A phase I trial of riluzole and sorafenib in patients with advanced solid tumors: CTEP #8850

BACKGROUND

Overexpression of metabotropic glutamate receptor 1 (GRM1) has been implicated in the pathogenesis of multiple cancers. Riluzole, an inhibitor of glutamate release, showed synergistic antitumor activity in combination with the multi-kinase inhibitor sorafenib in preclinical models. This phase I trial identified the toxicity profile, dose-limiting toxicities, maximum tolerated dose (MTD), and pharmacokinetic and pharmacodynamic properties of riluzole combined with sorafenib in patients with advanced cancers.

PATIENTS AND METHODS

Patients with refractory solid tumors were enrolled utilizing a 3+3 dose-escalation design. Riluzole was given at 100 mg PO BID in combination with sorafenib, beginning at 200 mg PO daily and escalating in 200 mg increments per level in 28-day cycles. Restaging evaluations were performed every 2 cycles.

RESULTS

35 patients were enrolled over 4 dose levels. The MTD was declared at dose level 3 (riluzole: 100 mg PO BID; sorafenib: 400 mg AM/200 mg PM). Pharmacokinetic analyses did not reveal definitive evidence of drug-drug interactions. Consistent decreases in phospho-forms of ERK and AKT in tumor tissue analyses with accompanying decrease in GRM1 expression and increase in pro-apoptotic BIM suggest target engagement by the combination. Best responses included a partial response in 1 (2.9%) patient with pancreatic acinar cell carcinoma with a KANK4-RAF1 fusion, and stable disease in 11 (36%) patients.

CONCLUSION

Combination therapy with riluzole and sorafenib was safe and tolerable in patients with advanced solid tumors. The partial response in a patient with a RAF1 fusion suggests that further exploration in a genomically selected cohort may be warranted.

A phase I study of veliparib with cyclophosphamide and veliparib combined with doxorubicin and cyclophosphamide in advanced malignancies

PURPOSE

Veliparib (V), an oral poly(ADP-ribose) polymerase (PARP) inhibitor, potentiates effects of alkylating agents and topoisomerase inhibitors in preclinical tumor models. We conducted a phase I trial of V with iv cyclophosphamide (C) and V plus iv doxorubicin (A) and C.

METHODS

Objectives were to establish the maximum tolerated dose (MTD) of the combinations, characterize V pharmacokinetics (PK) in the presence and absence of C, measure PAR in peripheral blood mononuclear cells (PBMCs) and γH2AX in circulating tumor cells (CTCs). In Group 1, dose escalations of V from 10 to 50 mg every 12 h Days 1-4 plus C 450 to 750 mg/m² Day 3 in 21-day cycles were evaluated. In Group 2, V doses ranged from 50 to 150 mg every 12 h Days 1-4 with AC (60/600 mg/m²) Day 3 in 21-day cycles. In Group 3, patients received AC Day 1 plus V Days 1-7, and in Group 4, AC Day 1 plus V Days 1-14 was given in 21-day cycles to evaluate effects on γH2AX foci.

RESULTS

Eighty patients were enrolled. MTD was not reached for V and C. MTD for V and AC was V 100 mg every 12 h Days 1-4 with AC (60/600 mg/m2) Day 3 every 21 days. V PK appears to be dose-dependent and has no effect on the PK of C. Overall, neutropenia and anemia were the most common adverse events. Objective response in V and AC treated groups was 22% (11/49). Overall clinical benefit rate was 31% (25/80). PAR decreased in PBMCs. Percentage of γH2AX-positive CTCs increased after treatment with V and AC.

CONCLUSION

V and AC can be safely combined. Activity was observed in patients with metastatic breast cancer.

Phase I trial of selenium plus chemotherapy in gynecologic cancers

PURPOSE

Preclinical studies performed in our laboratory have shown that high-dose selenium inhibits the development of carboplatin drug resistance in an ovarian cancer mouse xenograft model. Based on these data, as well as the potential serious toxicities of supranutritional doses of selenium, a phase I trial of a combination of selenium/carboplatin/paclitaxel was designed to determine the maximum tolerated dose, safety, and effects of selenium on carboplatin pharmacokinetics in the treatment of chemo-naive women with gynecologic cancers. Correlative studies were performed to identify gene targets of selenium.

METHODS

Chemo-naïve patients with gynecologic malignancy received selenious acid IV on day 1 followed by carboplatin IV and paclitaxel IV on day 3. A standard 3 + 3 dose-escalating design was used for addition of selenium to standard dose chemotherapy. Concentrations of selenium in plasma and carboplatin in plasma ultrafiltrate were analyzed.

RESULTS

Forty-five patients were enrolled and 291 treatment cycles were administered. Selenium was administered as selenious acid to 9 cohorts of patients with selenium doses ranging from 50 μg to 5000 μg. Grade 3/4 toxicities included neutropenia (66.7%), febrile neutropenia (2.2%), pain (20.0%), infection (13.3%), neurologic (11.1%), and pulmonary adverse effects (11.1%). The maximum tolerated dose of selenium was not reached. Selenium had no effect on carboplatin pharmacokinetics. Correlative studies showed post-treatment downregulation of RAD51AP1, a protein involved in DNA repair, in both cancer cell lines and patient tumors.

CONCLUSION

Overall, the addition of selenium to carboplatin/paclitaxel chemotherapy is safe and well tolerated, and does not alter carboplatin pharmacokinetics. A 5000 μg dose of elemental selenium as selenious acid is suggested as the dose to be evaluated in a phase II trial.

Abstract CT025: Phase I trial of selenium plus chemotherapy in gynecologic cancers

PURPOSE: The effectiveness of standard-of-care platinum-taxane chemotherapy in the treatment of patients with advanced gynecologic cancers is limited by the development of chemotherapy resistance in nearly all patients. Based on our preclinical findings that selenium, an essential trace element, inhibits the development of carboplatin drug resistance in an ovarian cancer mouse model, a phase I trial of a combination of selenious acid/carboplatin/paclitaxel was designed to determine the maximum tolerated dose (MTD) and safety of selenium administered with chemotherapy in chemo-naïve women with gynecologic cancers. In addition, the effects of selenium on carboplatin pharmacokinetics were evaluated in this group of patients, and correlative studies were performed to identify potential gene targets of selenium.

