Efficacy of repeated high-dose hepatitis B vaccine (80 microg) in patients with chronic liver disease

Patients with chronic liver disease (CLD) respond poorly to standard hepatitis B (HBV) vaccine given as sequential 20 microg IM shots because of an overall impaired immune response. Many of these patients go on to liver transplantation and are at risk of acquiring recurrent or de novo HBV infection. To evaluate the efficacy and safety of high-dose (80 microg) IM HBV vaccination in patients with CLD who had previously failed to respond to a standard three-dose schedule of 40 microg IM vaccine given monthly. A retrospective review was undertaken at our institution of 79 patients with CLD who were treated with high-dose (80 microg) HBV vaccinations. All had previously failed a three-dose course of 40 microg HBV vaccine. An HBV vaccine response was defined as an anti-HBs titer greater than 100 mIU/ml. Liver enzymes, creatinine, age, prothrombin time, total vaccine dose, and MELD score were recorded. No adverse events were reported. Seventy-two per cent (57/79) of the subjects had an adequate response after receiving a mean total dose of 220 mug vaccine (range 80-800 microg). Twenty-eight per cent (22/79) of the subjects did not respond after receiving a mean total dose of 420 microg vaccine (range 240-720 microg). Non-responders had more severe hepatic disease defined as a higher mean total bilirubin level (p = 0.003) and a lower mean albumin level (p < 0.05). Age, prothrombin time, MELD score, and creatinine were not statistically significant between the responders and non-responders. Repeated high-dose (80 microg) HBV vaccination, in patients who do not respond to standard HBV vaccine doses, is safe and effective in the majority of patients with CLD.

Prevalence of HIV, hepatitis B and C amongst health workers of Civil Hospital Karachi

OBJECTIVE

To determine the prevalence of HIV, Hepatitis B (HBV) and Hepatitis C (HCV) amongst the health workers of Civil Hospital Karachi (CHK).

MATERIAL AND METHODS

Prospective study. A precoded Proforma was filled out which included questions regarding the knowledge, attitude and practices (KAP) of HIV, HBV and HCV.

SETTING

Departments of a tertiary health care facility at CHK. Antibodies to HIV, HCV and Hepatitis B surface antigen (HBsAg) were done using enzymes linked immunosorbent assay [ELISA].

RESULTS

Uptake of screening was 98% to those offered. The prevalence was 5.6% for antibodies to HCV, 2.4% for HBsAg, while none of those studied had antibodies to HIV.

CONCLUSION

Our results show the prevalence of antibodies to HCV in health workers are 20 folds higher than health workers in the developed countries. Similarly, the prevalence of HBV although not as high as HCV is significant. Seroprevalence of HIV does not exist in this group. We need to ensure better training; regulations regarding preventive and safety measures also need to be enforced (JPMA 52:92; 2002).

[Aseptic osteonecrosis of the femoral head in thalassemia minor: a case report]

We report a case of aseptic necrosis of the femoral head in a 14-year-old black adolescent with thalassemia minor disclosed by physical examination and blood tests. No other anomaly could be identified. Despite the very probably secondary nature of the aseptic osteonecrosis of the femoral head and the absence of any other etiology, it is highly difficult to demonstrate the causal effect of thalassemia minor. We reviewed the literature and discuss the pathogenesis of this association.

Coronary heart disease risk-factor profile in a lower middles class urban community in Pakistan

We determined the risk-factor profile and prevalence of coronary heart disease in Metroville, a lower middle class urban community in Karachi, and compared them to the Pakistan health survey PNHS 1990-94, and the US health and nutrition survey 1988-94 NHANES111. Subjects < 18 years and pregnant women were excluded as were people with extreme ranges BMI [corrected] heart rate, height and waist. The prevalence of hypertension was 23% in men and women, hypercholesterolaemia was 17% in men and 22% in women (P < 0.001). Hyperglycaemia was present in 5% of men and women and obesity in 33% of men and 47% of women (P < 0.001). Compared to PNHS, the prevalences of obesity, hypertension, hypercholesterolaemia and WHR were higher in our population. Mean values of BMI [corrected] cholesterol, WHR were higher in the US population while mean values were lower for diastolic blood pressure and blood glucose.

