Biomedical subjects

Lili Liu

Publications and source records attributed to Lili Liu.

34 records · Page 2Linked to original sources

PubMed2004

Therapeutic impact of methoxyamine: blocking repair of abasic sites in the base excision repair pathway.

A major obstacle to effective treatment with alkylating agents in cancer is the presence of elaborate mechanisms of DNA repair. For instance, the methylating therapeutic agent, temozolomide forms O6-methylguanine (O6mG), 7-methylguanine (N7mG) and 3-methyladenine (N3mA) DNA adducts that are repaired by at least two mechanisms. The O6mG DNA adduct, a cytotoxic and genotoxic lesion, is repaired by O6-methylguanine DNA-methyltransferase (MGMT). Thus, MGMT is a major mechanism of resistance to methylating agents. Meanwhile, cell death caused by O6mG adducts is promoted by mismatch repair (MMR) system, such that deficiency in MMR is associated with pronounced resistance to methylating agents. N7mG, the dominant lesions formed by methylating therapeutic agents, and N3mA DNA adducts are removed by the base excision repair (BER) pathway. Efficient BER repair minimizes the impact of these lesions in normal and tumor cells. Thus, only when BER is disrupted, do these abundant N-methylated DNA adducts become highly cytotoxic. Most importantly, BER disruption is able to bypass other resistance factors such as MMR defects and high MGMT activity. BER, in fact, is an important drug-resistant factor because of its variety of substrates and the ability to rapidly and efficiently repair these DNA lesions. However, the impact of both active BER and inactive BER on anticancer therapy has yet to be fully studied. This review will establish the premise that targeting abasic sites formed during BER will disrupt this pathway and enhance the therapeutic efficacy of alkylating agents.

Animals↗

PubMed2004

[Gene expression differences between the anti-BPDE-transformed and normal cells by suppression subtractive hybridization].

OBJECTIVE: To screen the gene expression differences between the BPDE-transformed and normal cells. METHODS: Suppression subtractive hybridization was performed to profile differentially expressed genes between BPDE and normal 16HBE cells. The BPDE-transformed cells was used as tester, and the normal cells as driver. The nested PCR products were inserted into TA vector after two subtractive hybridization and two PCR. The clones were picked up randomly and analyzed with PCR. Dot blot was used to test the same source with the tester. The overexpressed cDNA fragments in BPDE cells were sequenced and compared with known genes in Genbank. RESULTS: Seven genes were identified being overexpressed in BPDE-transformed cells: translation elongation factor 1 alpha 1, mitochondrion gene, solute carrier family 25, EphA2, tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein, lactate dehydrogenase A (LDHA), tripartite motif-containing 28 (TRIM28), etc. One fragment could not be found in the known genes, it could be found in the EST database. CONCLUSION: These over-expressed genes may be related to the carcinogenesis of BPDE, in addition, one unknown gene may be responsible for the malignant transforming effect of BPDE.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed2003

Expression of Deinococcus radiodurans PprI enhances the radioresistance of Escherichia coli.

PprI, a newly identified gene switch responsible for extreme radioresistance of Deinococcus radiodurans, plays a central regulatory role in multiple DNA damage repair and protection pathways in response to radiation stress [Biochem. Biophy. Res. Commun. 306 (2003) 354]. To evaluate whether PprI also functions in the radioresistance in other organisms, D. radiodurans PprI protein (Deira-PprI) was expressed in Escherichia coli. The complemented E. coli strain showed an increase of approximately 1.6-fold radioresistance with a high dose of gamma irradiation. Immunoblotting assays showed that the expression of Deira-PprI in E. coli resulted in a significant increase in RecA protein expression following high dose ionizing radiation. The expression of Deira-PprI protein also significantly enhanced the scavenging ability of free radicals by inducing the enzymatic activity of KatG. These results indicate that exogenous expression of Deira-PprI promotes DNA repair and protection pathways and enhances the radioresistance of E. coli.

Catalase↗

PubMed2003

Measurement of anti-cancer agent methoxyamine in plasma by tandem mass spectrometry with on-line sample extraction.

