Abstract #LB-143: Epothilone B induces class I Human Leukocyte Antigen (HLA) and HLA-A2 expression in ovarian cancer cells.
Authors: Ilenia Pellicciotta, Gary Goldberg, Shohreh Shahabi
Journal: Cancer Research (2009)

AACR Annual Meeting-- Apr 18-22, 2009; Denver, CO

Background : Ovarian cancer is the leading causeof death from gynecologic cancers in the United States. Standardfirst line chemotherapy treatment for ovarian cancer includes paclitaxel and platinum based agents. Epothilone B (EpoB), like Paclitaxel, belongs to a family of anti-neoplastic agents that specifically stabilizes microtubules and arrests cells in the G2/M phase ofthe cell cycle. Little is known about the effect of EpoB on the immune response to tumors. There is compelling evidence that cancer cells use multiple strategies to evade immune recognition. One of these mechanisms is the down-regulation of HLA Class I molecule expression on the tumor cell surface, allowing the cancer cell to escape immune recognition and destruction. Objective : Our data illustrate the effect of EpoB on HLA class I expression in ovarian cancer cells. The effect on the expression of HLA-A2, the most common class I allele in the Caucasian population, has been evaluated as well. We also evaluated the relationship between EpoB-mediated surface HLA expression and transcriptional modification of HLA induced by EpoB. Methods : IC50 was determined for EpoB based on a 72 h cytotoxicity assay, using the Hey ovarian cancer cell line. Cells were treated with different concentrations of EpoB, ranging from 1-fold IC50 to 50-fold IC50, and incubated at 37°C for 24 h, 48 h and 72 h. Cell surface expression of HLA class I molecules and HLA-A2 was examined by flow cytometry, using anti-HLA-A,B,C antibody (G46-2.6 clone) and HLA-A2 (BB7.2 clone). RT-PCR and real time quantitative PCR were used to amplify HLA genes, using Platinum Taq DNA Polymerase and Power SYBR Green master mix respectively. Results: Low dose EpoB (50 nM) increased cell surface expression of HLA Class I up to four-fold in Hey ovarian cancer cells. HLA-A2 expression increased up to two-fold. The highest HLA Class I and HLA-A2 expression increase was achieved after 72 hr treatment of 50 nM EpoB. EpoB transcriptionally activated HLA class I mRNA in Hey cells after 48 hr treatment with 20 and 50 nM EpoB. In the HLAlow ovarian cancer cell line OVCAR3, surface HLA-A2 expression increased up to 3-fold. Conclusions: Low nanomolar concentrations of EpoB enhances surface expression of HLA Class I and HLA-A2 molecules in the Hey ovarian cancer cell line. HLA expression is dose- and time-dependent. EpoB transcriptionally activates HLA Class I mRNA synthesis in Hey cells. EpoB induces HLA-A2 surface overexpression in the HLAlow ovarian cancer cell line OVCAR3. HLA low cancer cell lines may be more sensitive to EpoB-induced HLA-A2 modulation. Our data suggest that low doses of EpoB can mediate the modulation of cell surface HLA and HLA-A2 expression on ovarian cancer cells and consequently enhance the immune recognition of tumor cells.

Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr LB-143.