CAS Enhances Chemotherapeutic Drug-Induced p53 Accumulation and Apoptosis: Use of CAS for High-Sensitivity Anticancer Drug Screening

Abstract

Cells attacked by cytotoxic toxins may express apoptosis-related proteins such as p53 to kill themselves, so as not to affect surrounding healthy cells. These apoptosis-related proteins are also crucial for inducing apoptosis of tumor cells in cancer chemotherapy. CSE1L/CAS is a cellular apoptosis susceptibility protein that plays important roles in mediating cell apoptosis induced by various cytotoxic toxins and chemotherapeutic drugs. Our studies showed that CAS over-expression increased p53 accumulation and apoptosis induced by 5-fluorouracil, doxorubicin, cisplatin, and tamoxifen in HT-29 cancer cells. A method based on coexpression of CAS with green fluorescence protein (GFP) was developed for high-sensitivity anticancer drug screening. Cancer cells transfected with CAS- and GFP-expressing vectors or the control and GFP-expressing vectors were grown on 96-well microplates, treated with compounds to be screened, and detected with a microplate fluorescence reader. GFP fluorescence decreased following cancer cell death induced by the anticancer compounds. CAS transfection enhanced the cytotoxicities of anticancer compounds and therefore increased the decline in GFP fluorescence. Thus, anticancer compounds could be identified more sensitively. Our study indicates that CAS is an important p53 and apoptosis regulator and may be used for high-throughput anticancer drug screening as well as cytotoxic toxin assays.

Cellular apoptosis susceptibility (CSE1L/CAS) protein in cancer metastasis and chemotherapeutic drug-induced apoptosis

“…CSE1L was recently shown to associate with a subset of p53 target promoters, and reduced CSE1L expression decreased 53-mediated transcription and thus lowered apoptosis [31]. Our studies showed that increased CSE1L expression can enhance doxorubicin-induced p53 accumulation [12,13]; therefore, CSE1L regulates p53 protein accumulation induced by chemotherapeutic drugs. Other studies of ours also showed that interferon-γ treatment increased CSE1L expression in cancer cells [23] and interferon-γ co-treatment enhanced doxorubicin-induced p53 accumulation of Hep G2 hepatoma cells [32].…”

“…CSE1L is a cellular apoptosis susceptibility protein and it is highly expressed in various cancers; our recent studies showed that CSE1L plays an important role in regulating cancer cell apoptosis induced by chemotherapeutic drugs [12,13]. Therefore, CSE1L may be a target for developing strategies to improve the efficacy of cancer chemotherapy as well as for screening more potent anticancer reagents.…”

“…CSE1L is highly expressed in cancer; therefore enhancing CSE1L expression rather than reducing CSE1L expression in cells is a more appropriate way to study CSE1L-mediated cancer cell apoptosis. We established HT-29 human colorectal cells and MCF-7 breast cancer cells stably transfected with the pcDNA-CSE1L vector, a eukaryotic expression vector carrying the full-length human CSE1L cDNA to study the effect of increased CSE1L expression on cancer cell apoptosis induced by chemotherapeutic drugs [12,13]. The chemotherapeutic drugs we tested including paclitaxel, doxorubicin, 5-fluorouracil, cisplatin, etoposide, and 4-OH-tamoxifen.…”

“…Our results showed that CSE1L regulated cancer cell apoptosis induced by most of the chemotherapeutic drugs that we tested [12,13]. Increased CSE1L expression enhanced apoptosis induced by doxorubicin, 5-fluorouracil, cisplatin, and 4-OH-tamoxifen, but decreased apoptosis induced by paclitaxel in HT-29 cancer cells and MCF-7 cancer cells [12,13]. Therefore, CSE1L-mediated apoptosis is not limited to apoptosis induced by ADP-ribosylating toxins and tumor necrosis factor.…”

Higher Prevalence of Secretory CSE1L/CAS in Sera of Patients with Metastatic Cancer

“…CAS can regulate apoptosis induced by IFN-g (13) and chemotherapeutic drugs (14,15). In pathologic studies, CAS expression has been positively correlated with high cancer grade, high cancer stage, and worse patient outcomes (16).…”