Combination Treatment Of Bortezomib Research Articles

Cytotoxic and Apoptotic Effects of Pinostilbene and Bortezomib Combination Treatment on Human Multiple Myeloma Cells.

Multiple myeloma (MM) is a cancer of plasma cells in the bone marrow characterized by bone lesions, hypercalcemia, anemia, and renal failure. Bortezomib (BTZ), a common treatment for MM, is a proteasome inhibitor that induces apoptosis in MM cells. However, high doses of BTZ can be very toxic, signifying a need for a synergistic drug combination to improve treatment efficacy. Resveratrol (RES), a phenolic compound found in grapes, has been shown to inhibit MM cell growth. We sought to identify a synergistic combination of BTZ with a RES derivative and analyze the effects on reducing viability and inducing apoptosis in human MM cells. BTZ as well as RES and its derivatives pinostilbene (PIN) and piceatannol (PIC) decreased MM cell viability in a dose- and time-dependent manner and increased expression of cleaved proapoptotic proteins poly(ADP-ribose) polymerase 1 (PARP1) and caspase-3 in a dose-dependent manner. The combination of 5 nM BTZ and 5 μM PIN was identified to have synergistic cytotoxic effects in MM RPMI 8226 cells. MM RPMI 8226 cells treated with this combination for 24 h showed increased cleaved PARP1 and caspase-3 expression and higher percentages of apoptotic cells versus cells treated with the individual compounds alone. The treatment also showed increased apoptosis induction in MM RPMI 8226 cells co-cultured with human bone marrow stromal HS-5 cells in a Transwell model used to mimic the bone marrow microenvironment. Expression of oxidative stress defense proteins (catalase, thioredoxin, and superoxide dismutase) in RPMI 8226 cells were reduced after 24 h treatment, and cytotoxic effects of the treatment were ameliorated by antioxidant N-acetylcysteine (NAC), suggesting the treatment impacts antioxidant levels in RPMI 8226 cells. Our results suggest that this combination of BTZ and PIN decreases MM cell viability synergistically by inducing apoptosis and oxidative stress in MM cells.

Combination treatment of bortezomib and epirubicin increases the expression of TNFRSF10 A/B, and induces TRAIL-mediated cell death in colorectal cancer cells

Colorectal cancer is one of the most common cancers worldwide, affecting the colon and rectum. A major problem in the treatment of colorectal cancer is acquired chemoresistance, including resistance against death receptor-induced apoptosis. Therefore, investigating new biomarkers for the treatment of the disease and sensitization strategies against TRAIL might be of high clinical importance. TNFRSF10A/B are known as death receptors for TRAIL-induced apoptotic cell death. In this study, we used multiple bioinformatic tools and experimental analyses to investigate the role of TRAIL receptors TNFRSF10A and TNFRSF10B in colorectal cancer. We also identified the potential effect of bortezomib and epirubicin in the induction of TRAIL-mediated apoptotic cell death. Here, we showed that TNFRSF10 A/B expressions are upregulated in various tumor types, including COAD, and its high expression is decreased with the different clinicopathological parameters in COAD. We also found an association between TNFRSF10 A/B expression and tumor molecular subtypes. We further detected the association between the expression of TNFRSF10 A/B and immune cell tumor infiltration, including B cells, CD8+ T cells, neutrophils and dendritic cells. In addition, we showed that combining bortezomib and epirubicin treatment leads to the upregulation of TNFRSF10 A/B in colorectal cancer cells in vitro. The increase in the expression of death receptors was correlated with higher active caspase-3 levels following the incubation of cells with recombinant TRAIL protein, which is a ligand for TNFRSF10 A/B receptors. Our results suggest that TNFRSF10 A/B may be a marker to differentiate tumor molecular subtypes in colorectal cancer. The expression of TNFRSF10 A/B may be associated with the recruitment of immune cells into tumors and the development of tumor suppression. The combination of bortezomib and epirubicin treatment might sensitize colorectal cancer cells to TRAIL-induced apoptosis via the upregulation of death receptor.

Successful AAV8 re-administration: Suppression of capsid-specific neutralizing antibodies by a combination treatment of bortezomib and CD20 mAb in a mouse model of Pompe disease.