In this work, we present the development and validation of a tandem mass spectrometry method for the quantitative determination of methoxyamine (CH3ONH2), a potential new chemotherapeutic agent, in human and mouse plasma. Methoxyamine together with the internal standard (I.S.) methoxyl-D3-amine was directly derivatized in plasma sample with a novel chemical agent 4-(N,N-diethylamino)benzaldehyde. The product solution was injected into an on-line Oasis HLB extraction column (2.1 mm x 20 mm) for analyte extraction. After the elution of extractives, the derivatized analytes were monitored by the positive-electrospray-ionization mass spectrometry (ESI-MS-MS). The structures of derivatized analytes were elucidated by fragmentation. Quantitation of plasma methoxyamine was carried out by the multiple reaction monitoring (MRM) mode. This method had a linear calibration range of 1.00-1000 ng/ml with a correlation coefficient of 0.9999 for methoxyamine in both human and mouse plasma. The limit of detection (LOD) and limit of quantification (LOQ) for methoxyamine in plasma were 0.150 and 0.500 ng/ml, respectively. It was demonstrated that the method had high recovery and accuracy (90.1-94.7 and 90.1-96.3%), as well as excellent intra- and inter-assay precision (2.2 and 3.7%), at three concentration levels (5.00, 50.0, 500 ng/ml). This method has been used to analyze the plasma levels of methoxyamine in samples obtained from male CD1 mice after bolus intraperitoneal injection of 2, 5 and 20mg methoxyamine hydrochloride (CH3ONH2.HCl) per kilogram mouse.

Animals↗

PubMed2003

Repopulating defect of mismatch repair-deficient hematopoietic stem cells.

Mismatch repair deficiency is associated with carcinogenesis, increased spontaneous and induced mutagenesis, and resistance to methylating agents. In humans, leukemias and lymphomas arise in the background of mismatch repair deficiency, raising the possibility that hematopoiesis is abnormal as well. To address hematopoiesis in MSH2-/- mice, we collected marrow and performed serial transplantations of these cells, alone or mixed with wild-type cells, into lethally irradiated healthy mice. Transplant recipients were observed or treated with the methylating agent, temozolomide (TMZ). Methylating agent tolerance was evident by the competitive survival advantage of MSH2-/- marrow progenitors compared with wild-type cells after each TMZ exposure. However, serial repopulation by MSH2-/- cells was deficient compared with wild-type cells. In recipients of mixed populations, the MSH 2-/- cells were lost from the marrow, and mice receiving MSH2-/- cells plus TMZ could not be reconstituted in the third passage, whereas all wild-type cell recipients survived. No differences in telomere length, cell cycle distribution, or homing were observed, but an increase in microsatellite instability was seen in the MSH2-/- early progenitor colony-forming unit (CFU) and Sca+Kit+lin--derived clones. Thus, mismatch repair deficiency is associated with a hematopoietic repopulation defect and stem cell exhaustion because of accumulation of genomic instability.

Animals↗

PubMed2003

Use of ISDN video-phones for clients receiving palliative and antenatal home care.

We examined the use of ISDN video-phones by health professionals and two types of home care clients: those receiving palliative care and those receiving antenatal care. In the palliative care group, there were four female clients and 15 health professionals; these clients on average had the video-phones at home for six weeks and made 12.5 calls per week. The antenatal care group consisted of six female clients and eight female registered nurses; these clients on average also had the video-phones at home for six weeks and made 12.5 calls per week. Exit interviews were conducted with three clients and eight staff in the palliative care group, and with six clients and three staff in the antenatal care group. Palliative care clients and their families commented that the visual feature of the phone enhanced the care that they received. In the antenatal group, the video-phone was used mainly for booking appointments and arranging home visits. In general, the technology was well received by clients and care providers.

Attitude of Health Personnel↗

PubMed2003

Blockage of abasic site repair enhances antitumor efficacy of 1,3-bis-(2-chloroethyl)-1-nitrosourea in colon tumor xenografts.

Methoxyamine (MX) has been shown to potentiate the antitumor effect of temozolomide (TMZ) in human tumor xenograft models. This potentiation is due to the reactivity of MX with apurinic/pyrimidinic (AP) sites in DNA, which are formed following DNA glycosylase removal of TMZ-induced methyl-purine adducts. MX-bound AP sites cannot be further processed by base excision repair (BER), resulting in cell death. On the basis of this finding, we investigated in vivo whether MX enhanced therapeutic efficacy of other agents, such as 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) that generates AP sites during DNA repair. Nude mice carrying human colon tumor xenografts, HCT116 and HCT116-Ch3, were treated by a single injection (i.p) of BCNU alone (30 mg/kg) or MX (2 mg/kg) combined with BCNU. The effect on tumor growth of BCNU alone was very moderate. Combined administration of MX and BCNU produced significant inhibition of tumor growth. Tumor growth delays were 14 +/- 3 days in HCT116 and 16 +/- 2 days in HCT116-Ch3 tumors, respectively (P < 0.05 versus control or BCNU alone groups). Similar results were also observed in SW480 and DLD1 tumors. Importantly, no systemic toxicity was noted with BCNU and MX. In contrast, BCNU (at dose of 25 mg/kg) combined with O(6)-benzylguanine (BG), an inhibitor of O(6)-alkylguanine-DNA alkyltransferase (AGT) being tested in clinical trials, caused toxic death in all treated mice. However, a lower dose BCNU (10 mg/kg) combined with BG and MX had significant antitumor effect without toxic death. Thus, targeting BER with MX is a promising strategy to improve the antitumor activity of BCNU and perhaps other DNA-damaging agents.

