the compounds are linked to beads and targets are abstracted from cell homogenates. This technique has proven effective for identifying targets of kinase, PARP, and HDAC inhibitors, and examples of new targets have been reported. Herein, a three-pronged approach to target deconvolution by affinity capture is described, including the implementation of a uniqueness index that helps discriminate between bona fide targets and background. The effectiveness of this approach is demonstrated using characterized compounds that act on known and noncanonical target classes. The platform is subsequently applied to phenotypic screening hits, identifying candidate targets. The success rate of bead-based affinity capture is discussed.

The investigational proteasome inhibitor ixazomib for the treatment of multiple myeloma.

Ixazomib is an investigational, reversible 20S proteasome inhibitor. It is the first oral proteasome inhibitor under clinical investigation in multiple myeloma (MM). Under physiological conditions, the stable citrate ester drug substance, ixazomib citrate (MLN9708), rapidly hydrolyzes to the biologically active boronic acid, ixazomib (MLN2238). Preclinical studies have demonstrated antitumor activity in MM cell lines and xenograft models. In Phase I/II clinical studies ixazomib has had generally manageable toxicities, with limited peripheral neuropathy observed to date. Preliminary data from these studies indicate ixazomib is active as a single agent in relapsed/refractory MM and as part of combination regimens in newly diagnosed patients. Phase III studies in combination with lenalidomide-dexamethasone are ongoing.

Preclinical data and early clinical experience supporting the use of histone deacetylase inhibitors in multiple myeloma.

Histone deacetylases (HDACs) mediate protein acetylation states, which in turn regulate normal cellular processes often dysregulated in cancer. These observations led to the development of HDAC inhibitors that target tumors through multiple effects on protein acetylation. Clinical evidence demonstrates that treatment with HDAC inhibitors (such as vorinostat, panobinostat, and romidepsin) in combination with other antimyeloma agents (such as proteasome inhibitors and immunomodulatory drugs) has promising antitumor activity in relapsed/refractory multiple myeloma patients. This mini-review highlights the role of protein acetylation in the development of cancers and the rationale for the use of HDAC inhibitors in this patient population.

Discovery of 2-((1H-benzo[d]imidazol-1-yl)methyl)-4H-pyrido[1,2-a]pyrimidin-4-ones as novel PKM2 activators.

The M2 isoform of pyruvate kinase is an emerging target for antitumor therapy. In this letter, we describe the discovery of 2-((1H-benzo[d]imidazol-1-yl)methyl)-4H-pyrido[1,2-a]pyrimidin-4-ones as potent and selective PKM2 activators which were found to have a novel binding mode. The original lead identified from high throughput screening was optimized into an efficient series via computer-aided structure-based drug design. Both a representative compound from this series and an activator described in the literature were used as molecular tools to probe the biological effects of PKM2 activation on cancer cells. Our results suggested that PKM2 activation alone is not sufficient to alter cancer cell metabolism.

New proteasome inhibitors in myeloma.

Proteasome inhibition has a validated role in cancer therapy since the successful introduction of bortezomib for the treatment of multiple myeloma (MM) and mantle cell lymphoma, leading to the development of second-generation proteasome inhibitors (PI) for MM patients in whom currently approved therapies have failed. Five PIs have reached clinical evaluation, with the goals of improving efficacy and limiting toxicity, including peripheral neuropathy (PN). Carfilzomib, an epoxyketone with specific chymothrypsin-like activity, acts as an irreversible inhibitor and was recently FDA approved for the response benefit seen in relapsed and refractory MM patients previously treated with bortezomib, thalidomide and lenalidomide. ONX-0912 is now under evaluation as an oral form with similar activity. The boronate peptides MLN9708 and CEP-18770 are orally bioactive bortezomib analogs with prolonged activity and greater tissue penetration. NPI-0052 (marizomib) is a unique, beta-lactone non-selective PI that has been shown to potently overcome bortezomib resistance in vitro. All of these second-generation PIs demonstrate encouraging anti-MM activity and appear to reduce the incidence of PN, with clinical trials ongoing.

Perifosine , an oral, anti-cancer agent and inhibitor of the Akt pathway: mechanistic actions, pharmacodynamics, pharmacokinetics, and clinical activity.