Emerging anticoagulant and thrombolytic drugs

Since its discovery, heparin has been used intensely as an anticoagulant for several medical and surgical indications. However, efforts are in progress to replace heparin because of its serious complications, such as intraoperative and postoperative bleeding, osteoporosis, alopecia, heparin resistance, heparin rebound, heparin-induced thrombocytopenia (HIT) and thrombosis syndrome (HITTS), and other disadvantages. Significant developments in the field of new anticoagulants have resulted in the evaluation and introduction of low molecular weight heparins (LMWHs) and heparinoids, hirudin, ancrod, synthetic peptides and peptidomimetics. However, despite significant progress in the development of these new anticoagulants, a better or an ideal anticoagulant for cardiovascular patients is not yet available and heparin still continues to amaze both basic scientists and the clinicians. To minimise the adverse effects of heparin, newer approaches to optimise its use in combination with the new anticoagulants may provide better clinical outcome. In our experience, the off-label use of argatroban at a dose of 300 microg/kg iv. bolus followed by 10 microg/kg/minute infusion in combination with aggrastat (a glycoprotein [GP] IIb/IIIa inhibitor) at a dose of 10 microg/kg iv. bolus followed by an infusion of 0.15 microg/kg/minute in patients with HIT undergoing percutaneous coronary interventions resulted in elevation of celite activated clotting time (ACT) to 300 seconds followed by a gradual decline and the ACT remained above 200 seconds even after 200 min of drug administration. A bewildering array of newer anticoagulants now exist, such as LMWHs and heparinoids, indirect or direct thrombin inhibitors, oral thrombin inhibitors, such as melagatran (AstraZeneca) and HC-977 (Mitsubishi Pharmaceuticals), Factor IXa inhibitors, indirect or direct Factor Xa inhibitors, Factor VIIa/tissue factor (TF) pathway inhibitor, newer antiplatelet agents, such as GPIIb/IIIa inhibitors, fibrin specific thrombolytic agent, such as tenecteplase and modulation of the endogenous fibrinolytic activity by thrombin activatable fibrinolytic inhibitor (TAFI), Factor XIIIa inhibitors and PAI-1 inhibitors. The quest for newer anticoagulant, antiplatelet and fibrinolytic agents will continue until ideal agents are found.

Successful Use of Recombinant Hirudin and Its Monitoring by Ecarin Clotting Time in Patients with Heparin-Induced Thrombocytopenia Undergoing Off-Pump Coronary Artery Revascularization

Refludan (lepirudin-rDNA for injection) is the first direct thrombin inhibitor approved by the United States FDA for anticoagulation to patients with heparin-induced thrombocytopenia (HIT). It was monitored by ecarin clotting time (ECT) assay in patients with HIT. Case histories and clotting parameters for three patients undergoing off-pump coronary artery revascularization procedure are discussed. The first patient received r-hirudin at a dose of 0.2 mg/kg intravenous (IV) bolus followed by 0.15 mg/kg/hour infusion. The second patient received 0.4 mg/kg IV bolus followed by infusion of 0.15 mg/kg/hour infusion. The third patient with renal failure received 0.2 mg/kg IV bolus followed by an infusion of 0.02 mg/kg/hour. Blood samples were drawn at baseline, 5 minutes post bolus and every 15 minutes during the coronary artery revascularization procedure. ECT was performed immediately on the citrated whole blood samples using the ECT cards in conjunction with the point-of-care, the thrombolytic assessment system (TAS) Analyzer (Pharmanetics, Raleigh, NC). The plasma samples were then analyzed for APTT and liquid ECT assay performed on a kinetic centrifugal analyzer (ACL 300 Plus). The ECT by cards was ideally maintained above 600 seconds during the surgical procedure. Additional boluses of Refludan were given as and when necessary (ECT < 600 sec) in order to maintain adequate anticoagulation. The calculated circulating concentrations of Refludan, following a bolus administration, based on the ECT cards, liquid ECT and APTT were 3.20 +/- 1.3, 3.51 +/- 1.35 and 2.02 +/- 1.19 microg/mL, respectively.