Animals↗

PubMed2002

Lung tumorigenesis associated with erb-B-2 and erb-B-3 overexpression in human erb-B-3 transgenic mice is enhanced by methylnitrosourea.

Erb-B-3 overexpression is associated with poor prognosis in non-small cell lung cancer and is often overexpressed in breast cancers. MMTVhuman-erb-B-3 transgenic mice were generated to evaluate the impact of erb-B-3 overexpression on lung and mammary gland tumorigenesis. These transgenic mice developed a high incidence of lung adenocarcinomas but not mammary gland tumors. The tumors overexpressed transgenic human [h]-erb-B-3 but also overexpressed endogenous erb-B-2, indicating that the heterodimer of h-erb-B-3-erb-B-2 was required for proliferative signal transduction to the nucleus. Lung tumor latency was shorter and the incidence higher in erb-B-3 transgenic mice treated with the methylating agent, methylnitrosourea [MNU]. In MNU treated mice, K-ras activating point mutations in codon 12, synergized with h-erb-B-3 in lung tumorogenesis. In bitransgenic MMTVrat-erb-B2/MMTV-human-erb-B-3 mice, lung tumor latency was also significantly shortened. Unlike over-expression of rat-erb-B-2, overexpression of h-erb-B-3 did not alter the incidence or latency of mammary tumors. Coupled erb-B-2 and erb-B-3 overexpression as well as K-ras activation induced signaling through mitogen-activated protein kinase (MAPK). This animal model links erb-B-3 with lung cancer, suggests that erb-B-2 and erb-B-3 heterodimerization is a necessary intermediate, and documents latency shortening by methylating agent-induced mutation of K-ras. This erb-B-3 mouse lung cancer model will help dissect genetic changes in lung tumorigenesis and may be useful for chemoprevention studies.

Animals↗

PubMed2002

Delivery of interleukin-12 in gelatin hydrogels effectively suppresses development of transplanted colonal carcinoma in mice.

PURPOSE: The sustained effects of interleukin-12 (IL-12) incorporated in biodegradable hydrogel on the development of transplanted colon carcinoma were investigated in C57BC/6 N mice. METHODS: IL-12 was given to the animals incorporated in gelatin hydrogels (GH) which allow its gradual release. As the control administration, IL-12 was given via two subcutaneous injections at an interval of 6 days. Growth of the tumors was evaluated in terms of volume. RESULTS: When IL-12 at 500 ng/animal was administered in GH, the tumor volume was decreased 9 and 12 days after administration, and the response was dose dependent in the range 0-500 ng/animal. The effect of IL-12 was stronger in mice treated with GH than in mice treated by subcutaneous injection at the same dose (i.e. 250 ng/animal twice at an interval of 6 days). Feeding behavior and the post-mortem wet weight of several visceral organs were unchanged after IL-12 administration. Serum parameters relative to the liver, heart and kidneys were unaffected by IL-12 treatment. No noticeable toxicity was detected when the dose of IL-12 in GH was increased to 1000 ng/animal. CONCLUSIONS: The results suggest that IL-12 is effective in suppressing the growth of colon carcinoma, and that delivery of this agent in GH is efficient in the treatment of carcinoma.

Animals↗

PubMed2002

Short-term granulocyte colony-stimulating factor and erythropoietin treatment enhances hematopoiesis and survival in the mitomycin C-conditioned Fancc(-/-) mouse model, while long-term treatment is ineffective.

Transient treatment with cytokines appears to improve hematopoietic function in Fanconi anemia; however, the effectiveness or adverse effect of long-term treatment is not known. The mitomycin C-treated Fancc(-/-) mouse provides a valuable model to address long-term efficacy of such treatment. Fancc(-/-) mice injected with granulocyte colony-stimulating factor, erythropoietin, or both cytokines showed a delay in mitomycin C (MMC)-induced bone marrow (BM) failure compared to untreated mice. However, long-term cytokine exposure followed by MMC challenges did not protect mice from the reduction of peripheral blood counts or the number of early myeloid progenitors. These results suggest that cytokine treatment may be beneficial only in the short-term, while long-term treatment is not protective for BM aplasia.

