Management of Neglected Rupture of Tendoachilles with Long Gap by Flexor Hallucis Longus Tendon Transfer.

The tendo achilles is one of most important tendon in human body which often injured through direct trauma or indirect stress on a weakened tendon. Longer the duration after injury the injured parts likely to move apart, fibrosis and degeneration leading to difficulty in repair or reconstruction. Usually a phase of 4 weeks or more without specific treatment is regarded as chronic or neglected rupture. Different authors described many management protocols about the tendo achilles rupture but there is no procedure of choice for neglected rupture with long gap. Prospective case series of 21 patients of neglected tendo achilles rupture with long gap treated with flexor hallucis longus tendon (FHLT) transfer was taken for study from January 2019 to December 2020 in Mymensingh Medical College Hospital, Bangladesh. Average age of patients was 39.47 years with range 22-65 years. Fifteen (15) cases of traumatic rupture in this study with average age 32.66 years and pathologic 6 cases with average age 56.5 years were recorded. We grafted FHLT from channel by incising Henry's knot. Krackow et al.'s technique was followed for tendon mobilization and bone fixation. We made procedure simpler and cheaper; instead of using interference screw the sutured tendon pulled through the heel and anchored over rubber tube or button by Cole method. Post-operative complications were less with one patient with superficial infection which eventually recovered 3 cases of mild pain and 2 cases of numbness. Questionnaire for surgical outcome measure are satisfactory in 19 patients (90.47%). Final follow up AOFAS score at 6 month (91.61±5.41) was highly significant (p<0.001) in comparison to preoperative score (38.71±9.78). These are comparable to other study. Above mentioned scores indicate the reliability of the surgical system. But our study is a prospective case series with minimum cases. To establish the best procedure for neglected tendo achilles rupture with long gap we recommend further study with larger group and Randomized Controlled Trial (RCT) study among different procedure.

Clinical Outcome on Comminuted Femoral Shaft Fractures in Adults Treated by Minimally Invasive Plate Osteosynthesis (MIPO) with Locking Plate.

Intramedullary nailing is a pillar in the treatment of femoral shaft fractures. But it is not possible in all cases especially in comminuted fractures. This study has been designed to explain the importance of Minimally Invasive Plate Osteosynthesis (MIPO) with the locking plate in the treatment of comminuted Femoral Shaft Fracture. Twenty (20) such patients were treated by MIPO and analysis has been done in this study to get fruitful result and to find out the effectiveness of this procedure who were admitted at Mymensingh Medical College Hospital, Mymensingh, a tertiary level hospital of Bangladesh from February 2018 to January 2019. Mean age of the patients were 49.20±14.41 years. Based on AO classification, there were 4, 8 and 8 patients belong to type A, B and C respectively. The union period for all the patients was in between 12 to 14 weeks. The mean union period was 12.90±1.997 weeks. Mean follow up period was 19.70±2.77 weeks. Mean full weight bearing period was 16.50±1.10 weeks. In Thoresen scoring system excellent result was 9(45%), good result was 10(20%) and fair result was 01(5%). Mal-alignment happened in two cases. However, delayed union and broken screws were found in two cases each of which was treated accordingly. Comminuted Femoral shaft fracture with MIPO procedure is more effective treatment than intramedullary nailing. Furthermore, mal-alignment is the basic complexity that must be taken away intraoperatively.

Clinical Significance of Circulatory miRNA-21 as an Efficient Non-Invasive Biomarker for the Screening of Lung Cancer Patients

Dysregulation in the miRNA-21 expression has been previously observed in a number of malignancies and not only in the tumor cell itself but also in the body fluids of the cancer patients. The present study aimed to find out the clinical significance of cell-free circulating miRNA-21 as an efficient non-invasive biomarker for the screening of lung cancer patients. The present case-control study included plasma samples from 80 lung cancer patients and 80 healthy controls. Magnetic bead technology was used for efficient miRNA isolation and advanced TaqMan miRNA assays were used for the quantification of miRNA-21 level in the plasma of the lung cancer patients and healthy individuals.The overall mean relative expression level of plasma miRNA-21 among lung cancer patients (2.32±1.7) was higher when compared to healthy individuals (0.715 ± 0.48) and it showed a significant difference of p<0.0001. The area under ROC curve was 0.8913 [95% confidence interval (CI): 0.8394 to 0.9431, p< 0.0001] and the sensitivity and specificity were both 80.0% when the cut-off value was 1.207. In conclusion, plasma miRNA-21 can be efficiently extracted by the magnetic bead technology and quantified by the advanced TaqMan miRNA assay. Plasma miRNA-21 showed a high ability to distinguish between lung cancer patients and healthy individuals, therefore can be used as an efficient non-invasive biomarker for the screening of Lung cancer patients.