A major challenge to AAV mediated gene therapy is the presence of anti-AAV capsid neutralizing antibodies (NAbs), which can block viral vector transduction even at very low titers. Here we examined the ability of a combination immunosuppression (IS) treatment with bortezomib and a mouse-specific CD20 mAb to suppress anti-AAV NAbs and enable re-administration of AAV vectors of the same capsid in mice. An AAV8 vector (AAV8-CB-hGAA) that ubiquitously expresses human α-glucosidase was used for initial gene therapy and a second AAV8 vector (AAV8-LSP-hSEAP) that contains a liver-specific promoter to express human secreted alkaline phosphatase was used for AAV re-administration. Plasma samples were used for determination of anti-AAV8 NAb titers. Cells isolated from whole blood, spleen, and bone marrow were analyzed for B-cell depletion by flow cytometry. The efficiency of AAV re-administration was determined by the secretion of hSEAP in blood. In näive mice, an eight-week IS treatment along with AAV8-CB-hGAA injection effectively depleted CD19+ B220+ B cells from blood, spleen, and bone marrow and prevented the formation of anti-AAV8 NAbs. Following administration of AAV8-LSP-hSEAP, increasing levels of hSEAP were detected in blood for up to 6 weeks, indicating successful AAV re-administration. In mice pre-immunized with AAV8-CB-hGAA, comparison of IS treatment for 8, 12, 16, and 20 weeks revealed that the 16-week IS treatment demonstrated the highest plasma hSEAP level following AAV8-LSP-hSEAP re-administration. Our data suggest that this combination treatment is an effective IS approach that will allow retreatment of patients with AAV mediated gene therapy.

Gambogenic Acid Enhances Chemosensitivity of Multiple Myeloma to Bortezomib through p53/ROS/p38 MAPK Apoptotic Pathway

Background: Multiple myeloma (MM) is the second most prevalent hematological cancer (10%) with a five-year survival rate of only 49%. Approval of bortezomib, the first in-class proteasome inhibitor, has significantly improved outcomes of MM in the last few years; however, the almost inevitable refractory or resistance has made a cure of MM remains out of reach. Identification and validation of novel effective targeted agents are necessary. As one of the natural compounds isolated from Traditional Chinese Medicine gamboge, gambogenic acid (GNA) is a very promising antitumor agent and has been proved to have more potent anticancer effect and less systemic toxicity according to early investigations. In our previous studies, we have demonstrated that GNA could synergistically potentiate bortezomib-induced apoptosis of MM. In this study, our aim was to further explore and understand the concrete apoptotic action mechanism of GNA and bortezomib combination treatment against MM in pre-clinical models.Methods: We performed pre-clinical studies in myeloma cell lines and mouse models treated by GNA and bortezomib, alone and in combination. Cell counting kit-8 (CCK-8) assay, combination index (CI) isobologram, flow cytometry (FCM), western blot, xenograft tumor models, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), immunohistochemistry (IHC) and oxidation-sensitive fluorescent dye carboxy-DCFDA were applied in this study. The thiol antioxidant N-acetylcysteine (NAC) and p38 MAPK inhibitor SB203580 were used to detect the effect of GNA and bortezomib combination therapy on ROS, p53 and p38 MAPK.Results: Both p53 wild type cell line MM.1S and mutant type cell line RPMI 8226 myeloma cell lines were sensitive to GNA therapy. Interestingly, GNA only enhanced the chemosensitivity of bortezomib on p53 wild type cell line MM.1S. Both 0.51μM GNA combined with 2.3nM bortezomib and 0.90μM GNA combined with 4.0nM bortezomib to MM.1S cells showed a more markedly apoptotic rate of MM compared with that of the single agent group of each accordingly (p <0.01; p <0.01), and the apoptosis was presented in a dosage- and time-dependent manner. Increased apoptosis of MM.1S cells was found via the activation of PARP cleavage, p53, Caspase-3 cleavage and Bax and inhibition of Bcl-2 expression. An increased antitumor effect of combination therapy of GNA and bortezomib on MM.1S xenograft models were also observed. A significant generation of ROS was detected after exposure of GNA and bortezomib in MM.1S cells. The expression level of phospho-p38MAPK was upregulated by combination therapy compared with that of single agent (p<0.05; p<0.05). To characterize the mechanisms of action of GNA in combination with bortezomib, we pretreated MM.1S cells with NAC and SB203580. We found that the apoptosis of MM.1S cells could be inhibited by both NAC and SB203580 (p<0.01; p<0.01). However, the generation of ROS could only be inhibited by NAC (p<0.05), and the elevated expression of p53 could be inhibited neither by NAC nor SB203580. These results indicated that p53/ROS/p38 MAPK pathway is a pre-requisite for GNA to accomplish the enhancement of chemosensitivity of MM to bortezomib.Conclusions: We demonstrate that GNA could potentiate apoptosis of MM induced by bortezomib in vivo and in vitro, and p53/ROS/p38 MAPK pathway plays a central role of the apoptotic action. Thus, our data provide a persuasive rationale for the successful utilization of dual GNA and bortezomib for chemotherapy in MM patients in the future. DisclosuresNo relevant conflicts of interest to declare.

