Enhanced paclitaxel cytotoxicity and prolonged animal survival rate by a nonviral-mediated systemic delivery of E1A gene in orthotopic xenograft human breast cancer

Abstract

Paclitaxel (Taxol) is a promising frontline chemotherapeutic agent for the treatment of human breast and ovarian cancers. The adenoviral type 5 E1A gene has been tested in multiple clinical trials for its anticancer activity. E1A has also been shown to sensitize paclitaxel-induced killing in E1A-expressing cells. Here, we show that E1A can sensitize paclitaxel-induced apoptosis in breast cancer cells in a gene therapy setting by an orthotopic mammary tumor model. We first showed that expression of E1A enhanced in vitro paclitaxel cytotoxicity, as compared to the control cells. We then compared the therapeutic efficacy of paclitaxel between orthotopic tumor models established with vector-transfected MDA-MB-231 (231-Vect) versus 231-E1A stable cells, using tumor weight and apoptotic index (TUNEL assay) as the parameters. We found paclitaxel was more effective in shrinking tumors and inducing apoptosis in tumor models established with stable 231-E1A cells than the control 231-Vect cells. We also tested whether E1A could directly enhance paclitaxel-induced killing in nude mice, by using a nonviral, surface-protected cationic liposome to deliver E1A gene via the mouse tail vein. We compared the therapeutic effects of E1A gene therapy with or without Taxol chemotherapy in the established orthotopic tumor model of animals inoculated with MDA-MB-231 cells, and found that a combination of systemic E1A gene therapy and paclitaxel chemotherapy significantly enhanced the therapeutic efficacy and dramatically repressed tumor growth (Po.01). In addition, survival rates were significantly higher in animals treated with combination therapy than in the therapeutic control groups (both Po.0001). Thus, the E1A gene therapy indeed enhances the sensitivity of tumor cells to chemotherapy in a gene therapy setting and, the current study provides preclinical data to support combination therapy between E1A gene and chemotherapy for future clinical trials.

Paclitaxel and vincristine potentiate adenoviral oncolysis that is associated with cell cycle and apoptosis modulation, whereas they differentially affect the viral life cycle in non-small-cell lung cancer cells

“…36 The found increase in E1A13S transcripts at later stages of viral infection may also account for enhanced cell death as previously also reported by others. 37,38 Presently, we cannot discriminate whether one or all of these phenomena contribute to the enhanced cytotoxicity observed in PTX co-treated cells when compared to cells infected with Ad5 alone. However, although this may be relevant for PTX, this is unlikely to mediate the effect of VCR that caused only a modest increase of E1A13S and Pent gene expression and without affecting ADP gene expression.…”

An oncolytic adenovirus defective in pRb-binding (dl922–947) can efficiently eliminate pancreatic cancer cells and tumors in vivo in combination with 5-FU or gemcitabine

“…49 ) and immune cells, including NK cells, macrophages and T cells, promoting apoptosis. 34,50,51 In fact, local administration of the E1A gene alone, expressed from plasmids delivered in liposome coating, has been evaluated in clinical trials phase I and II targeting ovarian, breast and head and neck cancers and was deemed safe with promising future applications. [52][53][54] However, as the spread of E1A expressed from this nonreplicating vector was limited to the site of delivery, significant efficacy was not demonstrated in these trials.…”

“…46,47 We speculate that early viral E1A expression was responsible for most of the synergistic effects based on the fact that E1A is a potent apoptosis inducer and synergizes with apoptosis-inducing cytotoxic drugs. [34][35][36]48 Adenoviral E1A proteins can interact with numerous cellular effector molecules such as tumor necrosis factora, NO, TNF-related apoptosis-inducing ligand, Fas ligand (reviewed in ref. 49 ) and immune cells, including NK cells, macrophages and T cells, promoting apoptosis.…”

“…Potent E1A expression was a requirement even in cells not supporting viral replication, in agreement with earlier reports. [34][35][36] Importantly, we demonstrate that E1A with the pRb-binding region deleted in dl922-947 can synergistically interact with 5-FU and gemcitabine in pancreatic cancer cells. Both replicationdependent and -independent mechanisms were indicated in the synergistic responses.…”

AIM2 suppresses human breast cancer cell proliferation in vitro and mammary tumor growth in a mouse model

“…3B). We further examined whether the human AIM2 gene can be used as a therapeutic gene in a gene therapy setting using a previously described mammary tumor model (24). Compared with pCMV-Tag2C (control), AIM2 DNA-SN liposome treatment significantly reduced the growth of MDA-MB-435 breast cancer xenografts (P < 0.01; Fig.…”