METHODS: Patients with gynecologic malignancy not previously treated with chemotherapy received 50-5000 µg elemental selenium IV in the form of selenious acid on day 1 followed by carboplatin (cycle 1, AUC 5; subsequent cycles, AUC 6) IV and paclitaxel 175mg/m2 IV on day 3. A standard 3+3 trial design was used in the selenium dose escalation phase. Concentrations of selenium in plasma and carboplatin in plasma ultrafiltrate were analyzed. RNA expression in tumor specimens and breast and ovarian cancer cell lines were compared before and after treatment with selenium plus chemotherapy using the Human Exon 1.0 ST exon microarray platform. In addition, Western immunoblotting was performed to evaluate protein expression of RAD51AP1, a protein involved in DNA repair, in untreated MCF-7/Adr cells and MCF-7/Adr cells treated with selenium, carboplatin, and the combination of selenium and chemotherapy.

RESULTS: Forty-five patients were enrolled and a total of 291 treatment cycles were administered. Grade 3/4 toxicities included neutropenia (66.6%), febrile neutropenia (2.2%), as well as pain (20.0%), infection (13.3%), neurologic (11.1%), and pulmonary adverse effects (11.1%). The MTD of elemental selenium was not reached. Selenium had no effect on carboplatin pharmacokinetics. In the subset of patients with stage III/IV ovarian cancer/fallopian tube/peritoneal cancer, median progression-free survival was 15 months; in those patients within this subset with measurable disease, 30%, 35%, and 23% experienced complete response, partial response, and stable disease, respectively. Correlative studies showed downregulation of RAD51AP1 by selenium plus chemotherapy in cancer cell lines as well as in tumors of patients treated within this clinical trial.

CONCLUSION: Selenium in combination with carboplatin and paclitaxel is safe and does not affect carboplatin pharmacokinetics. It is possible that selenium-mediated downregulation of RAD51AP1 plays a role in circumventing the development of resistance to carboplatin/paclitaxel chemotherapy. A phase II study to further investigate these findings is underway.

Citation Format: Mihae Song, Muthu N. Kumaran, Murugesan Gounder, Darlene Gibbon, Wilberto Nieves-Neira, Ami Vaidya, Mira Hellman, Michael P. Kane, Brian Buckley, Lorna Rodriguez-Rust. Phase I trial of selenium plus chemotherapy in gynecologic cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT025.

What hides behind the MASC: clinical response and acquired resistance to entrectinib after ETV6-NTRK3 identification in a mammary analogue secretory carcinoma (MASC)

Here, we describe the dramatic response of a patient with an ETV6-NTRK3-driven mammary analogue secretory carcinoma to treatment with a pan-Trk inhibitor, and the development of acquired resistance linked to a novel NTRK3 mutation that interferes with drug binding. This case emphasizes how molecular profiling can identify therapies for rare diseases and dissect mechanisms of drug resistance.

Background

Mammary analogue secretory carcinoma (MASC) is a recently described pathologic entity. We report the case of a patient with an initial diagnosis of salivary acinic cell carcinoma later reclassified as MASC after next-generation sequencing revealed an ETV6-NTRK3 fusion.

Patients and methods

This alteration was targeted with the pan-Trk inhibitor entrectinib (Ignyta), which possesses potent in vitro activity against cell lines containing various NTRK1/2/3 fusions.

Results

A dramatic and durable response was achieved with entrectinib in this patient, followed by acquired resistance that correlated with the appearance of a novel NTRK3 G623R mutation. Structural modeling predicts that this alteration sterically interferes with drug binding, correlating to decreased sensitivity to drug inhibition observed in cell-based assays.

Conclusions

This first report of clinical activity with TrkC inhibition and the development of acquired resistance in an NTRK3-rearranged cancer emphasize the utility of comprehensive molecular profiling and targeted therapy for rare malignancies (NCT02097810).

Abstract 2624: Pre-clinical studies of a mutant p53 reactivating drug in pancreatic cancer

Pancreatic cancer therapy suffers from a lack of effective chemotherapy. TP53 is second only to Kras as the most commonly mutated gene in pancreatic cancer with point mutations occurring in 75% of patients. Recently, our laboratory identified ZMC1 as an allele specific p53 mutant reactivating compound. This compound selectively kills cancer cells that express the p53-R175H mutation by restoring wildtype structure and function to this mutant. It does not reactivate the DNA contact mutant, p53-R273H or p53-R248H. This established ZMC1 as a lead compound for mutant p53 targeted drug development. We are currently investigating the potential of ZMC1 as novel anti-cancer drug through pre-clinical studies in pancreatic cancer. Previously we reported the ZMC1 allele specificity in murine pancreatic cancer cell lines derived from the KPC mouse model expressing mutant KrasG12D and different alleles of TP53 (WT, null, p53R172H, p53R270H). We have investigated the pharmacokinetics (PK) and pharmacodynamics (PD) of ZMC1 in the KPC mouse model. Using LC/MS/MS we developed a sensitive assay for detection of ZMC1 in mouse plasma. We measured drug concentrations in mouse plasma and tumor tissues in different delivery routes and different dosages in the PK studies. We have developed a PD assay for ZMC1 with cleaved caspase-3 immunostaining with which we have tested several doses of ZMC1 and found that we detect activity of ZMC1 in KPCp53-R172H xenograft tumors while at the same time relatively no activity in KPCp53-R270H tumors. These same assays were also performed on KPC autochthanous tumors and again revealed activity of ZMC1 in the KPCp53-R172H mice. Efficacy studies in the KPCp53-R172H xenografts showed potent tumor growth inhibition at both intravenous (1mg/kg) and intraperitoneal (5mg/kg) dosing while no evidence of growth inhibition in KPCp53-R270H. Furthermore, ZMC1 extended the survival days from average 15 days to 26 days in the KPCp53-R172H mice but it was not significantly observed in the KPCp53-R270H mice. The tumor growth rate was also decreased in the KPCp53-R172H but not in the KPCp53-R270H mice. These studies indicated that ZMC1 is an allele-specific p53 mutant reactivating compound and holds promise for future applications in pancreatic cancer.

Citation Format: Xin Yu, Ashley T. Tsang, Zhe Li, Oliver S. Eng, Hongxia Lin, Murugesan Gounder, Darren R. Carpizo. Pre-clinical studies of a mutant p53 reactivating drug in pancreatic cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2624. doi:10.1158/1538-7445.AM2015-2624

Suppression of Cytosolic NADPH Pool by Thionicotinamide Increases Oxidative Stress and Synergizes with Chemotherapy

NAD(+) kinase (NADK) is the only known cytosolic enzyme that converts NAD(+) to NADP(+), which is subsequently reduced to NADPH. The demand for NADPH in cancer cells is elevated as reducing equivalents are required for the high levels of nucleotide, protein, and fatty acid synthesis found in proliferating cells as well as for neutralizing high levels of reactive oxygen species (ROS). We determined whether inhibition of NADK activity is a valid anticancer strategy alone and in combination with chemotherapeutic drugs known to induce ROS. In vitro and in vivo inhibition of NADK with either small-hairpin RNA or thionicotinamide inhibited proliferation. Thionicotinamide enhanced the ROS produced by several chemotherapeutic drugs and produced synergistic cell kill. NADK inhibitors alone or in combination with drugs that increase ROS-mediated stress may represent an efficacious antitumor combination and should be explored further.

