Discovery of allosteric regulators with clinical potential to stabilize alpha-L-iduronidase in mucopolysaccharidosis type I.

Mucopolysaccharidosis type I (MPS I) is an inherited lysosomal disease caused by lowered activity of the enzyme alpha-L-iduronidase (IDUA). Current therapeutic options show limited efficacy and do not treat some important aspects of the disease. Therefore, it may be advantageous to identify strategies that could improve the efficacy of existing treatments. Pharmacological chaperones are small molecules that protect proteins from degradation, and their use in combination with enzyme replacement therapy (ERT) has been proposed as an alternative therapeutic strategy. Using the SEE-Tx® proprietary computational drug discovery platform, a new allosteric ligand binding cavity in IDUA was identified distal from the active site. Virtual high-throughput screening of approximately 5 million compounds using the SEE-Tx® docking platform identified a subset of small molecules that bound to the druggable cavity and functioned as novel allosteric chaperones of IDUA. Experimental validation by differential scanning fluorimetry showed an overall hit rate of 11.4%. Biophysical studies showed that one exemplary hit molecule GT-01803 bound to (Kd = 22 µM) and stabilized recombinant human IDUA (rhIDUA) in a dose-dependent manner. Co-administration of rhIDUA and GT-01803 increased IDUA activity in patient-derived fibroblasts. Preliminary in vivo studies have shown that GT-01803 improved the pharmacokinetic (PK) profile of rhIDUA, increasing plasma levels in a dose-dependent manner. Furthermore, GT-01803 also increased IDUA enzymatic activity in bone marrow tissue, which benefits least from standard ERT. Oral bioavailability of GT-01803 was found to be good (50%). Overall, the discovery and validation of a novel allosteric chaperone for rhIDUA presents a promising strategy to enhance the efficacy of existing treatments for MPS I. The compound's ability to increase rhIDUA activity in patient-derived fibroblasts and its good oral bioavailability underscore its potential as a potent adjunct to ERT, particularly for addressing aspects of the disease less responsive to standard treatment.

Rollable and implantable intraocular pressure sensor for the continuous adaptive management of glaucoma.

We designed and tested a new rollable and implantable medical device to directly and continuously measure intraocular pressure. Since high intraocular pressure is a leading risk factor for glaucoma, such a system could solve the difficulties encountered in the management of this condition. In fact, glaucoma is one among those pathologies that could most benefit of an adaptive patient-specific medicine device. The presented prototype was realized with standard industrial microelectronic technologies (Flip-Chip on Kapton flexible PCB) and off-the-shelf IC components. Detailed system description and measurements, obtained during in-vitro and laboratory characterizations, are reported.

Mechanism of action: the unique pattern of bendamustine-induced cytotoxicity.

Bendamustine has demonstrated substantial efficacy in the treatment of hematologic malignancies and continues to distinguish itself from other alkylating agents with regard to its activity in tumor cells. The mechanistic and clinical differences associated with bendamustine may be directly related to its unique structural features. Although the precise mechanisms of action are still poorly understood, bendamustine is associated with extensive and durable DNA damage. The increased potency of bendamustine may be due to secondary mechanisms such as inhibition of mitotic checkpoints, inefficient DNA repair, and initiation of p53-dependent DNA-damage stress response, all of which lead to mitotic catastrophe and apoptosis. It has also been hypothesized that the presence of a benzimidazole ring in addition to the nitrogen mustard group may influence the way bendamustine interacts with DNA and/or confer antimetabolite properties. Further elucidation of the mechanisms of action for bendamustine and the signaling pathways involved in the response to bendamustine-induced DNA damage is essential to maximize its therapeutic potential, identify biomarkers for response, and understand the potential for synergy with other agents involved in DNA damage and inhibition of DNA repair. This review will discuss the current understanding and hypotheses regarding bendamustine mechanisms of action and suggest future investigations that would shed light on the many unanswered questions.

Conclusion and future directions.

