Samuel Litwin

Paclitaxel and carboplatin in combination in the treatment of advanced non-small-cell lung cancer: a phase II toxicity, response, and survival analysis.

PURPOSE To determine the activity and toxicity of combination paclitaxel (24 hours) and carboplatin in advanced non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS Eligibility required measurable disease (stage IV or stage IIIB with malignant pleural effusion), Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1, absolute neutrophil count > or = 2,000/microL, platelet count > or = 100,000/microL serum creatinine concentration < or = 1.5 mg/dL, and bilirubin level < or = 2 mg/dL. Paclitaxel was initially administered at a dose of 135 mg/m2/d, followed by carboplatin on day 2 at a targeted area under the concentration-time curve (AUC) of 7.5 using the Calvert formula. Granulocyte colony-stimulating factor (G-CSF) 5 micrograms/kg subcutaneously (SC) on days 3 to 17 was introduced during the second and subsequent cycles. In patients who sustained less than grade 4 myelosuppression, the paclitaxel dose was sequentially escalated 40 mg/m2 per cycle to a maximum of 215 mg/m2. Treatment was repeated at 3-week intervals for six cycles. RESULTS From June 1993 through February 1994, 54 patients were enrolled; 53 are assessable for toxicity and response. The median age was 62 years (range, 34 to 84). Sixty-nine percent were male, 65% had adenocarcinoma, and 93% had stage IV disease. Two hundred sixty-eight cycles were administered; 32 patients (59%) completed all six cycles. Twenty-five unanticipated hospitalizations occurred during treatment (9.3% of cycles) in 20 patients (37%). Myelosuppression was the principal toxicity; grade 3 or 4 granulocytopenia occurred in 57% of patients after the first cycle, but decreased to 35% during the second cycle after introduction of G-CSF and consistently remained < or = 22% during subsequent cycles. Seven episodes of neutropenic fever occurred, all during the first cycle. Grade 3 or 4 thrombocytopenia and anemia occurred in 47% and 33% of patients, respectively. Eight patients (15%) required platelet transfusions and 16 (30%) required packed RBC support. Neuropathy, myalgias/arthralgias, and thrombocytopenia, although generally mild, were cumulative. The paclitaxel dose was boosted to 215 mg/m2 in > or = 70% of patients who received three or more cycles. At an AUC of 7.5, the median first-cycle carboplatin dose was 424 mg/m2 (range, 273 to 709 mg/m2). The objective response rate was 62%, with five (9%) complete responses and 28 (53%) partial responses. The median progression-free survival time was 28 weeks and the median survival time 53 weeks. The 1-year survival rate is 54%. CONCLUSION The paclitaxel-carboplatin combination is active in advanced NSCLC and may enhance survival; it merits further investigation in phase III trials.

Phase II study of estramustine and vinblastine, two microtubule inhibitors, in hormone-refractory prostate cancer

PURPOSE Estramustine phosphate (EMP) and vinblastine are two microtubule inhibitors with distinct molecular targets and at least additive antimicrotubule effects in vitro. Their modest single-agent activities in hormone-refractory prostate cancer, nonoverlapping toxicities, and lack of cross-resistance prompted a phase II trial in hormone-refractory prostate cancer. PATIENTS AND METHODS Thirty-six assessable patients at the Fox Chase Cancer Center and seven Fox Chase Cancer Center Network institutions were treated with oral EMP 600 mg/m2 on days 1 to 42 and vinblastine 4 mg/m2 intravenously (IV) once a week for 6 weeks. Courses were repeated every 8 weeks. Response assessment was based on a change in serum prostate-specific antigen (PSA) levels and was correlated with change in pain scores. RESULTS PSA decreased from baseline by at least 50% in 22 patients (61.1%) and by > or = 75% in eight patients (22.2%). A 50% or more decrease in PSA on three successive 2-week measurements together with an improved or stable pain score, performance status, and measurable soft tissue disease (if present) was required for a partial response (PR), which occurred in 11 patients for an overall response rate of 30.5% (95% confidence interval, 15.6% to 45.6%). In seven patients with measurable nonosseous disease, there was one PR (14%) and one minor response (MR). In 28 patients with assessable pain, major pain responses occurred in 12 (42.9%). PSA response (> or = 50% decrease times three measurements) was predictive of major pain response with a 93.7% specificity, a 50% sensitivity, and a positive predictive value of 85.7%. CONCLUSION We conclude that EMP and vinblastine is an active combination in hormone-refractory prostate cancer.