Abstract CT219: Selenium counteracts carboplatin drug resistance through Rad51-AP1 induction: A phase I trial in women with gynecologic cancers

Objective: The development of drug resistance is a major cause of gynecologic cancer deaths. Selenium (Se) inhibits the development of carboplatin (C) drug resistance in a mouse ovarian cancer xenograft model. Based on this data, a Phase I trial of a combination of Se, (C) and paclitaxel (P) was designed to determine the maximum tolerated dose (MTD), dose-limiting toxicities (DLTs), safety, and effects of Se in (C) pharmacokinetics (PK) in the treatment of chemo-naive women with gynecologic cancers. Correlative studies identified Se gene targets responsible for reversal of drug resistance.

Methods: Se (50-5000 mcg) IV was given on day 1, and (C) (AUC 5 in cycle 1, AUC 6 in subsequent cycles) IV and (P) 175mg/m2 IV on day 3. A standard 3 + 3 design was used in the selenium dose escalation phase. (C) and Se concentrations in plasma and ultrafiltrate were analyzed.

Results: 45 patients were enrolled. Worst grade toxicities from 291 cycles included neutropenia (Gr 3, n=24; Gr 4, n=19), febrile neutropenia (Gr 3, n=2), anemia (Gr 3, n=1), constitutional (Gr 3, n=3), gastrointestinal (Gr 3, n=5), neurolgic (Gr 3, n=6), pain (Gr 3, n=12), and pulmonary (Gr 3, n= 5). DLT was not reached but IV site pain was recorded at selenium doses higher than 2000 mcg. GFR did not change with Se treatment. Se also had no effect on (C) pharmacokinetics. The average observed AUC was the same as target AUC in each cycle. Between cycle 1 and cycle 2, the estimated PK parameters, clearance (138 vs 133 ml/min) and half-life (312 vs 305 min), were not significantly different. Plasma Se AUC showed dose proportionate increase at higher doses. Of 38 patients with ovarian cancer, there were 9 complete response, 8 partial response, 6 stable disease and 12 disease progression. The median progression-free survival from these 38 patients was 35 months. 33/45 pts had elevated serum CA125 at initiation of therapy. 21/33 had normalization of CA125 after cycle 2 (n=14), and after cycle 6 (n= 7). RNA expression of the tumors as well as cell lines was measured and compared before and after selenium treatment. The samples were run on the Human Exon 1.0 ST exon microarray platform. The results of this analysis pointed to Rad51-AP1 as a gene that is downregulated by selenium. Validation experiments done in vitro confirmed that treatment with Se decreased Rad51-AP1 protein levels, and the cells become more sensitive to (C). Also, cells treated with increasing amounts of (C) showed increased levels of Rad51-AP1.

Conclusion: Se in combination with (C) and (P) is safe, well tolerated and does not affect (C) pharmacokinetics. Although selenium DLT was not reached, at the dose of 5000 mcg, the patients needed central lines for selenium infusion, secondarily to IV site pain. Responses and protracted stable disease are noted in patients with gynecologic cancers. Downregulation of Rad51-AP1, a protein involved in DNA repair, may counteract the development of platinum based drug resistance by selenium.

Citation Format: Lorna Rodriguez-Rodriguez, Mihae Song, Neelakandan Muthukumaran, Murugesan Gounder, Darlene Gibbon, Wilberto Nieves-Neira, Ami Vaidya, Mira Hellmann, Susan Goodin, Brian Buckley. Selenium counteracts carboplatin drug resistance through Rad51-AP1 induction: A phase I trial in women with gynecologic cancers. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT219. doi:10.1158/1538-7445.AM2014-CT219

Abstract 3692: Preclinical studies of a mutant p53 reactivating drug in pancreatic cancer

Pancreatic cancer therapy suffers from a lack of effective chemotherapy. TP53 is second only to Kras as the most commonly mutated gene in pancreatic cancer with point mutations occurring in 75% of patients. Recently, our laboratory identified NSC319726 (726) as an allele specific p53 mutant reactivating compound (Yu, et al. 2012, Cancer Cell). This compound selectively kills cancer cells that express the p53-R175H mutation by restoring wildtype structure and function to this mutant. It does not reactivate the DNA contact mutant, p53-R273H or p53-R248H. This established 726 as a lead compound for mutant p53 targeted drug development. We are currently investigating the potential of 726 as novel anti-cancer drug through pre-clinical studies in pancreatic cancer. We have investigated the pharmacokinetics (PK) and pharmacodynamics (PD) of 726 in murine pancreatic cancer cell lines derived from the KPC mouse model expressing mutant KrasG12D and different alleles of TP53 (WT, null, p53R172H, p53R270H). Using LC/MS/MS we developed a sensitive assay for detection of 726 in mouse plasma. PK studies indicate a half-life of approximately 4 hours with an AUC of 199.78 ng/ml/h for a single 1mg/kg dose given Intravenously. Treatment of KPC cell lines with 726 indicates that the murine p53R172H protein is reactivated as indicated by loss of mutant conformation and induction of p53 target gene transcription. Cell growth inhibition assays reveal that the cell line KPCp53-R172H is sensitive to 726 while the KPCp53-R270H is not. We have developed a PD assay for 726 consisting of cleaved caspase-3 immunostaining and measurement of transcriptional levels of p53 targets PUMA, Noxa and p21. Using these assays we have tested several doses of 726 and found that we detect activity of 726 in KPCp53-R172H xenograft tumors while at the same time relatively no activity in KPCp53-R270H tumors. These same assays were also performed on KPC autochthanous tumors and again reveal activity of 726 in the KPCp53-R172H mice. Efficacy studies in the KPCp53-R172H xenografts reveal potent tumor growth inhibition at both IV (1mg/kg) and IP (5mg/kg) dosing while no evidence of growth inhibition in KPCp53-R270H. These studies confirm that 726 is an allele-specific p53 mutant reactivating compound and holds promise for future applications in pancreatic cancer.

