Molecular alterations in apoptotic pathways after PKB/Akt-mediated chemoresistance in NCI H460 cells

Abstract

Protein kinase B/Akt has been described as a central mediator of antiapoptotic signals in cancer cells. Furthermore, Akt has been shown to affect cell cycle progression and proliferative pathways and to possess a potential function in tumorigenesis and chemoresistance. In this study, we show that the ectopic expression of a constitutively active form of Akt1 (CA-Akt1) results in enhanced chemoresistance of NCI H460 human NSCLC cells towards a panel of chemotherapeutic agents. To understand the molecular alterations leading to impaired chemosensitivity mediated by activated Akt, we analysed various apoptotic pathways, including the activation of p53, caspases 3, 7, 8, and 9, release of cytochrome c from mitochondria, and the expression levels of proand antiapoptotic proteins such as Bcl-2, Bcl-x L , Bcl-x s , Bax, or Bfl-1. We observed that expression of CA-Akt did not interfere with single defined apoptotic switches, but modulated the apoptotic threshold of several apoptotic pathways towards increasing the threshold of onset. In particular, we found that CA-Akt-expressing cells displayed increased expression of the antiapoptotic Bcl-2 family member protein Bcl-x l , and a delayed onset of the p53 pathway after treatment with cisplatin or Mitoxantrone. Thus, our data suggest that Akt mediates chemoresistance in NHI H460 cells by interfering with and delaying the onset of various apoptotic pathways. A complete inactivation of apoptotic pathways was observed in none of the molecular alterations investigated. Our data strengthen the role of Akt as a central mediator of cell survival signals and/or chemoresistance and as an attractive target for cancer cell chemosensitisation.

Activated AKT regulates NF-κB activation, p53 inhibition and cell survival in HTLV-1-transformed cells

“…These data indicate that Tax's ability to protect apoptotic cell death may, in part, be regulated through AKT and Bcl-xL pathways. Numerous studies reported that blocking AKT by LY294002 induces p53-dependent apoptosis and delays onset of the p53 pathway after treatment with drugs, such as cisplatin or mitoxantrone (Ren et al, 2003;Hovelmann et al, 2004). Our data demonstrated that inhibition of AKT induces p53 transcription activity and apoptosis in HTLV-1 cells.…”

“…Hovelmann et al (2004). previously demonstrated that AKT increases expression of the antiapoptotic Bcl-2 family member protein Bcl-xL using a constitutively active form of AKT (CA-AKT)-expressing cells.…”

Administration of isothiocyanate (E-4IB) and cisplatin leads to altered signalling and lysosomal export in human ovarian carcinoma sensitive- and cisplatin-resistant cells

“…Several results referred that alterations in apoptotic pathways are re lated to alterations in P-I3K/Akt signaling pathway. Cells ex pressing Akt1, Akt2 and Akt3 displaeyd CDDP resistance with threshold modulation for several apoptotic pathways in cluding increased Bcl-x(L) ex pression and delayed p53 ac ti vation, when Akt knockout reduced CDDP resistance [25,45].…”

Activation of PI3K/Akt and ERK signaling pathways antagonized sinomenine-induced lung cancer cell apoptosis

“…Cells were then incubated at room temperature in the dark for 30 min, and DNA content was determined by flow cytometry using a FACScan flow cytometer (Becton-Dickinson, San Jose, CA, USA). The data were analyzed using MODIFIT software (Becton-Dickinson) (20). Control cells were treated with medium only.…”