Improvement of combination chemotherapy tolerance by introduction of polycistronic retroviral vector drug resistance genes MGMT and MDR1 into human umbilical cord blood CD34+ cells

Traditional Chinese Medicine Preparation Combined Therapy May Improve Chemotherapy Efficacy: A Systematic Review and Meta-Analysis

Background

Whether traditional Chinese medicine preparation combined therapy can improve the efficacy of chemotherapy is controversial. This meta-analysis evaluates the efficacy of traditional Chinese medicine preparation combined with chemotherapy.

Method

Three databases were searched from inception through August 2018. Eligible randomized controlled trials (RCTs) involving the combined treatment of chemotherapy and traditional Chinese medicine preparation compared to chemotherapy alone for treating cancer were retrieved. The methodological quality of the included RCTs was assessed with Cochrane Collaboration's risk of bias assessment tool. Meta-analysis was adopted to make comprehensive comparisons between the experimental and control groups.

Results

Four RCTs were included in this review, comprising 256 subjects. The majority of the RCTs were judged as being of poor methodological quality. Meta-analysis showed that the combination of traditional Chinese medicine preparation and chemotherapy appeared to be more effective than chemotherapy alone, for the treatment of cancer, as assessed by the disease control rate (RR: 1.41, 95% CI: 1.11 to 1.79) and the objective response rate (RR: 2.71, 95% CI: 1.28 to 5.77). There were no statistically significant differences between the groups in terms of bone marrow suppression (RR: 0.88, 95% CI: 0.57 to 1.37) or gastrointestinal reaction (RR: 1.12, 95% CI 0.75 to 1.69).

Conclusions

Traditional Chinese medicine preparation combined with chemotherapy may improve objective response rates and disease control rates more than chemotherapy alone. The evidence that combined traditional Chinese medicine preparation can reduce the side effects of chemotherapy is insufficient. More rigorous randomized controlled trials are needed to confirm these conclusions.

F2A sequence linking MGMT(P140K) and MDR1 in a bicistronic lentiviral vector enables efficient chemoprotection of haematopoietic stem cells

Chemoprotection of haematopoietic stem cells (HSCs) by gene therapeutic transfer of drug-resistance genes represents the encouraging approach to prevent myelosuppression, which is one of the most severe side effects in tumor therapy. Thus, we cloned and evaluated six different bicistronic lentiviral SIN vectors encoding two transgenes, MGMT(P140K) (an O(6)-benzylguanine-resistant mutant of methylguanine-DNA methyltransferase) and MDR1 (multidrug resistance 1), using various linker sequences (IRESEMCV, IRESFMDV and 2A-element of FMDV (F2A)). Expression of both transgenes in HL-60 and in K562 cells was assayed by quantitative real-time PCR. Combination therapy with ACNU plus paclitaxel in HL-60 cells and with carmustin (BCNU) plus doxorubicin in K562 cells resulted in the most significant survival advantage of cells transduced with the lentiviral vector HR'SIN-MGMT(P140K)-F2A-MDR1 compared with untransduced cells. In human HSCs, overexpression of both transgenes by this vector also caused significantly increased survival and enrichment of transduced cells after treatment with BCNU plus doxorubicin or temozolomide plus paclitaxel. In summary, we could show significant chemoprotection by overexpression of MDR1 and MGMT(P140K) with a lentiviral vector using the F2A linker element in two different haematopoietic cell lines and in human primary HSCs with various combination regimens. Consequently, we are convinced that these in vitro investigations will help to improve combination chemotherapy regimens by reducing myelotoxic side effects and increasing the therapeutic efficiency.