INTRODUCTION: Perifosine is a novel targeted oral Akt inhibitor currently in Phase III clinical development for treatment of colorectal cancer (CRC, in combination with capecitabine) and multiple myeloma (MM, in combination with bortezomib and dexamethasone). AREAS COVERED: The mechanism, preclinical testing, and clinical activity of perifosine in CRC and MM are discussed, with supportive pharmacokinetic information presented. Appropriate literature searches were carried out for background and discussion purposes. EXPERT OPINION: In preclinical models, perifosine has been shown to target phosphatidylinositol 3-kinase-Akt signaling. In CRC cell lines, preclinical studies indicate that perifosine may enhance the cytotoxic effects of fluorouracil, likely primarily through the nuclear transcription factor-kappa B pathway. A placebo-controlled Phase II randomized trial of capecitabine ± perifosine in previously treated patients with metastatic CRC showed the combination to be superior. In MM, Phase I/II clinical trials have established the optimal dosing schedule for perifosine and bortezomib in combination, and demonstrated that perifosine can sensitize to, or overcome resistance to, bortezomib, associated with prolonged responses and a favorable side effect profile. Ultimately, the favorable tolerability of perifosine will allow for its testing in combination with multiple targeted therapies to improve PFS and OS, which represent an important unmet need in these populations.

Tailoring treatment for multiple myeloma patients with relapsed and refractory disease.

Responses to treatment of relapsed and refractory multiple myeloma are characteristically short, and median survival is as brief as 6 months. Although prognostic factors in the context of relapsed and refractory disease require further characterization, high-risk patients include those with certain cytogenetic abnormalities, high beta2-microglobulin, and low serum albumin. The development of novel therapies targeting disease biology and tumor microenvironment has significantly improved the outlook for patients with relapsed and refractory disease, with bortezomib (Velcade), a first-in-class proteasome inhibitor, and the immunomodulatory agents thalidomide (Thalomid) and lenalidomide (Revlimid) constituting "backbone"agents in this setting. More recent approaches for treating relapsed and refractory myeloma that are recommended by the National Comprehensive Cancer Network include single-agent bortezomib, single-agent lenalidomide, bortezomib/dexamethasone, bortezomib plus pegylated liposomal doxorubicin, lenalidomide/dexamethasone, and lenalidomide/bortezomib/dexamethasone. Individualized treatment of progressive myeloma should take into account the time to progression and/or the type of prior therapy. Additional clinical challenges discussed in this article are renal dysfunction, extramedullary disease, and advanced bone disease. Finally, participation in clinical trials is especially encouraged in this patient population.

Impact of high-dose chemotherapy on the ability to deliver subsequent local-regional radiotherapy for breast cancer: analysis of Cancer and Leukemia Group B Protocol 9082.

PURPOSE: To report, from Cancer and Leukemia Group B Protocol 9082, the impact of high-dose cyclophosphamide, cisplatin, and BCNU (HD-CPB) vs. intermediate-dose CPB (ID-CPB) on the ability to start and complete the planned course of local-regional radiotherapy (RT) for women with breast cancer involving >or=10 axillary nodes. METHODS AND MATERIALS: From 1991 to 1998, 785 patients were randomized. The HD-CPB and ID-CPB arms were balanced regarding patient characteristics. The HD-CPB and ID-CPB arms were compared on the probability of RT initiation, interruption, modification, or incompleteness. The impact of clinical variables and interactions between variables were also assessed. RESULTS: Radiotherapy was initiated in 82% (325 of 394) of HD-CPB vs. 92% (360 of 391) of ID-CPB patients (p = 0.001). On multivariate analyses, RT was less likely given to patients who were randomized to HD treatment (odds ratio [OR] = 0 .38, p < 0.001), older (p = 0.005), African American (p = 0.003), postmastectomy (p = 0.02), or estrogen receptor positive (p = 0.03). High-dose treatment had a higher rate of RT interruption (21% vs. 12%, p = 0.001, OR = 2.05), modification (29% vs. 14%, p = 0.001, OR = 2.46), and early termination of RT (9% vs. 2%, p = 0.0001, OR = 5.35), compared with ID. CONCLUSION: Treatment arm significantly related to initiation, interruption, modification, and early termination of RT. Patients randomized to HD-CPB were less likely to initiate RT, and of those who did, they were more likely to have RT interrupted, modified, and terminated earlier than those randomized to ID-CPB. The observed lower incidence of RT usage in African Americans vs. non-African Americans warrants further study.