Additive Benefits of Radium-223 Dichloride and Bortezomib Combination in a Systemic Multiple Myeloma Mouse Model.

Osteolytic bone disease is a hallmark of multiple myeloma (MM) mediated by MM cell proliferation, increased osteoclast activity, and suppressed osteoblast function. The proteasome inhibitor bortezomib targets MM cells and improves bone health in MM patients. Radium-223 dichloride (radium-223), the first targeted alpha therapy approved, specifically targets bone metastases, where it disrupts the activity of both tumor cells and tumor-supporting bone cells in mouse models of breast and prostate cancer bone metastasis. We hypothesized that radium-223 and bortezomib combination treatment would have additive effects on MM. In vitro experiments revealed that the combination treatment inhibited MM cell proliferation and demonstrated additive efficacy. In the systemic, syngeneic 5TGM1 mouse MM model, both bortezomib and radium-223 decreased the osteolytic lesion area, and their combination was more effective than either monotherapy alone. Bortezomib decreased the number of osteoclasts at the tumor–bone interface, and the combination therapy resulted in almost complete eradication of osteoclasts. Furthermore, the combination therapy improved the incorporation of radium-223 into MM-bearing bone. Importantly, the combination therapy decreased tumor burden and restored body weights in MM mice. These results suggest that the combination of radium-223 with bortezomib could constitute a novel, effective therapy for MM and, in particular, myeloma bone disease.

Regulation of Fas in response to bortezomib and epirubicin in colorectal cancer cells

Bortezomib is a reversible proteasome inhibitor affects the ubiquitin-proteasome mechanism to kill cancer cells, and inhibition of the proteasome modulates the expression of multiple target genes at the transcriptional level. Epirubicin is known as an anthracycline agent that interferes with DNA and RNA synthesis, and it can be used with other chemotherapeutic drugs in the treatment of post-surgical breast cancer. Epirubicin may have an anti-tumor effect against broad-spectrum tumor cells. However, it is a non-specific chemotherapeutic agent that can cause high toxicity if not used in appropriate doses. Here, we hypothesize that a combination treatment of bortezomib and epirubicin will induce immunogenic cell death in colorectal cancer cells by increasing expression of death receptors such as Fas, which will make these cancer cells more susceptible to Fas/FasL mediated tumor cell killing. Our data demonstrate that a combination of bortezomib and epirubicin significantly increases the sensitivity of colorectal carcinoma cells, but not healthy non-malignant epithelial cells, to apoptosis. The combination treatment significantly upregulates the transcriptional activation of Fas in colorectal cancer cells but not in normal cells. Our results suggest that combining bortezomib and epirubicin may simultaneously enhance tumor immunogenicity and the induction of antitumor immunity.

The Effect of Olaparib and Bortezomib Combination Treatment on Ovarian Cancer Cell Lines

Objective: Ovarian cancer (OC) is the deadliest gynecologic malignancy and has a poor survival rate due to late diagnosis and chemoresistance development. In the standard treatment of OC, platinum-based chemotherapeutics are used. However, following several rounds of chemotherapy, these drugs’ efficacy eventually becomes limited due to the development of chemoresistance in most patients who previously responded to this treatment. Therefore, overcoming chemoresistance in the treatment of OC is of high importance. In this study, we investigated the effect of combinatorial inhibition of poly(ADPribose) polymerase (PARP) and proteasome by olaparib and bortezomib on chemosensitive and chemoresistant OC cell lines. Materials and Methods: We used sulphorhodamine B assay to screen cell viability following drug treatments alone or in combination, and used the cytotoxicity data to model the effect of drugs on cell death in R programming environment. In addition to olaparib and bortezomib, we performed cytotoxicity screenings where we applied cisplatin to OC cells. We also carried out flow cytometry analysis to quantify apoptotic cells following treatments. Results: We showed that combination treatment was more effective on chemosensitive OC cell lines when cisplatin was not used. In the presence of cisplatin, olaparib and bortezomib combination treatment resulted in higher cytotoxicity in chemoresistant OC lines compared to chemosensitive OC cell lines. Combinatorial inhibition of PARP and proteasome led to a higher number of apoptotic cells in OV2008 chemosensitive cell line compared to drugs alone. Conclusion: Our data shows that olaparib and bortezomib combination treatment might show promise in vivo in the treatment of OC. Also, the efficacy of this combination treatment might be dependent on OC cells’ chemosensitivity profiles.