Citation Format: Xin Yu, Zhe Li, Oliver S. Eng, Ashley T. Tsang, Hongxia Lin, Murugesan Gounder, Darren R. Carpizo. Preclinical studies of a mutant p53 reactivating drug in pancreatic cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3692. doi:10.1158/1538-7445.AM2014-3692

E5501: phase II study of topotecan sequenced with etoposide/cisplatin, and irinotecan/cisplatin sequenced with etoposide for extensive-stage small-cell lung cancer

PURPOSE

Sequence-dependent improved efficacy of topoisomerase I followed by topoisomerase 2 inhibitors was assessed in a randomized phase II study in extensive-stage small-cell lung cancer (SCLC).

METHODS

Patients with previously untreated extensive-stage SCLC with measurable disease, ECOG performance status of 0-3 and stable brain metastases were eligible. Arm A consisted of topotecan (0.75 mg/m(2)) on days 1, 2 and 3, etoposide (70 mg/m(2)) and cisplatin (20 mg/m(2)) (PET) on days 8, 9 and 10 in a 3-week cycle. Arm B consisted of irinotecan (50 mg/m(2)) and cisplatin (20 mg/m(2)) on days 1 and 8 followed by etoposide (85 mg/m(2) PO bid) on days 3 and 10 (PIE) in a 3-week cycle.

RESULTS

We enrolled 140 patients and randomized 66 eligible patients to each arm. Only 54.5 % of all patients completed the planned maximum 6 cycles. There were grade ≥3 treatment-related adverse events in approximately 70 % of the patients on both arms including 6 treatment-related grade 5 events. The overall response rates (CR + PR) were 69.7 % (90 % CI 59.1-78.9, 95 % CI 57.1-80.4 %) for arm A and 57.6 % (90 % CI 46.7-67.9, 95 % CI 44.8-69.7 %) for arm B. The median progression-free survival and overall survival were 6.4 months (95 % CI 5.4-7.5 months) and 11.9 months (95 % CI 9.6-13.7 months) for arm A and 6.0 months (95 % CI 5.4-7.0 months) and 11.0 months (95 % CI 8.6-13.1 months) for arm B.

CONCLUSION

Sequential administration of topoisomerase inhibitors did not improve on the historical efficacy of standard platinum-doublet chemotherapy for extensive-stage SCLC.

Abstract C151: Contribution of serine, folate, and glycine metabolism to the ATP, NADPH, and purine requirements of cancer cells

Background: Recent observations on cancer cell metabolism indicate increased serine synthesis from glucose as a marker of poor prognosis. Expression of genes in this pathway also correlate with sensitivity to the antifolate methotrexate (Vazquez A, et al, Cancer Res. 2013 Jan 15;73(2):478-82). Using a large-scale model of human cell metabolism we have predicted that serine synthesis can be routed to a pathway for ATP production. The pathway is composed by reactions from the serine synthesis, one carbon (folate) metabolism and the glycine cleavage system (SOG pathway) and its flux is predicted to increase at high proliferation rates.

Results: Here we show that the SOG pathway is upregulated at the level of gene expression in a subset of human tumors and its level of expression correlates with gene signatures of cell proliferation and Myc targets activation. To investigate the activity of the SOG pathway at the level of metabolic fluxes we estimated the metabolic fluxes of the NCI60 panel of tumor derived cell lines, using previously reported exchange fluxes and a flux balance model of cell metabolism. We show that the estimated rates of reactions in the SOG pathway are highly correlated with the proliferation rates of these cell lines. We also find that the SOG pathway contributes significantly to the energy requirements of biosynthesis, the NADPH requirements of fatty acid synthesis and to the synthesis of purines. Finally, when the PC-3 prostate cancer cell line is subject to treatment with the antifolate methotrexate, we observe a decrease in the ATP levels, an inhibition of the proliferation rate and a decrease in the ribonucleotides and fatty acids synthesized from glucose.

Conclusions: Taken together our results indicate that the SOG pathway activity increases with the rate of cell proliferation and it contributes to the biosynthetic requirements of purines, ATP and NADPH.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C151.

Citation Format: Philip M. Tedeschi, Elke K. Markert, Murugesan Gounder, HongXia Lin, Sonia C. Dolfi, Leo Li-Ying Chan, Jean Qiu, Kim M. Hirshfield, Laszlo G. Boros, Joseph R. Bertino, Zoltan N. Oltvai, Alexei Vazquez. Contribution of serine, folate, and glycine metabolism to the ATP, NADPH, and purine requirements of cancer cells. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C151.

Contribution of serine, folate and glycine metabolism to the ATP, NADPH and purine requirements of cancer cells

Recent observations on cancer cell metabolism indicate increased serine synthesis from glucose as a marker of poor prognosis. We have predicted that a fraction of the synthesized serine is routed to a pathway for ATP production. The pathway is composed by reactions from serine synthesis, one-carbon (folate) metabolism and the glycine cleavage system (SOG pathway). Here we show that the SOG pathway is upregulated at the level of gene expression in a subset of human tumors and that its level of expression correlates with gene signatures of cell proliferation and Myc target activation. We have also estimated the SOG pathway metabolic flux in the NCI60 tumor-derived cell lines, using previously reported exchange fluxes and a personalized model of cell metabolism. We find that the estimated rates of reactions in the SOG pathway are highly correlated with the proliferation rates of these cell lines. We also observe that the SOG pathway contributes significantly to the energy requirements of biosynthesis, to the NADPH requirement for fatty acid synthesis and to the synthesis of purines. Finally, when the PC-3 prostate cancer cell line is treated with the antifolate methotrexate, we observe a decrease in the ATP levels, AMP kinase activation and a decrease in ribonucleotides and fatty acids synthesized from [1,2-¹³C₂]-D-glucose as the single tracer. Taken together our results indicate that the SOG pathway activity increases with the rate of cell proliferation and it contributes to the biosynthetic requirements of purines, ATP and NADPH of cancer cells.

High-risk features in radiation-associated breast angiosarcomas

BACKGROUND

Radiation-associated breast angiosarcoma (RT-AS) is an uncommon malignancy with an incidence of less than 1 % of all soft tissue sarcomas. The overall prognosis is quite dismal with high rates of recurrences and poor overall survival. There is an obvious paucity of data regarding clinical outcomes of patients with breast RT-AS.

METHODS

We identified all patients with RT-AS treated at the Memorial Sloan-Kettering Cancer Center between 1982-2011 and collected their correlative clinical information.