Pyrimidine nucleosides in molecular PET imaging of tumor proliferation.

Human thymidine kinase (TK1) is a key enzyme that is up-regulated in cancer cells and phosphorylates thymidine and some of its analogs to their monophosphates. The monophosphates are converted to their di- and triphosphates by the nucleoside kinases, and some of these nucleoside triphosphates are incorporated into DNA by DNA polymerase. The nucleoside analogs are transported into cells by concentrative nucleoside transporter or equilibrative nucleoside transporter. Given the unique property of TK1 and the nucleoside transporter systems, thymidine and its analogs have been radiolabeled for positron emission tomography (PET) imaging of tumor proliferation and DNA synthesis. Because thymidine is catabolized in vivo by thymidine phosphorylase, radiolabeled thymidine has not been successful in PET imaging of tumor proliferation. However, some of its analogs have been radiolabeled and successfully used in PET imaging of cell proliferation as well as DNA synthesis. Much work has been done in synthesis, radiosynthesis, and biological evaluation of these analogs for PET imaging of tumor proliferation. We review the chemistry, radiochemistry, and biological studies published to date, including structure activity relationship and PET imaging of the radiolabeled thymidine analogs. Information on radiolabeling and PET imaging with various nucleoside analogs is presented.

Intranasal meningoencephalocoele-a rare childhood condition.

Congenital or acquired intranasal meningocoele or meningoencephalocoele is a rare condition ever reported in world literature. We report a case of intranasal meningoencephalocoele in which a 10 month old male child presented with left sided progressive nasal obstruction, nasal mass and reluctant to feed. On examination slight broadening of the bridge of the nose with obliteration of left nasomaxillary fold, mucoid discharge and a pinkish, polypoidal, non tender, non pulsatile mass with prominent blood vessels on the surface occupying almost 3/4(th) of the nasal cavity was observed. On probing it appeared to be attached to roof of left nasal cavity. Computed tomography revealed a hypodense area in the nasal cavity but there was no bony defect in the skull base. Peroperatively on aspiration of nasal cystic mass revealed free flow of clear fluid which was biochemically CSF. A one stage, Lynch Howarth approach, correctional procedure was performed. We present here a discussion of findings and surgical treatment. Early diagnosis and referral are of paramount importance, because failure to identify this leads to fatal outcome if surgery performed.

Hearing status of elderly people: study in a tertiary level hospital.

A study was carried out from April 2003 to March 2004 at the Department of Otolaryngology and Head-Neck Surgery, BSMMU, with the aim to evaluate the prevalence of hearing loss and to find out the pattern and extent of hearing loss among the elderly people. The study included 100 people aged over 50 years. Out of 100 cases 59% were found with normal hearing and 41% had variable degree of hearing impairment. The highest prevalence of hearing impairment was found 100% in 9th decade with gradually decreasing tendency and lowest was 29.50% in 6th decade. Most of the cases were found to be bilateral (65.85%). Majority (65.85%) of the hearing impaired people had sensorineural type of loss with a significant number (21.95%) of conductive loss. Irrespective of type of impairment. Most of the people (73%) had no complaint of ear problem during presentation. Only 27% had some sorts of otological symptoms like hearing loss, tinnitus and vertigo and among them about 96.29% complained of hearing loss. About 44.44% of the hearing impaired person of 6th decade, showed mild hearing loss. In the 7th decade maximum (50%) had moderate to severe hearing loss. About 31% of persons of 8th decade and 50% of 9th decade had severe degree of hearing loss.

Outcome of management of differentiated thyroid carcinoma.

