NCI-60 Cell Line Screen Research Articles

Preclinical Characterization of Mitochondria-Targeted Small Molecule Hsp90 Inhibitors, Gamitrinibs, in Advanced Prostate Cancer

This study aimed to characterize the preclinical activity of the first class of combinatorial, mitochondria-targeted, small molecule heat shock protein-90 (Hsp90) inhibitors, gamitrinibs, in models of hormone-refractory, drug-resistant, localized, and bone metastatic prostate cancer in vivo. Mitochondrial permeability transition, apoptosis, and changes in metabolic activity were examined by time-lapse videomicroscopy, multiparametric flow cytometry, MTT, and analysis of isolated mitochondria. Drug-resistant prostate cancer cells were generated by chronic exposure of hormone-refractory PC3 cells to the Hsp90 inhibitor 17-allylaminogeldanamycin (17-AAG). The effect of gamitrinibs on s.c. or intratibial prostate cancer growth was studied in xenograft models. Bone metastatic tumor growth and bone parameters were quantified by micro-computed tomography imaging. In the NCI 60-cell line screening, gamitrinibs were active against all tumor cell types tested, and efficiently killed metastatic, hormone-refractory, and multidrug-resistant prostate cancer cells characterized by overexpression of the ATP binding cassette transporter P-glycoprotein. Mechanistically, gamitrinibs, but not 17-AAG, induced acute mitochondrial dysfunction in prostate cancer cells with loss of organelle membrane potential, release of cytochrome c, and caspase activity, independently of proapoptotic Bcl-2 proteins Bax and Bak. Systemic administration of gamitrinibs to mice was well tolerated, and inhibited s.c. or bone metastatic prostate cancer growth in vivo. Gamitrinibs have preclinical activity and favorable safety in models of drug-resistant and bone metastatic prostate cancer in vivo.

Abstract 747: Development and evaluation of rational combination therapy with imidazoacridinones for human bladder cancer patients through the COXEN algorithm

Abstract In most patients, bladder cancer metastasis is incurable with current chemotherapy. To try to address this challenge, we have recently employed the novel COXEN algorithm (1) for in silico drug discovery. This approach utilized publicly available gene expression and in vitro sensitivity data for >40k compounds in NCI-60 cell line screen, from which concordant gene expression prediction models from COXEN enabled our discovery of an imidoazacridinone drug, NSC-637993, with high activity in vitro against forty bladder cancer cell lines (2). Examination of additional “hits” provided by COXEN revealed another compound in this class, C1311 (NSC-645809, Symadex) which is undergoing clinical trials in other tumor types. Our objective was to develop the foundation for use of C1311 in bladder cancer, alone and in rational combination with other clinically relevant agents. Herein, we demonstrate in a panel of 40 human bladder cancer cells that in vitro cytotoxicity profile for C1311 closely correlates that of NSC-637993 and compares favorably to that of standard of chemotherapeutics. Using genome-wide patterns of synthetic lethality of C1311 with ORF knockouts in budding yeast, we determined that combining C1311 with taxanes could provide mechanistically rational combinations for patients that have failed first line therapy with platinum based chemotherapy. To evaluate the biological relevance of these yeast findings in bladder cancer, we evaluated C1311 singly and in doublet combination with paclitaxel in the hollow fiber assay in mice, observing striking efficacy of the agents in vivo. Last, applying COXEN gene expression prediction from 40 bladder cancer cell lines to human patient tumors with known cisplatin-based chemotherapy response data (N=30) (3), we provide evidence that signatures of C1311 sensitivity exist even within patients exhibiting no change or progressive disease on standard of care agents. Taken together, these findings provide an exemplar for COXEN-based drug discovery and development, while demonstrating the utility of yeast genetics in guidance of rational combinations in vivo. Most importantly, the high activity of these agents in vitro and in vivo calls for clinical trials of these agents, while COXEN provides genomic biomarkers that may be used for patient selection. (1) Crunkhorn S. Nat Rev Drug Discov 2007;6:782-3. (2) Lee JK et al. PNAS 2007;104:13086-91. (3) Als et al. Clin Cancer Res. 2007 Aug 1;13(15 Pt 1):4407-14. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 747.