RESULTS

We identified 79 women with RT-AS with a median age of 68 (range 36-87). The median interval between radiation and development of RT-AS was 7 years (range 3-19). The median time to local and distant recurrence was 1.29 years (95 % CI 0.72-NA) and 2.48 years (95 % CI 1.29-NA), respectively. The median disease-specific survival was 2.97 years (95 % CI 2.21-NA). Independent predictors of worse disease-specific survival included age 68 years (HR 3.11, 95 % CI 1.20-8.08, P=0.020) and deep tumors (HR 3.23, 95 % CI 1.02-10.21, P=0.046.)

CONCLUSION

RT-AS has high local/distant recurrence rates, limited duration on standard chemotherapy and poor disease-specific survival.

Assessment of γH2AX levels in circulating tumor cells in patients treated with veliparib in combination with doxorubicin and cyclophosphamide in metastatic breast cancer

2582

Background: Veliparib (V) is a potent PARP inhibitor that delays repair of DNA damage induced by chemotherapeutic agents. In metastatic breast cancer pts, we evaluated V with doxorubicin (A) and cyclophosphamide (C) given both on day 1 with V at 100 mg po BID for 7 days post-chemotherapy every 21 days, to increase DNA damage. We report use of γH2AX, (phosphorylated histone protein), a marker of DNA double-strand breaks, in circulating tumor cells (CTCs) to assess DNA damage. We evaluated number of CTCs and percentage of γH2AX-positive CTCs pre- and post-treatment. Methods: Eligibility included prior A ≤ 300 mg/m2 and EF ≥ 50%. Further A was omitted after a cumulative dose of 420 mg/m2. Primary objective was to assess DNA damage response to treatment by measuring γH2AX-positive CTCs during cycle 1 on days 1 (pre-treatment), 2, 7, and 14. Cell Search System was used to enumerate CTCs. γH2AX was quantitated using a validated assay. Results: Eleven pts enrolled. Median age was 53 (34 – 73); median ECOG PS 1 (0 – 2); there were 1 ER-negative/HER2+, 4 triple-negative (BRCA2+, n =1), and 6 ER+/PR+/HER2-negative (BRCA2+, n =2) tumors. Most common drug-related toxicities were grade (gr) 4 neutropenia, gr 2 anemia and thrombocytopenia, and gr 1 nausea and vomiting. In BRCA2+ pts, there were 2 PRs and 1 SD. In BRCA wt or unknown status, 5 pts had SD ≥ 3 mo and there were 3 PDs. CTCs (≥ 8) were detected in 10/11 pts on days 1 and 2. Day 7 samples were not obtainable in 2 pts. On day 7, 1/8 pts had 0 CTCs and rest had ≥ 3 CTCs. A decrease in CTCs (p < 0.0001) occurred from day 1 (median: 22, range, 8-1216) to day 7 (median: 5, range 3-37). At baseline, 7 pts had ≥ 10% γH2AX-positive CTCs. Fraction of CTCs positive for γH2AX increased to ≥ 50% by day 7 in 6/7 pts and persisted to day 14 in 5 pts. Conclusions: The toxicity profile of V 100 mg BID days 1-7 with AC (60/600 mg/m2) on day 1 on a 21-day cycle was expected. Objective antitumor activity was seen in BRCA mutation carriers. CTCs decreased and percentage of γH2AX-positive CTCs increased after combination treatment with a PARP inhibitor and chemotherapy. This observation is notable and we plan to extend dosing of V to 14 days. This work is supported by NCI U01-CA132194. Clinical trial information: NCT00740805.

A second target of benzamide riboside: dihydrofolate reductase

Dihydrofolate reductase (DHFR) is an essential enzyme involved in de novo purine and thymidine biosynthesis. For several decades, selective inhibition of DHFR has proven to be a potent therapeutic approach in the treatment of various cancers including acute lymphoblastic leukemia, non-Hodgkin's lymphoma, osteogenic sarcoma, carcinoma of the breast, and head and neck cancer. Therapeutic success with DHFR inhibitor methotrexate (MTX) has been compromised in the clinic, which limits the success of MTX treatment by both acquired and intrinsic resistance mechanisms. We report that benzamide riboside (BR), via anabolism to benzamide adenine dinucleotide (BAD) known to potently inhibit inosine monophosphate dehydrogenase (IMPDH), also inhibits cell growth through a mechanism involving downregulation of DHFR protein. Evidence to support this second site of action of BR includes the finding that CCRF-CEM/R human T-cell lymphoblasic leukemia cells, resistant to MTX as a consequence of gene amplification and overexpression of DHFR, are more resistant to BR than are parental cells. Studies of the mechanism by which BR lowers DHFR showed that BR, through its metabolite BAD, reduced NADP and NADPH cellular levels by inhibiting nicotinamide adenine dinucleotide kinase (NADK). As consequence of the lack of NADPH, DHFR was shown to be destabilized. We suggest that, inhibition of NADK is a new approach to downregulate DHFR and to inhibit cell growth.

Rationally designed treatment for solid tumors with MAPK pathway activation: a phase I study of paclitaxel and bortezomib using an adaptive dose-finding approach

In the preclinical setting, phosphorylation and subsequent proteosomal degradation of the proapoptotic protein BIM confers resistance to paclitaxel in solid tumors with RAS/RAF/MAPK pathway activation. Concurrent administration of the proteasome inhibitor bortezomib enables paclitaxel-induced BIM accumulation, restoring cancer cell apoptosis in vitro and producing tumor regression in mice in vivo. A phase I study was conducted to determine the maximum tolerated dose (MTD) of paclitaxel and bortezomib combinatorial treatment. Sixteen patients with refractory solid tumors commonly exhibiting mitogen-activated protein kinase (MAPK) pathway activation were treated weekly with paclitaxel and bortezomib. Starting doses were 40 mg/m(2) for paclitaxel and 0.7 mg/m(2) for bortezomib. A modified continual reassessment method adapted for 2-drug escalation was used for MTD determination with 3-patient cohorts treated at each dose level. MTD was reached at 60 mg/m(2) paclitaxel and 1.0 mg/m(2) bortezomib, the recommended phase II dose. Therapy was overall well tolerated. Most frequently observed toxicities included anemia (in 43.75% of patients, one grade 3 event), fatigue (in 43.75% of patients, one grade 3 event beyond cycle 1), and neuropathy (in 31.25% of patients, one grade 3 event after cycle 1). Of 15 evaluable patients, one non-small-cell lung carcinoma (NSCLC) patient with paclitaxel exposure at the adjuvant setting had a partial response and five patients had stable disease (SD); median disease stabilization was 143.5 days; three NSCLC patients had SD lasting 165 days or longer. Thus, rationally designed weekly treatment with paclitaxel and bortezomib in solid tumors with MAPK pathway activation, including previously taxane-treated malignancies, is a tolerable regimen with preliminary signals of antitumor activity worthy of further investigation.