Bendamustine is a bifunctional mechlorethamine derivative that shares similarities to other alkylators; however, the presence of a benzimidazole ring may confer "nucleoside-like" properties and may allow the stabilization of the molecule leading to longer lasting DNA damage. Though bendamustine has demonstrated promising response rates in preclinical and clinical studies, particularly in follicular lymphoma, chronic lymphocytic leukemia, diffuse B-cell lymphoma, and mantle cell lymphoma, the unique and exact mechanism of action of this agent remains unclear. Several studies have been initiated to address this question, and it is hoped that emerging data will provide the basis for more effective utilization of this interesting drug. Several recent clinical trials have reported impressive results with bendamustine in lymphoid malignancies, and appropriate clinical use of this agent and the rationale behind its use are of growing importance. This review discussed emerging data and aimed to provide clinical updates and scientific rationales that are relevant to practicing clinicians who provide care to patients with lymphoid malignancies, and/or who are interested in understanding the evolving role of bendamustine in this setting.

Bendamustine: rescue of an effective antineoplastic agent from the mid-twentieth century.

Although the alkylating agent bendamustine was developed in Germany in the mid-twentieth century, it has only recently come to the forefront in the rest of the world as an effective chemotherapeutic agent for the treatment of several hematologic malignancies. Based on the activity demonstrated in single-arm and randomized trials, this nitrogen mustard is approved by the US Food and Drug Administration (FDA) for the treatment of chronic lymphocytic leukemia and rituximab-refractory indolent non-Hodgkin lymphoma. The unique structural and mechanistic features of bendamustine differentiate it from other alkylating agents, providing increased stability and potency in DNA cross linking and subsequent cytotoxicity. Due to its unusual development, few studies have closely examined the mechanisms of action for this nitrogen mustard and many unanswered questions remain. Additionally, phase I and pharmacokinetic studies are limited, although increased understanding of the clinical pharmacology of bendamustine led to development of dosing recommendations by international experts based on the available data. The clinical activity of bendamustine as a single agent and in combination with other chemotherapeutic and immunotherapeutic drugs, coupled with its potential lack of cross-resistance with many other chemotherapy agents, make bendamustine an attractive therapy for patients with newly diagnosed and refractory hematologic malignancies. This review will discuss the development of bendamustine, its structural and pharmacologic characteristics, and current data regarding the optimal dosing of this agent in specific clinical settings.

Pharmacokinetics and toxicity of intravesical TMX-101: a preclinical study in pigs.

OBJECTIVE: • To study the pharmacokinetic and toxicity profile of intravesically administered TMX-101, with its active ingredient R-837, a synthetic Toll-like receptor (TLR)-7 agonist, in a pig model. MATERIALS AND METHODS: • TLR-7 expression was determined by immunohistochemistry in human and pig bladder tissue. • Four groups of six pigs received a 1-h intravesical instillation with R-837 of different formulations. • Pharmacokinetic analysis was performed on plasma. Toxicity evaluation included monitoring the well-being of the animals, peripheral blood cell counts, and interleukin-6 and creatinine measurements. Urine was collected for R-837 measurement and dipstick analysis. • In total, three pigs per group were sacrificed 24 h post-treatment, and the remaining animals were sacrificed after 1 week. Histopathological examination of the bladder wall was performed. RESULTS: • TLR-7 was homogeneously expressed in human and pig urothelium. • R-837 and vehicle were well tolerated without deterioration in animal well-being. • Systemic R-837 absorption was low. • Mean maximum plasma concentration of R-837 differed depending on the formulation. Post-treatment, plasma levels were negligible at 24 h. • Histopathological examination of the bladders did not show significant abnormalities, apart from the intended inflammatory reaction in the R-837 treated groups. CONCLUSION: • Intravesically administered R-837 in pigs, which showed a similar TLR-7 distribution in bladder tissue as humans, is well tolerated and causes no bladder wall toxicity, and formulations with poloxamer and hydroxypropyl-ß-cyclodextrin showed less systemic absorption.

Bendamustine: mechanism of action and clinical data.

