The Src inhibitor AZD0530 blocks invasion and may act as a radiosensitizer in lung cancer cells.

BACKGROUND: With the emergence of Src inhibitors in clinical trials, improved knowledge of the molecular responses of cancer cells to these agents is warranted. This will facilitate the development of tests to identify patients who may benefit from these agents, allow drug activity to be monitored and rationalize the combination of these agents with other treatment modalities. METHODS: This study evaluated the molecular and functional effects of Src inhibitor AZD0530 in human lung cancer cells, by Western blotting and reverse transcription-polymerase chain reaction, and by assays for cell viability, migration, and invasion. RESULTS: Src was activated in four of five cell lines tested and the level corresponded with the invasive potential and the histologic subtype. Clinically relevant, submicromolar concentrations of AZD0530 blocked Src and focal adhesion kinase, resulting in significant inhibition of cell migration and Matrigel invasion. Reactivation of STAT3 and up-regulation of JAK indicated a potential mechanism of resistance. AZD0530 gave a potent and sustained blockage of AKT and enhanced the sensitivity to irradiation. CONCLUSIONS: The results indicated that AZD0530, aside from being a potent inhibitor of tumor cell invasion which could translate to inhibition of disease progression in the clinic, may also lower resistance of lung cancer cells to pro-apoptotic signals.

Bortezomib plus gemcitabine/carboplatin as first-line treatment of advanced non-small cell lung cancer: a phase II Southwest Oncology Group Study (S0339).

INTRODUCTION: Bortezomib is a small-molecule proteasome inhibitor with single-agent activity in patients with non-small cell lung carcinoma (NSCLC) and synergy with gemcitabine in preclinical studies. This phase II study of bortezomib in combination with gemcitabine/carboplatin was conducted in chemotherapy-naive advanced NSCLC patients to assess efficacy and safety. METHODS: Patients with selected stage IIIB/IV NSCLC, performance status 0-1, and no history of brain metastasis received up to six 21-day cycles of gemcitabine 1000 mg/m, days 1 and 8, carboplatin area under curve 5.0, day 1, and bortezomib 1.0 mg/m, days 1, 4, 8, and 11. RESULTS: One-hundred-fourteen patients (52% adenocarcinoma, 85% stage IV) received a median of 3.6 treatment cycles. Median follow-up was >3 years. Median overall survival was 11 months; 1-year and 2-year survival rates were 47% and 19%, respectively. Median progression-free survival was 5 months; 1-year progression-free survival rate was 7%. Response rate was 23%, and disease control rate (responses + stable disease) was 68%. The most common grade 3/4 toxicities were thrombocytopenia (63%) and neutropenia (52%). One patient experienced febrile neutropenia. Grade 3/4 neuropathy occurred in 4%, and a further 6% experienced grade 2 sensory neuropathy. CONCLUSIONS: Bortezomib plus gemcitabine/carboplatin resulted in a notable survival benefit in patients with advanced NSCLC, with the anticipated primary toxicity of myelosuppression. Further studies designed to investigate the role of bortezomib in advanced NSCLC are warranted.

Impairment of the DNA repair and growth arrest pathways by p53R2 silencing enhances DNA damage-induced apoptosis in a p53-dependent manner in prostate cancer cells.

p53R2 is a p53-inducible ribonucleotide reductase that contributes to DNA repair by supplying deoxynucleotide triphosphate pools in response to DNA damage. In this study, we found that p53R2 was overexpressed in prostate tumor cell lines compared with immortalized prostatic epithelial cells and that the protein was induced upon DNA damage. We investigated the effects of p53R2 silencing on DNA damage in LNCaP cells (wild-type p53). Silencing p53R2 potentiated the apoptotic effects of ionizing radiation and doxorubicin treatment as shown by increased sub-G(1) content and decreased colony formation. This sensitizing effect was specific to DNA-damaging agents. Comet assay and gamma-H2AX phosphorylation status showed that the decreased p53R2 levels inhibited DNA repair. Silencing p53R2 also reduced the levels of p21(WAF1/CIP1) at the posttranscriptional level, suggesting links between the p53-dependent DNA repair and cell cycle arrest pathways. Using LNCaP sublines stably expressing dominant-negative mutant p53, we found that the sensitizing effect of p53R2 silencing is mediated by p53-dependent apoptosis pathways. In the LNCaP sublines (R273H, R248W, and G245S) that have defects in inducing p53-dependent apoptosis, p53R2 silencing did not potentiate DNA damage-induced apoptosis, whereas p53R2 silencing was effective in a LNCaP subline (P151S) which retains the ability to induce p53-dependent apoptosis. This study shows that p53R2 is a potential therapeutic target that could be used to enhance the effectiveness of ionizing radiation or DNA-damaging chemotherapy in a subset of patients with prostate cancer.

