Min Jian Xu

Potentiation of platinum analogue cytotoxicity by hyperthermia

SummaryCarboplatin and iproplatin, two new analogues of cisplatin, appear to have comparable activity in the treatment of advanced ovarian cancer, but minimal nephro- and neurotoxicities. Hyperthermia can potentiate the cytoxicity of cisplatin in vitro and in vivo, but systemic treatment with the combination has proven unsafe in patients. To provide the rationale for an alternative approach, we evaluated the relative degree of additivity between hyperthermia and the three platinum analogues in vitro against a human ovarian adenocarcinoma cell line, UACC-66. All drug and heat treatments were simultaneous for 1 h. Platinum analogue concentrations covered a five-log range from 0.001 to 100 μg/ml and hyperthermia temperatures included 38.5°, 40°, 41.5°, and 43° C. A tumor clonogenic assay was used to quantitate heat-drug interactive effects against the UACC-66 cells, and statistical analysis was performed using the median-effect equation of Chou. When combined with heat, the in vitro concentrations of the three platinum analogues were between 5% and 25% of those required at 37° C to inhibit 50%–70% of the UACC-66 tumor colony-forming units. For each drug when combined with heat, a 3° C incremental increase in temperature (i.e., from 37° C to 40° C or from 40° C to 43° C) was associated with a ten-fold decrease in ID50 drug concentration. We conclude that the synergistic effects of both carboplatin and iproplatin with hyperthermia at all temperatures above 37° C provide a rationale for design of clinical trials in patients with ovarian cancer using these hyperthermia-drug combinations.

Reproducibility and Expression of Skin Biomarkers in Sun-Damaged Skin and Actinic Keratoses

Objectives: To explore p53 and proliferating cell nuclear antigen (PCNA) expression and polyamine content as biomarkers in skin cancer chemoprevention trials, we evaluated their expression in early stages of UV-induced squamous cell tumorigenesis. Methods: Biopsies were collected from three groups: 78 subjects with sun damage on forearms, 33 with actinic keratosis (AK) on forearms, and 32 with previous squamous cell carcinoma. Participants with sun damage were randomized to sunscreen or no sunscreen. Results: We found significant differences in p53 and polyamines in forearms from the sun-damaged group (11.5 ± 1.2% for p53, 65.5 ± 1.9 nmol/g for putrescine, and 187.7 ± 3.3 nmol/g for spermidine) compared with the group with sun damage plus AK (20.9 ± 2.3% for p53, P = 0.0001; 81.7 ± 3.9 nmol/g for putrescine, P = 0.0001; 209.4 ± 8.2 nmol/g for spermidine, P < 0.06). PCNA was not different. When lesion histology was considered, there was a stepwise significant increase in p53 in biopsies without characteristics of AK compared with early AK (P = 0.02) and AK (P = 0.0006) and a similar pattern for PCNA with the only significant difference between early AK and AK. There was a stepwise increase in putrescine and spermidine in normal, sun-damaged forearm, forearm from subjects with AK, and the AK lesion itself (P < 0.0001). No significant differences in p53 or polyamines were seen in 3-month biopsies or, as a result of sunscreen use, although PCNA in the sun-damaged group not using sunscreen decreased significantly. Conclusions: p53 expression and polyamines in skin were elevated in early stages of skin tumorigenesis and were not affected by sunscreen, adding validity to their use as biomarkers in skin cancer chemoprevention trials. (Cancer Epidemiol Biomarkers Prev 2006;15(10):1841–8)

Chemoprevention of Human Actinic Keratoses by Topical DL-α-Tocopherol

Prior research shows that topical application of free, nonfatty acid–conjugated vitamin E (dl-α-tocopherol) prevents skin cancer in mice, as well as immunosuppression induced by UVB radiation. This study investigated the chemopreventive potential of dl-α-tocopherol in humans through monitoring surrogate end point biomarkers in sun-damaged skin. Contralateral arms of healthy human volunteers with actinic keratoses (AK) were randomly assigned to receive either 12.5% dl-α-tocopherol or placebo in a crème base for 6 months. Changes in number of AKs, levels of p53 protein expression, proliferating cell nuclear antigen, and polyamines were assessed along with skin and systemic vitamin E levels. Following treatment, plasma concentration levels of dl-α-tocopherol were unchanged, but skin levels were highly elevated (P < 0.001). Levels of p53 and proliferating cell nuclear antigen did not change significantly, whereas number of AKs declined insignificantly in both placebo and treatment arms. Regression models showed significant decreases in putrescine, spermidine, spermine, and total polyamine concentrations following treatment. Topically applied dl-α-tocopherol was substantially absorbed in skin, but the 6-month application did not significantly reduce numbers of preexisting AKs on moderately to severely sun-damaged forearms. Increases in polyamine synthesis are expected during tumor initiation and promotion; conversely, the significant reductions in polyamine levels resulting from the topical dl-α-tocopherol application are consistent with reductions in tumorigenesis potential. Topical tocopherol did not normalize established sun-induced lesions, but dl-α-tocopherol–induced reductions in polyamine metabolism are consistent with the inhibition of skin squamous cell carcinogenesis as seen in previous human trials and animal models.

