Phase II trial of fludarabine phosphate (F-Ara-AMP) in patients with advanced breast cancer

The Pro-Survival Oct4/Stat1/Mcl-1 Axis Is Associated with Poor Prognosis in Lung Adenocarcinoma Patients

The embryonic stem cell marker Oct4 is expressed in several human cancers and is positively correlated with a poor outcome in cancer patients. However, its physiological role in cancer progression remains poorly understood. Tumor cells block apoptosis to escape cell death so that they can proliferate indefinitely, leading to ineffective therapy for cancer patients. In this study, we investigated whether Oct4 regulates the apoptosis pathway and contributes to poor prognosis in patients with lung adenocarcinoma. Our results revealed that Oct4 expression is correlated with Stat1 expression in lung adenocarcinoma patients and Oct4 is directly bound to the Stat1 promoter to transactivate Stat1 in lung adenocarcinoma cells. Expression of the Stat1 downstream gene Mcl-1 increased in Oct4-overexpressing cancer cells, while Stat1 knockdown in Oct4-overexpressing cancer cells sensitized them to cisplatin-induced apoptosis. Furthermore, Oct4 promoted Stat1 expression and tumor growth, whereas silencing of Stat1 reduced Oct4-induced tumor growth in human lung tumor xenograft models. Taken together, we demonstrate that Oct4 is a pro-survival factor by inducing Stat1 expression and that the Oct4/Stat1/Mcl-1 axis may be a potential therapeutic target for lung adenocarcinoma.

Annexin V-Directed Enzyme Prodrug Therapy Plus Docetaxel for the Targeted Treatment of Pancreatic Cancer

OBJECTIVES

The bleak prognosis associated with pancreatic cancer (PDAC) drives the need for the development of novel treatment methodologies. Here, we evaluate the applicability of 3 enzyme prodrug therapies for PDAC, which are simultaneously targeted to the tumor, tumor vasculature, and metastases via annexin V. In these therapies, annexin V is fused to an enzyme, creating a fusion protein that converts nontoxic drug precursors, prodrugs, into anticancer compounds while bound to the tumor, therefore mitigating the risk of side effects.

METHODS

The binding strength of fusion proteins to the human PDAC cell lines Panc-1 and Capan-1 was measured via streptavidin-horseradish peroxidase binding to biotinylated fusion proteins. Cytotoxic efficacy was evaluated by treatment with saturating concentrations of fusion protein followed by varying concentrations of the corresponding prodrug plus docetaxel.

RESULTS

All fusion proteins exhibited strong binding to PDAC cells, with dissociation constants between 0.02 and 1.15 nM. Cytotoxic efficacy was determined to be very good for 2 of the systems, both of which achieved complete cell death on at least 1 cell line at physiologically attainable prodrug concentrations.

CONCLUSIONS

Strong binding of fusion proteins to PDAC cells and effective cytotoxicity demonstrate the potential applicability of enzyme prodrug therapy to the treatment of PDAC.

RB1 status in triple negative breast cancer cells dictates response to radiation treatment and selective therapeutic drugs

Triple negative breast cancer (TNBC) includes basal-like and claudin-low subtypes for which only chemotherapy and radiation therapy are currently available. The retinoblastoma (RB1) tumor suppressor is frequently lost in human TNBC. Knockdown of RB1 in luminal BC cells was shown to affect response to endocrine, radiation and several antineoplastic drugs. However, the effect of RB1 status on radiation and chemo-sensitivity in TNBC cells and whether RB1 status affects response to divergent or specific treatment are unknown. Using multiple basal-like and claudin-low cell lines, we hereby demonstrate that RB-negative TNBC cell lines are highly sensitive to gamma-irradiation, and moderately more sensitive to doxorubicin and methotrexate compared to RB-positive TNBC cell lines. In contrast, RB1 status did not affect sensitivity of TNBC cells to multiple other drugs including cisplatin (CDDP), 5-fluorouracil, idarubicin, epirubicin, PRIMA-1^met, fludarabine and PD-0332991, some of which are used to treat TNBC patients. Moreover, a non-biased screen of ∼3400 compounds, including FDA-approved drugs, revealed similar sensitivity of RB-proficient and -deficient TNBC cells. Finally, ESA⁺/CD24^−/low/CD44⁺ cancer stem cells from RB-negative TNBC lines were consistently more sensitive to gamma-irradiation than RB-positive lines, whereas the effect of chemotherapy on the cancer stem cell fraction varied irrespective of RB1 expression. Our results suggest that patients carrying RB-deficient TNBCs would benefit from gamma-irradiation as well as doxorubicin and methotrexate therapy, but not necessarily from many other anti-neoplastic drugs.

Purine nucleoside phosphorylase targeted by annexin v to breast cancer vasculature for enzyme prodrug therapy

BACKGROUND AND PURPOSE

The targeting of therapeutics is a promising approach for the development of new cancer treatments that seek to reduce the devastating side effects caused by the systemic administration of current drugs. This study evaluates a fusion protein developed as an enzyme prodrug therapy targeted to the tumor vasculature. Cytotoxicity would be localized to the site of the tumor using a protein fusion of purine nucleoside phosphorylase (PNP) and annexin V. Annexin V acts as the tumor-targeting component of the fusion protein as it has been shown to bind to phosphatidylserine expressed externally on cancer cells and the endothelial cells of the tumor vasculature, but not normal vascular endothelial cells. The enzymatic component of the fusion, PNP, converts the FDA-approved cancer therapeutic, fludarabine, into a more cytotoxic form. The purpose of this study is to determine if this system has a good potential as a targeted therapy for breast cancer.