Effectiveness of transient immunosuppression using cyclosporine for xenomyoblast transplantation for cardiac repair

We studied the survival of human myoblast for cellular myocardial reconstruction in a porcine model of chronic myocardial ischemia with immune tolerance using transient immunosuppression. A porcine model of chronic cardiac ischemia was created in 10 pigs (DMEM medium-injected n = 4; myoblast transplanted n = 6) by clamping ameroid ring around left circumflex coronary artery. Three weeks later, 3 x 10(8) human myoblasts carrying lac-z reporter gene were transplanted in multiple sites (0.25 mL each) into the left ventricular wall. Immunosuppression was achieved with 5 mg/kg cyclosporine for 6 weeks after cell transplantation. After animals were euthanized between 6 and 30 weeks after cell transplantation; the heart was removed for histological studies. Discontinuation of immunosuppression after 6 weeks of cell transplantation did not result in donor cell rejection. The lac-z-positive donor cells were detected in porcine host cardiac tissue for up to 30 weeks posttransplantation, expressing human skeletal myosin heavy chain. The results highlight the effectiveness of transient immunosuppression for myoblast transplantation for cardiac repair.

Evaluation and comparison of coronary heart disease risk factor profiles of children in a country with developing economy

OBJECTIVE

To define the risk factors (RF) profile and prevalence rates of high risk factors in an urban Pakistani community and compare it to the RF profile and prevalence rates of Pakistan National Health Survey.

METHODS

The present study included RF relevant data of 400 house hold children selected by open invitation as a part of Metroville Health Study (MHS), a risk factor modification study which was a cooperation between National Heart Lung Blood institute (NHLBI) USA and National Institute of Cardiovascular Diseases Pakistan. The base line data of 389 girls and 417 boys age 5-17 was included. PMRC data of 5067 and NHANES III survey data of 10,252 US children was used for comparison with MHS. RF analyzed were height weight, SBP, DBP, BMI and serum cholesterol. Comparisons between MHS and PMRC and US were made by using two tailed student t test and of high RF were defined as those exceeding US standards and expressed as percentages.

RESULTS

The RF factor profile of urban Metroville children was worse than the national average of PMRC children. Except for diastolic blood pressure in both boys and girls and SBP in PMRC boys, all other RF were less than US children. Prevalence rates were higher in urban Metroville community, i.e., MHS compared to the PMRC which represents national average data.

CONCLUSION

RF profile of Pakistani children has been presented and effect of urbanization demonstrated by comparing the PMRC and MHS RF profile. Hypertension in Pakistani children has emerged as a single most important RF requiring urgent prevention.

[Lateral dislocation of the elbow: pathophysiological and therapeutic analysis]

Lateral dislocation of the elbow is exceptional, and its pure form even more so. We report a case of lateral dislocation of the elbow observed in a 65-year-old woman following a fall on the medial aspect of the elbow in the flexion position. Reduction could not be achieved because of the anconeus muscle interposition. Analysis of the mechanism involved and the displacements observed enabled to propose a reduction manoeuvre using gentle traction on the elbow with extension and progressive supination of the forearm, pushing the olecranon backward then pulling it medialy. This enabled avoiding incarceration of the nerve bundle or capsulo-ligamentary structures.

Pregnancy following cardiac surgery

OBJECTIVE

To determine the pregnancy outcome in women with cardiac disease who have undergone cardiac surgery.

DESIGN AND SETTING

Prospective study in a tertiary care hospital.