A prospective study was done on 93 cases of differentiated thyroid carcinoma to find out the outcome of management according to the protocol followed in the Department of ENT-Head and Neck Surgery of Bangabandhu Sheikh Mujib Medical University Hospital. Here Papillary carcinoma is more common (76.35%) than follicular carcinoma. Papillary carcinoma affected in the younger patients more commonly than the follicular carcinoma with a mean age of 34.37years (SD=12.81) for papillary carcinoma and 44.93 years (SD=16.01) for follicular carcinoma; but age as a risk factor showed no significant difference between two histological types (p>0.05). Female was the predominant sex with a ratio of 3.04:1. In this series majority of patients were categorized as high risk group (75.27%). There is strong association between histological type & risk group (P<0.05). High risk group is more common in follicular carcinoma (95.45% Vs 69.01%). There was a significant differences between the two histological types for extrathyroidal extention and distant metastasis as risk factors (p<0.01 and p<0.001); but tumour size and lymphatic metastasis showed no significant difference (p>0.05). All low risk patients were treated by hemithyriodectomy followed by life long thyroxine. All high risk cases were treated with total thyroidectomy with (35.71%) or without (62.86%) different types of neck dissection (according to the degree of lymph node involvement) followed by radioiodine ablasion and lifelong thyroxine therapy routinely. Overall rate of complication of thyroid surgery was 23.08%. The commoner complications were vocal cord palsy (5.5%), hypoparathyroidism (5.5%) and haemorrhage (4.4%). Less common complications were laryngeal oedema (2.2%), wound infection (2.2%), tracheal injury (1.1%) and death (2.2%). Many cases lost to follow up. Sixty seven cases (73.64%) responded well for follow-up. Mean duration of follow up was 3.40 years (SD=1.41). There was recurrence in thyroid remnant in 9.09% of hemithyroidectomy cases and were treated by completion thyroidectomy followed by radioiodine ablasion. Regional lymphatic metastasis was seen in six cases and was treated by different types of neck dissection. Recurrence at distal site was seen in 4 cases (18.18% of follicular carcinoma). These were treated by radioiodine ablation; two of them died during the period of follow-up.

Genital fistula--our experience.

Genital fistulas cause immense physical and psychosocial problem in women's life. The present study was conducted to note the varieties of genital fistula as well as their causative factors and the results of the operative corrections. Altogether 42 patients with different varieties of genital fistula were enrolled in the study. The causative factors of the genital fistulas, specially, that of vesicovaginal fistulas were thoroughly enquired. After confirming the diagnosis, the operative corrections were undertaken. Among the varieties of genital fistula, 76.19% were vesicovaginal fistula, 11.90% were rectovaginal fistula and 4.76%, 4.76% and 2.38% cases of ureterovaginal, urethrovaginal and vesicocervical fistulas respectively. The primipara women were the major sufferers of genital fistulas due to obstetric grounds. Regarding aetiologies of vesicovaginal fistulas, 71.87% patients had obstetric reasons, after prolonged labour, instrumental delivery and after caesarean section due to obstructed labour. Abdominal hysterectomy (44.44%) topped the list of the gynaecological causes of vesicovaginal fistulas. The cases of ureterovaginal fistulas were after abdominal hysterectomy. One case of urethrovaginal fistula was due to some chemical application for correction of genital prolapses. The rectovaginal fistulas were mostly due to obstetric reasons. The success rate after the first attempt of repair of vesicovaginal fistula was 82.75% and overall failure was 10.34%. The other varieties of fistulas were repaired with 100% success rate. The incidence of genital fistulas can be reduced by vigilant obstetric care and meticulous surgery.

Head and neck squamous cell carcinoma (HNSCC) 5 year study at BSMMU.

Head and Neck Squamous Cell Carcinoma (HNSCC) are generally similar in their clinical features, epidemiology and etiology although their natural and clinical history and treatment differ. Despite lot of improvement in diagnostic and management technique, there is little improvement in survival rate over the last few decades. This study was carried-out in a multidisciplinary tertiary level hospital (BSMMU), with a country-wide catchment area to see the burden of HNSCC existing in our country and their clinical pattern. The overall incidence rate of HNSCC in this study was (0.15%) i.e. 150 person in 1,00,000 population. Male incidence (0.19%) was higher than female (0.12%). This study revealed that carcinoma of the larynx (25.22%) and pyriform fossae (20.57%) were the main culprit, whereas buccal carcinoma was the main component (37.70%) in the female series. Highest incidence was found in the 6th decade in both sexes. As the treatment of HNSCC may be time consuming, requires multidisciplinary approach, demands lot of clinical, social and financial consideration, therefore, the best treatment can be offered through a combined board consisting of Surgical, Radiation, Medical oncologists, Histopathologist and Speech therapist as required.

Management of thyroid carcinoma-an experience in Bangladesh.