Combination treatment with 2-methoxyestradiol overcomes bortezomib resistance of multiple myeloma cells

Bortezomib is a proteasome inhibitor used for the treatment of relapsed/refractory multiple myeloma (MM). However, intrinsic and acquired resistance to bortezomib has already been observed in MM patients. In a previous report, we demonstrated that changes in the expression of mitochondrial genes lead to changes in mitochondrial activity and bortezomib susceptibility or resistance, and their combined effects contribute to the differential sensitivity or resistance of MM cells to bortezomib. Here we report that the combination treatment of bortezomib and 2-methoxyestradiol (2ME), a natural estrogen metabolite, induces mitochondria-mediated apoptotic cell death of bortezomib-resistant MM KMS20 cells via mitochondrial reactive oxygen species (ROS) overproduction. Bortezomib plus 2ME treatment induces a higher level of cell death compared with treatment with bortezomib alone and increases mitochondrial ROS and Ca2+ levels in KMS20 cells. Pretreatment with the antioxidant N-acetyl-L-cysteine scavenges mitochondrial ROS and decreases cell death after treatment with bortezomib plus 2ME in KMS20 cells. Moreover, we observed that treatment with bortezomib plus 2ME maintains the activation of c-Jun N-terminal kinase (JNK) and mitogen-activated protein kinase kinase kinase 4/7 (MKK4/7). Collectively, combination treatment with bortezomib and 2ME induces cell death via JNK-MKK4/7 activation by overproduction of mitochondrial ROS. Therefore, combination therapy with specific mitochondrial-targeting drugs may prove useful to the development of novel strategies for the treatment of bortezomib-resistant MM patients.

Identification of repurposed small molecule drugs for chordoma therapy

Chordoma is a rare, slow growing malignant tumor arising from remnants of the fetal notochord. Surgery is the first choice for chordoma treatment, followed by radiotherapy, although postoperative complications remain significant. Recurrence of the disease occurs frequently due to the anatomy of the tumor location and violation of the tumor margins at the initial surgery. Currently, there are no effective drugs available for patients with chordoma. Due to the rarity of the disease, there is limited opportunity to test agents in clinical trials and no concerted effort to develop agents for chordoma in the pharmaceutical industry. To rapidly and efficiently identify small molecules that inhibit chordoma cell growth, we screened the NCGC Pharmaceutical Collection (NPC) containing approximately 2800 clinically approved and investigational drugs at 15 different concentrations in chordoma cell lines, U-CH1 and U-CH2. We identified a group of drugs including bortezomib, 17-AAG, digitoxin, staurosporine, digoxin, rubitecan, and trimetrexate that inhibited chordoma cell growth, with potencies from 10 to 370 nM in U-CH1 cells, but less potently in U-CH2 cells. Most of these drugs also induced caspase 3/7 activity with a similar rank order as the cytotoxic effect on U-CH1 cells. Cantharidin, digoxin, digitoxin, staurosporine, and bortezomib showed similar inhibitory effect on cell lines and 3 primary chordoma cell cultures. The combination treatment of bortezomib with topoisomerase I and II inhibitors increased the therapeutic potency in U-CH2 and patient-derived primary cultures. Our results provide information useful for repurposing currently approved drugs for chordoma and potential approach of combination therapy.

Abstract 3312: Oncolytic HSV (34.5ENVE) sensitizes bortezomib-induced cancer cell killing through induction of RIP1 dependent necroptosis.