Chemoprotection of human hematopoietic stem cells by simultaneous lentiviral overexpression of multidrug resistance 1 and O(6)-methylguanine-DNA methyltransferase(P140K)

Myelotoxicity is a dose-limiting effect of many chemotherapeutic regimens. Thus, there is great interest in protecting human hematopoietic stem cells by the transfer of drug resistance genes. The main focus of this study was the simultaneous overexpression of multidrug resistance 1 (MDR1) and the O(6)-benzylguanine (O(6)-BG)-resistant mutant MGMT(P140K) (O(6)-methylguanine-DNA methyltransferase) with a bicistronic lentiviral vector (HR'SIN-MDR1-IRES-MGMT(P140K)), with regard to the capability to convey chemoprotection in the leukemia cell line, HL60, and human hematopoietic stem cells (CD34(+)). Combination therapy with O(6)-BG/1-(2-chloroethyl)-3-(4-amino-2-methylpyrimidine-5-yl)methyl-1-nitrosourea) (ACNU) plus paclitaxel showed a significant survival advantage of HL60 cells transduced with this combination vector. In CD34(+) cells, monotherapy with O(6)-BG/temozolomide (TMZ) resulted in an increased percentage of MGMT-positive cells (vs untreated cells) after transduction with HR'SIN-MDR1-IRES-MGMT(P140K) (28.3%). For combination therapy with O(6)-BG/temozolomide plus paclitaxel the increase was higher with the combination vector (52.8%) than with a vector expressing MGMT(P140K) solely (29.1%). With regard to MDR1-positive cells the protective effect of the combination vector (88.5%) was comparable to the single vector HR'SIN-MDR1 (90.0%) for monotherapy with paclitaxel and superior for combination therapy with O(6)-BG/temozolomide plus paclitaxel (84.6 vs 69.7%). In conclusion, the combination vector presents simultaneous protective effects of two drug-resistance genes, offering an opportunity to increase the cancer therapeutic index.

Local Effects of Retrovirally Transduced Endostatin-Expressing Human Umbilical Cord Blood CD34+ Cells on Transplanted Malignancy in a Mouse Model of Hepatic Cancer

Antiangiogenesis has been exploited as an effective approach to inhibit the growth of solid tumors. This technique has been evaluated using various vectors in several xenograft animal models to demonstrate the efficacy of endostatin gene therapy against cancer growth. However, previous studies have not examined the use of cord blood CD34+ cells as endostatin-producing cells for gene therapy against hepatoma. This exploratory study was done to investigate the local effects of CD34+ cells transduced with the endostatin gene on a mouse xenograft tumor model. The human endostatin gene was transferred into CD34+ cells using the recombinant retrovirus plasmid, pLncx/endo. Expression was verified by RT-PCR and Western blot analyses, confirming the stable expression and secretion of endostatin from the transferred CD34+ cells. The proliferation of vascular endothelial cells was evaluated by MTT assay and found to decrease by about 59.9% when treated with the supernatant of cultured transfected CD34+ cells in vitro. These genetically modified cord blood CD34+ cells were implanted intratumorally and tumor regression was evaluated after 2 weeks. The average size of a xenograft tumor in the CD34+/endo group was reduced 31.39% compared to that in the untreated mice or those transplanted with CD34+ cells transduced with a control vector. The microvascular density of the tumor decreased 62.45% in the treated group. The expression of proliferation cell nuclear antigen (PCNA) also decreased significantly in the treated group. Moreover, the apoptotic index (AI) of tumors, as evaluated by TUNEL staining, was significantly enhanced in the treatment group. Our findings indicate that angiogenesis of the xenograft tumor in mice may be inhibited by local administration of genetically modified CD34+ cells expressing the endostatin gene. This novel approach may lead to a new direction of cell-based gene therapy for malignancy.

Vector design for expression of O6-methylguanine-DNA methyltransferase in hematopoietic cells