The proteasome inhibitor bortezomib in combination with gemcitabine and carboplatin in advanced non-small cell lung cancer: a California Cancer Consortium Phase I study.

INTRODUCTION: Bortezomib is a small-molecule proteasome inhibitor with single-agent activity in patients with non-small cell lung carcinoma (NSCLC) and synergy with gemcitabine in preclinical studies. The combination of gemcitabine and carboplatin is an accepted first-line treatment for advanced NSCLC. We conducted a phase I study of gemcitabine and carboplatin in combination with bortezomib. METHODS: Bortezomib was administered on days 1, 4, 8, and 11, after gemcitabine on days 1 and 8, and carboplatin on day 1 of a 21-day cycle. Three escalating dose levels were evaluated: bortezomib 1.0 mg/m2/gemcitabine 800 mg/m2, bortezomib 1.0 mg/m2/gemcitabine 1000 mg/m2, and bortezomib 1.3 mg/m2/gemcitabine 1000 mg/m2, in combination with carboplatin AUC 5.0. RESULTS: Twenty-six patients with advanced NSCLC were treated; 21 were chemotherapy-naive. The median age was 59 years (range, 34-74), and 23 patients were stage IV. The Karnofsky performance score was 80% in 16 patients. Dose-limiting toxicities were grade 3 thrombocytopenia with bleeding and febrile neutropenia accompanied by grade 4 thrombocytopenia and grade 3 hyponatremia. The maximum-tolerated dose was defined as bortezomib 1.0 mg/m2, gemcitabine 1000 mg/m2, and carboplatin AUC 5.0. The most common grade 3/4 toxicities were thrombocytopenia (rarely associated with bleeding), and neutropenia. Nine of 26 patients (35%) achieved partial response, and eight patients had stable disease. CONCLUSIONS: The combination of bortezomib 1.0 mg/m2, gemcitabine 1000 mg/m2, and carboplatin AUC 5.0 demonstrated manageable toxicities and encouraging activity in NSCLC. This regimen was used in a phase II study.

Schedule-dependent apoptosis in K-ras mutant non-small-cell lung cancer cell lines treated with docetaxel and erlotinib: rationale for pharmacodynamic separation.

BACKGROUND: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) given concurrently with chemotherapy in 4 large randomized clinical trials did not improve patient outcomes compared with chemotherapy alone in advanced non-small-cell lung cancer (NSCLC). We hypothesized that the lack of benefit resulted from a negative interaction between chemotherapy and EGFR TKIs. MATERIALS AND METHODS: Herein, we report the cell cycle and apoptotic effects of treatment with erlotinib and docetaxel in the NSCLC cell lines A549 and Calu-1, both of which are mutant for K-ras and wild-type for EGFR. RESULTS: Treatment with erlotinib resulted in accumulation of cells in G(1) phase in A549 cells, with no evidence of apoptosis. Docetaxel treatment led to apoptosis as assessed by increased sub-G1 DNA content and cleavage of caspase 3 and poly (ADP-ribose) polymerase. The sequence of docetaxel followed by erlotinib resulted in significantly enhanced apoptosis compared with single-agent docetaxel in both cell lines. However, in the reverse sequence of erlotinib followed by docetaxel, a reduction of apoptosis was observed. We hypothesize that cell cycle arrest induced by erlotinib accounts for these findings in the presence of wild-type EGFR and that pharmacodynamic separation of the 2 drug classes will ameliorate these effects. CONCLUSION: These studies provide a rationale for intermittent dosing of EGFR TKIs with chemotherapy in order to enhance cytotoxicity.