Abstract The aim of this study is to evaluate the combination of oncolytic herpes simplex virus (34.5ENVE) and bortezomib in the treatment of solid tumors. Although phase 1 clinical trials of oncolytic viruses have established the relative safety of this approach, evidence for efficacy has remained elusive. Therefore, strategies to enhance the efficacy of this treatment are being explored. We investigated the impact of 34.5ENVE in combination with bortezomib, a potent and selective proteosome inhibitor, in the treatment of multiple solid tumor models. In vitro, various human cancer cells were treated with bortezomib alone, 34.5ENVE alone, or the combination of the two. We analyzed the treatments for synergism in cancer cell killing using Chou-Talalay analysis (CI index &amp;lt;1: synergy; CI index &amp;lt; 0.8: strong synergy). Combination treatment of bortezomib and 34.5ENVE displayed strong synergism in multiple cell lines from ovarian cancer, head &amp; neck cancer, and glioma (CI index &amp;lt; 0.8). In vivo, subcutaneous and intracranial tumor xenografts were utilized to study the impact of bortezomib+34.5ENVE on anti-tumor efficacy. Survival was analyzed by the Kaplan-Meier method and evaluated with a two-sided log-rank test. In vivo, the combination of bortezomib and 34.5ENVE significantly enhanced anti-tumor efficacy and prolonged mouse survival. The impact of bortezomib on 34.5ENVE replication was measured by quantifying virus titer. Sub lethal doses of bortezomib increased virus replication (p value &amp;lt;0.001), and treatment of cells with higher doses did not change the absolute viral titer. To understand the mechanism of the synergistic interaction between 34.5ENVE and bortezomib, we analyzed western blotting for cellular markers of ER stress and the JNK signaling pathway. Bortezomib treatment induced ER stress with strong induction of Grp78, CHOP, PERK and IRE1α (western blot analysis). Additionally, the combination of bortezomib and 34.5ENVE increased phosphorylation of JNK and c-Jun more so than the single treatments alone. Production of reactive oxygen species (ROS) was then measured by FACS analysis of cells treated with CellROX. Consistent with JNK activation, increased ROS was observed in both bortezomib and 34.5ENVE treated cells. Furthermore, cells treated with both bortezomib and 34.5ENVE displayed much higher ROS levels compared to cells treated with either agent alone. Both N-acetylcysteine, a ROS scavenger, and dipheylene iodide, an NADPH oxidase inhibitor, rescued the increased synergistic killing. We also treated SP0600125, a selective JNK inhibitor, and necrostatin-1, an inhibitor of RIP1, to investigate the initiation of cell killing. Pretreatment with both inhibitors was able to rescue synergy (CI&amp;gt;0.8). These findings suggest that the combination of bortezomib and 34.5ENVE leads to synergistic cell killing mediated by RIP1 dependent necroptosis induction. Citation Format: Brian S. Hurwitz, Ji Young Yoo, Chelsea Bolyard, Jun-Ge Yu, Jeffery Wojton, Matthew Old, Balveen Kaur. Oncolytic HSV (34.5ENVE) sensitizes bortezomib-induced cancer cell killing through induction of RIP1 dependent necroptosis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3312. doi:10.1158/1538-7445.AM2013-3312

Bortezomib Sensitizes HCC Cells to CS-1008, an Antihuman Death Receptor 5 Antibody, through the Inhibition of CIP2A

Previously, we have shown that bortezomib overcame TRAIL resistance in hepatocellular carcinoma (HCC) cells via the inhibition of Akt. Here, we report that bortezomib sensitizes these TRAIL-resistant cells, including Huh-7, Hep3B, and Sk-Hep1, to CS-1008, a humanized agonistic antihuman death receptor 5 antibody. Cancerous inhibitor of protein phosphatase 2A (CIP2A) mediated the sensitizing effect of bortezomib to CS-1008 through inhibiting protein phosphatase 2A (PP2A) activity. Combination treatment of bortezomib and CS-1008 downregulated CIP2A in a concentration- and time-dependent manner, and increased PP2A activity in HCC cells. Importantly, ectopic expression of CIP2A decreased Akt-related PP2A activity, indicating that CIP2A negatively regulates Akt-related PP2A activity in HCC cells. Moreover, silencing CIP2A by short interfering RNA enhanced CS-1008-induced apoptosis in HCC cells and ectopic expression of CIP2A in HCC cells abolished CS-1008-induced apoptosis, indicating that CIP2A plays an important role in the sensitizing effect of bortezomib to CS-1008. Finally, our in vivo data showed that CS-1008 and bortezomib combination treatment decreased tumor growth significantly. In conclusion, bortezomib sensitized HCC cells to CS-1008 through the inhibition of CIP2A.

Tanespimycin and bortezomib combination treatment in patients with relapsed or relapsed and refractory multiple myeloma: results of a phase 1/2 study

This open-label, dose escalation, multicentre phase 1/2 trial was undertaken to determine the safety and tolerability of the heat shock protein 90 (HSP90) inhibitor tanespimycin (100-340 mg/m(2) )+ bortezomib (0·7-1·3 mg/m(2) ) given on days 1, 4, 8 and 11 in each 21-d cycle. Phase 2 expansion occurred at the highest tested dose of tanespimycin at 340 mg/m(2) and bortezomib at 1·3 mg/m(2) . Seventy-two patients (median age, 60 years) with relapsed or relapsed and refractory multiple myeloma (MM) were enrolled; 63 patients (89%) completed the study. Tanespimycin in combination with bortezomib was well tolerated; few patients experienced significant neutropenia, constipation and anorexia (<10%), and no patients developed severe peripheral neuropathy. Among 67 efficacy-evaluable patients, there were 2 (3%) complete responses and 8 (12%) partial responses, for an objective response rate (ORR) of 27%, including 8 (12%) minimal responses. Response rates were highest among bortezomib-naive patients and proved durable in all patient subgroups, including those with bortezomib-refractory disease. Pharmacodynamic analyses indicated that tanespimycin plus bortezomib effectively inhibited the proteasome, as evidenced by decreased 20S proteasome activity, and inhibited HSP90, as reflected by increased HSP70 expression. The results of this study support additional studies of this combination approach in MM.