Emerging therapies for multiple myeloma.

Multiple myeloma (MM) is a clonal plasma cell malignancy clinically characterized by osteolytic lesions, immunodeficiency, and renal disease. There are an estimated 750,000 people diagnosed with MM worldwide, with a median overall survival of 3 - 5 years. Besides chromosomal aberrations, translocations, and mutations in essential growth and tumor-suppressor genes, accumulating data strongly highlight the pathophysiologic role of the bone marrow (BM) microenvironment in MM pathogenesis. Based on this knowledge, several novel agents have been identified, and treatment options in MM have fundamentally changed during the last decade. Thalidomide, bortezomib, and lenalidomide have been incorporated into conventional cytotoxic and transplantation regimens, first in relapsed and refractory and now also in newly diagnosed MM. Despite these significant advances, there remains an urgent need for more efficacious and tolerable drugs. Indeed, a plethora of preclinical agents awaits translation from the bench to the bedside. This article reviews the scientific rationale of new therapy regimens and newly identified therapeutic agents - small molecules as well as therapeutic antibodies - that hold promise to further improve outcome in MM.

Charged amino acid residues 997-1000 of human apolipoprotein B100 are critical for the initiation of lipoprotein assembly and the formation of a stable lipidated primordial particle in McA-RH7777 cells.

We previously demonstrated that a portion, or perhaps all, of the residues between 931 and 1000 of apolipoprotein (apo) B100 are required for the initiation of apoB-containing particle assembly. Based on our structural model of the first 1000 residues of apoB (designated as apoB:1000), we hypothesized that this domain folds into a three-sided lipovitellin-like "lipid pocket" via a hairpin-bridge mechanism. We proposed that salt bridges are formed between four tandem charged residues 717-720 in the turn of the hairpin bridge and four tandem complementary residues 997-1000 located at the C-terminal end of the model. To identify the specific motif within residues 931 and 1000 that is critical for apoB particle assembly, apoB:956 and apoB:986 were produced. To test the hairpin-bridge hypothesis, the following mutations were made: 1) residues 997-1000 deletion (apoB:996), 2) residues 717-720 deletion (apoB:1000Delta717-720), and 3) substitution of charged residues 997-1000 with alanines (apoB:996 + 4Ala). Characterization of particles secreted by stable transformants of McA-RH7777 cells demonstrated the following. 1) ApoB:956 did not form stable particles and was secreted as large lipid-rich aggregates. 2) ApoB:986 formed both a lipidated particle that was denser than HDL(3) and large lipid-rich aggregates. 3) Compared with wild-type apoB:1000, apoB:1000Delta717-720 displayed the following: (i) significantly diminished capacity to form intact lipidated particles and (ii) increased propensity to form large lipid-rich aggregates. 4) In striking contrast to wild-type apoB:1000, (i) apoB:996 and apoB:996 + 4Ala were highly susceptible to intracellular degradation, (ii) only a small proportion of the secreted proteins formed stable HDL(3)-like lipoproteins, and (iii) a majority of the secreted proteins formed large lipid-rich aggregates. We conclude that the first 1000 amino acid residues of human apoB100 are required for the initiation of nascent apoB-containing lipoprotein assembly, and residues 717-720 and 997-1000 play key roles in this process, perhaps via a hairpin-bridge mechanism.

Application of a high-density oligonucleotide microarray approach to study bacterial population dynamics during uranium reduction and reoxidation.