Pharmacodynamic separation of epidermal growth factor receptor tyrosine kinase inhibitors and chemotherapy in non-small-cell lung cancer.

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) given concurrently with chemotherapy do not improve patient outcomes compared with chemotherapy alone in advanced-stage non-small-cell lung cancer (NSCLC). One potential explanation for this lack of benefit is a negative interaction or antagonism between chemotherapy and EGFR TKIs when delivered concomitantly. Support for this line of reasoning is provided by preclinical data demonstrating that EGFR TKIs induce primarily a cytostatic effect resulting from a G1 cell cycle arrest in cell lines with wild-type EGFR, reducing cell cycle phase-dependent activity of chemotherapy, whereas they induce apoptotic cell death in tumors with EGFR-activating mutations. Because the great majority of NSCLC tumors consist of wild-type EGFR, sequence-specific interactions of EGFR TKI/chemotherapy combinations might negatively influence the efficacy of these regimens in patients with NSCLC. Further evidence is provided by EGFR mutational analysis in patient tumor specimens from the TRIBUTE study. Herein we provide the preclinical and clinical rationale for studies examining the concept of pharmacodynamic separation as a means for overcoming hypothesized antagonism of EGFR TKIs and chemotherapy.

Spontaneous immortalization of human epidermal cells with naturally elevated telomerase.

This work explores spontaneous immortalization in keratinocytes, derived from two skin samples, that display naturally elevated telomerase activity. Serially passaged with 3T3 feeder layer support, the keratinocytes were examined for colony-forming ability, telomerase activity, telomere length, and finally gene expression using Affymetrix DNA microarrays. The cells initially exhibited normal karyotypes and low colony-forming efficiencies typical of normal epidermal cells, but after 40 passages (approximately 400 generations) colony-forming ability increased markedly, yielding immortalized lines exhibiting a small number of chromosomal aberrations and functionally normal p53. An improved protocol for analysis of microarray data permitted detection of 707 transcriptional changes accompanying immortalization including reduced p16(INK4A) mRNA. Telomerase activity was clearly elevated in cells even at low passage from both samples, and telomerase catalytic subunit mRNA was greatly elevated in those with elevated colony-forming ability. The data raise the possibility of an unusual natural phenotype in which aberrant telomerase regulation extends keratinocyte lifespan until rare variants evade senescence. In addition to revealing a potential tumor-prone syndrome, the findings emphasize the desirability of carefully minimizing the degree or timing of elevated expression of telomerase used to immortalize cells for therapeutic purposes.

Gefitinib therapy in advanced bronchioloalveolar carcinoma: Southwest Oncology Group Study S0126.

PURPOSE: Advanced bronchioloalveolar carcinoma (BAC) is a distinct subtype of non-small-cell lung cancer (NSCLC) for which there is currently no optimal therapy. Based on preclinical and clinical data suggesting relevance of the epidermal growth factor receptor (EGFR) axis in BAC, the Southwest Oncology Group initiated a phase II trial (S0126) to evaluate the EGFR tyrosine kinase inhibitor gefitinib in chemotherapy-naïve and chemotherapy-pretreated patients with advanced BAC. METHODS: A total of 136 eligible and assessable patients (101 untreated, 35 previously treated) received gefitinib 500 mg daily until progression or prohibitive toxicity. RESULTS: The median age was 68.0 years (range, 34.3 to 88.6); 51% were female; 89% had a performance status (PS) of 0% or 1% and 11% had a PS of 2. The Response Evaluation Criteria in Solid Tumors response rate was 17%, with 6% complete responses (CRs) among 69 previously untreated patients with measurable disease, and 9% with no CRs among 22 pretreated patients. Median survival was 13 months for both chemo-naïve (95% CI, 8 to 18) and previously treated patients (95% CI, 6 to 17). Overall survival at 3 years was 23% (95% CI, 14% to 32%). Toxicity consisted mainly of rash and diarrhea, but 2% of patients died of presumed interstitial lung disease. Exploratory subset analyses revealed improved survival among women (P = .031), patients developing a rash (P = .003), never-smokers (P = .061), and patients with a PS of 0 or 1 (P = .015). CONCLUSION: Gefitinib is an active agent in advanced stage BAC. Several subsets demonstrate significantly improved clinical outcomes.