Animals↗

PubMed2002

Hepatic branch vagotomy can block liver regeneration enhanced by ursodesoxycholic acid in 66% hepatectomized rats.

The effect of hepatic branch vagotomy on liver regeneration induced by ursodesoxycholic acid was examined in 66% hepatectomized rats. A standard feeding was obtained from animals with hepatic branch vagotomy, and all rats examined received pair food intake. Liver regeneration was evaluated by the hepatocyte mitotic index. When ursodesoxycholic acid 12.5 mg kg(-1) day(-1) was administered orally, a significant increase in the mitotic index was observed 2 and 3 days after hepatectomy, and the mitotic index response 2 days after hepatectomy was dose-dependent in the range of 0-25 mg kg(-1) day(-1). Hepatic branch vagotomy suppressed the mitotic index 2 days after hepatectomy, and the mitotic index increase due to ursodesoxycholic acid was blocked by hepatic branch vagotomy, but not by gastric branch vagotomy. It was also noted that hepatic branch vagotomy or ursodesoxycholic acid or both did not affect serum parameters indicating liver and kidney function. Because ursodesoxycholic acid exists in the bile juice, these results suggest that the hepatic vagus nerve is specifically active with endogenous bile acids in the control of liver regeneration.

Animals↗

PubMed2002

Chemotherapy-induced O(6)-benzylguanine-resistant alkyltransferase mutations in mismatch-deficient colon cancer.

The ability of O(6)-benzylguanine (BG) to inactivate alkyltransferase (AGT) to potentiate the antitumor efficacy of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) is being tested in clinical trials. As of now, there are no examples of acquired resistance to BG+BCNU in the clinical setting. However, we hypothesized that genetically unstable tumors might develop resistance to the combination after repeated drug-exposures to achieve therapeutic efficacy. To evaluate this possibility, we treated three colon cancer cell lines that are either proficient in mismatch repair (MMR) [SW480 (MMR wild type)] or deficient in MMR [HCT116 (hMLH1 mutant) and HCT15 (hMSH6 mutant)] with three cycles of BG+BCNU. After drug-treatments, HCT116 and HCT15 were completely resistant to BG-potentiated cytotoxicity of BCNU. In these two cell lines, the acquired BG resistance resulted from two de novo and different mutations at amino acid 165 in AGT: 165-lysine (K) to glutamic acid (E) (K165E in HCT116), and 165-lysine to asparagine (N) (K165N in HCT15). Both K165-mutated AGTs had markedly decreased enzymatic activity because of unstable AGT protein but were remarkably resistant to BG inactivation. FISH analysis showed that only one copy of MGMT gene exists in HCT116 cells, and the status of promoter methylation of MGMT in HCT15 showed that one allele of the MGMT promoter has an aberrant methylation. Thus, the MGMT gene expressing AGT either from one copy (HCT116) or from unmethylated allele (HCT15) was mutated because of the exposure to BG+BCNU in these two MMR-deficient cell lines. Conversely, MMR-proficient SW480 cells, treated with three cycles of BG+BCNU, maintained wt AGT and the sensitivity to BG-potentiated BCNU-cytotoxicity. To confirm that K165-mutated AGT proteins were responsible for resistance to BG+BCNU, we transfected K165E and K165N MGMT cDNAs into Chinese hampster ovary (CHO) cells. Transfected CHO cells had low AGT activity but increased IC(50) for either BCNU or temozolomide (TMZ), compared with parental CHO cells. BG did not potentiate the cytotoxicity of these two alkylating agents at concentrations up to 200 microM; in contrast, BG, at 25 microM, sensitized CHO-AGT (transfected with wt MGMT cDNA) cells to BCNU or TMZ-cytotoxicity by 3-4 fold. These results suggest that K165 AGT mutants arising in MMR-deficient tumor cells after treatment with chemotherapeutic agents are both resistant to BG-inactivation and are active in the repair of alkylated DNA adducts.

Adaptor Proteins, Signal Transducing↗

PubMed2002

Liver regeneration enhanced by orally administered ursodesoxycholic acid is mediated by immunosuppression in partially hepatectomized rats.

