Experimental study of humidity effect on charge measurement of reference ionization chambers in clinical high-energy photon beams

PURPOSE

In the practice code of dosimetry, humidity effect is assumed to be constant as far as the measurements are performed in the relative humidity (RH) range of (20-80)%; thus, the humidity effect can be ignored with a dose uncertainty of 0.15%. This assumption is based on the previous experimental results by Niatel and Guiho. Rogers and Ross calculated the stopping power ratio of humid air and dry air for high-energy electron beams by using a Monte Carlo code. They demonstrate that the W value, the mean energy required to create an ion pair in air, is independent of the beam quality when the air is dry, and that the traditional humidity correction can be used also for high-energy photon and electron beams; however, this was only a computational study. In the present study, we measured the humidity correction of Farmer-type ionization chambers in high-energy photon beams and determined the W values of humid air using the calculated energy deposition of humid air with a Monte Carlo code. Furthermore, we proposed an analytical expression to determine a practical humidity correction for an ionization chamber as a function of absolute humidity.

METHOD

Experiments were carried out using a clinical linear accelerator (linac, Elekta Precise) at the National Metrology Institute of Japan (NMIJ). A shield box was constructed downstream of the linac and connected to an air processor, which maintained the temperature around 22°C and controlled the humidity in the range of (10-70)% inside the box. We prepared two Farmer-type ionization chambers: PTW 30013 and Exradin A19. Each ionization chamber was placed inside the box and irradiated with 6-, 10-, and 15-MV high-energy photon beams from the clinical linac. The energy deposition to the humid air inside the ionization chamber was calculated using the Electron Gamma Shower Version 5 (EGS5) code system.

RESULTS

Stabilization for the humidity of the ionization chamber was completed within 3 h. The polarity and ion recombination corrections did not show any change in the humidity range studied. The measured humidity correction and the evaluated W values of humid air in high-energy photon beams were in good agreement with those by Rogers in TG-21 and by Niatel in the range of RH (10-70)%.

CONCLUSION

Humidity correction of ionization chambers in high-energy photon beams from the clinical linac was determined experimentally. Using the analytical expression for the energy depositions by EGS5, the analytical expression for the W values was also derived.

High-dose nebulized budesonide is effective for mild asthma exacerbations in children under 3 years of age

Background. High-dose inhaled steroid therapy has been shown to be effective in children and adults with asthma exacerbations. However, few reports are available regarding its efficacy for asthma exacerbations in younger children. Objective. In this study, we administered high-dose nebulized budesonide therapy for mild asthma exacerbations in children < 3 years of age and compared its efficacy and safety with systemic steroid therapy. Methods. This study included children < 3 years old with mild asthma exacerbations. Patients were randomly assigned to two groups: the BIS group was given 1 mg of nebulized budesonide twice daily, and the PSL group received prednisolone 0.5 mg/kg iv three times daily. Days to disappearance of wheezing, days of steroid use, days of oxygen use, serum cortisol level, and incidence of adverse events during treatment were compared between the groups. Result. Wheezing disappeared after an average of five days, and steroids were administered for an average of five days in both groups, with no significant difference in days of oxygen use. Serum cortisol levels at initiation and during the course of treatment remained unchanged in the BIS group, and were decreased in the PSL group; however, the decrease in the latter group was not pathologic. Conclusion. For children < 3 years old with mild asthma exacerbations, high-dose nebulized budesonide therapy is equally as effective as systemic steroid therapy.

338 EFFECT OF OXYGEN CONCENTRATION ON NUCLEAR MATURATION, CUMULUS EXPANSION AND GLUTATHIONE LEVEL IN PORCINE OOCYTES DURING IN VITRO MATURATION