POPULATION

One hundred and thirteen pregnant women who had cardiac surgery due to valvular disease (commisurotomy as well as valve replacement), or other cardiac defects. These women were followed up in 170 pregnancies between January 1990 and December 1999.

RESULTS

Rheumatic heart disease (91%) affecting the mitral valve, was the commonest indication for cardiac surgery (89%). Valve replacement with mechanical prostheses followed by anticoagulant therapy was carried out in 45%. There was no maternal death. Maternal morbidity from complications included pulmonary oedema (16%), cardiac arrythmias (4%), postpartum haemorrhage (3.5%). Other bleeding complications included epistaxis and haematoma at episiotomy site (2%). Impaired functioning of prosthesis (4%), severe pregnancy induced hypertension (2%) and thromboembolism (0.6%) were also observed. The abortion rate was 10.6%. There were 3 stillbirths (2%), another 6.7% babies were born preterm and 28% were lighter than appropriate for the period of gestation. There were no neonatal deaths. Coumarin derivatives were not associated with obvious foetal malformation.

CONCLUSION

With appropriate care, the outcome of pregnancy in women who have had cardiac surgery is favourable, if their functional class is good.

Living-related pediatric renal transplants: a single-center experience from a developing country

We retrospectively analyzed the results of 75 living-related pediatric renal transplants performed at our center between January 1986 and December 1999. The major causes of end-stage renal disease (ESRD) were glomerulonephritis (26%) and nephrolithiasis (16%), while the etiology was unknown in 50%. The mean age of the recipients was 12 yr (range 6-17 yr) and that of the donors was 39 yr (range 20-65 yr). The majority (73%) of donors were parents. Eighty five per cent of donors were one-haplotype matched and the rest identical. Immunosuppression was based on a triple drug regimen. Thirty per cent of recipients were rapid metabolizers of cyclosporin A (CsA) (area under the curve [AUC]: < 6,000 ng/mL/h), while 16% were slow metabolizers (AUC: > 8,000 ng/mL/h). Forty three (57%) children encountered 59 rejection episodes, the majority of which (59%) were recorded in the first month post-transplant. Seventy-four per cent of the rejection episodes were steroid sensitive and the rest, except two, were resolved by therapy with antithymocyte globulin (ATG) or orthoclone thymocyte 3 (OKT3). After a mean follow-up of 37 months, 17 (22%) grafts had chronic rejection and 76% of these recipients had previously experienced acute rejection episodes. The overall infection rate was high, necessitating two hospital admissions/patient/year. The majority (53%) of the infections were bacterial. Urinary tract infections (UTIs) were seen in 17 (23%) recipients. Twelve of these had ESRD as a result of stone disease and eight grafts were lost because of UTIs. Eight per cent of recipients developed tuberculosis (TB), and extra-pulmonary lesions were seen in 50%. Surgical complications were encountered in eight patients. Free medication to all recipients and parental support ensured a compliance rate of 93%. Baseline growth deficit was seen in children of the two groups studied (the 6-12 yr and 13-17 yr age-groups), with Z-scores of - 2.39 and - 2.12, respectively. No growth catch-up was observed at 12 and 24 months in either group. Post-donation complications were seen most commonly in donors > 50 yr of age and included: proteinuria (> 300 mg/24 h, four patients), hypertension (three patients), and diabetes (one patient). Twenty-four grafts were lost, 54% as a result of immunological and the rest as a result of non-immunological causes, and 17 recipients died during the follow-up period. Infections were the main cause of patient and graft loss. Overall 1- and 5-yr graft and patient survival rates were 88% and 65%, and 90% and 75%, respectively.

Existing record keeping system in government teaching hospitals of Karachi

OBJECTIVE

To determine the deficiencies in the existing record keeping system (ERKS) in government teaching hospitals of Karachi.

STUDY DESIGN

Descriptive, qualitative study to determine the deficiencies in the ERKS in government teaching hospitals of Karachi.