Enhancing DNA repair activity of hematopoietic cells by stably integrating gene vectors that express O(6)-methylguanine-DNA-methyltransferase (MGMT) is of major interest for innovative approaches in tumor chemotherapy and for the control of hematopoietic chimerism in the treatment of multiple other acquired or inherited disorders. Crucial determinants of this selection principle are the stringency of treatment with O(6)-alkylating agents and the level of transgenic MGMT expression. Attempts to generate clinically useful MGMT vectors focus on the design of potent expression cassettes, an important component of which is formed by enhancer sequences that are active in primitive as well as more differentiated hematopoietic cells. However, recent studies have revealed that vectors harboring strong enhancer sequences are more likely to induce adverse events related to insertional mutagenesis. Safety-improved vectors that maintain high levels of MGMT expression may be constructed based on the following principles: choice of enhancer-promoter sequences with relatively mild long-distance effects despite a high transcription rate, improved RNA processing (export, stability and translation), and protein design. The need for optimizing MGMT protein design is supported by recent observations suggesting that the P140K mutant of MGMT, developed to be resistant to inhibitors such as O(6)-benzylguanine, may confer a selective disadvantage when expressed at high levels. Here, we provide a review of the literature exploring MGMT expression vectors for bone marrow chemoprotection, and describe experimental evidence suggesting that high expression of MGMT P140K induces a selective disadvantage in the absence of alkylating agents. We conclude that the appropriate design of expression vectors and MGMT protein features will be crucial for the long-term prospects of this promising selection principle.

Acquisition of resistance to antitumor alkylating agent ACNU: a possible target of positron emission tomography monitoring

Early detection of tumor response to chemotherapy is of great importance for appropriate treatment of tumors. In this study, characteristics of two positron emission tomography (PET) tracers, [(18)F]2-fluoro-2-deoxy-D-glucose (FDG) and[(18)F]3'-fluoro-3'-deoxy-thymidine (FLT), in the early detection of tumor cell response as well as tolerance development to chemotherapy was compared using rat C6 glioma cells and 1-(4-amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-chloroethyl)-3-nitrosoureahydrochloride (ACNU). ACNU is an alkylating agent known to induce drug resistance through expression of O(6)-methylguanine-deoxyribonucleic acid methyl transferase (O(6)-MGMT). We established an ACNU-resistant C6 glioma cell line (C6/ACNU) and investigated the effect of ACNU on the uptake of FLT and FDG. In C6 cells, DNA synthesis presented as [(3)H]thymidine ([(3)H]Thd) incorporation into DNA was quickly suppressed by ACNU. In C6/ACNU cells, the suppression was recovered promptly, indicating that DNA alkylation occurs initially but highly expressed O(6)-MGMT repairs DNA, leading to the recovery of DNA synthesis. The patterns of FLT uptake in C6 and C6/ACNU were difficult to distinguish in the very early stage of the treatment, though it was reported that FLT uptake well correlated with proliferation in certain conditions. FDG uptake showed different patterns between the resistant and control cells, with significantly decreased uptake in C6 cells and unchanged uptake in C6/ACNU cells at 18-24 h after the treatment. Though difficult to be directly translated into clinical situation, the present study will provide a base to develop an appropriate protocol to assess tumor response to treatment by PET and to design effective treatment plans.

Human-yeast chimeric repair protein protects mammalian cells against alkylating agents: enhancement of MGMT protection

Chemotherapeutic DNA alkylating agents are common weapons employed to fight both pediatric and adult cancers. In addition to cancerous cells, nontarget tissues are subjected to the cytotoxicity of these agents, and dose-limiting toxicity in the form of myelosuppression is a frequent result of treatment. One approach to prevent myelosuppression that results from the use of chemotherapeutic agents is to increase the levels of DNA repair proteins in bone marrow cells. Here we report our second successful attempt to create a fusion protein that possesses both direct reversal and base excision repair pathway DNA repair activities. The chimeric protein is composed of the human O(6)-Methylguanine-DNA Methyltransferase (MGMT) and the yeast Apn1 proteins and retains both MGMT and AP endonuclease activities as determined by biochemical analysis. We have also demonstrated that the chimeric protein is able to protect mammalian cells from the DNA alkylating agents 1,3-bis (2-chloroethyl)-1-nitrosourea (BCNU) and methyl methanesulfonate (MMS). The protection by the chimeric protein against BCNU is even greater than MGMT alone, which has potential translational significance given that MGMT is currently in clinical trials. Additionally, we show that the chimeric MGMT-Apn1 protein can protect mammalian cells from dual treatments of BCNU and MMS and that this effect is greater than that provided by MGMT alone. The data support our previous finding that a protein with multiple DNA repair activities can be constructed and that this and other constructs may play an important clinical role in guarding against dose-limiting effects of chemotherapy, particularly in situations of multiple drug use.