Contrary to experimental animals, it is well known that pig oocytes show low developmental competence after IVM, fertilization and culture despite of the attempts to improve the IVM technology. One of the reasons causing such low developmental ability of porcine oocytes seems to be the culture condition, especially the gas phase for IVM because there is a large differences in oxygen tension between in vitro and in vivo conditions. Indeed, our preliminary study revealed that oocytes matured in vivo had larger perivitelline space than oocytes matured in vitro, which could be affected by in vitro culture condition. The present study was conducted to evaluate the effect of oxygen tensions on nuclear maturation, cumulus expansion and glutathione synthesis of porcine oocytes during IVM. COCs at the germinal vesicle stage were collected from ovaries of prepubertal gilts and cultured in modified NCSU37 either under 2, 5, or 20% O2 for 44 h (Group 2%, Group 5%, and Group 20%, respectively). Five percent CO2 was used for all groups. After culture, the cumulus expansion was morphologically evaluated by classification to three grades (Grade 1: excellent [the length of expanded cumulus cells was longer than the diameter of the oocyte], Grade 2: good [the length of expanded cumulus cells was less than the diameter of oocyte], Grade 3: poor [oocyte having partial or single layer of expanded cumulus cells]). All experiments in this study were replicated more than 5 times. Data were analyzed by ANOVA and then shown as mean ± SD%. The rate of Grade 1 in Group 2% (16.8 ± 8.3%, 32/189) was significantly lower than those in Group 5% (68.2 ± 11.2%, 149/228) and Group 20% (78.6 ± 6.9%, 162/201) (P < 0.05). As for rates of Grade 2 and Grade 3, there were no significant differences between the groups. After evaluation of cumulus expansion, cumulus cells were removed and oocytes were stained by aceto-orcein for evaluation of nuclear maturation. The rates of metaphase II-stage oocytes were 41.0 ± 12.4% (86/210), 47.6 ± 20.5% (119/263) and 47.7 ± 12.9% (100/199) in Group 2%, Group 5%, and Group 20%, respectively. There were no significant differences among the groups. In order to clarify the effect of oxygen concentration on cytoplasmic maturation, COCs were cultured for 44 h and glutathione level of the oocytes was measured by 5,5′-dithio-bis-2-nitro-benzonic acid-glutathione disulfide reductase recycling method. Regardless the oxygen concentration, glutathione level was increased from the start of culture (6.2 ± 3.9 pmol/oocyte). But there were no significant differences in the glutathione level among groups. These results suggest that oxygen concentration during IVM could affect cumulus expansion but not nuclear maturation and cytoplasmic glutathione level in pig oocytes. This work was supported in part by the Promotion and Mutual Aid Corporation for Private Schools of Japan, Grant-in-Aid for Matching Fund Subsidy for Private Universities to J.I. and N.K.

94 VITRIFICATION OF WHOLE OVARIES IN YOUNG RATS

Cryopreservation of reproductive organs is an important technology for preservation of genetic resources of experimental, domestic, and wild animals. In addition, cryopreservation of the ovary could be applied to restore the fertility of young women diagnosed with cancer because it could not only provide future fertility, but could also decrease the emotional consequences of cancer therapy for women afflicted with such devastating diseases. Cryopreservation of whole ovary particularly would enable such females to be pregnant by natural mating after transplantation. The aim of the present study was to evaluate the possible of vitrification for young rat ovaries as a possible model for human ovaries using a Cryotop method. Whole ovaries were collected from 10-day-old female rats (Brown-Norway × Wistar) and then washed several times in PB1 medium containing 20% (v/v) fetal calf serum (FCS). The ovaries were submerged in equilibration solution [10% (v/v) dimethyl sulfoxide (DMSO), 10% (v/v) ethylene glycol (EG), and 20% (v/v) FCS in PB1] for 1, 3, 5 or 10 min and then vitrified in vitrification solution (20% DMSO, 20% EG, and 20% FCS in PB1) for 5 min, being plunged into liquid nitrogen on Cryotops. Vitrified ovaries were later warmed in 37°C in PB1 containing 1 M sucrose and 20% FCS for 5 min and then PB1 containing 0.5 M sucrose and 20% FCS for 5 min. Eight ovaries were embedded in paraffin and cut into 4 μm slices. The slices were stained by hematoxylin-eosin (HE) and integrity of nuclei and cytoplasm in the follicles was histologically evaluated. In each group, 3 ovaries were used for the staining of live/dead (Invitrogen LIVE/DEAD Viability/Cytotoxicity Kit for mammalian cells, #L3224). Follicles were separated from the ovary with enzyme and then classified into 2 categories by staining. Follicles possessing more than 50% of green-stained and red-stained granulosa cells were divided as live and dead, respectively. Data were analyzed by Tukey’s test. Results of the HE staining showed that integrity of nuclei and cytoplasm in ovaries equilibrated for 10 min (11%) was lower than those for 1 min (25%), 3min (42%), and 5 min (30%). As for evaluation by live/dead staining, most of follicles in ovaries equilibrated for 10 min (25%) were stained with red (dead). In vitrified ovaries equilibrated for 1 min, 3 min, and 5 min (18%, 16%, and 18%, respectively), there were no significant differences in red-stained follicles. These results suggest that optimal equilibration time is 3 to 5 min for vitrification of whole ovaries of 10-day-old rats. Using this equilibration time, we are now trying to evaluate the capability of vitrified/warmed ovaries after transplantation to recipient rats. The work was supported in part by Grant-in-Aid for Scientific Research from JSPS (KAKENHI) (21789253) to J. I. This work was also supported in part by the Promotion and Mutual Aid Corporation for Private Schools of Japan through a Grant-in-Aid for Matching Fund Subsidy for Private Universities to J.I. and N.K.