Reduction of soluble uranium U(VI) to less-soluble uranium U(IV) is a promising approach to minimize migration from contaminated aquifers. It is generally assumed that, under constant reducing conditions, U(IV) is stable and immobile; however, in a previous study, we documented reoxidation of U(IV) under continuous reducing conditions (Wan et al., Environ. Sci. Technol. 2005, 39:6162-6169). To determine if changes in microbial community composition were a factor in U(IV) reoxidation, we employed a high-density phylogenetic DNA microarray (16S microarray) containing 500,000 probes to monitor changes in bacterial populations during this remediation process. Comparison of the 16S microarray with clone libraries demonstrated successful detection and classification of most clone groups. Analysis of the most dynamic groups of 16S rRNA gene amplicons detected by the 16S microarray identified five clusters of bacterial subfamilies responding in a similar manner. This approach demonstrated that amplicons of known metal-reducing bacteria such as Geothrix fermentans (confirmed by quantitative PCR) and those within the Geobacteraceae were abundant during U(VI) reduction and did not decline during the U(IV) reoxidation phase. Significantly, it appears that the observed reoxidation of uranium under reducing conditions occurred despite elevated microbial activity and the consistent presence of metal-reducing bacteria. High-density phylogenetic microarrays constitute a powerful tool, enabling the detection and monitoring of a substantial portion of the microbial population in a routine, accurate, and reproducible manner.

The genome sequence of the obligately chemolithoautotrophic, facultatively anaerobic bacterium Thiobacillus denitrificans.

The complete genome sequence of Thiobacillus denitrificans ATCC 25259 is the first to become available for an obligately chemolithoautotrophic, sulfur-compound-oxidizing, beta-proteobacterium. Analysis of the 2,909,809-bp genome will facilitate our molecular and biochemical understanding of the unusual metabolic repertoire of this bacterium, including its ability to couple denitrification to sulfur-compound oxidation, to catalyze anaerobic, nitrate-dependent oxidation of Fe(II) and U(IV), and to oxidize mineral electron donors. Notable genomic features include (i) genes encoding c-type cytochromes totaling 1 to 2 percent of the genome, which is a proportion greater than for almost all bacterial and archaeal species sequenced to date, (ii) genes encoding two [NiFe]hydrogenases, which is particularly significant because no information on hydrogenases has previously been reported for T. denitrificans and hydrogen oxidation appears to be critical for anaerobic U(IV) oxidation by this species, (iii) a diverse complement of more than 50 genes associated with sulfur-compound oxidation (including sox genes, dsr genes, and genes associated with the AMP-dependent oxidation of sulfite to sulfate), some of which occur in multiple (up to eight) copies, (iv) a relatively large number of genes associated with inorganic ion transport and heavy metal resistance, and (v) a paucity of genes encoding organic-compound transporters, commensurate with obligate chemolithoautotrophy. Ultimately, the genome sequence of T. denitrificans will enable elucidation of the mechanisms of aerobic and anaerobic sulfur-compound oxidation by beta-proteobacteria and will help reveal the molecular basis of this organism's role in major biogeochemical cycles (i.e., those involving sulfur, nitrogen, and carbon) and groundwater restoration.

A novel carbohydrate-based therapeutic GCS-100 overcomes bortezomib resistance and enhances dexamethasone-induced apoptosis in multiple myeloma cells.

Human multiple myeloma is a presently incurable hematologic malignancy, and novel biologically based therapies are urgently needed. GCS-100 is a polysaccharide derived from citrus pectin in clinical development for the treatment of cancer. Here we show that GCS-100 induces apoptosis in various multiple myeloma cell lines, including those resistant to dexamethasone, melphalan, or doxorubicin. Examination of purified patient multiple myeloma cells showed similar results. Specifically, GCS-100 decreases viability of bortezomib/PS-341-resistant multiple myeloma patient cells. Importantly, GCS-100 inhibits multiple myeloma cell growth induced by adhesion to bone marrow stromal cells; overcome the growth advantage conferred by antiapoptotic protein Bcl-2, heat shock protein-27, and nuclear factor-kappaB; and blocks vascular endothelial growth factor-induced migration of multiple myeloma cells. GCS-100-induced apoptosis is associated with activation of caspase-8 and caspase-3 followed by proteolytic cleavage of poly(ADP-ribose) polymerase enzyme. Combined with dexamethasone, GCS-100 induces additive anti-multiple myeloma cytotoxicity associated with mitochondrial apoptotic signaling via release of cytochrome c and Smac followed by activation of caspase-3. Moreover, GCS-100 + dexamethasone-induced apoptosis in multiple myeloma cells is accompanied by a marked inhibition of an antiapoptotic protein Galectin-3, without significant alteration in Bcl-2 expression. Collectively, these findings provide the framework for clinical evaluation of GCS-100, either alone or in combination with dexamethasone, to inhibit tumor growth, overcome drug resistance, and improve outcome for patients with this universally fatal hematologic malignancy.