Phase I study of at-101 (R-(-)-gossypol) in combination with paclitaxel (P) and carboplatin (C) in solid tumors including castrate-resistant prostate cancer (CRPC)

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Background: The combination of paclitaxel (P) and carboplatin (C) has broad anti-tumor activity in multiple tumor types including prostate and bladder cancer. Overexpression of Bcl-2 is a common mechanism of resistance to cytotoxic chemotherapy. AT-101 is an oral inhibitor of Bcl- 2-family-anti-apoptotic proteins. We conducted a phase I study of the combination of AT-101, P and C.

Methods: Ph I study in pts with refractory solid tumors, ECOG 0-1, using a standard 3+3 design to evaluate safety, tolerability and pharmacokinetics/pharmacodynamics (PK/PD). AT-101 was administered orally on Days 1-3 Q12 hr. P and C were administered intravenously on day 1 every 21 days. Dosing levels (DL) were 1: AT-101 40 mg BID, P 150mg/m2, C AUC 5; and DL 2: AT-101 40 mg BID, P 175/m2, C AUC 6. 12 additional pts treated at the MTD dose level were divided into two groups – with AT-101 omitted in the morning of C1D1 or C2D1 to assess apoptotic markers during P and C chemotherapy with and without AT-101.

Results: 24 pts (CRPC-11, colon-3, breast-3 melanoma-2, penile-1, esophageal adeno-1, thymus adeno-1, bladder neuroendocrine-1, NSCLC-1) with median age of 61.5 were enrolled. 6 pts were treated in DL1, and 18 in DL2 (the MTD). Dose limiting toxicities were G3 abdominal pain (1 pt, DL1) and G3 ALT (1pt, DL2). Common G1/G2 AEs were nausea, vomiting, fatigue, anorexia and neutropenia. 4 pts had dose reductions after cycle 1 due to AEs. 12 pts had GCSF added after C1 due to neutropenia. 4/11 (36%) pts with CRPC (all previously treated with docetaxel) had PSA declines of ≥50% and 4 pts had stable disease from 4 to 14 cycles. 2 pts with CRPC had a PR by RECIST. Additionally, 1 pt with esophageal CA had a CR and 1 pt with NSCLC had a PR. PK analysis demonstrated P PK was not influenced by co- administration of C and AT-101 when compared with historical reports (Siddiqui BJC 1997). The PK of AT-101 was not altered significantly by the P dose levels.

Conclusions: The addition of AT-101 to PC chemotherapy is well tolerated and clinically active in advanced cancer pts. The combination of AT-101 and PC may be appropriate for further study in pts with chemorefractory CRPC.

No significant financial relationships to disclose.

Targeting tumor metabolism with 2-deoxyglucose in patients with castrate-resistant prostate cancer and advanced malignancies

BACKGROUND

A profound difference between cancer and normal tissues is the preferential utilization of glycolysis by cancer cells. To translate this paradigm in the clinic, we completed a phase I study of 2-deoxyglucose (2DG), and assessed 2DG uptake with fluorodeoxyglucose (FDG) positron emission tomography (PET) and the autophagy substrate p62 as a marker of 2DG resistance.

METHODS

Patients received 2DG orally on days 1-14 of a 21-day cycle in cohorts of three in a dose-escalating manner. Correlative assessments included PET scans at baseline and day 2 and p62 protein in peripheral blood mononuclear cells as a potential marker of 2DG resistance.

RESULTS

The dose of 45 mg/kg was defined as the recommended phase II dose, secondary to dose-limiting toxicity of grade 3 asymptomatic QTc prolongation at a dose of 60 mg/kg. PK evaluation of 2DG revealed linear pharmacokinetics with C(max) 45 microg/ml (277 microM), 73.7 microg/ml (449 microM), and 122 microg/ml (744 microM) in dose levels 30, 45, and 60 mg/kg, respectively. Five of eight patients assessed with FDG-PET scanning demonstrated decreased FDG uptake by day 2 of therapy, suggesting competition of 2DG with FDG. Five of six patients assessed for p62 had a decrease in p62 at 24 hr.

CONCLUSIONS

These data support the safety of 2DG, defined 2DG PK, demonstrated the effect of 2DG on FDG-PET imaging, and demonstrated the feasibility of assessment of p62 as an autophagic resistance marker. These data support future studies of 2DG alone or in combination with approaches to abrogate autophagy.

Deficiency of the dual ubiquitin/SUMO ligase Topors results in genetic instability and an increased rate of malignancy in mice

Background

Topors is a nuclear protein that co-localizes with promyelocytic leukemia bodies and has both ubiquitin and SUMO E3 ligase activity. Expression studies implicated Topors as a tumor suppressor in various malignancies. To gain insight into the function of Topors, we generated a Topors-deficient mouse strain.

Results

Mice homozygous for a mutant Topors allele exhibited a high rate of perinatal mortality and decreased lifespan. In addition, heterozygotes were found to have an increased incidence of malignancy, involving a variety of tissues. Consistent with this finding, primary embryonic fibroblasts lacking Topors exhibited an increased rate of malignant transformation, associated with aneuploidy and defective chromosomal segregation. While loss of Topors did not alter sensitivity to DNA-damaging or microtubule-targeting agents, cells lacking Topors exhibited altered pericentric heterochromatin, manifested by mislocalization of HP1α and an increase in transcription from pericentric major satellite DNA. Topors-deficient cells exhibited a transcriptional profile similar to that of cells treated with histone deacetylase inhibitors, and were resistant to the anti-proliferative effects of the histone deacetylase inhibitor trichostatin A.

Conclusion

These results indicate a unique role for Topors in the maintenance of genomic stability and pericentric heterochromatin, as well as in cellular sensitivity to histone deacetylase inhibitors.