Maintained Salivary Function after Brachytherapy in Patients with Head and Neck Carcinomas - Evaluation Using Quantitative Salivary Gland Scintigraphy

The purpose of this study was to determine whether or not salivary gland dysfunction occurs within the first three months after brachytherapy in patients with head and neck carcinoma. Of the 20 patients with head and neck squamous cell carcinoma included in this study, 11 were treated with brachytherapy and the remaining 9 patients received external irradiation. All the patients underwent a salivary gland scintigraphy before and after radiotherapy. The scintigraphic parameters of each major salivary gland were then compared before and after the radiotherapy. In the brachytherapy group, none of the scintigraphic functional parameters showed a significant change before and after the radiotherapy. In contrast, all of the parameters with the exception of the uptake ratio (UR) of the submandibular glands significantly decreased after external irradiation. This observation was to be expected owing to the different irradiation doses administered by the two techniques. The scintigraphic technique used to evaluate salivary gland function should be used in future intensity-modulated radiation therapy salivary-gland-sparing studies in order to evaluate both the acute and chronic effects of irradiation in head and neck cancer patients.

273 REMOVAL OF ACROSOME FROM SPERM HEADS IMPROVES DEVELOPMENT OF RAT ZYGOTES THROUGH INTRACYTOPLASMIC SPERM INJECTION

In intracytoplasmic sperm injection (ICSI), sperm chromatin is introduced into the oocyte together with acrosome, which does not enter cytoplasm of oocytes during normal fertilization. In mice, acrosome of sperm head has a detrimental effect on embryonic development of the ICSI oocytes (Morozumi et al. 2006 Proc. Natl. Acad. Sci. USA 103, 17 661–17 666). We examined the effect of acrosome removal of frozen/thawed (F/T) rat sperm on development to term of the ICSI oocytes in order to improve production efficiency of live offspring from F/T rat spermatozoa through ICSI. In experiment 1, epididymal spermatozoa of the Wistar rats were frozen as described previously (Seita et al. 2005 Reprod. Fertil. Dev. 18, 256 abst). The F/T spermatozoa were sonicated to separate sperm heads. The sperm heads were divided into 3 treatment groups; nontreated sperm head (control), sperm heads exposed in 0.02% of Triton X-100 solution for 1 min (TX), sperm heads exposed in 0.02% lysolectin solution for 1 min (LL). Acrosomal status of the sperm heads was then examined by FITC-peanut agglutinin stain. In experiment 2, sperm heads of the control, TX, and LL treatments were microinjected into denuded oocytes obtained from superovulated females (Hirabayashi et al. 2002 Transgenic Res. 11, 221–228). The ICSI oocytes were cultured and observed for the formation of pronuclei (2PN) for 6 h and blastocyst formation at 120 h of culture. In experiment 3, the ICSI oocytes cultured for 6 h were transferred to recipient females to examine development to term. Statistical analyses of the results were carried out by 1-way ANOVA. In experiment 1, the TX (76%) and LL (89%) treatments showed higher rates of acrosome removal than that of the control (24%) group (P < 0.05). In experiment 2, the percentage of 2PN formation at 6 h after ICSI was not significantly different among sperm-treated groups, although the TX (76%) and LL (70%) groups were higher than the control (24%) group at 4 h (P < 0.05). The percentages of blastocyst formation were not significantly different among sperm-treated groups (control: 10%; TX: 25%; and LL: 25%). In experiment 3, the efficiency of development to term of the TX treatment group (21%: 12/57) was significantly higher than the control (5%: 3/55; P < 0.05), although the LL treatment group (16%: 12/75) was not significantly different from the control and TX treatment groups. These results indicate that acrosome removal using TX of F/T rat sperm heads before ICSI improves development to term of the ICSI oocytes. This benefical effect of acrosome removal may be due to the quick release of sperm-activating factors from sperm heads after ICSI in the rat.