Dose-Dependent Effects of Selenized Yeast on Total Selenium Levels in Prostatic Tissue of Men With Prostate Cancer

Although a negative association between serum selenium (or selenium supplementation) and prostate cancer risk has been widely reported (1–8), very little is known about the effects of oral supplementation with selenized yeast on selenium levels in prostate tissue of men with prostate cancer.

The role of serum and tissue pharmacology studies in the design and interpretation of chemoprevention trials

The design and interpretation of chemoprevention trials are challenging tasks. Innovative methodological approaches to these investigations are in initial stages of development. Important pharmacologic issues should be addressed as early as possible in these trials to facilitate the optimal design of large, Phase III, randomized trials. These include determining the optimal dose of the compound and the toxicity profile. Other key areas involve the use of serum concentrations to monitor subject compliance, the evaluation of concentration of the chemopreventive agent in the target tissue, adequate assessment of the drug delivery systems, and the evaluation of the relationship between the dose administered and the serum or tissue concentrations achieved. Whenever possible the investigation of the relationship between serum or tissue concentrations of a chemopreventive agent vs its biologic activity should be determined. Specific examples involving the retinoids and carotenoids are presented.

In vitro evaluation of cisplatin interaction with doxorubicin or 4-hydroperoxycyclophosphamide against human gynecologic cancer cell lines.

SummaryDoxorubicin, cisplatin, and cyclophosphamide are the three drugs most commonly used in the treatment of ovarian cancer, but no effect greater than additivity was observed for any combination of these drugs in the present study. Only a few studies have been reported concerning the degree of their additivity or their best order of sequencing. In our in vitro studies, cisplatin in combination with doxorubicin or 4-hydroperoxycyclophosphamide (4HC) was tested against seven human gynecologic tumor-cell lines in different sequences, using a double-agar layer tissue-culture system. Drug interactions with respect to inhibition of tumor clonogenicity were evaluated by isobologram and fractional survival methods. Doxorubicin and 4HC were sequenced simultaneously and at 1, 6 and 24 h after cisplatin, and cisplatin was sequenced at 1, 6 and 24 h after 4HC. The isobolograms constructed for doxorubicin or 4HC plus cisplatin revealed strict additivity between these agents against ovarian cancer clonogenicity. Both doxorubicin and 4HC showed the greatest additivity when used simultaneously and at 1 h vs 6 or 24 h after cisplatin. Although the mechanisms by which these sequencing effects occur are unknown, these studies provide new leads for the design of clinical trials with combinations of these three agents.

A phase I trial of AUC-directed carboplatin with infusional doxorubicin and ifosfamide plus G-CSF in patients with advanced gynecologic malignancies.

Abstract The effect of the addition of G-CSF to carboplatin, ifosfamide and doxorubicin (CIA) at the maximally tolerated dose (MTD) was studied in a phase I clinical trial. Nine patients with incurable solid tumors were treated: six endometrial and epithelial ovarian cancers, one colon cancer with pelvic masses and two unknown primary cancers. The carboplatin dose was calculated using the Calvert formula and administered in a standard 30-min intravenous infusion. The initial carboplatin dose was AUC 4.0 mg/ml per min. Fixed doses of ifosfamide (1.25 g/m2 per day), mesna (1.0 g/m2 per day, and doxorubicin (15 mg/m2 per day) were combined and given as a 4-day continuous intravenous infusion in an attempt to decrease nonhematologic toxicity. The dose-limiting toxicity of CIA was myelosuppression, mainly neutropenia and thrombocytopenia. Nonhematologic toxicities were hemorrhagic cystitis, weakness, fatigue, and nausea and vomiting. The MTD for CIA was established at the first dose level of carboplatin (4.0 mg/ml per min). Following this, G-CSF was added to the regimen in an unsuccessful effort to escalate the carboplatin dose. Free and total carboplatin pharmacokinetics were determined using flameless atomic absorption spectroscopy. There was one complete response and one partial response among eight evaluable patients. Both responding patients had advanced ovarian cancer. We conclude that carboplatin dose intensification beyond an AUC of 4.0 mg/ml per min is not made feasible by the addition of G-CSF to infusional doxorubicin and ifosfamide in patients with advanced gynecologic cancer.