All patients (n=154) of thyroid malignancy admitted in the Otoluryngology Department of Bangabandhu Sheikh Mujib Medical University (former IPGMR) between 1986 and 2000 were retrospectively analyzed to find out the extent and result of surgery used for thyroid carcinoma. The other objectives were to find out the incidence of differentiated thyroid carcinoma among the thyroid malignancy and also to find out the age, sex and clinical presentation of papillary and follicular carcinoma. Among all the thyroid malignancy (n-154), Differentiated Thyroid Carcinoma (DTC) was seen in 130 (84.41%) cases, where as papillary carcinoma occurred in 98(63.64%), and follicular carcinoma in 32(20.77%)cases. On the basis of risk factors, the DTC were designated as low and high risk. The year-wise incidence of DTC revealed increasing trend from 1986 (3 cases) to 2000 (23 cases).Among the 98 papillary thyroid carcinoma highest number of cases (35.71%) were seen in 31-40 year age group. The male to female ratio was 1: 1.64. In follicular carcinoma, highest number (35.25%) of cases were also seen in 31-40 year age group. The male to female ratio was 1:1.66. The commonest presentation in papillary carcinoma was thyroid swelling (96.93%). The other presentations were occult thyroid (3.06%), Cervical lymph node metastasis (38.77%) and distant metastasis (2.04%). In Follicular carcinoma, the presentations were thyroid swelling (100%), Cervical lymph node metastasis (6.25%) and Distant metastasis (21.87%).In this series, low risk DTC were treated by Lobectomy & Isthmusectomy plus Thyroxin. In low risk group the rate of recurrence was 6.89% and the mortality was nil in five years follow-up. Except two inoperable cases, all high risk patients were managed by Total thyroidectomy (with or without neck dissection, plus removal of metastatic lesion when required) with Radioiodine ablation plus Thyroxin. . The rate of recurrence was 7.81% and mortality was 1.56% in high risk group in similar period of time.Vocal cord palsy were noted in 5 (3.84%) unilateral, and inane (0.76%) bilateral cases. Hypoparathyroidism was found in 4.61%.

Carcinoma larynx--topographical distribution.

One hundred and sixty subjects were included in our study, collected from four hospitals in Dhaka City. The mean age (+/- SD) of study subjects were 54.67 +/- 11.27 years. Out of 160 subjects 155 was males and 5 were females, and male to female ratio was 31:1. The highest number of study subjects was related to cultivation (40.62%). The majority of study subjects were from the low socio-economic status (68.72%). Carcinoma larynx is a multifactorial disease. Smoking and chewing habit are the most important factors associated with carcinoma larynx. Most of the male (93.12%) subjects were smoker. One hundred and fifteen (71.87%) subjects were found chewing habit of betel leaves with other ingredients. Hoarseness of voice was the commonest symptom 65.62%. Regional distribution of tumour showed supraglottic carcinoma topping the list (69.38%) followed by glottic carcinoma (30.62%) and there was no subglottic carcinoma. Site involvement in supraglottic carcinoma was found in combined location topping the list (89.20%). In glottic carcinoma majority was found glottic with supraglottic extension (65.31%). In majority cases growth were exophytic 52.50%. Palpable lymph mode was found in 48.75% of cases. All the carcinoma of larynx was found histologically of squamous cell type.

Comparative study between tubotympanic and atticoantral types of chronic suppurative otitis media.

This prospective study was done to compare the different aspects of tubotympanic (group I) and atticoantral types (group II) of chronic suppurative otitis media. The study included 200 patients of chronic suppurative otitis media, of them 100 were of tubotympanic type and 100 were with atticoantral disease. The age (mean +/- SD) of group I and II were 17 +/- 2.7 years and 12 +/- 2.3 years respectively (P < 0.05). The majority of the patients having poor socio-economic condition 69% in group I and 87% in-group II. In both groups, slum dwellers with bathing habit in pond or river and illiterate were more sufferer (P < 0.05). There was central perforation in all patients in-group I, and in-group II, 67% were with attic and 33% were with marginal perforations. In group I, aural discharge was mucoid or mucopurulent in majority of cases 80% and in-group II foul smelling scanty ear discharge was from 88% of subjects. In atticoantral type, hearing impairment was more than tubotympanic disease. Complications were more in atticoantral type of disease. In-group II, post auricular sinus 25% was the commonest extracranial complication followed by subperiosteal abscess 18%, and meningitis 10% was the commonest intracranial complication followed by brain abscess 8%. In tubotympanic type conservative treatment with reconstructive surgery were the treatment of choice, whereas radical or some modifications of radical surgery (with or without reconstruction) were the treatment plan for atticoantral disease. Among the groups the mortality rate was only 4% in-group II and was due to intracranial complications. The study recommends early detection and effective surgical treatment of the disease to improve the situation.