Combination Therapy of Bortezomib (PS-341) and SAHA (Vorinostat) in Non-Small Cell Lung Cancer Cell Lines

Purpose: The recent introduction of targeted therapy for non-small cell lung cancer (NSCLC) has changed the paradigm of lung cancer chemotherapy. However, only a small portion of NSCLC patients received the benefit of these new drugs. A proteasome inhibitor (bortezomib) and a histone deacetylase inhibitor (SAHA) were approved for clinical use for treating some hematologic malignancies. In this study, we investigated the combination treatment of bortezomib and SAHA in NSCLC cell lines. Materials and Methods: The combined effects of bortezomib and SAHA on lung cancer cell lines were measured by Calcusyn software. Induction of apoptosis was examined by performing an Annexin V assay. Generation of reactive oxygen species (ROS) and protection by N-acetylcysteine were measured by flow cytometry after staining with DCFH-DA. The effect of the combination of drugs on apoptosis and autophagy was investigated by Western blot assay. Results: Strong synergism was found for the combination of bortezomib and SAHA. The synergistic interaction was mediated by strong apoptosis. Increased ROS generation was partly responsible for the induction of apoptosis, and this was suppressed by the ROS scavenger N-acetylcysteine. Combined treatment induced the strong activation of caspase-3 and the breakdown of the antiapoptotic molecule Bcl-2. Furthermore, increased breakdown of beclin-1, which is known to be an autophagic molecule, was also found. Conclusion: Combination therapy with bortezomib and SAHA showed a strong synergistic antitumor effect on human lung cancer cell lines. Enhanced induction of apoptosis was a responsible mechanism, and this was partly mediated by ROS generation. Further studies are warranted for determining the role of apoptosis and autophagy for this combination therapy. (J Lung Cancer

Effects of combination treatment of bortezomib and dexamethasone in SCCHN cell lines depend on tumor cell specificity.

Bortezomib has recently become the new treatment standard for relapsed or refractory multiple myeloma. We previously demonstrated that bortezomib also had a significant growth-inhibiting and apoptotic effect on squamous cell carcinoma of the head and neck (SCCHN) cells in vitro. Preclinical evidence has provided a rationale for combining bortezomib with dexamethasone in multiple myeloma, suggesting that the therapeutic effects of the two agents might be additive. These findings are in contrast with the results achieved in solid tumor models where the addition of dexamethasone reduced the efficacy of other antineoplastic drugs. In the present study, we investigated the effect of dexamethasone in combination with bortezomib in SCCHN cell lines for the first time. The antiproliferative effect of bortezomib alone or in combination with increasing concentrations of dexamethasone was investigated in four SCCHN cell lines. Cell growth inhibition and viability were measured quantitatively using WST and LDH assays. Bortezomib alone inhibited the growth of all four SCCHN cell lines significantly (p<0.047). The addition of dexamethasone leads to a clear tumor cell decline and showed a trend in enhancing the growth-inhibitory effect of bortezomib although the difference failed to reach statistical significance (p>0.05). Our first results show that dexamethasone increased the cytotoxic activity of bortezomib in most SCCHN cell lines investigated. These findings might be dependent on molecular factors such as the degree of tumor cell differentiation and proliferation rate. Therefore, further studies will be required to elucidate these molecular factors to substantiate our findings from a cancer biological point of view.

Proteasome inhibitors sensitize ovarian cancer cells to paclitaxel induced apoptosis

To explore the sensitivity of ovarian cancer cell line SKOV3 to paclitaxel, proteasome inhibitors, bortezomib, and their combination. The methyl thiazolyl tetrazolium (MTT) assay was applied to examine the cell viability after treatment. The annexin V-propidium iodide apoptosis detection kit was used to determine the apoptosis rate of different groups. Western blot assay was used to evaluate the expression levels of phosphorylated protein kinase B (AKT) and glycogen synthase kinase-3 beta (GSK-3beta). In MTT assay, the cell viability ratios of the combination group at serial time points from 12, 24, 36, 48 and 72 hours were (65.2 +/- 5.8)%, (58.3 +/- 14.4)%, (35.3 +/- 5.0)%, (19.2 +/- 1.5)%, and (11.4 +/- 2.5)%, which were significantly lower than those of the paclitaxel group (P < 0.05). After drug treatments, apoptosis rates of paclitaxel group, bortezomib group and the combination group were (14.7 +/- 0.5)%, (15.1 +/- 0.8)% and (20.5 +/- 0.7)% respectively. The rate of the combination group was significantly higher than that of non-treated group and paclitaxel group (P < 0.05). Western blot assay showed the changes in expression levels of phosphorylated AKT and GSK-3beta, which were decreased significantly after paclitaxel and bortezomib combination treatment [(3.2 +/- 0.8)%, (19.3 +/- 0.4)%; P < 0.05]. The lethal effect of paclitaxel on tumor cells could be increased significantly by its combination with proteasome inhibitors, bortezomib. The AKT/GSK-3beta signaling pathway plays an important role in the molecular mechanism of the combination treatment.