Phase I trial of patupilone (P) and RAD001 in patients (pts) with advanced solid tumors

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Background: P is an epothilone with activity in solid tumors including docetaxel (D) resistant prostate cancer. R is an oral mTOR inhibitor that demonstrates synergy with P in pre-clinical models, possibly by decreasing resistance to apoptosis. This on-going phase I study is assessing the tolerability of P in combination with R in pts with advanced solid tumors. Methods: Eligible patients with ECOG PS 0–2, adequate organ function and no more than 3 prior chemotherapy treatment received P every 21 days and weekly R using a standard 3+3 dose escalation schema in a 21 day(d) cycle starting at 50% of the phase II dose of P and 60% of the standard weekly dosing of R. Dosing levels are (1) P 5mg/m2 D1, R 30mg D1; (2) P 7.5mg/m2 D1, R 30mg D1 (3) P 7.5mg/m2 D1 R 30mg D1, D8 (3A) P 7.5mg/m2 D1 R 30mg D1, D8, D15 (3B) P 8mg/m2 D1 R 50mg D1, D8 (4) P 10 mg/m2 D1, D8 R 30mg D1, D8 (5) P 10 mg/m2 D1, D8 R 50mg D1, D8. Pharmacokinetic (PK) levels of R were obtained D1, D2 and PBMC were obtained to assess phospho-S6 and to assess markers of apoptosis and autophagy. Results: A total of 24 pts have been enrolled and 23 pts are evaluable for toxicity (tumor types: colon-7, prostate-6, lung-3, ampulla-3, leiomyosarcoma-2, cervical cancer-1). DLTs of grade(g) 3 diarrhea, g3 colitis and g3 fatigue were observed in dose levels 5, 4 and 1 pt in cohort 3A with a colostomy. Cohorts 1–3 were well tolerated with the common AEs of g1 diarrhea, g2 neuropathy after cycle 7, g1/g2 anemia, g1 triglycerides. In pts with prostate cancer (all previously pretreated with D) PSA declines of >50% occurred in 3/5 pts treated with >2 cycles; 1/7 pts with colon cancer had a PR and 3/7 pts with colon cancer had stable disease (SD) > 8 cycles; 1/3 pts with ampullary ca had a PR and a pt with cervical ca had SD x10 cycles. Conclusions: P 7.5mg/m2 and R 30mg D1, D8 is safe and well tolerated. Encouraging evidence of clinical activity is observed in prostate, colon and other tumor types. Enrollment to cohort 3A is ongoing.

[Table: see text]

Bisphosphonate use and osteonecrosis of the jaw: Pharmacovigilance and reporting of this serious adverse event from the Research on Adverse Drug Events and Reports (RADAR) project

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Background: Two years after zoledronate, received FDA approval, four dental professionals treated 107 cases of osteonecrosis of the jaw (ONJ). We review the timeline and source for initial recognition of ONJ and the comprehensiveness of dissemination of information on this adverse drug event. Methods: Data sources included primary case series from dental professionals; published case reports, clinical trials, and cases reported to the manufacturers or the FDA. Exposure adjusted incidence rates estimates were derived from manufacturer sponsored and investigator initiated review of claims data from large cancer centers. Safety notifications were disseminated by the manufacturers, regulatory authorities, and academic investigators. Results: Between 2001 and 2003, 107 patients with ONJ received care from dental professionals. In late 2003, and 2004 peer-reviewed case series were published. By 2006, safety databases maintained by the FDA, the manufacturer, and the RADAR project included information on 2,270, 1,178, and 368 cases of ONJ, respectively. In 2004 and 2005, incidence estimates of 0.8 and 22 ONJ cases per 1,000 person-years of intravenous bisphosphonate therapy were reported by the manufacturer and academic investigators. From 2003 to 2006, safety information from manufacturers, national regulatory authorities, case series, and clinical guidelines were disseminated. Conclusions: Recognition and reporting of ONJ occurred two years after FDA approval of zoledronate, dissemination of safety information occurred in the third year, and publications were disseminated from year three to year five. The life-cycle for identification and information dissemination for this serious adverse drug reaction was short and comprehensive.

[Table: see text] [Table: see text]

A study of the interactions between carboplatin and blood plasma proteins using size exclusion chromatography coupled to inductively coupled plasma mass spectrometry

To study the carboplatin-protein interaction, a sensitive method using size exclusion chromatography coupled to inductively coupled plasma mass spectrometry (SEC-ICP-MS) was developed. The complexes formed between plasma proteins and carboplatin were monitored and identified with this method. Composite blood plasma samples from patients who were undergoing chemotherapy were analyzed, and carboplatin was found to bind plasma proteins. In addition, blank plasma samples were spiked with carboplatin and were analyzed as a time course study, and the results confirmed that carboplatin formed complexes with plasma proteins, primarily albumin and gamma-globulin. To further substantiate the study, these two proteins were incubated with carboplatin. The binding between carboplatin and these proteins was then characterized qualitatively and quantitatively. In addition to a one-to-one binding of Pt to protein, protein aggregation was observed. The kinetics of the binding process of carboplatin to albumin and gamma-globulin was also studied. The initial reaction rate constant of carboplatin binding to albumin was determined to be 0.74 M(-1) min(-1), while that for gamma-globulin was 1.01 M(-1) min(-1), which are both lower than the rate constant of the cisplatin-albumin reaction previously reported.

Lack of necessity of granuloctye-colony stimulating factor (GF) in Hodgkin’s disease (HD) treated with ABVD

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Background: DI is important in the therapy of HD, and GF has been used to maintain DI. Recent data suggest that toxicity (bleomycin pulmonary toxicity [BPT]) is higher in patients (pts) who receive GF (JCO 2005;23:7614). We reviewed all HD pts treated since Jan 1996 with attention to GF use, DI, blood counts, BPT and survival. Methods: We analyzed biopsy-confirmed HD pts who received all of their therapy at NU from Jan 1996 to Oct 2005. BPT was defined as: pulmonary symptoms, bilateral infiltrates on scans and no infection. Results: We identified 95 pts, of whom 77 (81%) received ABVD, 7 (7.4%) Stanford V, and 11 (11.6%) other. Of the 77 ABVD pts, 51 completed all cycles with no GF, 23 received GF and 3 are unknown. In the “no GF” group, median age was 31 yrs, 31% had stage III/IV disease (33% Hasenclever Index > 3); 18% had bulky disease, 37% B symptoms and 53% received radiation (RT). In the GF group (n = 23), median age was 33, 42% had stage III/IV disease (21% Hasenclever index > 3); 17% had bulky disease, 42% B symptoms and 50% had RT. Among the 51 “no GF” ABVD pts (287 cycles), median treatment-day ANC were 0.9, while % monocytes were consistently elevated (see Table). There were no dose adjustments or treatment delays for ANC on day of treatment. Normalized DI was > 99% for all treatment days and median cycle duration was 28.6 days (planned = 28 days). 1/51 of these pts had BPT and 2 episodes of uncomplicated neutropenic fever were seen (2/287 cycles = 0.6% incidence). If Stanford V pts are included (n = 7, 2 without and 5 with GF), BPT occurred in 1/53 with “no GF” and 2/28 with GF (see Table). CR rate (100%), PFS and OS were similar in all groups (see Table). Conclusion: 1) GF is not necessary in order to administer ABVD at > 99% DI, and its absence is associated with low toxicity. 2) ABVD should be given at 100% dose with no delay despite ANC on day of treatment. 3) GF should not be used routinely in HD pts treated with ABVD.