Orally administered Endoxifen is a new therapeutic agent for breast cancer

Endoxifen is the key active metabolite of tamoxifen, a widely used breast cancer drug. Orally administered tamoxifen, is extensively metabolized by cytochrome P450 (CYP) enzymes, namely CYP3A4 and CYP2D6, into active metabolites, especially endoxifen. Due to genetic polymorphism of CYP2D6, significant numbers of women metabolize tamoxifen to varying degree and may not receive the optimal benefit from tamoxifen treatment. We show that oral administration of endoxifen achieved the optimally effective systemic levels reliably, which may eliminate variability associated with tamoxifen metabolism that leads to unpredictability in efficacy. Furthermore, use of endoxifen may avoid a potential serious drug interaction found between tamoxifen and commonly used selective serotonin reuptake inhibitors, antidepressants. Endoxifen was active in inhibiting the growth of various breast tumor cell lines in NCI 60-Cell Line Screen. Orally administered endoxifen is rapidly absorbed and systemically available when tested in female rats. The endoxifen-treated rats showed 787% higher exposure (AUC(0-infinity)) and 1,500% higher concentration (C (max)) levels of endoxifen when compared with tamoxifen. Oral endoxifen administration once a day for 28 consecutive days at dosages 2, 4, and 8 mg/kg proved safe and resulted in progressive inhibition of the growth of the human mammary tumor xenografts in female mice. This is the first ever in vivo report on endoxifen as a potentially new therapeutic agent for breast cancer.

Bone marrow CFU-GM and human tumor xenograft efficacy of three antitumor nucleoside analogs

Nucleoside analogs are rationally designed anticancer agents that disrupt DNA and RNA synthesis. Fludarabine and cladribine have important roles in the treatment of hematologic malignancies. Clofarabine is a next generation nucleoside analog which is under clinical investigation. The bone marrow toxicity, tumor cell cytotoxicity and human tumor xenograft activity of fludarabine, cladribine and clofarabine were compared. Mouse and human bone marrow were subjected to colony forming (CFU-GM) assays over a 5-log concentration range in culture. NCI-60 cell line screening data were compared. In vivo, a range of clofarabine doses was compared with fludarabine for efficacy in several human tumor xenografts. The IC90 concentrations for fludarabine and cladribine for mouse CFU-GM were >30 and 0.93 microM, and for human CFU-GM were 8 and 0.11 microM, giving mouse to human differentials of >3.8- and 8.5-fold. Clofarabine produced IC90s of 1.7 microM in mouse and 0.51 microM in human CFU-GM, thus a 3.3-fold differential between species. In the NCI-60 cell line screen, fludarabine and cladribine showed selective cytotoxicity toward leukemia cell lines while for clofarabine there was no apparent selectivity based upon origin of the tumor cells. In vivo, clofarabine produced a dose-dependent increase in tumor growth delay in the RL lymphoma, the RPMI-8226 multiple myeloma, and HT-29 colon carcinoma models. The PC3 prostate carcinoma was equally responsive to clofarabine and fludarabine. Bringing together bone marrow toxicity data, tumor cell line cytotoxicity data, and human tumor xenograft efficacy provides valuable information for the translation of preclinical findings to the clinic.

The Sequence-Selective DNA Cross-Linking Agent SJG-136 (SG2000, BN2629) Is Highly Potent in Multiple Myeloma Cells and Is Synergistic with Bortezimib