Bendamustine is a chemotherapeutic agent that displays a unique pattern of cytotoxicity compared with conventional alkylating agents. Bendamustine was originally synthesized in the former East German Democratic Republic in the 1960s. It was designed to have both alkylating and antimetabolite properties. The alkylating agent properties are similar to those seen with cyclophosphamide, chlorambucil, and melphalan, and the benzimidazole ring is similar to cladribine. Molecular analyses have revealed that bendamustine differs from other alkylating agents in its mechanism of action. Differences have been observed in regard to its effects on DNA repair and cell cycle progression. Moreover, bendamustine can induce cell death through both apoptotic and nonapoptotic pathways, thereby retaining activity even in cells without a functional apoptotic pathway. Bendamustine has demonstrated significant efficacy in patients with indolent lymphomas and chronic lymphocytic leukemia (CLL), including in patients with disease refractory to conventional alkylating agents and rituximab. The toxicity profile of bendamustine is also superior to that of conventional alkylating agents. Combination therapy with bendamustine and rituximab has demonstrated superior efficacy to a standard rituximab-containing chemotherapy regimen in patients with previously untreated indolent B-cell non-Hodgkin lymphoma, and it is currently being compared against the standard first-line regimen in CLL: fludarabine, cyclophosphamide, and rituximab. Ongoing and planned studies are evaluating new strategies in which bendamustine is being combined with existing agents and with novel therapies to optimize use in different clinical settings.

Intravesical Toll-like receptor 7 agonist R-837: optimization of its formulation in an orthotopic mouse model of bladder cancer.

OBJECTIVE: To study the immune response caused by the intravesical administration of the immunomodulator R-837 in various formulations and to estimate its therapeutic potential for bladder cancer. METHODS: Female C57BL/6 mice were intravesically treated with different formulations of R-837, a Toll-like receptor 7 agonist used for treating genital warts and skin malignancy. The tested formulation mixtures contained different ratios of lactic acid, a thermosensitive poloxamer polymer (Lutrol F127) and 2-(hydroxypropyl)-beta-cyclodextrin (HPbetaCD). Induction of tumor necrosis factor alpha (TNFalpha) and keratinocyte-derived chemokine (KC) was analyzed by Luminex microbeads assay. The therapeutic potential of intravesical administration of R-837 was assessed in an orthotopic, syngeneic mouse model of bladder cancer using MB49 cells. RESULTS: Intravesical administration of R-837 in lactic acid alone induced systemic and bladder TNFalpha and KC in a dose-dependent manner. Formulations including poloxamer decreased systemic absorption of R-837 and significantly reduced systemic and local induction of KC. Addition of HPbetaCD in the poloxamer formulation particularly reversed levels of systemic and local levels of TNFalpha and KC. Histological examination showed that poloxamer-HPbetaCD formulation allowed infiltration of mononuclear cells into urothelium and lamina propria. In studies using orthotopic mouse bladder cancer, the tumor loads in R-837-treated mice were significantly lower than those in vehicle-treated or non-treated mice. CONCLUSION: The optimized poloxamer-HPbetaCD formulation of R-837 shows therapeutic potential for bladder cancer while avoiding adverse side-effects.

Bendamustine (Treanda) displays a distinct pattern of cytotoxicity and unique mechanistic features compared with other alkylating agents.

PURPOSE: Bendamustine has shown clinical activity in patients with disease refractory to conventional alkylator chemotherapy. The purpose of this study was to characterize the mechanisms of action of bendamustine and to compare it with structurally related compounds. EXPERIMENTAL DESIGN: Bendamustine was profiled in the National Cancer Institute in vitro antitumor screen. Microarray-based gene expression profiling, real-time PCR, immunoblot, cell cycle, and functional DNA damage repair analyses were used to characterize response to bendamustine and compare it with chlorambucil and phosphoramide mustard. RESULTS: Bendamustine displays a distinct pattern of activity unrelated to other DNA-alkylating agents. Its mechanisms of action include activation of DNA-damage stress response and apoptosis, inhibition of mitotic checkpoints, and induction of mitotic catastrophe. In addition, unlike other alkylators, bendamustine activates a base excision DNA repair pathway rather than an alkyltransferase DNA repair mechanism. CONCLUSION: These results suggest that bendamustine possesses mechanistic features that differentiate it from other alkylating agents and may contribute to its distinct clinical efficacy profile.

Pharmacological profiling of novel non-COX-inhibiting indole-pyran analogues of etodolac reveals high solid tumour activity of SDX-308 in vitro.