79 DEVELOPMENT TO TERM OF RAT ZYGOTES DERIVED FROM CRYOPRESERVED MATURE OOCYTES AND SPERM THROUGH INTRACYTOPLASMIC SPERM INJECTION

The rat, as well as the mouse, is one of the most valuable experimental animals for biomedical and physiological research. There are numerous valuable mutant rats including transgenetic strains. Cryopreservation of rat oocytes and sperm as haploid germ cells is a key technology for banking the genetic resources efficiently. The aim of the present study was to examine survival of vitrified/warmed oocytes and developmental competence of resultant zygotes in the rat. Rats used in the present study were all Wistar rats. Epididymal spermatozoa were frozen as described previously (Seita et al. 2005 Reprod. Fertil. Dev. 18, 256). After thawing, spermatozoa were sonicated to obtain sperm heads for intracytoplasmic sperm injection (ICSI). Oocytes were collected from immature females superovulated with eCG and hCG. Oocytes were equilibrated in 7.5% (v/v) ethylene glycol (EG) + 7.5% (v/v) dimethylsulfoxide (DMSO) + 20% (v/v) FCS in PB1 for 5 min and then transferred into 15.0% EG (v/v) + 15.0% DMSO (v/v) + 20% FCS + 0.5 m sucrose in PB1 (vitrification solution) for 1 min at room temperature (22–24�C). During exposure to the vitrification solution, oocytes were loaded on a Cryotop� (Kitazato Supply Co., Tokyo, Japan). At warming, the film of Cryotop was directly immersed into PB1 containing 0.5 m sucrose and 20% FCS at 37.5�C. The warmed oocytes were washed three times and put into a HEPES-buffered (22 mm) modified R1ECM (310 mOsm) medium. The sperm heads were microinjected intracytoplasmically into the warmed oocytes. Then, presumptive zygotes were transferred surgically into the oviducts of recipient females (Day 0), and Caesarean section of the recipients was performed on Day 22. After vitrification and warming, 245 of 275 (88%) oocytes survived morphologically, 240 of the warmed oocytes were injected, and 156 oocytes (65%) were morphologically normal after the injection. To confirm development to term of zygotes derived from cryopreserved oocytes and sperm, 143 injected oocytes were transferred to 9 recipients, resulting in 3 pregnancies and the generation of one live pup. The results indicate that rat zygotes derived from cryopreserved oocytes and sperm through ICSI can develop to term, and full developmental competence can be preserved in rat oocytes after cryopreservation.

Salivary gland scintigraphy in gastro-esophageal reflux disease

Gastro-esophageal reflux disease (GERD) is associated with a decreased salivary flow as well as gastric acid production. This study therefore aimed to investigate functional disorders of salivary glands in patients with GERD.

METHODS

Thirty-one consecutive patients with GERD underwent salivary gland scintigraphy.