Effects of the proteasome inhibitor bortezomib alone and in combination with chemotherapeutic agents in gastric cancer cell lines

The proteasome plays a pivotal role in controlling cell proliferation, apoptosis, and differentiation in a variety of tumor cells. Bortezomib is a boronic acid dipeptide derivative, which is a selective and potent inhibitor of the proteasome and has prominent effects in vitro and in vivo against several solid tumors. We examined the anti-proliferative and apoptotic effects of bortezomib in three gastric cancer cell lines (SNU638, MUGC-3 and MKN-28), along with its antitumor combination effects with other chemotherapeutic agents. Tumor cell growth inhibition and apoptosis was measured by MTT assay and FACS analysis, respectively. Apoptosis- and cell cycle-associated protein expression levels were measured by Western blot assay. Bortezomib induced the suppression of tumor cell growth and apoptosis in a dose-dependent manner with an inhibitory dose (ID)50 of approximately 0.5 microg/ml in all gastric cancer cell lines tested. Further combination treatment with cisplatin and docetaxel, in particular with docetaxel displayed dramatically increased tumor cell growth suppression in all three gastric cancer cell lines, as compared to single drug treatment alone. This was concomitant with the induction patterns of apoptotic cells. Bortezomib treatment increased the Bax protein expression. Moreover, combination treatment of bortezomib plus docetaxel resulted in a dramatic increase in the Bax expression. In contrast, Bcl-2 expression was decreased by combination treatment with bortezomib plus docetaxel in SNU638 cells. Finally, bortezomib, docetaxel and to a greater degree bortezomib plus docetaxel increased the expression levels of p27 proteins even without influencing p53 expression levels. Bortezomib has profound effects on tumor cell growth inhibition and induction of apoptosis in human gastric cancer cells, suggesting that bortezomib may be an effective therapeutic drug for patients with gastric cancer. Further combination studies with other chemotherapeutic drugs, in particular docetaxel showing more tumor cell growth inhibition and apoptosis suggest that combining bortezomib with docetaxel might be more effective for displaying tumor cell growth inhibitory effects in gastric cancer cells through regulation of Bcl-2, Bax and p27 proteins in vitro.

Bortezomib in Combination with Conventional Chemotherapeutic Agents for Multiple Myeloma Compared with Bortezomib Alone

Recent studies have demonstrated synergy between bortezomib and a number of conventional cytotoxic agents. This study examined whether or not the speed of the response, progression and safety from a combination treatment of bortezomib with common chemotherapeutic drugs is superior to bortezomib monotherapy. Fifty-seven patients with relapsed, refractory multiple myeloma (MM) who had received at least two cycles of treatment including bortezomib were enrolled in this study. The median age was 56 (35-79) years and 49.1% were male. Thirty-two patients were treated with bortezomib alone and 25 were treated with chemotherapeutic agents that were given in combination with bortezomib. The monoclonal immunoglobulin (mIg) or free light chain (FLC) concentrations were determined in the sera before and after two cycles of bortezomib treatment. The adverse events were assessed and graded according to the NCI Common Toxicity Criteria (version 2.0). Thirty-one of the 57 patients (54.4%) attained an early objective response (EOR) after the second bortezomib treatment, defined as a >/=50% decrease in the serum mIg or FLC concentration. Improvements in the response were observed when common chemotherapeutic agents were added to bortezomib monotherapy. In patients who received bortezomib combined with chemotherapeutic agents, 19 out of 25 patients (76%) showed an EOR, whereas 12 out of 32 patients (37.5%) given bortezomib monotherapy achieved an EOR after the second cycle of bortezomib treatment (P = 0.004); the median decrease from the baseline in the paraprotein level was 74.6 +/- 5.9 and 39.7 +/- 4.2%, respectively (P = 0.003). A statistically significant elevation of serum lactic dehydrogenase (P = 0.007) and alkaline phosphatase (P = 0.027) from baseline within two cycles of bortezomib treatment was observed in responding patients. With the combination treatment, peripheral neuropathy of >/=Grade II occurred in 12 out of 25 patients (48%) compared with 12 of 32 (37.5%) in those given bortezomib alone (P = 0.589). The median time to progression of disease was similar in the two groups (359 +/- 43.5 versus 365 +/- 103.5, P = 0.688). The multivariate Cox regression model showed that a high serum albumin and low beta2-microglobulin are favorable factors for the progression-free survival following bortezomib treatment. Bortezomib in combination with common chemotherapeutic agents is more active in the treatment of relapsed, refractory MM than with bortezomib alone. However, more effective post-bortezomib treatment is needed to reduce the rate of disease progression particularly in patients with high tumor burden.