SDX-308 and SDX-309 are potent indole-pyran analogues of SDX-101 (R-etodolac) which has anti-tumour activity unrelated to cyclooxygenase-2 inhibition. Their cytotoxic activity was further studied herein using a well-characterized human tumour cell-line panel containing ten cell lines, as well as in 58 primary tumour cell samples from a variety of diagnoses. The indole-pyran analogues of SDX-101 were in general considerably more active in both cancer cell lines and primary tumour samples. Low cross-reactivity with standard agents was observed, indicating a unique mechanism of action. No apparent influence on efficacy was observed via classical mechanisms of multidrug-resistance. SDX-101 and SDX-309 showed higher relative activity in haematological compared to solid tumour samples, while SDX-308 had pronounced solid-tumour activity. High SDX-308 cytotoxic efficacy was observed in non-small cell lung cancer, renal cancer and ovarian cancer samples, and also in chronic lymphocytic leukaemia. In conclusion, the indole-pyran analogues showed a favourable pharmacological profile and represent a potentially important new class of drugs for cancer treatment.

R-Etodolac decreases beta-catenin levels along with survival and proliferation of hepatoma cells.

BACKGROUND/AIMS: Inhibition of hepatoma cells by cyclooxygenase (COX)-2-dependent and -independent mechanisms has been shown previously. Here, we examine the effect of Celecoxib, a COX-2-inhibitor and R-Etodolac, an enantiomer of the nonsteroidal anti-inflammatory drug Etodolac, which lacks COX-inhibitory activity, on the Wnt/beta-catenin pathway and human hepatoma cells. METHODS: Hep3B and HepG2 cell lines were treated with Celecoxib or R-Etodolac, and examined for viability, DNA synthesis, Wnt/beta-catenin pathway components, and downstream target gene expression. RESULTS: Celecoxib at high doses affected beta-catenin protein by inducing its degradation via GSK3beta and APC along with diminished tumor cell proliferation and survival. R-Etodolac at physiological doses caused decrease in total and activated beta-catenin protein secondary to decrease in its gene expression and post-translationally through GSK3beta activation. In addition, increased beta-catenin-E-cadherin was also observed at the membrane. An associated inhibition of beta-catenin-dependent Tcf reporter activity, decreased levels of downstream target gene products glutamine synthetase and cyclin-D1, and decreased proliferation and survival of hepatoma cells was evident. CONCLUSIONS: The antitumor effects of Celecoxib (at high concentrations) and R-Etodolac (at physiological doses) on HCC cells were accompanied by the down-regulation of beta-catenin demonstrating a useful therapeutic strategy in hepatocellular cancer.

SDX-308, a nonsteroidal anti-inflammatory agent, inhibits NF-kappaB activity, resulting in strong inhibition of osteoclast formation/activity and multiple myeloma cell growth.

Multiple myeloma is characterized by increased osteoclast activity that results in bone destruction and lytic lesions. With the prolonged overall patient survival achieved by new treatment modalities, additional drugs are required to inhibit bone destruction. We focused on a novel and more potent structural analog of the nonsteroidal anti-inflammatory drug etodolac, known as SDX-308, and its effects on osteoclastogenesis and multiple myeloma cells. SDX-101 is another structural analog of etodolac that is already used in clinical trials for the treatment of B-cell chronic lymphocytic leukemia (B-CLL). Compared with SDX-101, a 10-fold lower concentration of SDX-308 induced potent (60%-80%) inhibition of osteoclast formation, and a 10- to 100-fold lower concentration inhibited multiple myeloma cell proliferation. Bone resorption was completely inhibited by SDX-308, as determined in dentin-based bone resorption assays. SDX-308 decreased constitutive and RANKL-stimulated NF-kappaB activation and osteoclast formation in an osteoclast cellular model, RAW 264.7. SDX-308 effectively suppressed TNF-alpha-induced IKK-gamma and IkappaB-alpha phosphorylation and degradation and subsequent NF-kappaB activation in human multiple myeloma cells. These results indicate that SDX-308 effectively inhibits multiple myeloma cell proliferation and osteoclast activity, potentially by controlling NF-kappaB activation signaling. We propose that SDX-308 is a promising therapeutic candidate to inhibit multiple myeloma growth and osteoclast activity and that it should receive attention for further study.