RESULTS

If the results defined the optimal cutoff point for determining the decreased salivary secretion as 51 % in parotid glands and 36 % in submandibular glands, a decreased salivary secretion of right parotid gland, left parotid gland, right submandibular gland, and left submandibular gland was found in 39 %, 32 %, 36 %, and 58 %, respectively. Overall, salivary function disorder of at least one major salivary gland was found in 24 patients (78 %) with GERD. There was no difference in the incidence of impaired salivary function between GERD patients with and without erosive esophagitis. Salivary gland function was more frequently diminished than expected in GERD. We concluded that the presence of impaired salivary gland function was considered to be one of risk factors for developing GERD symptoms.

[New method of estimating effective energy for X-ray CT scanners]

Because the exposure dose in X-ray computed tomography examinations is sometimes difficult to determine, it is important to be able to estimate the dose for these examinations. The effective energy of the X-ray CT scanner is required to estimate exposure dose. Although the half-value-layer (HVL) method has been used to calculate effective energy, it is not an easy method. This paper proposes a technique by which effective energy can be easily calculated. Certain details were found to cause change in effective energy, and the ratio (inner-metal center-air ratio: IMCAR) between air dose and dose in fixing the metallic pipe in the isocenter of an X-ray CT scanner was necessary. The IMCAR from a different X-ray CT scanner was required, and, when effective energy was calculated, it showed an error of less than 0.7% for the half-value-layer method. The effect of this error on dose estimation was slight (0.4%). This technique is useful, because effective energy can easily be calculated with a high degree of accuracy.

Experimental evaluation of conversion factors, N(D,w)/N(X), for Roos-type and Advanced-Markus-type plane-parallel ionization chambers

A Japanese code of practice for clinical dosimetry, titled "Standard Dosimetry of Absorbed Dose in External Beam Radiotherapy" was published by the Japan Society of Medical Physics (JSMP) in 2002. It mostly followed IAEA Technical Reports Series No. 398, which was based on N(D,w), i.e., the calibration factor in terms of absorbed dose to water for a dosimeter. The Japanese primary standard dosimetry laboratory, however, has not supplied N(D,w) but N(X), as the calibration factor in terms of exposure. The unique feature of the Japanese code was provision of a data table of calculated conversion factors, N(D,w) / N(X) values, for many types of ionization chambers, excluding new plane-parallel ionization chambers. This paper describes the experimental evaluation of the conversion factors for the new plane-parallel ionization chambers, such as the Roos-type and Advanced Markus chambers. The obtained N(D,w) / N(X) values for PTW 34001, Wellhöfer PPC 40 and PTW 34045 were 37.96 +/- 0.19, 37.85 +/- 0.36 and 37.90 +/- 0.26 (Gy/C kg(-1)), respectively. They agreed with estimations based on Monte Carlo calculations.

Determination of the depth of 50% of maximum ionization, I50, for electron beams by the divided difference method

A new characterization of depth-ionization parameters for electron beams is empirically deduced from our data analysis based on the divided difference method (the DD method), which employs the numerical differential of an ionization curve. The important feature of the present method is that it does not necessarily require normalized percent depth-ionization (NPDI) data. The depth of 50% of maximum ionization, I50, which is an important parameter for electron beam dosimetry, can be deduced from the analysis of an unnormalized (or partial) depth-ionization (UDI) curve obtained over a short interval of depth. The values of I50 determined by the DD method are in agreement to within 0.1 mm for energies of 4, 6, and 9 MeV, compared with the ones determined by the TG-51 protocol method (or the conventional method), and the difference was 0.9 mm for 12 and 15 MeV. The dose at the reference depth, dref, calculated from I50 by the DD method, is found to be in agreement with TG-51 to within 0.1%. The field size dependence of the DD method using UDI data was studied for three field sizes: 6 x 6, 10 x 10, and 20 x 20 cm2. For all energies, the discrepancies of I50 as determined by both methods were 0.9 mm on average for the 6 x 6 cm2 fields and 0.6 mm for the other two field sizes. This dependence was remarkable for 6 x 6 cm2 fields for 12 and 15 MeV, and the discrepancies shown by the DD method were 1.2 mm for 12 MeV and 1.8 mm for 15 MeV, respectively. Since the reference field size in clinical dosimetry is usually 10 x 10 cm2, this dependence will not affect clinical dosimetry. The DD method could be an alternative option for checking beam quality in dose calibration.