A randomized phase II trial of the matrix metalloproteinase inhibitor BMS-275291 in hormone-refractory prostate cancer patients with bone metastases.

BACKGROUND: BMS-275291 is a selective matrix metalloproteinase inhibitor (MMPI) that does not inhibit sheddases implicated in the dose-limiting arthritis of older MMPIs. We conducted a randomized phase II trial of two doses of BMS-275291 (1,200 versus 2,400 mg) in hormone-refractory prostate cancer (HRPC) patients with bone metastases to probe for a dose-response relationship and to assess differential toxicities. Serial serum and urine specimens were collected to assess for markers of bone metabolism. METHODS: The primary end point was 4-month progression-free survival (PFS). Eligibility criteria included documentation of androgen-independent disease (including anti-androgen withdrawal), skeletal metastasis, adequate end-organ function and performance status, and no more than one prior chemotherapy regimen. Patients were randomized to 1,200 mg orally once daily (arm A) or 1,200 mg orally twice daily (arm B). Response was assessed every 56 days. RESULTS: Eighty patients were enrolled: 39 in arm A and 41 in arm B. There were no responders by prostate-specific antigen or measurable disease to treatment. Stable disease was noted at 8 weeks in 39% of patients in arm A and in 17% of patients in arm B. Progression of disease at 8 weeks was seen in 61% of patients in arm A versus 83% of patients in arm B. Median survival time was 21.6 months (95% confidence interval, 17.5; not reached), whereas median PFS time was 1.8 months (95% confidence interval 1.74; 2) for all patients. Patients in arm A had a median survival time that was not reached, whereas patients on arm B has a median survival time of 21 months (P = 0.2). PFS at 4 months favored arm A: 22% versus 10% (log-rank, P = 0.008). Grade 3 toxicities occurred in 5 (13%) patients in arm A and in 9 (22%) patients in arm B. Grade 4 toxicities were uncommon (only 4% of patients): one each of thrombosis, fatigue, and motor neuropathy was seen in the arm B. Bone marker studies showed that baseline serum levels of N-telopeptide, osteocalcin, procollagen I NH2-terminal propeptide, and PICP had prognostic significance for PFS and/or overall survival. CONCLUSIONS: Regardless of dose schedule, BMS-275291 was well tolerated in HRPC patients and had no dose-limiting arthritis. Toxicities differed modestly according to the dose schedule employed. As overall survival and PFS favored the once daily schedule, this dose schedule is recommended for future studies. Baseline markers of bone metabolism may have prognostic value in HRPC patients with bone metastases.

Bortezomib (PS-341) in relapsed or refractory extensive stage small cell lung cancer: a Southwest Oncology Group phase II trial (S0327).

BACKGROUND: In preclinical models, the proteasome inhibitor bortezomib (PS-341) inhibits the growth of small cell lung cancer (SCLC) by inhibiting the antiapoptotic Bcl-2 signaling pathway. We conducted a phase II trial of PS-341 in previously treated patients with platinum-sensitive and -refractory extensive stage SCLC to determine response rate, toxicity, and survival. METHODS: Patients with histologically confirmed SCLC, measurable disease, Zubrod performance status 0-1, and previous treatment with platinum-based therapy were enrolled. They were stratified by platinum-sensitivity status: sensitive (relapse >90 days after platinum) or refractory (progression during or < or =90 days after platinum). PS-341 was administered at 1.3 mg/m intravenously on days 1, 4, 8, and 11 every 21 days. RESULTS: Of 56 eligible patients, 28 were platinum sensitive and 28 refractory. Twenty-nine patients (52%) had received two or more previous chemotherapy regimens. One platinum-refractory patient had a confirmed partial response. A majority of assessable patients (91%) progressed. Median progression-free survival and overall survival were 1 month and 3 months, respectively. Ten patients (18%) discontinued treatment due to adverse events or side effects. CONCLUSION: Although PS-341 induced a response in a patient with platinum-refractory disease, it has limited single-agent activity in this heavily pretreated cohort. As shown in preclinical models, testing of PS-341 in combination with an apoptotic trigger such as chemotherapy, is a rational clinical approach. A trial of topotecan plus PS-341 has been initiated to test this concept.

