HDAC Profiling In Mantle Cell Lymphoma Unveils HDAC11 and HDAC10 as Potential Molecular Targets

Epigenetic changes in chromatin structure involving histone modifications have been recently implicated in the deregulated expression of critical genes in MCL, including cyclin D1 and some tumor suppressor genes. Special emphasis has been given therefore to the assessment of the therapeutic role of epigenetic modifiers in MCL. Among these, a family of compounds known as histone deacetylase inhibitors (HDI) display antitumor activity both in experimental models as well as in recently completed clinical trials in MCL patients. Given that aberrant expression of histone deacetylases (HDACs) has been shown to influence disease aggressiveness and response to treatment in several malignancies^1,2,3, we seek to determine the expression of specific HDACs in human MCL.

Expression of HDAC class I (HDAC1, 2, 3, 8), class II (HDAC4, 5, 6, 9, 10) and Class IV (HDAC11) was determined by quantitative real-time RT-PCR using specific HDAC primers in four human MCL cell lines (JEKO, Z138, MINO, SP53), primary malignant cells from lymph nodes of patients with MCL and in B-lymphocytes isolated from normal donors (Control). Protein expression of selected HDACs was evaluated by western blot. Knocking down of specific HDACs was performed using shRNAs lentiviruses targeting specific human HDAC sequences. Cell proliferation and cell cycle analysis of MCL cells lacking a specific HDAC were performed using standard techniques.

No significant differences in class I HDAC expression was found among normal B-lymphocytes, MCL cell lines and malignant B-cells from MCL patients. In contrast, the expression all class II HDACs, but HDAC9, was reduced in MCL cell lines and primary human MCL cells relative to normal B-cells. Of note, HDAC10 expression was consistently absent or significantly decreased in all MCL cell lines and primary MCL cells. Analysis of HDAC11 revealed interesting findings: increased expression of HDAC11 mRNA was observed in human MCL cell lines and primary human MCL cells, with the highest expression among two patients with the blastoid variant of MCL and the lowest expression in cells from two patients with a clinically indolent MCL. Next, we knocked-down HDAC11 in Z138 MCL cells and generated two stable clones (HDAC11KD) that displayed a slower cell proliferation relative to non-target shRNA control cells. Cell cycle analysis revealed that HDAC11KD clones are cycling at a significantly lower rate than control cells.

HDAC11 over-expression in MCL seems to confer a proliferation/survival advantage to malignant cells. This finding provides a rationale to selectively disrupt this HDAC in MCL. Given that decreased HDAC10 expression is associated with a more aggressive behavior in other malignancies¹, our findings of diminished HDAC10 expression in MCL warrant further investigation.

1. Tatematsu et al. Int J Cancer 112:26–32, 2004

2. Zhang Z et al. Clin Cancer Res. 15;10:6962–8, 2004

3. Villagra et al. Oncogene 24:157–73, 2010.

Leonard: Hospira: Consultancy, Honoraria; Cell Therapeutics: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; GlaxoSmithKline: Consultancy, Honoraria; Biogen IDEC: Consultancy, Honoraria; Calistoga: Consultancy, Honoraria; Johnson and Johnson: Consultancy, Honoraria; EMD Serono: Consultancy, Honoraria; Sanofi Aventis: Consultancy, Honoraria; Millenium: Consultancy, Honoraria; Biotest: Consultancy, Honoraria; Cephalon: Consultancy, Honoraria; Pharmion: Consultancy, Honoraria; Eisai: Consultancy, Honoraria; Cougar Biotechnology: Consultancy, Honoraria; Immunomedics: Honoraria; Genentech: Consultancy, Honoraria; Novartis: Consultancy, Honoraria.