Maintained salivary function after brachytherapy in patients with head and neck carcinomas--evaluation using quantitative salivary gland scintigraphy

The purpose of this study was to determine whether or not salivary gland dysfunction occurs within the first three months after brachytherapy in patients with head and neck carcinoma. Of the 20 patients with head and neck squamous cell carcinoma included in this study, 11 were treated with brachytherapy and the remaining 9 patients received external irradiation. All the patients underwent a salivary gland scintigraphy before and after radiotherapy. The scintigraphic parameters of each major salivary gland were then compared before and after the radiotherapy. In the brachytherapy group, none of the scintigraphic functional parameters showed a significant change before and after the radiotherapy. In contrast, all of the parameters with the exception of the uptake ratio (UR) of the submandibular glands significantly decreased after external irradiation. This observation was to be expected owing to the different irradiation doses administered by the two techniques. The scintigraphic technique used to evaluate salivary gland function should be used in future intensity-modulated radiation therapy salivary-gland-sparing studies in order to evaluate both the acute and chronic effects of irradiation in head and neck cancer patients.

[Comparative evaluation of absorbed dose and image quality in X-ray head CT scanning for hospital facilities in Gunma.]

Recently, the number of scans for X-ray computed tomography (CT) examinations has been rising due to the wide-spread use of multi-slice CT (MSCT) scanners. There is a concern that the total medical exposures will be increased by these examinations. In order to lower exposures, routine parameters for head CT examinations done at several hospitals in Gunma were investigated. In this study, the computed tomography dose index (CTDI(100, C)), noise, and low contrast resolution were measured. The CTDI(100, C) for all the hospitals exceeded the guideline (40mGy) suggested by the Japan Association of Radiological Technologists (JART). Low contrast resolution showed the coefficient of variation of +/-5% between hospitals. In conclusion, it was proposed that the technologists should reconsider the parameters of the head X-ray CTs, in cases where their output dose far exceeds the standard.

[A monitor unit verification calculation independent on RTP systems and output factor]

In order to confirm quality assurance and quality control in radiation therapy, it is common to perform a monitor unit verification calculation independent on RTP system. Generally, this verification calculation is often to perform at manual calculation level separately from RTP system. Characteristics of output factors included in this calculation were explained on the basis of the situation in the world. Khan et al. had proposed the concept of collimator scatter factor and phantom scatter factor. The validity of these factors was addressed in of role played in dose monitor unit calculation. If we will utilize SMR, which was derived from zero-area phantom scatter factor, and zero-area TMR in dosimetry, a simple and accurate Clarkson integration is possible. These scatter factors and Clarkson integration is able to use not only for monitor unit calculation in a simple treatment technique, but also in an excellent technique as IMRT. These factors had been also used in the convolution method to improve an accuracy of dose calculation. These factors are not family in Japan, but it is expected to be got an agreement of the usage in future.

Inhalation of nebulized nitroglycerin in dogs with experimental pulmonary hypertension induced by U46619

BACKGROUND

Pulmonary hypertension (PH) causes mortality in some congenital and acquired heart and lung diseases. However, inhalation of NO gas requires complicated and expensive instruments and elaborate preparations to avoid toxic gas administration. We tested the effectiveness and safety of inhaled nebulized nitroglycerin (Neb-NTG) in dogs with experimental PH.

METHODS

Experimental PH was induced by continuous infusion of a thromboxane analog (U46619). The U46619 infusion rate was adjusted to maintain a systolic pulmonary artery pressure (PAP) at 40 mmHg in 10 anesthetized and mechanically ventilated dogs. Then, 20 micrograms/kg of NTG liquid nebulized by compressed air was inhaled.