Kinetics of Hepadnavirus Loss from the Liver during Inhibition of Viral DNA Synthesis

ABSTRACT Hepadnaviruses replicate by reverse transcription, which takes place in the cytoplasm of the infected hepatocyte. Viral RNAs, including the pregenome, are transcribed from a covalently closed circular (ccc) viral DNA that is found in the nucleus. Inhibitors of the viral reverse transcriptase can block new DNA synthesis but have no direct effect on the up to 50 or more copies of cccDNA that maintain the infected state. Thus, during antiviral therapy, the rates of loss of cccDNA, infected hepatocytes (1 or more molecules of cccDNA), and replicating DNAs may be quite different. In the present study, we asked how these losses compared when woodchucks chronically infected with woodchuck hepatitis virus were treated with L-FMAU [1-(2-fluoro-5-methyl-β-l-arabinofuranosyl) uracil], an inhibitor of viral DNA synthesis. Viremia was suppressed for at least 8 months, after which drug-resistant virus began replicating to high titers. In addition, replicating viral DNAs were virtually absent from the liver after 6 weeks of treatment. In contrast, cccDNA declined more slowly, consistent with a half-life of ∼33 to 50 days. The loss of cccDNA was comparable to that expected from the estimated death rate of hepatocytes in these woodchucks, suggesting that death of infected cells was one of the major routes for elimination of cccDNA. However, the decline in the actual number of infected hepatocytes lagged behind the decline in cccDNA, so that the average cccDNA copy number in infected cells dropped during the early phase of therapy. This observation was consistent with the possibility that some fraction of cccDNA was distributed to daughter cells in those infected hepatocytes that passed through mitosis.

RAD001 (Everolimus) Delays Tumor Onset and Progression in a Transgenic Mouse Model of Ovarian Cancer

The mammalian target of rapamycin (mTOR) is thought to play a critical role in regulating cell growth, cell cycle progression, and tumorigenesis. Because the AKT-mTOR pathway is frequently hyperactivated in ovarian cancer, we hypothesized that the mTOR inhibitor RAD001 (Everolimus) would inhibit ovarian tumorigenesis in transgenic mice that spontaneously develop ovarian carcinomas. We used TgMISIIR-TAg transgenic mice, which develop bilateral ovarian serous adenocarcinomas accompanied by ascites and peritoneal dissemination. Fifty-eight female TgMISIIR-TAg mice were treated with 5 mg/kg RAD001 or placebo twice weekly from 5 to 20 weeks of age. To monitor tumor development, mice were examined biweekly using magnetic resonance microimaging. In vivo effects of RAD001 on Akt-mTOR signaling, tumor cell proliferation, and blood vessel area were analyzed by immunohistochemistry and Western blot analysis. RAD001 treatment markedly delayed tumor development. Tumor burden was reduced by approximately 84%. In addition, ascites formation, together with peritoneal dissemination, was detected in only 21% of RAD001-treated mice compared with 74% in placebo-treated animals. Approximately 30% of RAD001-treated mice developed early ovarian carcinoma confined within the ovary, whereas all placebo-treated mice developed advanced ovarian carcinoma. Treatment with RAD001 diminished the expression of vascular endothelial growth factor in tumor-derived cell lines and inhibited angiogenesis in vivo. RAD001 also attenuated the expression of matrix metalloproteinase-2 and inhibited the invasiveness of tumor-derived cells. Taken together, these preclinical findings suggest that mTOR inhibition, alone or in combination with other molecularly targeted drugs, could represent a promising chemopreventive strategy in women at high familial risk of ovarian cancer.