Despite recent advances in the treatment of multiple myeloma (MM), including the introduction of bortezimib, it remains an incurable disease with a short median survival. The development of new agents with efficacy in MM therefore remains both important and urgent. SJG-136 (SG2000, BN2629) is a novel DNA cross-linking agent that binds in a sequence-selective manner in the minor groove of the DNA helix. It is structurally novel compared with other clinically used DNA cross-linking agents and has exhibited a unique pattern of activity in the NCI 60-cell line screen. We have previously shown that this agent is highly effective against primary chronic lymphocytic leukaemia cells. In this study we evaluated its potential as a therapy for MM in cell lines and plasma cells derived from patients. The MM cell lines H929, U266 and JJN3 were shown to have a mean LD50 of 5.1nM (±3.4) following in vitro culture with SJG-136 for 48 hours. This was accompanied by a dose-dependent increase in the percentage of apoptotic cells as evidenced by Annexin V positivity and caspase-3 activation. In comparison to the standard therapies for MM, SJG-136 demonstrated significantly lower LD50 values than doxorubicin (P=0.004), Melphalan (P=0.004) and bortezimib (P=0.03). We also assessed the ability of SJG-136 to kill plasma cells from primary myeloma samples (identified by CD38 and CD138 positivity). These cells were sensitive to SJG-136 with a mean LD50 of 2.3nM (± 0.96) following 48 hour exposures to SJG-136. In contrast, normal bone marrow was significantly less affected by SJG-136 than the myeloma samples (P<0.0001). Finally, we assessed the potential for synergy between SJG-136 and these standard treatments using the H929 cell line as a model. SJG-136 was combined with doxorubicin (1:125), melphalan (1:4000) and bortezimib (1:8) and the combination index (CI) was calculated to assess synergy. A CI of less than 1 was considered synergistic. We found no evidence for synergy between SJG-136 and doxorubicin or melphalan (CI=1.29 and 1.75 respectively). However, SJG-136 was synergistic with bortezimib (CI=0.47) possibly reflecting their different mechanisms of action. In conclusion, SJG-136 is a potentially valuable addition to the battery of drugs available for treatment of MM. Not only was SJG-136 highly potent as a single agent in MM cell lines and primary plasma cells but it also showed a high level of synergy with the proteasome inhibitor bortezimib.

Discovery of genetic profiles impacting response to chemotherapy: application to gemcitabine

Chemotherapy is a major treatment modality for individuals affected by cancer. Currently, a number of genome-based technologies are being adopted to identify genes associated with drug response; however, large-scale genetic association applications are still limited. Here we describe a novel strategy based on the genetic and drug response data of the NCI60 cell lines to discover potential candidate genetic variants associated with variable response to chemotherapy. As an example we have applied this strategy to discover single genetic markers and haplotypes from candidate genes previously implicated in the pharmacobiology of gemcitabine. Single-marker association analyses have implicated the association of four SNPs within the gene loci of CDC5L, EPC2, POLS, and PARP1. We have also investigated the combined effect of SNPs using haplotype-based analysis. Accordingly, we have shown modest association of haplotypes in six genes, whereas the most significant associations included a haplotype of the POLS gene. The hypothesis-generating tool presented in this study can be applied to drugs profiled in the NCI60 cell line screen and provides an effective means for the identification of genes associated with drug response. The results obtained using this novel methodology can be used to better design the clinical trials for effective study of the chemotherapeutic agents and thus provide a basis for individualized chemotherapy.

Application of the Stille Coupling Reaction to the Synthesis of C2‐Substituted endo—exo Unsaturated Pyrrolo[2,1‐c][1,4]benzodiazepines (PBDs).

AbstractFor Abstract see ChemInform Abstract in Full Text.

The novel sequence-specific DNA cross-linking agent SJG-136 (NSC 694501) has potent and selective in vitro cytotoxicity in human B-cell chronic lymphocytic leukemia cells with evidence of a p53-independent mechanism of cell kill.

SJG-136 (NSC 694501) is a novel DNA cross-linking agent that binds in a sequence-selective manner in the minor groove of the DNA helix. It is structurally novel compared with other clinically used DNA cross-linking agents and has exhibited a unique multilog differential pattern of activity in the NCI 60-cell line screen (i.e., is COMPARE negative to other cross-linking agents). Given this profile, we undertook a preclinical evaluation of SJG-136 in primary tumor cells derived from 34 B-cell chronic lymphocytic leukemia (B-CLL) patients. SJG-136 induced apoptosis in all of the B-CLL samples tested with a mean LD50 value (the concentration of drug required to kill 50% of the cells) of 9.06 nmol/L. Its cytotoxicity was undiminished in B-CLL cells derived from patients treated previously, those with unmutated VH genes, and those with p53 mutations (P=0.17; P=0.63; P=0.42, respectively). SJG-136-induced apoptosis was associated with the activation of caspase-3 that could be partially abrogated by the caspase-9 inhibitor Z-LEHD-FMK. Furthermore, SJG-136 did not trigger the phosphorylation of p53 or the up-regulation of GADD45 expression in B-CLL cells whereas the cross-linking agent chlorambucil elicited both of these effects. This suggests that SJG-136 cross-linking adducts are not subject to p53-mediated DNA excision repair mechanisms in B-CLL cells. Taken together, these data demonstrate a novel mechanism of action for SJG-136 that appears to circumvent the effects of poor prognostic markers. This unique cytotoxicity profile warrants further investigation and supports the evaluation of this agent in Phase I clinical trials for patients with B-CLL.