Bortezomib plus docetaxel in advanced non-small cell lung cancer and other solid tumors: a phase I California Cancer Consortium trial.

BACKGROUND: This phase I study was performed to determine the dose-limiting toxicity and maximum tolerated dose (MTD) of docetaxel in combination with bortezomib in patients with advanced non-small cell lung cancer (NSCLC) or other solid tumors. METHODS: Patients were enrolled in cohorts of three over six dose levels. Each treatment cycle was 3 weeks long and consisted of one docetaxel infusion (day 1) and four bortezomib injections (days 1, 4, 8, and 11). Dose escalation and MTD determination were based on the occurrence of dose-limiting toxicities in cycle 1 only. RESULTS: A total of 36 patients were enrolled, 26 of whom had NSCLC. All patients received at least one dose of study drug at one of five dose levels. The MTD of the combined regimen was determined to be 1.0/75 mg/m bortezomib/docetaxel. The combination was generally well tolerated. Toxicities were manageable, and no additive toxicities were observed. The most common adverse events were fatigue (67% of patients), nausea (50%), diarrhea (39%), and neutropenia (39%). Two patients with NSCLC achieved a partial response, and seven (19%) patients achieved stable disease (including six patients with NSCLC). CONCLUSION: The combination of bortezomib and docetaxel was feasible and well tolerated in patients with advanced NSCLC or other solid tumors. The recommended phase II dose is bortezomib 1.0 mg/m on days 1, 4, 8, and 11 plus docetaxel 75 mg/m on day 1, cycled every 21 days. Therapeutic doses of docetaxel and bortezomib are achievable for this combination.

Therapeutic strategies for combined-modality therapy of locally advanced non-small-cell lung cancer: rationale for consolidation docetaxel therapy.

Currently, there is no accepted standard of care for locally advanced and surgically unresectable non-small-cell lung cancer. Typically, treatment for patients with good performance status consists of a combination of chemotherapy and thoracic radiation therapy (RT), but the integration of these modalities and the respective dose schedules vary considerably. Herein, we review the rationale for a treatment paradigm employing consolidation docetaxel therapy after concurrent chemotherapy/RT and the results of recent clinical trials using this approach.

Bortezomib-based combinations in the treatment of non-small-cell lung cancer.

Lung cancer is the most common cause of cancer-related death among men and women in the United States. Current trials are focusing on the integration of novel therapeutic agents into current non-small-cell lung cancer (NSCLC) treatment paradigms. Bortezomib, a small-molecule proteasome inhibitor, has single-agent activity in NSCLC and in combination with agents commonly used in NSCLC. This article will review the rationale and preclinical data supporting bortezomib combinations and the clinical trials with bortezomib alone and in combination in NSCLC to date.

Proteasome inhibition in small-cell lung cancer: preclinical rationale and clinical applications.

Small-cell lung cancer (SCLC) is a tobacco-related malignancy that usually presents in an extensive and therefore incurable stage. Although initially sensitive to platinum agent-based therapy, SCLC rapidly becomes refractory to chemotherapy, leading to disease recurrence and ultimately patient death. Treatment options following failure of first-line platinum agent-based therapy are limited. Small-cell lung cancer is characterized by molecular aberrancies such as overexpression of the antiapoptotic protein Bcl-2, which is regulated in part by the inhibitory IkappaB, a target of the ubiquitin-proteasome degradative pathway. Bortezomib is a proteasome inhibitor that can decrease Bcl-2 expression through diminished IkappaB degradation. Efforts to promote apoptosis in SCLC through the integration of bortezomib into therapy are under way.

The cyclin-dependent kinase inhibitor UCN-01 plus cisplatin in advanced solid tumors: a California cancer consortium phase I pharmacokinetic and molecular correlative trial.