Genome-Wide Analyses of Avian Sarcoma Virus Integration Sites

ABSTRACT The chromosomal features that influence retroviral integration site selection are not well understood. Here, we report the mapping of 226 avian sarcoma virus (ASV) integration sites in the human genome. The results show that the sites are distributed over all chromosomes, and no global bias for integration site selection was detected. However, RNA polymerase II transcription units (protein-encoding genes) appear to be favored targets of ASV integration. The integration frequency within genes is similar to that previously described for murine leukemia virus but distinct from the higher frequency observed with human immunodeficiency virus type 1. We found no evidence for preferred ASV integration sites over the length of genes and immediate flanking regions. Microarray analysis of uninfected HeLa cells revealed that the expression levels of ASV target genes were similar to the median level for all genes represented in the array. Although expressed genes were targets for integration, we found no preference for integration into highly expressed genes. Our results provide a more detailed description of the chromosomal features that may influence ASV integration and support the idea that distinct, virus-specific mechanisms mediate integration site selection. Such differences may be relevant to viral pathogenesis and provide utility in retroviral vector design.

Hepatocyte turnover during resolution of a transient hepadnaviral infection

We estimated the amount of hepatocyte turnover in the livers of three woodchucks undergoing clearance of a transient woodchuck hepatitis infection by determining the fate of integrated viral DNA as a genetic marker of the infected cell population. Integrated viral DNA was found to persist in liver tissue from recovered animals at essentially undiminished levels of 1 viral genome per 1,000–3,000 liver cells, suggesting that the hepatocytes in the recovered liver were derived primarily from the infected cell population. We determined the single and multicopy distribution of distinct viral cell junctions isolated from small pieces of liver after clearance of the infection to determine the cumulative amount of hepatocyte proliferation that had occurred during recovery. We estimated that proliferation was equivalent to a minimum of 0.7–1 complete random turnovers of the hepatocyte population of the liver. Our results indicated that during resolution of the transient infections a large fraction of the infected hepatocyte population was killed and replaced by hepatocyte cell division.

Genomic imbalances in human lung adenocarcinomas and squamous cell carcinomas

Comparative genomic hybridization analysis was performed on 67 non‐small‐cell lung cancers (NSCLCs), including 32 squamous cell carcinomas (SCCs) and 35 adenocarcinomas (ACs), to identify differences in the patterns of genomic imbalance between these two histologic subtypes. Among the entire tumor set, the chromosome arms most often overrepresented were 1q, 3q, 5p, and 8q, each detected in 50–55% of cases. The most frequently underrepresented arms were 9q, 3p, 8p, and 17p. The number of imbalances was similar in SCCs and ACs (median number/case: 12 and 11, respectively). Moreover, many imbalances, such as gains of 1q, 5p, and 8q, occurred at a high frequency in both histologic subgroups. Several statistically significant differences, however, were found. The most prominent difference was gain of 3q24‐qter, seen in 81% of SCCs compared with 31% of ACs (P < 0.0001), with amplification at 3q25‐26 being detected in eight of 32 (25%) SCCs but in only two of 35 (6%) ACs. Gain of 20p13 and loss of 4q also were seen at a significantly higher rate in SCCs than in ACs, whereas overrepresentation of 6p was more common in ACs. Gains of 7q and 8q each were associated with higher‐stage tumors and either positive nodal involvement or higher tumor grade. These data suggest that genes located in several chromosomal regions, particularly 3q25‐26, may be associated with phenotypic properties that differentiate lung SCCs from ACs. Furthermore, certain imbalances, prominent among them gains of 7q and 8q, may be indicative of tumor aggressiveness in NSCLCs.