R-etodolac (SDX-101) and the related indole-pyran analogues SDX-308 and SDX-309 potentiate the antileukemic activity of standard cytotoxic agents in primary chronic lymphocytic leukaemia cells.

OBJECTIVE: SDX-101 is the non-cyclooxygenase 2-inhibiting R-enantiomer of the non-steroid anti-inflammatory drug etodolac, and has anti-tumour activity in chronic lymphocytic leukaemia (CLL). SDX-308 and SDX-309 are more potent, structurally related indole-pyran analogues of SDX-101. The current study was performed to investigate and quantify the cytotoxic potentiating effects resulting from a combination of either SDX-101, SDX-308 or SDX-309 with standard cytotoxic agents used in the CLL treatment today. METHODS: The lymphoma cell line U937-gtb was used, together with primary tumour cells isolated from seven CLL patients. Combinations between chlorambucil and each one of the agents etodolac, SDX-101, SDX-308 and SDX-309 were studied. In addition, SDX-309 was combined with fludarabine, doxorubicin or vincristine. Both simultaneous and sequential exposures were explored using the median-effect method. RESULTS: Most combinations were additive, which could be of clinical benefit since SDX-101 has been shown to be well tolerated. At the 70% effect level, synergy was observed between SDX-308 and chlorambucil in U937-gtb cells and in two-third of the CLL samples. Since chlorambucil is the most important drug in CLL therapy today and SDX-308 is presently targeted as the lead clinical candidate, this combination would be interesting for further studies. Vincristine and SDX-309 were synergistic in two-fourth of CLL samples. CONCLUSIONS: To conclude, the non-COX-inhibiting etodolac-derivatives SDX-101, SDX-308 and SDX-309 are potential candidates for combination treatment of CLL. Especially, SDX-308 in combination with chlorambucil warrants further evaluation.

Lack of methylthioadenosine phosphorylase expression in mantle cell lymphoma is associated with shorter survival: implications for a potential targeted therapy.

PURPOSE: To determine the methylthioadenosine phosphorylase (MTAP) gene alterations in mantle cell lymphoma (MCL) and to investigate whether the targeted inactivation of the alternative de novo AMP synthesis pathway may be a useful therapeutic strategy in tumors with inactivation of this enzyme. EXPERIMENTAL DESIGN: MTAP gene deletion and protein expression were studied in 64 and 52 primary MCL, respectively, and the results were correlated with clinical behavior. Five MCL cell lines were analyzed for MTAP expression and for the in vitro sensitivity to L-alanosine, an inhibitor of adenylosuccinate synthetase, and hence de novo AMP synthesis. RESULTS: No protein expression was detected in 8 of 52 (15%) tumors and one cell line (Granta 519). Six of these MTAP negative tumors and Granta 519 cell line had a codeletion of MTAP and p16 genes; one case showed a deletion of MTAP, but not p16, and one tumor had no deletions in neither of these genes. Patients with MTAP deletions had a significant shorter overall survival (mean, 16.1 months) than patients with wild-type MTAP (mean, 63.6 months; P < 0.0001). L-Alanosine induced cytotoxicity and activation of the intrinsic mitochondrial-dependent apoptotic pathway in MCL cells. 9-beta-D-Erythrofuranosyladenine, an analogue of 5'-methylthioadenosine, selectively rescued MTAP-positive cells from L-alanosine toxicity. CONCLUSIONS: MTAP gene deletion and lack of protein expression are associated with poor prognosis in MCL and might identify patients who might benefit from treatment with de novo AMP synthesis pathway-targeted therapies.

Homozygous deletions of methylthioadenosine phosphorylase in human biliary tract cancers.