BACKGROUND: UCN-01 (7-hydroxy-staurosporine) is a novel antineoplastic agent targeting cyclin-dependent kinases, which shows potent in vitro and in vivo activity against a broad range of tumor types. Our group has previously shown that UCN-01 potentiates the apoptotic response of agents such as cisplatin in vitro by preventing sequence-specific abrogation of G2 arrest caused by DNA-damaging chemotherapies. PATIENTS AND METHODS: This National Cancer Institute-sponsored phase I trial was designed to determine the safety, maximum tolerated dose, and pharmacokinetics of escalating doses of cisplatin in combination with UCN-01 in patients with advanced malignant solid tumors, as well as to do molecular correlative studies on tumor specimens. Cisplatin was infused over 1 hour before UCN-01 (45 mg/m2/d) given as a 72-hour continuous infusion. Escalation of cisplatin was planned through five dose levels at 20, 30, 45, 60, and 75 mg/m2. RESULTS: Ten patients were accrued. Accrual was halted at dose level 2 (cisplatin, 30 mg/m2) due to dose-limiting toxicities consisting of grade 5 sepsis with respiratory failure associated with grade 3 creatinine (one patient) and grade 3 atrial fibrillation (one patient). Plasma and salivary pharmacokinetics of UCN-01 were unaffected by cisplatin. Pretreatment and posttreatment tumor biopsies showed that UCN-01 was active against a key molecular target, the checkpoint kinase Chk1. CONCLUSIONS: This phase I trial failed to achieve targeted therapeutic dose levels of cisplatin when combined with prolonged infusion UCN-01. However, because preclinical data indicate that UCN-01 potentiates response to platinum, further studies with alternative dose schedules of the combination, or with other platinum analogues, are warranted.

A phase II study of flavopiridol in patients with advanced renal cell carcinoma: results of Southwest Oncology Group Trial 0109.

PURPOSE: Flavopiridol is a cyclin-dependent kinase inhibitor that prevents cell cycle progression and tumor growth. In initial phase I studies, encouraging responses were seen in advanced renal cell cancer (RCC). In a phase II study of flavopiridol given as a 72-h continuous infusion every 2 weeks in RCC, a response rate of 6% was seen but with considerable grade 3 or 4 asthenia, diarrhea, and thrombosis. Subsequently, an alternative 1-h bolus schedule was reported to have enhanced tolerability in a phase I trial. We therefore conducted a phase II study of this bolus regimen. METHODS: A total of 38 patients with advanced RCC were entered into this multi-institutional phase II study. Flavopiridol (50 mg/m(2) per day) was administered by bolus intravenous injection daily for three consecutive days, repeated every 3 weeks. RESULTS: Out of 34 eligible patients, one complete response and three partial responses were observed, for an overall response rate of 12% (95% CI 3-27%). Of the 34 patients, 14 (41%) had stable disease (SD). The probability of not failing treatment by 6 months was 21% (95% CI 9-35%). Median overall survival time was 9 months (95% CI 8-18 months). The most common grade 3 or 4 toxicities were diarrhea (35%) and tumor pain (12%) along with anemia, dyspnea, and fatigue (9% each). CONCLUSIONS: Flavopiridol at this dose and schedule is feasible with an acceptable toxicity profile. Flavopiridol has some modest biologic activity against advanced RCC, as evidenced by its single-agent objective response and SD rates.

Glycogen synthesis correlates with androgen-dependent growth arrest in prostate cancer.

BACKGROUND: Androgen withdrawal in normal prostate or androgen-dependent prostate cancer is associated with the downregulation of several glycolytic enzymes and with reduced glucose uptake. Although glycogen metabolism is known to regulate the intracellular glucose level its involvement in androgen response has not been studied. METHODS: We investigated the effects of androgen on glycogen phosphorylase (GP), glycogen synthase (GS) and on glycogen accumulation in the androgen-receptor (AR) reconstituted PC3 cell line containing either an empty vector (PC3-AR-V) or vector with HPV-E7 (PC3-AR-E7) and the LNCaP cell line. RESULTS: Androgen addition in PC3 cells expressing the AR mimics androgen ablation in androgen-dependent prostate cells. Incubation of PC3-AR-V or PC3-AR-E7 cells with the androgen R1881 induced G1 cell cycle arrest within 24 hours and resulted in a gradual cell number reduction over 5 days thereafter, which was accompanied by a 2 to 5 fold increase in glycogen content. 24 hours after androgen-treatment the level of Glucose-6-P (G-6-P) had increased threefold and after 48 hours the GS and GP activities increased twofold. Under this condition inhibition of glycogenolysis with the selective GP inhibitor CP-91149 enhanced the increase in glycogen content and further reduced the cell number. The androgen-dependent LNCaP cells that endogenously express AR responded to androgen withdrawal with growth arrest and increased glycogen content. CP-91149 further increased glycogen content and caused a reduction of cell number. CONCLUSION: Increased glycogenesis is part of the androgen receptor-mediated cellular response and blockage of glycogenolysis by the GP inhibitor CP-91149 further increased glycogenesis. The combined use of a GP inhibitor with hormone therapy may increase the efficacy of hormone treatment by decreasing the survival of prostate cancer cells and thereby reducing the chance of cancer recurrence.