SETTING

The study was conducted in four government teaching hospitals of Karachi from 1.1.1998 to 1.11.1998.

METHODS

A total of 9725 pre-coded proformas were filled from 136 units of all hospitals including out patient departments (OPD), wards and emergency units.

RESULTS

Majority of the records (52.2%) were retrievable within one hour. The mean +/- S.D of patients seen per day at all hospitals were 122.49 +/- 92.25 (57 OPDs), 30.04 +/- 16.24 (75 wards) and 186.25 +/- 145.80 (4 emergencies). In majority of units (57.4%), the stationary for record keeping system was either not provided or was not enough. Only 39.0% units have 75% or more required information on records. The important information (except age) i.e. temperature, pulse rate, blood pressure, diagnosis, weight, history of patient, laboratory findings, previous record and discharge report and prescribed doses of medicine were lacking.

CONCLUSION

The ERKS in the government hospitals of Karachi is inadequate. It is therefore essential that uniform OPD, ward and emergency slips should be developed having all-important queries. So that data could be utilized for research purposes along with better planning and management of the hospital and procurement plan for the government.

Prevalence of HIV, hepatitis B and C amongst health workers of Civil Hospital Karachi

OBJECTIVE

To determine the prevalence of HIV, Hepatitis B (HBV) and Hepatitis C (HCV) amongst the health workers of Civil Hospital Karachi (CHK).

MATERIAL AND METHODS

Prospective study. A precoded Proforma was filled out which included questions regarding the knowledge, attitude and practices (KAP) of HIV, HBV and HCV.

SETTING

Departments of a tertiary health care facility at CHK. Antibodies to HIV, HCV and Hepatitis B surface antigen (HBsAg) were done using enzymes linked immunabsorbant assay [ELISA].

RESULTS

Uptake of screening was 98% to those offered. The prevalence was 5-6% for antibodies to HCV, 2.4% for HBsAg, while none of those studied had antibodies to HIV.

CONCLUSION

Our results show the prevalence of antibodies to HCV in health workers are 20 folds higher than health workers in the developed countries. Similarly, the prevalence of HBV although not as high as HCV is significant. Seroprevalence of HIV does not exist in this group. We need to ensure better training; regulations regarding preventive and safety measures also need to be enforced.

Immunohistochemical cathepsin-D expression in breast cancer: correlation with established pathological parameters and survival

Breast cancer is an increasingly important cause of illness and death among women. In recent years, several novel prognostic determinants of breast cancer have been identified, including Cathepsin-D (CD) protein. CD protein expression was analyzed immunohistochemically (IHC) in tumor specimens (315 patients) of infiltrating ductal breast carcinoma. These patients also had axillary lymph node sampling. Overexpression of CD was observed in 39% of the tumors. IHC results were compared with the histological grade. Seventy nine percent (n = 95; 79%) tumor positivity was seen in grade II tumors, followed by grade I (n = 13; 11%) and grade III tumors (n = 12; 10%). Axillary lymph node metastasis had no significant correlation with CD positivity (p > 0.05). Bone metastases were significantly correlated with CD positivity (p < 0.05). CD positivity showed no significant correlation with disease-free and overall survival (p > 0.05). At a median follow-up of 48 (4 years) months in CD-positive patients, overall survival was 3.17 years, and disease-free survival 2.67 years. The overall survival of CD-negative tumor patients was 3.50 years, and disease-free survival was 2.93 years. We conclude that in comparison with cytosol-based quantitative studies, CD expression is not a good prognostic marker when, as in all ICH studies, only the expression in the tumor is considered.

Impact of socioeconomic conditions on perinatal mortality in Karachi

OBJECTIVE

To study and compare the perinatal mortality (PNM) in hospitals located in various socio-economic areas of Karachi.

DESIGN

A prospective review of all births was done from May 1996 to April 1997. Precoded proformas were provided to each hospital and the birth and details of each mother and baby delivered recorded.