The p16(INK4A)/CDKN2A gene on chromosome 9p21 is a site of frequent allelic loss in human cancers, and in a subset of cases, homozygous deletions at this locus encompass the telomeric methylthioadenosine phosphorylase (MTAP) gene. The MTAP gene product is the principal enzyme involved in purine synthesis via the salvage pathway, such that MTAP-negative cancers are solely dependent on de novo purine synthesis mechanisms. Inhibitors of the de novo pathway can then be used to selectively blockade purine synthesis in cancer cells while causing minimal collateral damage to normal cells. In this study, we determine that 10 of 28 (35%) biliary tract cancers show complete lack of Mtap protein expression. In vitro analysis using a selective inhibitor of the de novo purine synthesis pathway, L-alanosine, shows robust growth inhibition in MTAP-negative biliary cancer cell lines CAK-1 and GBD-1 accompanied by striking depletion of intracellular ATP and failure to rescue this depletion via addition of exogenous methylthioadenosine, the principal substrate of the MTAP gene product; in contrast, no significant effects were observed in MTAP-expressing HuCCT1 and SNU308 cell lines. Colony formation studies confirmed that L-alanosine reduced both number and size of CAK-1 colonies in soft agar assays. Knockdown of Mtap protein by RNA interference in L-alanosine-resistant HuCCT1 cells conferred sensitivity to this agent, confirming that intracellular Mtap protein levels determine response to L-alanosine. Inhibitors of de novo purine synthesis can be a potential mechanism-based strategy for treatment of biliary tract cancers, one third of which show complete loss of MTAP function.

Concordant loss of MTAP and p16/CDKN2A expression in gastroesophageal carcinogenesis: evidence of homozygous deletion in esophageal noninvasive precursor lesions and therapeutic implications.

The gene that encodes methylthioadenosine phosphorylase (MTAP), an enzyme involved in adenine and methionine salvage pathways, is located on chromosome 9p21 telomeric to the p16INK4A/CDKN2A tumor suppressor gene. Inactivation of the p16INK4A/CDKN2A gene occurs by three different mechanisms: hypermethylation of the gene promoter, intragenic mutation coupled with loss of the second allele, and homozygous deletion. Immunohistochemical labeling for the p16INK4A/CDKN2A gene product parallels gene status but does not elucidate the mechanism of gene inactivation. Since the MTAP gene is often co-deleted with p16INK4A/CDKN2A, concurrent immunolabeling for both proteins can identify cases with homozygous p16INK4A/CDKN2A gene deletion. MTAP loss itself has therapeutic implications since it may confer selective sensitivity to inhibitors of de novo purine biosynthesis, such as L-alanosine. Twelve tissue microarrays were constructed from 92 cases of Barrett-associated adenocarcinomas and precursor lesions and 112 cases of gastric adenocarcinoma and precursor lesions comprising 1161 individual cores. Multiple cores were arrayed from any given case, and when available, included the entire histologic spectrum of intestinal metaplasia-dysplasia-carcinoma. Tissue microarrays were labeled with monoclonal antibodies against MTAP protein (clone 6.9, Salmedix, Inc) and p16 (clone 16P07, Neomarkers). Complete loss of labeling was considered negative, while any labeling (p16: nuclear; MTAP: cytoplasmic and nuclear) was considered positive. Loss of MTAP labeling occurred exclusively in conjunction with loss of p16 labeling, confirming that the previous findings from this group that concurrent loss of MTAP and p16 labeling is a surrogate marker of 9p21 homozygous deletions. Complete loss of MTAP and p16 was seen in 4 of 25 (16%) patients with Barrett's esophagus, 4 of 18 (22%) with low-grade dysplasia, 5 of 39 (13%) with high-grade dysplasia, 17 of 78 (22%) with invasive adenocarcinoma, and 8 of 36 (22%) of metastases. There were 7 cases of esophageal adenocarcinoma with loss of both MTAP and p16 for which precursor lesions were available. In 6 on these 7 cases (85%), the precursor lesion(s) had loss of both MTAP and p16. Lack of MTAP and p16 expression was seen in 11 of 106 (10%) cases of gastric adenocarcinoma. All metaplastic (30 biopsies from 20 cases) and dysplastic (15 biopsies from 13 cases) gastric tissues had both intact MTAP and p16INK4A/CDKN2A gene products. No precursor lesions were available from the gastric cancers that had loss of both MTAP and p16. Two benign gastric hyperplastic polyps also had intact p16 and MTAP. Concurrent MTAP and p16 loss detected by immunohistochemistry can serve as a convenient surrogate for p16INK4A/CDKN2A gene homozygous deletion in archival tissues. Inactivation of p16INK4A/CDKN2A by homozygous deletion appears to be an early event in Barrett carcinogenesis, occurring in noninvasive precursor lesions, including nondysplastic Barrett mucosa, in subsets of cases. In the absence of MTAP, cells depend exclusively on the de novo synthesis pathway for production of adenosine. This loss of MTAP during 9p21 homozygous deletion might be exploited therapeutically using de novo purine synthesis antimetabolites to treat a subset of invasive gastroesophageal adenocarcinomas and esophageal precursor lesions.