Preclinical evaluation of the penciclovir analog 9-(4-[(18)F]fluoro-3-hydroxymethylbutyl)guanine for in vivo measurement of suicide gene expression with PET.

UNLABELLED: The gene for herpes simplex virus thymidine kinase (HSV-tk) is widely used as a suicide gene in experimental gene therapy of cancer. 9-(4-Fluoro-3-hydroxymethylbutyl)guanine (FHBG) is an antiviral nucleoside analog that is rapidly phosphorylated by viral thymidine kinase but is a poor substrate for mammalian thymidine kinase. Recently, FHBG labeled in the 4-fluoro position with (18)F has shown promise relative to other similar compounds for imaging in vivo expression of HSV-tk using PET. In this study, we evaluated the uptake of [(18)F]FHBG in vitro and in vivo using transduced and wild-type human colon cancer cells (HT-29). We also imaged [(18)F]FHBG and measured the radioactivity concentrations of circulating [(18)F]FHBG and its metabolites in monkeys. METHODS: Sterile, pyrogen-free [(18)F]FHBG was produced routinely in good yields. Cells were transduced with the retroviral vector G1Tk1SvNa containing HSV-tk gene. In vitro uptake studies were performed by incubating cells with [(18)F]FHBG at 37 degrees C for 1 and 5 h. Biodistribution studies were performed at 2 and 5 h after injection in nude mice bearing tumors grown from wild-type or transduced cells. Sequential, whole-body PET scans of cynomolgus monkeys were obtained over a period of >2 h after intravenous injection of [(18)F]FHBG. Arterial plasma samples obtained from monkeys 15-120 min after intravenous injection were subjected to acid extraction, and the acid-soluble fractions were analyzed by high-performance liquid chromatography. RESULTS: In vitro studies showed 31 and 71 (P < 0.001) times higher uptake of the probe at 1 and 5 h, respectively, in transduced cells compared with nontransduced cells. In vivo studies in mice showed that tumor uptake of the radiotracer was 4-fold (P < 0.05) and 13-fold (P < 0.001) higher at 2 and 5 h, respectively, in tumors grown from transduced cells compared with control cells. Transduced tumor-to-normal tissue ratios ranged from 2 to 25 at 2 h and from 2 to 22 at 5 h. Recirculating labeled metabolites had only a minor effect on the biodistribution of radiolabel from [(18)F]FHBG in monkeys. CONCLUSION: These results indicate that [(18)F]FHBG may yield high-contrast PET images of HSV-tk expression in tumors and, therefore, it is a very promising radiotracer for monitoring of gene therapy of cancer with PET.

Blocking catabolism with eniluracil enhances PET studies of 5-[18F]fluorouracil pharmacokinetics.

UNLABELLED: Noninvasive methods for measuring the pharmacokinetics of chemotherapeutic drugs such as 5-fluorouracil (FU) are needed for individualized optimization of treatment regimens. PET imaging of [18F]FU (PET/[18F]FU) is potentially useful in this context, but PET/[18F]FU is severely hampered by low tumor uptake of radiolabel and rapid catabolism of FU in vivo. Pretreatment with eniluracil (5-ethynyluracil) prevents catabolism of FU. Hypothesizing that suppression of catabolism would enhance PET/[18F]FU, we examined the effects of eniluracil on the short-term pharmacokinetics of the radiotracer. METHODS: Anesthetized rats bearing a subcutaneous rat colorectal tumor were given eniluracil or placebo and injected intravenously 1 h later with [18F]FU or [3H]FU. In the 18F studies, dynamic PET image sequences were obtained 0-2 h after injection. Tumors were excised and frozen at 2 h and then analyzed for labeled metabolites by high-performance liquid chromatography. Biodistribution of radiolabel was determined by direct tissue assay. RESULTS: Eniluracil improved tumor visualization in PET images. With eniluracil, tumor standardized uptake values ([activity/g]/[injected activity/g body weight]) increased from 0.72 +/- 0.06 (mean +/- SEM; n = 6) to 1.57 +/- 0.20 (n = 12; P < 0.01), and tumor uptake increased by factors of 2 or more relative to plasma (P < 0.05) and bone, liver, and kidney (P < 0.01). Without eniluracil (n = 5), 57% +/- 4% of recovered radiolabel in tumor at 2 h was on catabolites, with the rest divided among FU (2% +/- 1%), anabolites of FU (38% +/- 7%), and unidentified peaks (4% +/- 2%). With eniluracil (n = 8), catabolites, FU, and anabolites comprised 2% +/- 1%, 41% +/- 5%, and 57% +/- 4%, respectively, of the recovered radiolabel in tumors. CONCLUSION: Eniluracil increased tumor accumulation of 18F relative to host tissues and fundamentally changed the biochemical significance of that accumulation. With catabolism suppressed, tumor radioactivity reflected the therapeutically relevant aspect of FU pharmacokinetics--namely, uptake and anabolic activation of the drug. With this approach, it may be feasible to measure the transport and anabolism of [18F]FU in tumors by kinetic modeling and PET. Such information may be useful in predicting and increasing tumor response to FU.