Intermittent dosing of the farnesyl transferase inhibitor tipifarnib (R115777) in advanced malignant solid tumors: a phase I California Cancer Consortium Trial.

Tipifarnib (R115777) inhibits farnesylation of key proteins that modulate signaling pathways implicated in cell growth and proliferation, including members of the Ras and Rho families. It has broad-spectrum antiproliferative activity in vitro and in vivo. Clinical trials employing a continuous administration schedule have demonstrated dose-limiting neurotoxicity and myelosuppression. Preclinical studies have shown that intermittent oral administration can suppress tumor growth comparable to continuous administration. We conducted a National Cancer Institute-sponsored phase I trial to determine the feasibility of an intermittent dosing schedule of R115777 given orally twice daily on weeks 1 and 3 of a 28-day cycle in patients with malignant solid tumors. Starting dose was 300 mg twice daily (b.i.d.) with escalation by 300 mg b.i.d. increments over six dose levels to a maximum of 1800 mg b.i.d. Dose-limiting toxicity (DLT) was defined as any grade 3 or 4 non-hematologic toxicity, grade 4 thrombocytopenia, grade 4 neutropenia (ANC) with fever (38.3 degrees C or above) or a documented infection. Twenty-one patients with advanced solid tumors, all of whom had prior systemic therapy, were accrued. Grade 3 fatigue was dose limiting for two of three patients at the 900 mg b.i.d. dose level. Although no responses were seen, four of six patients with stable disease remained on study for at least a year (16, 17, 13 and 12 months) before developing progressive disease. Three of these prolonged stable disease patients had non-small cell lung cancer. We conclude that intermittent dosing of R115777 is feasible and tolerable. The recommended phase II dose is 600 mg orally b.i.d. on alternate weeks.

Enhancement of radiation cytotoxicity by UCN-01 in non-small cell lung carcinoma cells.

Thoracic ionizing radiation is a standard component of combined-modality therapy for locally advanced non-small cell lung cancer. To improve low 5-year survival rates (5- 15%), new strategies for enhancing the effectiveness of ionizing radiation are needed. The kinase inhibitor UCN-01 has multiple cell cycle effects, including abrogation of DNA damage-induced S- and G(2)-phase arrest, which may limit DNA repair prior to mitosis. To test the hypothesis that therapy-induced cell cycle effects would have an impact on the efficacy of a combination of UCN-01 plus ionizing radiation, the cell cycle responses of the non-small cell lung cancer cell lines Calu1 (TP53-null) and A549 (wild-type TP53) to 2 Gy ionizing radiation were correlated with clonogenic survival after irradiation plus UCN-01. Irradiated cells were exposed to UCN-01 simultaneously and at 3-h increments after irradiation. In Calu1 cells but not A549 cells, sequence-dependent potentiation of radiation by UCN-01 was observed, with maximal interaction occurring when UCN-01 was administered 6 h after irradiation. This coincided with the postirradiation time with the greatest depletion of cells from G(1). Abrogation of G(2) arrest was observed regardless of TP53 status. The role of TP53 was investigated using siRNA to achieve gene silencing. These studies demonstrated that radiation plus UCN-01 was more effective in cells with diminished TP53 activity, associated with a reduced G(1) checkpoint arrest. These studies indicate that simultaneous elimination of multiple DNA damage-induced checkpoints in G(1), S and G(2) may enhance the effects of radiation and that drug scheduling may have an impact on clinical efficacy.