TRAIL therapy in non–small cell lung cancer cells: sensitization to death receptor–mediated apoptosis by proteasome inhibitor bortezomib

Activation of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor pathway is a promising therapeutic strategy to selectively eradicate cancer cells, including non-small cell lung cancer (NSCLC) cells. Recombinant human (rh) TRAIL/Apo-2L, a TRAIL-encoding adenovirus, and monoclonal antibodies directed against TRAIL receptors R1 and R2 were used to study cytotoxicity of TRAIL therapy in NSCLC cells. NSCLC cells showed differential sensitivity to TRAIL therapy, regardless of the agent used. Combination treatment of bortezomib and rhTRAIL led to synergistic apoptosis induction in NSCLC cell lines. Enhancement of rhTRAIL-induced apoptosis by bortezomib was caspase dependent, implicating extrinsic as well as intrinsic apoptosis activation, as shown by increased processing of caspase-8 as well as caspase-9, and could be abrogated completely by overexpression of caspase-8 inhibitor cytokine response modifier A (CrmA), and partially by overexpression of Bcl-2. Enhanced surface expression of TRAIL-R2, but also TRAIL-R1, was associated with bortezomib treatment, which is likely to contribute to the increased processing of caspase-8 in the combination treatment. Furthermore, TRAIL-induced activation of prosurvival transcription factor nuclear factor-kappaB was prevented by cotreatment with bortezomib, which may contribute to the observed synergistic apoptosis induction. Our preclinical data indicate that combination therapy of TRAIL and bortezomib may be an effective strategy for NSCLC.

Bortezomib Enhances Melphalan Response by Altering Fanconi Anemia (FA)/BRCA Pathway Expression and Function.

The FA/BRCA pathway is involved in DNA damage repair and its importance in oncogenesis has only recently been implicated. Briefly, 8 FA/BRCA pathway family members facilitate the monoubiquitination of FANCD2. Upon monoubiquitination, FANCD2 translocates to the DNA repair foci where it interacts with other proteins to initiate DNA repair. Previously, we reported that the FA/BRCA pathway is upregulated in multiple myeloma cell lines selected for resistance to melphalan (Chen, et al, Blood 2005). Further, reducing FANCF in the melphalan resistant 8226/LR5 myeloma cell line partially reversed resistance, whereas overexpressing FANCF in the drug sensitive 8226/S myeloma line conferred resistance to melphalan. Others have reported, and we have also verified, that bortezomib enhances melphalan response in myeloma cells; however, the mechanism of enhanced melphalan activity in combination with bortezomib has not been reported. Based on our observation that the FA/BRCA pathway confers melphalan resistance, we hypothesized that bortezomib enhances melphalan response by targeting FA/BRCA DNA damage repair pathway genes. To investigate this hypothesis, we first analyzed FA/BRCA gene expression in 8226/S and 8226/LR5 cells treated with bortezomib, using a customized microfluidic card (to detect BRCA1, BRCA2, FANCA, FANCC, FANCD2, FANCE, FANCF, FANCG, FANCL, RAD51 and RAD51C) and q-PCR. Interestingly, we found that low dose (5nM) bortezomib decreased many FA/BRCA pathway genes as early as 2 hours, with maximal decreases seen at 24 hours. Specifically, 1.5- to 2.5-fold decreases in FANCA, FANCC, FANCD2, FANCE and RAD51C were seen 24 hours post bortezomib exposure. Moreover, pre-treatment of myeloma cells with low dose bortezomib followed by melphalan treatment revealed a greater than 2-fold reduction in FANCD2 gene expression levels. We also found that melphalan treatment alone enhanced FANCD2 protein expression and activation (monoubiquitination), whereas the combination treatment of bortezomib followed by melphalan decreased activation and overall expression of FANCD2 protein. Taken together, these results suggest that bortezomib enhances melphalan response in myeloma by targeting the FA/BRCA pathway. Further understanding of the role of the FA/BRCA pathway in determining melphalan response may allow for more customized and effective treatment of myeloma.