SETTING

All mothers and their newborn delivered during the time period mentioned.

OUTCOME MEASURES

Comparison of PNM in hospitals located in various socio-economic areas of Karachi.

RESULTS

A total of 4957 proformas were filled, 63.5% by doctors, 32% by LHVs, 2.9% by administrator and 2.3% by paramedics. Overall 92.3% mothers were housewives, less than 45% of the mothers received primary/secondary education; 42% mothers were of the age 21 to 25 years. More than 52.3% fathers were unskilled labourers. Only 27% mothers were booked while the rest were unbooked or came to deliver on walk in basis. Majority (62%) of the mothers had a > 37 week duration of pregnancy and 51% newborns were male and 49% female. Twenty three percent of the newborns weighed < 2500 grams, remaining weighed > 2500 grams but less than 4500 grams; 24.5% newborns died on day one of birth. The PNM per 1000 births in the high, middle and low socioeconomic hospital was 16.4 +/- 23.6, 24.9 +/- 51.20 and 80.4 +/- 177.78 respectively. A statistical significance (p < 0.0000) by the Chi-square for several proportions was seen between the high middle and low socioeconomic hospitals of Karachi.

CONCLUSION

The present socioeconomic conditions will take some time to change. However, this study indicates that perinatal mortality rate may be changed by an improvement in antenatal care of the mother, hence the fetus.

A multicenter, randomized, controlled trial of Celsior for flush and hypothermic storage of cardiac allografts

BACKGROUND

A multicenter, randomized, controlled, open-label trial was conducted to evaluate the safety and efficacy of Celsior when used for flush and hypothermic storage of donor hearts before transplantation.

METHODS

Heart transplant recipients were randomized to one of two treatment groups in which donor hearts were flushed and stored in either Celsior or conventional preservation solution(s) (control). Study subjects were followed for 30 days after transplantation.

RESULTS

A total of 131 heart transplant recipients were enrolled (Celsior, n = 64; control, n = 67). The treatment groups were evenly distributed in donor and recipient base line characteristics. Graft loss rate was lower in the Celsior group on day 7 (3% versus 9%) and on day 30 (6% versus 13%), but the difference was not statistically significant based on 95% confidence interval analysis. No significant difference was measured between the Celsior and control groups in 7-day patient survival (97% versus 94%) and the proportion of patients with one or more adverse events (Celsior, 88%; control 87%) or serious adverse events (Celsior, 38%; control, 46%). Significantly fewer patients in the Celsior group developed at least one cardiac-related serious adverse event (13% versus 25%).

CONCLUSIONS

Celsior was demonstrated to be as safe and effective as conventional solutions for flush and cold storage of cardiac allografts before transplantation.

A genetic epidemiological study of carcinoma of the fallopian tube

OBJECTIVE

The goal of this work was to evaluate the importance of genetic factors in the etiology of fallopian tube cancer.

METHODS

All pathologically confirmed cases of fallopian tube cancer diagnosed in Ontario from 1990 to 1998 were identified from the records of the Ontario Cancer Registry. Living patients were approached to provide information about their family history and to provide a blood sample for testing for mutations in BRCA1 and BRCA2.

RESULTS

A modest increase in the risk of ovarian cancer (relative risk (RR) = 2.2; 95% confidence interval (CI) = 0.4, 6.3) and of early-onset breast cancer (RR = 2.4; 95% CI = 0.6, 6.1) was observed in the first-degree relatives of the fallopian cancer cases. Five of the forty-four cases were positive for a mutation in BRCA1 (11%) and two were positive for a BRCA2 mutation (5%). Five of eighteen women diagnosed at or before age 55 were positive (28%). Two of the seven mutation carriers had a strong family history of breast and ovarian cancer, and three carriers had a modest family history. Three of the forty-four cases were Jewish, and of these, two carried a founder mutation characteristic of this population.

