Purpose: HDAC inhibitors (HDACIs) have been shown to inhibit cancer cell proliferation, stimulate apoptosis, and induce cell cycle arrest. Our purpose was to investigate the antiproliferative effects of the HDACIs [suberoyl anilide bishydroxamine, valproic acid (VPA), trichostatin A, and sodium butyrate] against six endometrial cancer cell lines.Experimental Design: Endometrial cancer cells were treated with a variety of HDACIs, and the effect on cell growth, cell cycle, and apoptosis was measured. The ability of VPA to inhibit the growth of endometrial tumors growing in immunodeficient mice was also assessed.Results: Clonogenic assays showed that all cancer cell lines were sensitive to the growth inhibitory effect of HDACIs. Cell cycle analysis indicated that treatment with HDACIs decreased the proportion of cells in S phase and increased the proportion of cells in the G 0 -G 1 and/or G 2 -M phases of the cell cycle. Terminal deoxynucleotidyl transferase-mediated nick end labeling assays showed that HDACIs induced apoptosis. This was concomitant with altered expression of genes related to malignant phenotype, including an increase in p21 Waf1 , p27 Kip7 , and E-cadherin and a decrease in Bcl-2 and cyclin-D1 and -D2. Chromatin immunoprecipitation analysis revealed a remarkable increase in levels of acetylated histones associated with the p21 promoter after suberoyl anilide bishydroxamine treatment. In nude mice experiments, VPA inhibited significantly human uterine tumor growth without toxic side effects.Conclusions: These results suggest that HDACIs are effective in inhibiting growth of endometrial cancer cells in vitro and in nude mice, without toxic side effects. The findings raise the possibility that HDACIs may prove particularly effective in treatment of endometrial cancers.
Biosimilars of biologics used for cancer treatment and supportive care are expected to enter the U.S. market soon. Biosimilars will be highly similar to their reference products, but unlike generic drugs, not identical. Differences between a biosimilar and its reference product may arise because of the complexity of biologics, and differences in the cell lines and processes used during manufacturing. Biosimilars will be approved in the United States through a regulatory pathway based on comparative analytical and clinical studies for their characterization and demonstration of no clinically meaningful differences from their reference products. Unlike generics, initial approval may not include interchangeability, as additional evidence may be required before a biosimilar could be approved as interchangeable with its reference product; interchangeable designation could allow pharmacy-level substitution without prescriber intervention. In some cases, the U.S. Food and Drug Administration (FDA) may extrapolate an indication that has not been formally investigated for the biosimilar but that is approved for the reference product. Robust safety monitoring of all biologics is important to track and accurately attribute adverse events, particularly because their inherent complexity and manufacturing differences make them susceptible to structural changes that can affect safety (e.g., immunogenicity). Accuracy of postapproval safety reports will partly depend on the biosimilar naming approach. Potential cost savings should be evaluated in the context of differences in manufacturers' patient-assistance programs, copayments, and institutional costs. A manufacturer's ability to ensure reliable supply of high-quality biosimilars should also be considered. Broad understanding of these issues is critical for oncologists preparing for their use in clinical practice.
Realization that many tumor suppressor genes are silenced by epigenetic mechanisms has stimulated the discovery of novel tumor suppressor genes. We used a variety of research tools to search for genes that are epigenetically silenced in human endometrial cancers. Changes in global gene expression of the endometrial cancer cell line Ishikawa was analyzed after treatment with the demethylating agent 5-aza-2V -deoxycytidine combined with the histone deacetylase inhibitor suberoylanilide bishydroxamide. By screening over 22,000 genes, candidate tumor suppressor genes were identified. Additional microarray analysis and real-time reverse transcription-PCR of normal and cancerous endometrial samples and search for CpG islands further refined the list. Tazarotene-induced gene-1 (Tig1) and CCAAT/enhancer binding protein-A (C/ebpa) were chosen for further study. Expression of both genes was low in endometrial cancer cell lines and clinical samples but high in normal endometrial tissues. Bisulfite sequencing, restriction analysis, and/or methylationspecific PCR revealed aberrant methylation of the CpG island in the Tig1 gene of all 6 endometrial cancer cell lines examined and 4 of 18 clinical endometrial cancers, whereas the C/ebpa promoter remained unmethylated in endometrial cancers. Chromatin immunoprecipitation showed increased acetylated histone H3 bound to both Tig1 and C/ebpa genes after treatment with 5-aza-2V -deoxycytidine and/or suberoylanilide bishydroxamide. Forced expression of either TIG1 or C/EBPa led to significant growth reduction of Ishikawa cells. Our data suggest that C/ebpa and Tig1 function as tumor suppressor proteins in endometrial cancers and that their reexpression may be a therapeutic target. (Mol Cancer Res 2005;3(5):261 -9)
BACKGROUND Human epidermal growth factor receptor 2 (HER2) is overexpressed in 25–30% of ovarian carcinoma cases and a correlation between increased HER2 expression and decreased survival has been demonstrated. HER2 is a ligand‐less member of the HER family that functions as the preferred coreceptor for epidermal growth factor receptor (EGFR), HER3, and HER4. METHODS An approach was developed to target HER2's role as a coreceptor using a monoclonal antibody, 2C4, which sterically hinders HER2's recruitment into a functional HER complex. RESULTS HER2 was robustly expressed in all eight ovarian carcinoma cell lines; expression of EGFR and HER3 was variable. Even though four of the eight cell lines responded to EGF, 2C4 antibody moderately inhibited in vitro proliferation of only two cell lines (OVCA433 and SK‐OV‐3). Furthermore, ligand‐stimulated p‐MAPK expression was inhibited by 2C4 only in these two cell lines after exposure to EGF. Immunoprecipitation and eTag analysis revealed that OVCA433 expressed heterodimers of EGFR/HER2, and these heterodimers were disrupted after treatment with 2C4, whereas OVCA432 cells did not have these heterodimers. In murine xenograft experiments, the in vivo growth of OVCA433, but not of OVCA432, ovarian carcinoma cells was significantly inhibited by 2C4 treatment of the mice. CONCLUSION 2C4 is able to disrupt the HER signaling pathway and inhibit the in vitro and in vivo growth of ovarian carcinoma cell lines. The response appears limited to lines in which HER2 heterodimers were able to transduce proliferative signals. Our findings suggest a strong rationale to conduct clinical trials of 2C4 in a subset of patients with ovarian tumors. Cancer 2005. © 2005 American Cancer Society.
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