Novel biological therapies for the treatment of multiple myeloma.

The therapeutic management of multiple myeloma (MM) for the last several decades has mainly involved regimens based on use of glucocorticoids and cytotoxic chemotherapeutics. Despite progress in delineating the activity of such regimens, at either conventional or high doses, MM has remained an incurable disease, without substantial improvement in the median overall survival. This has sparked major interest in the development of novel therapies that in part capitalize on recent advances in our understanding of the biology of MM, including the molecular mechanisms by which MM cell-host bone marrow (BM) interactions regulate tumor-cell growth, survival, and drug resistance in the BM milieu. The development of in vitro and in vivo models of MM-stromal interactions has allowed not only for better characterization of these molecular phenomena but also for identification of specific therapeutic strategies to overcome these interactions and achieve an enhanced anti-MM effect, even against MM resistant to conventional therapies. Herein, we review the latest progress in the development of these novel anti-MM therapies, with major focus on therapies which have translated from preclinical evaluation to clinical application, including thalidomide and its more potent immunomodulatory (IMiD) derivatives, the first-in-class proteasome inhibitor bortezomib (formerly known as PS-341), and arsenic trioxide (As2O3).

Honokiol overcomes conventional drug resistance in human multiple myeloma by induction of caspase-dependent and -independent apoptosis.

Honokiol (HNK) is an active component purified from magnolia, a plant used in traditional Chinese and Japanese medicine. Here we show that HNK significantly induces cytotoxicity in human multiple myeloma (MM) cell lines and tumor cells from patients with relapsed refractory MM. Neither coculture with bone marrow stromal cells nor cytokines (interleukin-6 and insulin-like growth factor-1) protect against HNK-induced cytotoxicity. Although activation of caspases 3, 7, 8, and 9 is triggered by HNK, the pan-caspase inhibitor z-VAD-fmk does not abrogate HNK-induced apoptosis. Importantly, release of an executioner of caspase-independent apoptosis, apoptosis-inducing factor (AIF), from mitochondria is induced by HNK treatment. HNK induces apoptosis in the SU-DHL4 cell line, which has low levels of caspase 3 and 8 associated with resistance to both conventional and novel drugs. These results suggest that HNK induces apoptosis via both caspase-dependent and -independent pathways. Furthermore, HNK enhances MM cell cytotoxicity and apoptosis induced by bortezomib. In addition to its direct cytotoxicity to MM cells, HNK also represses tube formation by endothelial cells, suggesting that HNK inhibits neovascurization in the bone marrow microenvironment. Taken together, our results provide the preclinical rationale for clinical protocols of HNK to improve patient outcome in MM.

Proteasome inhibition in the treatment of cancer.

The proteasome is the main extralysosomal system involved in intracellular proteolysis. A number of proteasome substrates, including cyclins, IkappaB, and p53, are critical to cell cycle progression and apoptosis. Interruption of the degradation of these substrates through proteasome inhibition is a novel and unique approach to the treatment of malignancies. First-generation proteasome inhibitors lacked usefulness because of broad specificity and irreversible binding to the proteasome. However, the later synthesis of the peptide boronic acid proteasome inhibitor bortezomib allowed for selective, reversible binding. Basic investigations have reported the antitumor activity of bortezomib in a variety of hematologic and solid tumor models and have demonstrated the ability of bortezomib to enhance chemosensitivity and overcome cellular mechanisms of drug resistance attributable, in part, to abrogation of NF-kappaB induction. In patients with relapsed, refractory multiple myeloma who had received a median of six prior regimens, treatment with bortezomib resulted in a 35% response rate (complete plus partial plus minimal response) using criteria of the European Group for Blood and Marrow Transplantation. Encouraging activity has been demonstrated with bortezomib in the first-line treatment of myeloma and in patients with mantle cell lymphoma. Investigations of its utility in the treatment of patients with solid tumors are ongoing.