Targeted Silencing of MLL5β Inhibits Tumor Growth and Promotes Gamma-Irradiation Sensitization in HPV16/18-Associated Cervical Cancers

Abstract

We previously identified a novel MLL5 isoform, MLL5b, which was essential for E6 and E7 transcriptional activation in HPV16/18-associated cervical cancers. In this report, we investigated the potential of RNAimediated silencing of MLL5b through the use of MLL5b-siRNA as a novel therapeutic strategy for HPV16/18-positive cervical cancer. We observed concurrent downregulation of E6 and E7 after MLL5b silencing, leading to growth inhibition via the activation of apoptosis and senescence in the HeLa cell model. This corresponded with the enhanced antitumor effects of MLL5b-siRNA compared with E6-or E7-siRNA single treatments. Significant reduction in tumor size after MLLb-siRNA treatment in the HeLa xenograft tumor model further emphasized the importance of MLL5b in HPV16/18-associated tumor growth and the potential of RNAi therapeutics that target MLL5b. We also identified MLL5b as a modulator of gamma-irradiation (IR) sensitization properties of cisplatin. We observed that while MLL5b silencing alone was enough to evoke cisplatin-like IR sensitization in tumor cells in vitro, overexpression of MLL5b inhibited the ability of cisplatin to sensitize HeLa cells to IR-induced cytotoxicity. MLL5b-siRNA-IR cotreatment was also observed to enhance tumor growth inhibition in vivo. Taken together, our findings highlight the potential of targeted silencing of MLL5b via the use of MLL5b-siRNA as a novel therapeutic strategy and propose that MLL5b-siRNA could be a viable alternative for cisplatin in the current cisplatin-based chemotherapeutics for HPV16/18-associated cervical cancers. Mol Cancer Ther; 13(11); 2572-82. Ó2014 AACR.

Reprogramming metabolism by histone methyltransferase NSD2 drives endocrine resistance via coordinated activation of pentose phosphate pathway enzymes

“…Although its histone methylase activity has been a matter of debate, its function in cancer is strongly suggested by a recent study demonstrating that it can suppress differentiation and promote self-renewal of cancer stem cells in pediatric glioblastomas (GBMs) through condensing chromatin structure at specific locations [40]. Interestingly, MLL5β, an isoform of MLL5, is shown to be important in radiation resistance of HPV16/ 18-positive cervical cancer models [41]. However, the role of PRDM16 in cancer is poorly investigated.…”

Set4 is a chromatin-associated protein, promotes survival during oxidative stress, and regulates stress response genes in yeast

“…Yeast Set3, mammalian MLL5, and the fly protein UpSET contain divergent SET domains that are predicted to lack catalytic activity based on amino acid substitutions in SAM binding sites and the lack of a tyrosine in a stereotypical position important for both SAM and target lysine binding (17,20). Whereas mammalian MLL5 had been postulated to catalyze H3K4 methylation, this activity has not been conclusively demonstrated, and the existence of catalytic activity for MLL5 altogether is unlikely based on biochemical and structural analyses (17,(21)(22)(23). Addition-ally, catalytic activity has not been detected for the fly protein UpSET (18).…”

Análise funcional da proteína KMT2E na leucemia mielóide aguda

“…Não é incomum que a superexpressão de um gene ou seu silenciamento possa causar efeitos análogos, pois demonstram multifunção na regulação do ciclo (CHENG et al, 2008 (CHENG et al, 2008). Por outro lado, estudos mostraram a ativação da via de apoptose associada ao silenciamento de KMT2E, sugerindo um possível papel protetor do mesmo na morte celular dependente de p53 (CHENG et al, 2011;NIN et al, 2015;Yew et al, 2011 MARCOS, 2008), quebra de DNA dupla fita (STEVENS et al, 2010), ativação de p53 (JIANG et al, 2001;DORSEY, 2003), indução de estresse oxidativo (ALARIFI et al, 2013), parada de ciclo celular e modulação de genes apoptóticos (ZHANG et al, 198;CHEN et al, 1996) e diminuição do potencial de membrana da mitocôndria (CAI et al, 2003) Figura 26 -Análises de diferenciação celular induzida pelo tratamento com 20 nM de TPA nas células U937 WT, U937 pMEG e U937 pMEG-KMT2E através da marcação com anticorpos anti-CD11b e anti-CD14. As amostras foram tratadas com a droga e incubadas por 48 e 72 horas e marcadas com anti-CD11b (PE) e anti-CD14 APC (BD Biosciences, EUA).…”