A SHANNON ENTROPY ANALYSIS OF IMMUNOGLOBULIN AND T CELL RECEPTOR

In 1970, before any antigen-bound immunoglobulin structure had been solved, Elvin Kabat proposed that regions of high amino acid diversity would be the antigen binding sites of immunoglobulin (Kabat, 1970). Conversely, sites of low variability were proposed to be structural, framework regions. This variability was defined by Wu and Kabat as the number of different amino acids found at a site divided by the relative frequency of the most common amino acid at that site (Wu and Kabat, 1970). Several groups have subsequently devised improvements of Kabat-Wu variability analysis (Litwin and Jores, 1992). While these methods are somewhat better than Kabat-Wu, they still suffer from Kabat-Wus basic limitation: they account for only the most common one or two amino acids in estimating diversity. This leads to underestimates of low diversities and exaggerations of high diversities. Shannon information analysis eliminates serious bias and is more stable than Kabat-Wu and second generation measures of diversity (Jores et al. 1990; Wu and Kabat, 1970). Statistical reliability can be measured using Shannon analysis, and Shannon measurements can be provided with error estimates. Here we use Shannons method to analyze the amino acid diversity at each site of T cell receptor Valpha and Vbeta to identify complementarity determining regions and framework sites. Our results reveal that the T cell receptor is significantly more diverse than immunoglobulin-suggesting T cell receptor has more than the previously-discovered four complementarity determining regions. These new complementarity determining regions may represent a larger antigen combining site, additional combining sites, or an evolutionary strategy to avoid inappropriate interaction with other molecules.

Phase II study of biochemical modulation of fluorouracil by low-dose PALA in patients with colorectal cancer.

Higher response rates in colorectal cancer have been observed with regimens that increase the cytotoxicity of fluorouracil (5-FU) by altering the biochemical milieu at its site(s) of action. Phosphonacetyl-L-aspartate (PALA), which inhibits aspartate transcarbamylase and depletes uridine nucleotide pools in vitro and in vivo, selectively potentiates the antitumor activity of 5-FU in preclinical models. In a phase I/II study in patients with advanced colorectal cancer, PALA 250 mg/m2 was given on day 1, followed 24 hours later by 5-FU 2,600 mg/m2 by 24-hour infusion repeated weekly. Through the use of subcutaneous ports and portable infusion pumps, all patients were treated outside the hospital setting. Thirty-nine patients without prior chemotherapy received 884 courses of treatment. The primary site was colon in 31, rectum in eight. Toxicity was generally mild to moderate except among four patients who were escalated to 5-FU 3,250 mg/m2: two developed severe gastrointestinal toxicity and myelosuppression. Among the remaining 35 patients, gastrointestinal and neurologic toxicities predominated, but usually did not develop until the third or fourth month of treatment. Two patients were inevaluable for response. Among the 37 evaluable patients there were three complete and 13 partial remissions for a total response rate of 43% (95% confidence interval [Cl], 27% to 59%). The median duration of response was 5 months (range, 1.5 to 15 months). The projected mean survival is in excess of 17 months. This high response rate is comparable to the best results obtained with other means of modulation of 5-FU. Demonstration of a survival benefit will require larger phase III studies.

Single-cell analysis of covalently closed circular DNA copy numbers in a hepadnavirus-infected liver

Hepatitis B virus (hepadnavirus) infections are maintained by the presence of a small and regulated number of episomal viral genomes [covalently closed circular DNA (cccDNA)] in the nuclei of infected cells. Although a number of studies have measured the mean copy number of cccDNA molecules in hepadnaviral-infected cells, the distribution of individual copy numbers have not been reported. Using a PCR-based assay, we examined the number of cccDNA molecules of the duck hepatitis B virus in single nuclei isolated from the liver of a chronically infected duck over the course of 131 days of infection. Nuclei were isolated from frozen serial biopsies and individually deposited into PCR microplates by flow sorting. Each nucleus was assayed by nested PCR for cccDNA and for cellular IFN-α genes as an internal control. We found that 90% of the nuclei assayed contained between 1 and 17 cccDNA molecules, with the remaining 10% containing more (90% confidence), and that differences in the mean number of copies and distribution of copy numbers occurred within the same animal at different times postinfection. Overall, the data suggest (i) that the number of cccDNA molecules per cell may fluctuate over time, and (ii) that, according to these fluctuations, a substantial fraction of cells may contain only one or a few copies. We infer from the results that infected hepatocytes express virus at different levels and that during cell division it is possible to segregate cells containing no cccDNA.