SDX-101, the R-enantiomer of etodolac, induces cytotoxicity, overcomes drug resistance, and enhances the activity of dexamethasone in multiple myeloma.

In this study we report that R-etodolac (SDX-101), at clinically relevant concentrations, induces potent cytotoxicity in drug-sensitive multiple myeloma (MM) cell lines, as well as in dexamethasone (MM.1R)-, doxorubicin (Dox40/RPMI8226)-, and bortezomib (DHL4)-resistant cell lines. Immunoblot analysis demonstrates that R-etodolac induces apoptosis characterized by caspase-8, -9, and -3 and PARP (poly-ADP [adenosine diphosphate]-ribose polymerase) cleavage and down-regulation of cyclin D1 expression. Subcytotoxic doses of R-etodolac up-regulate myeloid cell leukemia-1 proapoptotic variant (Mcl-1S), while enhancing dexamethasone (Dex)-induced caspase activation and apoptosis. The combination of R-etodolac with Dex results in a highly synergistic cytotoxic effect. R-etodolac also induces apoptosis against primary cells isolated from patients with MM refractory to chemotherapy. Although interleukin 6 (IL-6) and insulin-like growth factor-1 (IGF-1) abrogate Dex-induced MM cell cytotoxicity, neither IL-6 nor IGF-1 protects against R-etodolac-induced cytotoxicity in MM cells. R-etodolac also inhibits viability of MM cells adherent to bone marrow stromal cells (BMSCs), thereby overcoming a mechanism of drug resistance commonly observed with other conventional chemotherapeutic agents. Our data, therefore, indicate that R-etodolac circumvents drug resistance in MM cells at clinically relevant concentrations, targets Mcl-1, and can be synergistically combined with Dex.

Concordant loss of MTAP and p16/CDKN2A expression in pancreatic intraepithelial neoplasia: evidence of homozygous deletion in a noninvasive precursor lesion.

The p16INK4A/CDKN2A (p16) gene on chromosome 9p21 is inactivated in >90% of invasive pancreatic cancers. In 40% of pancreatic cancers the p16 gene is inactivated by homozygous deletion, in 40% by an intragenic mutation coupled with loss of the second allele, and in 10-15% by hypermethylation of the p16 gene promoter. Immunohistochemical labeling for the p16 gene product parallels gene status, but does not provide information of the mechanism of p16 gene inactivation. The methylthioadenosine phosphorylase gene (MTAP) gene also resides on chromosome 9p21, approximately 100 kb telomeric to the p16 gene. The MTAP gene is frequently contained within p16 homozygous deletions, producing concordant loss of both p16 and MTAP gene expression. Concordant loss of both p16 and MTAP protein expression can therefore be used as a surrogate marker for p16 homozygous deletion. Here we immunolabeled a series of pancreatic intraepithelial neoplasia (PanIN) lesions of various histologic grades for the p16 and MTAP gene products using a high-throughput PanIN tissue microarray (TMA) format. We demonstrate concordant loss of p16 and MTAP protein expression in 6/73 (8%) PanINs, including five high-grade lesions and one low-grade lesion. Immunolabeling for both p16 and MTAP protein expression provides a tool to evaluate tissues with intact morphology for p16 gene homozygous deletions. The concordant loss of expression of both genes in PanIN lesions demonstrates that homozygous deletions of the p16 tumor suppressor gene can occur in noninvasive precursor lesions.