[Table: see text]

No significant financial relationships to disclose.

A phase I and pharmacologic study of the combination of marimastat and paclitaxel in patients with advanced malignancy

BACKGROUND

Marimastat is a potent inhibitor of matrix metalloproteinases and in preclinical studies enhances the anti-tumor activity of certain chemotherapeutics. We performed a phase I clinical evaluation of the combination of oral marimastat and intravenous paclitaxel, to determine if these drugs could be co-administered safely, and to determine whether marimastat alters paclitaxel pharmacokinetics.

MATERIAL/METHODS

Marimastat was administered twice daily and paclitaxel as a three hour infusion every three weeks. Doses of both marimastat and paclitaxel were escalated in cohorts of patients up to maximal doses of 10 mg for marimastat and 175 mg/m2 for paclitaxel. Paclitaxel plasma pharmacokinetic parameters were assessed in the absence (cycle 1) and presence (cycle 2) of marimastat. Trough marimastat plasma levels were evaluated during cycle 2.

RESULTS

A total of 19 patients were treated at three different dose levels. There were no dose-limiting toxicities during the first cycle of therapy, resulting in dose escalation up to the planned maximal dose for each drug. Neutropenia was the most common significant toxicity at the highest dose level, with grade 3 or higher neutropenia occurring in 38% of patients. There were no complete or partial responses. Pharmacokinetic analyses indicate that marimastat does not alter paclitaxel clearance. At the 10 mg dose, the mean trough marimastat level was 14.8 Kg/L.

CONCLUSIONS

Marimastat and paclitaxel can be co-administered safely at doses equivalent to those recommended for single-agent administration. Additional studies are necessary to determine whether this combination is more effective in controlling tumor progression than paclitaxel alone.

Phase I evaluation of sequential topoisomerase targeting with irinotecan/cisplatin followed by etoposide in patients with advanced malignancy

PURPOSE

To investigate pharmacologically guided addition of etoposide to a weekly irinotecan/cisplatin chemotherapy.

PATIENTS AND METHODS

Patients with advanced nonhematologic malignancies were eligible. Treatment consisted of i.v. administration of 50 mg/m(2) irinotecan and 20 mg/m(2) cisplatin on days 1, 8, 15, and 22 of a 42-day cycle or on days 1 and 8 of a 21-day cycle. Etoposide was administered in a dose-escalating fashion 2 days after each dose of irinotecan/cisplatin, either i.v. as a single dose or p.o. as two doses administered 12 h apart. Pharmacologic analyses included measurement of plasma concentrations of irinotecan, SN-38, and SN-38 glucuronide, as well as quantitation of topoisomerase protein levels in peripheral blood mononuclear cells (PBMNCs).

RESULTS

A total of 40 patients with a variety of malignancies received 122 cycles of therapy. Dose-limiting toxicities included neutropenia and diarrhea, with the 21-day cycle tolerated better than the 42-day cycle. For the 21-day cycle, the maximum tolerated dose was 75 mg/m(2) for i.v. etoposide and 85 mg/m(2) for oral etoposide. Objective responses were observed in four patients with previously treated mesothelioma, gastric, breast, and ovarian cancer, respectively. PBMNC levels of topoisomerase IIalpha were increased at the time of etoposide administration in two patients, with these patients having the highest SN-38 glucuronide peak-plasma-concentration and area-under-the-curve values among 15 patients with available pharmacokinetic data. One of these patients had a partial response to therapy.

CONCLUSIONS

Pharmacologically guided administration of etoposide in combination with irinotecan/cisplatin using a 21-day cycle is associated with acceptable toxicity and significant antitumor activity. The finding that PBMNC topoisomerase IIalpha protein levels increased after irinotecan/cisplatin treatment in two of six patients supports the continued development of sequential topoisomerase targeting in the treatment of malignancy.

Inactivation of DNA-dependent protein kinase by protein kinase Cdelta: implications for apoptosis

Protein kinase Cdelta (PKCdelta) is proteolytically cleaved and activated at the onset of apoptosis induced by DNA-damaging agents, tumor necrosis factor, and anti-Fas antibody. A role for PKCdelta in apoptosis is supported by the finding that overexpression of the catalytic fragment of PKCdelta (PKCdelta CF) in cells is associated with the appearance of certain characteristics of apoptosis. However, the functional relationship between PKCdelta cleavage and induction of apoptosis is unknown. The present studies demonstrate that PKCdelta associates constitutively with the DNA-dependent protein kinase catalytic subunit (DNA-PKcs). The results show that PKCdelta CF phosphorylates DNA-PKcs in vitro. Interaction of DNA-PKcs with PKCdelta CF inhibits the function of DNA-PKcs to form complexes with DNA and to phosphorylate its downstream target, p53. The results also demonstrate that cells deficient in DNA-PK are resistant to apoptosis induced by overexpressing PKCdelta CF. These findings support the hypothesis that functional interactions between PKCdelta and DNA-PK contribute to DNA damage-induced apoptosis.

Hereditary antithrombin III deficiency: case report and review of recent therapeutic advances

We report on a newly diagnosed family with hereditary antithrombin III deficiency, with thromboembolic complications in the propositus. Both the propositus and his asymptomatic sister had decreased plasma levels of antithrombin III antigen and activity (28-52% of normal with good agreement between functional and immunologic assays). The propositus developed deep venous thrombosis, followed by massive pulmonary emboli despite heparin therapy and was treated with streptokinase and heparin with excellent results. Shortly thereafter, small bowel obstruction required surgical intervention, and antithrombin III concentrate, recently available in the United States as an investigational new drug (I.N.D.), was administered with no postoperative thrombotic complications. He was subsequently asymptomatic while on warfarin prophylaxis but twice developed venous thrombosis when he failed to take warfarin. The addition of danazol therapy led to a sustained rise in the antithrombin III level. Each of these therapeutic approaches is discussed and the literature reviewed with emphasis on the newer agents--streptokinase, antithrombin III concentrate, and danazol.