CONCLUSIONS

Fallopian tube carcinoma should be considered to be a clinical component of the hereditary breast-ovarian cancer syndrome, and may be associated with BRCA1 and BRCA2 mutations. Genetic evaluation should be offered to women who present with fallopian tube carcinoma. It is important to consider the risk of fallopian tube carcinoma when prophylactic oophorectomy is performed in high-risk women.

Bilirubin-IXbeta is a marker of meconium, like zinc coproporphyrin

BACKGROUND

Because meconium accumulates continuously in the fetal intestine, analysis of the postnatally excreted material could yield important information of intrauterine metabolism and maturation. Therefore, a study of the bilirubin pigments in meconium and in the first neonatal stools was carried out.

METHODS

Meconium and stools from 37 neonates of various gestational ages were collected carefully, and stored at -20 degrees C, protected by aluminium foil. Samples were defrosted, vortex mixed with an equal amount of dimethyl sulfoxide, centrifuged, and submitted to analysis by high-pressure liquid chromatography using newly developed methods to identify and to quantitate the bilirubin-IXalpha, -IXbeta, -IXgamma, and -IXdelta isomers. In addition, samples were also submitted to diazo coupling with ethyl anthranilate. Total coproporphyrins and zinc coproporphyrin were assayed for comparison.

RESULTS

Unconjugated bilirubin-IXalpha and -IXbeta were detected in meconium but not the -IXgamma or the -IXbeta isomer. Bilirubin-IXbeta was the predominant pigment and comprised 63% to 96% of the unconjugated bilirubins in the first sample of meconium excreted. Its amount decreased rapidly during the first 5 days in full-term newborns, but this occurred more slowly in preterm neonates, especially in those with a gestational age less than 30 weeks. The decrease of bilirubin-IXbeta over time correlated with that of coproporphyrin.

CONCLUSIONS

Bilirubin-IXbeta is the prevailing bile pigment in the first excreted sample of meconium. It gradually decreases after birth and can be considered a biochemical marker of meconium, like zinc coproporphyrin.

Multiple factors other than p53 influence colon cancer sensitivity to paclitaxel

PURPOSE

To determine factors which influence the sensitivity of human colorectal carcinoma cell lines to paclitaxel.

METHODS

The paclitaxel sensitivity of ten human colorectal carcinoma cell lines, and a panel of RKO colon carcinoma cell lines, isogenic except for p53 status, were studied. The inhibitory concentrations causing a 50% decrease in growth (IC50) were assayed after 3, 24, and 96 h after paclitaxel exposure. The doubling time (DT) and cell cycle parameters of cells were also measured. The expression of the multidrug resistance glycoprotein-1 (MDR-1), bcl-2 and bax was quantitatively assessed by immunoblotting.

RESULTS

Mean IC50 values at 24 and 96 h drug exposure were about 1.5 logs lower than the IC50 values at 3 h, regardless of the p53 status. No difference was found between the IC50 values of wild-type and mutant p53 cells, or among the RKO panel of cells. Correlation analysis showed that: (1) resistance was associated with longer DTs, but this was generally abated by a 96-h exposure; (2) with a 3-h exposure, the combination of MDR, bcl-2 and bax parameters with DT (DT + MDR + bcl-2 bax) best correlated with IC50 values (r = 0.77); (3) with a 96-h exposure, in spite of the generally decreased IC50 values, a combination of MDR-1, bcl-2 and bax parameters (MDR + bcl-2-bax) best correlated with the IC50 values (r = 0.71).

CONCLUSIONS

These results suggest that the exposure duration, DT, and expression of MDR-1, bcl-2 and bax each contribute to paclitaxel sensitivity of human colorectal carcinoma cells. In assessing paclitaxel drug resistance, multiple factors should always be considered. There may be a therapeutic window for taxanes in colon cancer by optimizing pharmacokinetics and modulating MDR-1 and bcl-2 resistance factors.