Single amino acid substitution in the Fc region of chimeric TNT-3 antibody accelerates clearance and improves immunoscintigraphy of solid tumors.

UNLABELLED: Recent studies in antibody catabolism have identified residues at the CH2-CH3 interface of the IgG heavy chain critical for serum persistence of immunoglobulins. Amino acid substitutions in the Fc region of murine IgG1 were shown to drastically accelerate antibody clearance in mice. Our laboratory has previously described a human-mouse chimeric TNT-3 (chTNT-3) monoclonal antibody directed against a universal nuclear antigen that has potential for the radioimmunotherapy of many solid tumors. In the current study, we engineered a chTNT-3 mutant containing a single amino acid substitution, to determine whether a more rapid clearance profile would make the antibody suitable for diagnostic imaging. METHODS: A single amino acid substitution in the CH2 domain of the human gamma1 constant region was made by polymerase chain reaction mutagenesis. High-level expression was achieved using the Glutamine Synthetase Gene Amplification System, and the chTNT-3 mutant was purified by protein A affinity and ion-exchange chromatography. A radioimmunoassay was performed to examine antigen binding, and in vivo studies were undertaken to evaluate clearance and tumor targeting in human tumor xenograft models. RESULTS: The chTNT-3 mutant retained the high affinity of chTNT-3, with a binding constant of 1.5 x 10(-9) mol/L. The mutant was eliminated rapidly from BALB/c mice, with a beta-phase half-life of 33.8 h, compared to 134.2 h for chTNT-3. Moreover, biodistribution studies in human colon tumor-bearing nude mice reflected this accelerated clearance. Tumor levels of the mutant were, respectively, 65%, 39%, and 36% of the tumor levels achieved with the parental chTNT-3 6, 12, and 24 h postinjection. The rapid clearance of the chTNT-3 mutant from the blood resulted in higher tumor-to-normal organ ratios for many normal tissues. Imaging of tumor-bearing mice with 99mTc-labeled chTNT-3 mutant demonstrated early visualization of tumors in 3 different solid tumor xenograft models. CONCLUSION: The accelerated clearance produced by a single amino acid substitution in the Fc region of chTNT-3 leads to improved imaging in tumor-bearing mice. These studies suggest that a rapidly clearing antibody generated by this approach may be useful for the immunoscintigraphy of human tumors.

Evaluation of 9-[(3-18F-fluoro-1-hydroxy-2-propoxy)methyl]guanine ([18F]-FHPG) in vitro and in vivo as a probe for PET imaging of gene incorporation and expression in tumors.

Preparation of 9-[(3-18F-fluoro-1-hydroxy-2-propoxy)methyl]-guanine ([18F]-FHPG) for clinical use, and its evaluation as a positron emission tomography (PET) imaging agent for gene incorporation and expression in tumors are reported. In vitro studies in human colon cancer cells, HT-29, transduced with the retroviral vector G1Tk1SvNa and nontransduced (wild type) showed 4, 8, 12, and 15 times higher uptake of the probe in 1, 3, 5, and 7 h, respectively, in transduced cells compared with the controls. In vivo studies in tumor-bearing nude mice demonstrated that the tumor uptake of the radiotracer is three and six-fold higher in 2 and 5 h, respectively, in transduced cells compared with the control cells. These results suggest that [18F]-FHPG is a potential in vivo PET imaging agent for monitoring gene incorporation and expression in gene therapy of cancer.

