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Irinotecan (Campto) is a topoisomerase I inhibitor currently approved for the treatment of metastatic colon cancer. Single-agent irinotecan has also demonstrated modest activity in a number of other advanced solid tumors, including lung, gastric and pancreatic cancer. Preclinical data suggest a potentially additive and/or synergistic interaction between irinotecan and gemcitabine (Gemzar). This combination has demonstrated improved response rates in patients with pancreatic cancer. Unfortunately, a recently reported Phase III trial of gemcitabine with or without irinotecan revealed no survival benefit for the combination. Future combinations of irinotecan continue to be explored in an effort to further improve the treatment of this relatively chemorefractory disease. Thus far, no single agent or combination has been shown to be superior to gemcitabine alone as palliative therapy for advanced/metastatic pancreatic cancer. A promising combination of irinotecan with oxaliplatin (Eloxatin) and fluorouracil will be assessed in a Phase III study.

The tumor suppressor protein p53 has been implicated in the response of cells to DNA damage. Studies to date have demonstrated a role for p53 in the transcriptional activation of target genes in the cellular response to DNA damage that results in either growth arrest or apoptosis. In contrast, here is demonstrated a role for p53 in regulating the basal level of expression of the cyclin-dependent kinase inhibitor p21 in the absence of treatment with DNA-damaging agents. Wild-type p53-expressing MCF10F cells had detectable levels of p21 mRNA and protein, whereas the p53-negative Saos-2 cells did not. Saos-2 cells were infected with recombinant retrovirus to establish a proliferating pool of cells with a comparable constitutive level of expression of wild-type p53 protein to that seen in untreated MCF10F cells. Restoration of wild-type but not mutant p53 expression recovered a basal level of expression of p21 in these cells. Constitutive expression of luciferase reporter constructs containing the p21 promoter was inhibited by co-transfection with the human MDM2 protein or a dominant-negative p53 protein and was dependent on the presence of p53 response elements in the reporter constructs. Furthermore, p53 in nuclear extracts of untreated cells was capable of binding to DNA in a sequence-specific manner. These results implicate a role for p53 in regulating constitutive levels of expression of p21 and demonstrate that the p53 protein is capable of sequence-specific DNA binding and transcriptional activation in untreated, proliferating cells.

588 Background: Genome-wide epigenetic events appear to play a role in the development and behavior of HPV+ cancers. The value of adjuvant therapy following chemoradiation for localized anal cancer (AC) remains unclear. Molecular prognostication to identify patients (pts) who may be at higher risk for recurrence would be valuable. The goal was to define methylomic profiles predictive of disease-free (DFS) and overall (OS) survival in pts with AC. Methods: Genomic DNA was extracted, processed and methylation status at ~450,000 CpG loci examined (Illumina HumanMethylation450 Array). A multistep bioinformatics methodology was applied to develop a prognostic methylomic classifier for OS and DFS: (1) feature selection for methylated regions (β-value interquartile range ≥ 0.2, ≥ 2 adjacent significant probes within a CpG Island and p < 0.05 by univariate Cox proportional hazards) (2) selected features were entered into a supervised principal component analysis (PCA) and 3 components (PC1, PC2, PC3) were derived (3) classifier was built using forward selection multivariate regression models [PC1, PC2, PC3 alone and in combination with clinical features (size: > T2 vs. ≤ T2, nodal status: N0 vs N+)] using a 10-fold cross-validation (4) final model prediction risk score was generated, dichotomized and evaluated for prognostic values in Cox regression analysis. Results: 121 AC specimens from RTOG 98-11 were examined. The methylomic-only classifier model trended towards statistical significance (log-rank p = 0.05; HR = 1.96; 95% CI 0.99-3.88) in DFS (PC1, PC3 selected). In the combined model with clinical features, the final classifier included T status and epigenetic features (PC1, PC3) and was strongly predictive for DFS (p < 0.0001, HR = 4.45; 2.02-9.76). Final OS classifier models [methylomic-only (p = 0.28 HR = 1.55; 0.70-3.44) or combined (p = 0.013 HR = 2.88; 1.20-6.89)] were not as accurate. Conclusions: Methylomic and clinical features synergize to predict DFS in AC. Multivariate modeling reveal independent contributions from clinical and methylomic variables. Epigenomic profiling may contribute to identification of high-risk pts who may benefit from adjuvant strategies. Support: U10CA180822, U10CA180868, U24CA196067

Supported by detailed understanding of their mechanism of action, and facilitated by chemical manipulations that have amplified their solubility, the camptothecins have advanced to the forefront of several areas of therapeutic and developmental chemotherapy. Additive and synergistic laboratory interactions with other cytotoxic drugs have been exploited to allow development of camptothecin-based multidrug regimens, which are showing important activity in several malignancies. Topotecan and irinotecan are already in widespread use in clinical practice, and newer agents with promising preclinical activity are in various stages of clinical assessment. As knowledge of molecular and biochemical mechanisms of action and resistance continues to expand, newer and better camptothecin-based strategies for treatment of malignant disease are likely to evolve.