Application of the Stille coupling reaction to the synthesis of C2-substituted endo–exo unsaturated pyrrolo[2,1-c][1,4]benzodiazepines (PBDs)

The Stille coupling reaction has been used to introduce novel vinyl, alkynyl and heterocyclic substituents to the C2-position of pyrrolo[2,1-c][1,4]benzodiazepine dilactams. Sodium borohydride reduction followed by N10-SEM deprotection has provided five analogues (6b, 8a–d) that contain C2-endo/exo-unsaturation and novel C2-substituents. These analogues have significant multilog cytotoxicity profiles in the NCI 60-Cell Line screen, and provide new SAR data for the PBD family.

A dose-escalation study of the quinoxaline antitumor agent R(+)XK469 (XK) in patients with refractory solid tumors

2021 Background: XK is a member of the quinoxaline family of antitumor agents. COMPARE analysis of cytotoxicity data from the NCI-60 cell line screen showed that its mechanism of action is not comparable to that of any marketed cytotoxic agent. In vitro studies suggest that the antitumor activity of XK may be due to inhibition of topoisomerase IIβ, induction of G2-M cell cycle arrest by p53-dependent and mitogen-activated protein (MAP) kinase pathways, and/or pro-apoptotic interactions with the peripheral benzodiazepine receptor. Methods: XK was administered as a 30-minute intravenous infusion for 5 days at 15, 30, 60, 120, and 240 mg/d and every other day for 3 doses at 360, 540, 675, 850, 1100, and 1400 mg/d, repeated every 21 days. The dosing schedule was changed when pharmacokinetic (PK) analysis revealed a long half-life. Results: To date 42 pts (21 male/21 female, median age 60, median Karnofsky performance status 90%) have been treated at 11 dose levels. The principle site of toxicity has been bone marrow. Grade 3 anemia and thrombocytopenia have been observed at 1100 and 1400 mg. Grade 4 neutropenia on the scheduled day 1 of cycle 2 and fever in the setting of grade 4 neutropenia have been the only dose-limiting toxicities (DLT). Non-hematologic toxicities include grade 1–2 alopecia, anorexia, diarrhea, fever, headache, nausea, peripheral neuropathy, rash, stomatitis, and vomiting and grade 3 fatigue. Plasma concentrations of XK decline in a biphasic manner with a long mean terminal phase half-life of 60 h (CV 63%). Steady-state volume of distribution is 13 L (CV 23%); and mean total body clearance (CL) is 0.20 L/h (CV 50%), which is not correlated with dose (p=0.69) or BSA (p=0.93). All pts who experienced DLT had CL < 1 standard deviation (SD) below the mean. Conclusions: XK can be safely administered on a d 1, 3, 5 schedule without BSA-based dosing. As AUC increases with dose and 15% of our pts had CL ≤ 1 SD below the mean, safety concerns preclude further dose escalation > 1100 mg/d on this schedule. Cohort expansion continues at the phase II recommended dose of 1100 mg/d. Pharmacogenomic studies are ongoing to investigate the basis for the large PK variability. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Bristol-Myers Squibb

A novel approach to the synthesis of cytotoxic C2–C3 unsaturated pyrrolo[2,1- c] [1,4]benzodiazepines (PBDs) with conjugated acrylyl C2-substituents

A concise synthesis of three novel C2–C3 unsaturated pyrrolo[2,1- c][1,4]benzodiazepine analogues ( 18– 20) containing conjugated acrylyl C2-substituents is reported that utilises Heck coupling to install the C2-acrylyl side chains. These analogues possess significant cytotoxicity according to the NCI 60-cell line screen with 18 surpassing anthramycin ( 1) in potency.