Synthesis and preliminary evaluation of 9-(4-[18F]-fluoro-3-hydroxymethylbutyl)guanine ([18F]FHBG): a new potential imaging agent for viral infection and gene therapy using PET.

Synthesis and preliminary biological evaluation of 9-(4-[18F]-fluoro-3-hydroxymethylbutyl)-guanine ([18F]FHBG) is reported. 9-(4-Hydroxy-3-hydroxymethylbutyl)-guanine (penciclovir) 4 was converted to 9-[N2, O-bis-(methoxytrityl)-3-(tosylmethybutyl)]guanine 7 by treatment with methoxytrityl chloride followed by tosylation. The tosylate 7 was reacted with either tetrabutylammonium fluoride or KF in the presence of kryptofix 2.2.2. to produce the 4-fluoro-N2-O-bis-(methoxytrityl) derivative 8. Removal of the methoxytrityl groups by acidic hydrolysis produced FHBG 5. Radiolabeled product [18F]FHBG was prepared by fluorination of the tosylate 7 with [18F]KF and kryptofix 2.2.2. The labeled product was isolated by HPLC purification on a reverse-phase C18 column, and eluted at 12 min with 15% acetonitrile in water at a flow rate of 2.25 mL/min. Radiochemical yield was 8.0-22.3% with an average of 12% in 7 runs (corrected for decay). Synthesis time was 90 to 100 min including HPLC purification with radiochemical purity >99%, and average specific activity of 320 mCi/micromol. In vitro studies of the compound in HT-29 colon cancer cells revealed 18.2-fold higher uptake into transduced cells compared to control in 3 h. The agent may be useful for imaging viral infection or transfected cells in gene therapy.

Improved tumor localization and radioimaging with chemically modified monoclonal antibodies.

A method for the chemical modification of monoclonal antibodies using the heterobifunctional crosslinker succinimidyl 3-(2-pyridyldithio)propionate (SPDP), has been developed which dramatically alters the physiochemical properties of antibody reagents. For these studies, three murine monoclonal antibodies, B72.3, Lym-1, and TNT-1 were used to demonstrate the effects of chemical modification on clearance and biodistribution in tumor-bearing nude mice. In vitro, all three antibodies, modified to the same degree with SPDP, showed equal immunoreactivities and lower non-specific binding. Modified antibodies also were found to have lower isoelectric points compared to unmodified controls. In vivo, modified antibodies unexpectedly were found to have 2-6 times faster clearance in tumor-bearing nude mice similar to rates obtained with their F(ab')2 fragments. Paired-label in vivo biodistribution and external imaging experiments with intact antibodies and F(ab')2 fragments demonstrated that chemically modified antibodies gave 1.5-3 fold higher tumor uptake and retained less activity in normal organs thus markedly increasing the tumor to normal organ ratios. Because of these results, chemically modified antibodies produced clearer images at earlier time points by external scintigraphy. As "stealth" molecules, chemically modified monoclonal antibodies appear to have significantly improved uptake in tumors and faster clearance times compared to native molecules. These results suggest that alteration of the physicochemical properties of monoclonal antibodies may generate improved reagents for in vivo use.

Synthesis of [11C-methyl]-alpha-aminoisobutyric acid (AIB).

Alpha-aminoisobutyric acid (AIB) labeled with the cyclotron-produced, positron-emitting radionuclide 11C has been synthesized with the label in the alpha-methyl group. Our previously published synthesis of [11C] AIB in the carboxyl position from [11C] HCN requires a rigorous quality assurance program to ensure that the concentration of cyanide in the final product is below certain levels. This can be avoided using the method described here with [11C] CH3I. The radiochemical yield calculated to end of bombardment (EOB) was 45-55% from [11C] CO2 with radiochemical purity of [11C-methyl] AIB exceeding 99%. Synthesis times from [11C] CO2 were about 55 min. Specific activities of 1 Ci/mumol were achieved on average. It has been shown that [11C-carboxyl] AIB is a useful imaging agent in patients with soft tissue cancers and melanoma, and it demonstrates tumor uptake in a spectrum of other animal tumor models. Because AIB is a nonmetabolized amino acid, [11C-methyl] AIB should be equally as useful. Either agent can be employed for the quantification of the A-type amino acid transport system in vivo with PET.