METHODS

A fusion of E. coli purine nucleoside phosphorylase and human annexin V was produced in E. coli and purified. Using human breast cancer cell lines MCF-7 and MDA-MB-231 and non-confluent human endothelial cells grown in vitro, the binding strength of the fusion protein and the cytotoxicity of the enzyme prodrug system were determined. Endothelial cells that are not confluent expose phosphatidylserine and therefore mimic the tumor vasculature.

RESULTS

The purified recombinant fusion protein had good enzymatic activity and strong binding to the three cell lines. There was significant cell killing (p<0.001) by the enzyme prodrug treatment for all three cell lines, with greater than 80% cytotoxicity obtained after 6 days of treatment.

CONCLUSION

These results suggest that this treatment could be useful as a targeted therapy for breast cancer.

Fludarabine combined with radiotherapy in patients with locally advanced NSCLC lung carcinoma: a phase I study

BACKGROUND AND PURPOSE

Fludarabine is an adenine nucleoside analogue that has significant activity in hematological malignancies and has shown promising activity in combination with radiation in preclinical solid tumor models. We designed a phase I trial exploring concurrent fludarabine and radiotherapy in patients with advanced non-small cell lung cancer (NSCLC) to determine the maximum tolerated dose (MTD) of fludarabine given with concurrent irradiation.

MATERIALS AND METHODS

Thirteen patients with stage IIIB NSCLC received thoracic irradiation of 60 Gy. Fludarabine was administered during the 5th and 6th week of radiotherapy. Doses started at 10 mg/m(2) per day and increased by steps of 3 mg/m(2) per day.

RESULTS

At a daily dose of 16 mg/m(2), one out of six patients developed a grade 4 leukopenia, and one a grad 3 pneumonitis. Further grade III toxicity was not observed. The dose of 13 mg/m(2) was identified as the MTD. All patients developed a fludarabine dose-dependent lymphocytopenia.

CONCLUSION

Fludarabine can be safely administered concurrently with radiation at a daily dose of 13 mg/m(2) during the final 2 weeks of radiotherapy. Further prospective clinical studies are required to establish the potential role of concurrent fludarabine and radiotherapy in the treatment of locally advanced inoperable NSCLC.

Purine analogs in the treatment of low-grade lymphomas and chronic lymphocytic leukemias

The purine analogs fludarabine (FAMP), 2-chlorodeoxy-adenosine (2-CDA) and 2-deoxycoformycin (DCF) comprise a novel group of agents with high activity in low-grade lymphoid malignancies. Although all three agents share several mechanisms of action, such as the induction of apoptosis, and toxic effects, such as prolonged immunosuppression, their activity appears to be different in different disorders. While FAMP and possibly also 2-CDA are highly active in chronic lymphocytic leukemia and low-grade follicular lymphomas, 2-CDA and DCF are most effective in hairy cell leukemia. However, prospective comparative evaluations are in progress and their results may ultimately help to define the appropriate indications for and potential side effects of these highly promising new agents.

Fludarabine phosphate. A new anticancer drug with significant activity in patients with chronic lymphocytic leukemia and in patients with lymphoma

Fludarabine phosphate is a purine antimetabolite approved for use in the management of patients with chronic lymphocytic leukemia. Fludarabine works primarily by inhibiting DNA synthesis. The compound also possesses lymphocytotoxic activity with preferential activity toward T-lymphocytes. Initial preclinical studies demonstrated antitumor activity with fludarabine against L1210 murine leukemia. In phase I studies, myelosuppression was identified as the dose-limiting toxicity in patients with solid tumors and fatal neurotoxicity as the dose-limiting toxicity in adult patients with acute hematologic malignancies. The recommended dose and schedule was determined to be 18-25 mg/m2/d for five days, repeated every 28 days. Unlike preclinical studies, phase II trials showed a lack of significant effect when fludarabine was given to patients with solid tumors. However, phase II investigations have confirmed the efficacy of fludarabine in lymphoid malignancies, including non-Hodgkin's lymphoma, mycosis fungoides, prolymphocytic leukemia, and chronic lymphocytic leukemia. The place of fludarabine in the management of leukemias in children is under investigation. Early results indicate an unusual degree of antitumor activity when the agent is used in combination chemotherapy for patients with refractory disease. Fludarabine is an effective antitumor agent in the management of lymphoid malignancies. Studies are ongoing to more completely define the role of fludarabine in these malignancies as well as in the pediatric leukemias. Additional studies evaluating the activity of fludarabine as an immunomodulator are warranted, due to the lymphocytotoxic properties associated with this agent.

Fludarabine: a review

The new fluorinated adenine analog, fludarabine, has been tested for efficacy in many tumor types over the past ten years. Two other similar nucleoside analogs are currently available for commercial use. Cytarabine is used principally as an antileukemic agent, and vidarabine as an antiviral. Unlike vidarabine, fludarabine is resistant to deactivation by adenosine deaminase. Data from Phase I and II trials suggest that fludarabine is potentially effective in a number of leukemias, including acute lymphocytic leukemia, acute nonlymphocytic leukemia, and chronic lymphocytic leukemia (CLL). Unfortunately, the doses required to achieve adequate response in the acute leukemias (greater than 75 mg/m2) were above the maximum tolerated dose, resulting in intolerable granulocytopenia, thrombocytopenia, and a life-threatening neurotoxic syndrome. In CLL: however, the dose required to achieve a satisfactory response is well within tolerated limits. Long-term survival statistics are not yet available, but historical perspective strongly correlates response to other agents with increased survival times. Toxicities seen at dose regimens of 15-40 mg/m2/d for five consecutive days include somnolence, metabolic acidosis, confusion, fatigue, nausea, vomiting, increase in serum creatinine and aminotransferase concentrations, and pulmonary and hepatic abnormalities. Mild to severe hematologic toxicity has been observed at all dose levels.