The relationship of liver regeneration to immunoactivity was examined after ursodesoxycholic acid (UDCA) administration to partially (about 66%) hepatectomized rats. The UDCA was given orally. Liver regeneration was evaluated by the hepatocyte mitotic index (MI) and immunoactivity by natural killer cell (NK) activity in the blood. When UDCA 12.5 mg/kg/day was administered, a significant increase in the MI was observed 2 and 3 days after hepatectomy, and the MI response 2 days after bepatectomy tended to be dose-dependent in the range of 0-25 mg/kg/day. NK activity was decreased 2 days after hepatectomy when UDCA was given, and a significant correlation between MI and NK activity was obtained. The increase in MI and decrease in NK activity was blocked completely or partially (respectively) by interleukin-2 administration. It was also noted that UDCA did not affect serum parameters indicating liver and kidney function. These findings suggest that liver regeneration can be modified by orally administered UDCA through a change in immunoactivity.

Animals↗

PubMed2002

Left ventricular resynchronization therapy in a canine model of left bundle branch block.

Positive responses to left (LV) and biventricular (BV) stimulation observed in heart failure patients with left bundle branch block (LBBB) suggest a possible mechanism of LV resynchronization. An anesthetized canine LBBB model was developed using radio frequency ablation. Before and after ablation, LV pressure derivative over time (dP/dt) and aortic pulse pressure (PP) were assessed during normal sinus rhythm with right ventricle (RV), LV, or BV stimulation combined with four atrioventricular delays in six dogs. In three more dogs, M-mode echocardiograms of septal and LV posterior wall motion were obtained before and after LBBB and during LV stimulation. LBBB caused QRS widening and hemodynamics deterioration. Before ablation, stimulation alone worsened LV dP/dt and PP. After ablation, LV and BV stimulation maximally increased LV dP/dt by 16% and PP by 7% (P < 0.001), whereas little improvement was observed during RV stimulation. M-mode echocardiogram showed that LBBB resulted in a paradoxical septal wall motion that was corrected by LV stimulation. In conclusion, LV and BV stimulation improved cardiac function in a canine LBBB model via resynchronization of LV excitation and contraction.

Animals↗

PubMed2002

Base excision repair as a therapeutic target in colon cancer.

Base excision repair (BER) is a fundamental cellular process used to reduce the cytotoxicity of alkylating agent chemotherapy. Heretofore, no therapeutic agents have targeted this DNA repair pathway. Methoxyamine (MX), which binds abasic sites, acting as an inhibitor of BER, was evaluated in combination with the methylating agent temozolomide (TMZ). Three human colon cancer cell lines were used, SW480 cells, which are wild-type for mismatch repair genes and have mutated p53, HCT116 cells, which are mutant in hMLH1 and wild-type for p53, and HCT15 cells, which are mutant in hMSH6 and mutant in p53 as well. Nude mice carrying these tumors received TMZ alone or in combination with MX or O(6)-benzylguanine (BG), an inhibitor of O(6)-alkylguanine DNA-alkyltransferase, daily i.p. for 5 consecutive days. At the highest tolerable dose of TMZ (120 mg/kg), a tumor growth delay of approximately 9.3 +/- 1.2 days was noted in SW480. Addition of BG resulted in a tumor growth delay of 25 +/- 2.4 days accompanied by significant weight loss (23%) and severe myelosuppression. In contrast, SW480 tumor-bearing mice treated with MX + TMZ had cessation of tumor growth for 50 +/- 13 days and very slow regrowth, yielding tumor growth delays of >70 +/- 14 days (P < 0.002) without additive systemic toxicity. HCT116 and HCT15 xenografts were completely resistant to treatment with TMZ alone or in combination with BG. However, treatment with MX + TMZ induced significant tumor growth delays (20 +/- 1.4 days in HCT116 and 14 +/- 3.1 days in HCT15 xenografts, P < 0.05). These studies demonstrate that a significant enhancement of the antitumor effect of TMZ by MX was observed in human colon cancer xenografts with mismatch repair proficiency and deficiency. DNA BER may be a useful pharmacological target through which tumor cells can be sensitized to alkylating therapeutic agents.

Animals↗

PubMedDate not supplied

Personal-professional connections in palliative care occupational therapy.

This qualitative study examined the experiences of occupational therapists working in palliative care. Multiple qualitative interviews were conducted with each of eight occupational therapists working with people who are terminally ill. The interviews were transcribed verbatim and analyzed for recurring and unique themes. Five themes emerged: satisfaction, hardship, coping, spirituality, and growth. Common themes, while resonating through all participants' stories, were experienced in a uniquely personal way by each participant. The result was the discovery of an individualized "personal-professional connection" for each participant. The exploration of personal-professional connections can contribute to the understanding of occupational therapy practice in palliative care. Furthermore, these individual stories may resonate for other occupational therapists and inspire personal and professional reflection; validation of feelings and issues can arise from parallel comparisons. Therapists may in tum gain insight into the relationship between their own personal and professional experiences.

Adaptation, Psychological↗