RESULTS

After infusion of U46619, the systolic, diastolic and mean PAP increased by 119%, 228% and 169%, respectively, and the systolic, diastolic and mean systemic arterial pressures (SAP) increased by 19%, 29% and 23%, respectively. The systolic pulmonary to systemic pressure ratio (Pp/Ps) and mean Pp/Ps increased by 83% and 113%, respectively, and the pulmonary vascular resistance (PVR), systemic vascular resistance (SVR) and pulmonary to systemic resistance ratio (Rp/Rs) increased by 341%, 100% and 145%, respectively. After inhalation of Neb-NTG in dogs with experimental PH, systolic, diastolic and mean PAP and PVR decreased by 25 +/- 4, 26 +/- 11, 25 +/- 9 and 31 +/- 21%, respectively. There were no significant changes in systolic, diastolic and mean SAP, SVR, cardiac output and plasma methemoglobin concentrations. The systolic and mean Pp/Ps decreased by 18 +/- 7 and 20 +/- 7%, respectively. The Rp/Rs decreased by 25 +/- 13%.

CONCLUSIONS

The results of this study demonstrate that Neb-NTG is an effective and selective pulmonary vasodilator and may offer a new therapeutic option for PH.

Successful interstitial treatment for bilateral tongue cancer

We report three cases of bilateral tongue cancer who received interstitial brachytherapy successively for each tumour. Tumour control following treatment are as good as that for unilateral tongue cancer and there have been no severe complications in, or around, the tumour area after using a mandibular protective spacer and dose reduction for the second treatment.

Factors affecting mandibular complications in low dose rate brachytherapy for oral tongue carcinoma with special reference to spacer

PURPOSE

To evaluate the efficacy of a spacer in the prevention of mandibular complications in low dose rate (LDR) brachytherapy (BRT) for oral tongue carcinoma.

METHODS AND MATERIALS

A retrospective analysis was conducted using 103 patients with T1 or T2 tongue carcinoma treated by a single plane implantation of iridium (192Ir) pins between 1979-1994. Of these patients, 60 were treated by BRT alone, and the rest were combined with external irradiation (Ext) and/or chemotherapy (CHT). Forty-eight and 55 patients were given BRT with and without a spacer, respectively. Spacers were individually made of acrylic resin according to a prosthetic technique so as to obtain the thickness of 7-10 mm at the lingual part of the implanted side. Variables, including a spacer, which may be associated with the development of osteoradionecrosis (ORN) of the mandible, were analyzed by the Cox proportional hazards regression analysis.

RESULTS

Our spacer reduced about 50% of the absorbed dose at the lingual side surface of the lower gingiva (LSG) to that in the absence of a spacer. Absolute incidence of ORN was 2.1% (1 of 48) and 40.0% (22 of 55), with and without a spacer, respectively, and the difference was statistically significant by univariate analysis (p = 0.0004). It was revealed by the Cox analysis that the spacer (p = 0.0247), combined CHT (p = 0.0295), and combined Ext (p = 0.0279) were significant independent factors associated with the development of ORN. The spacer was shown to be a significant factor by univariate analysis (p = 0.0037), but not by multivariate analysis when analysis was restricted to the patients who did not receive CHT. The absorbed dose, dose rate, and biological effective dose (BED) reflecting early or late response were estimated at the LSG, and prognosticators associated with the incidence of ORN were also determined by the Cox analysis. Particularly, BED for late response by BRT, the total absorbed dose, and any BED by Ext plus BRT were highly significant factors in the whole population. Essentially similar results were obtained in the patients without receiving CHT.

CONCLUSIONS

It was clarified that our spacer effectively prevents mandibular complications in LDR BRT by 192Ir for oral tongue carcinoma. Furthermore, introduction of a spacer provided novel information concerning the development of ORN, where BED particularly for late response given by BRT, the total absorbed dose, and any BED by Ext plus BRT could be good prognostic factors only when estimated at the LSG.

External and interstitial radiotherapy in the treatment of oropharyngeal squamous cell carcinoma

The records of 165 patients with squamous cell carcinoma of the oropharynx treated at our hospital with external and/or interstitial radiotherapy between 1971 and 1990 were reviewed to evaluate the treatment results, focusing on primary control and complications. All cancers were restaged according to the UICC 1987 TNM staging system. Of these 165 patients, 11% were in Stage I, 55% in Stage II, 24% in Stage III and 8.5% in Stage IV. Local control and complications were analysed in 140 patients. The remaining 25 patients died of intercurrent or metastatic disease during the first 2 years following treatment and were excluded from the analysis. 70 patients were treated by interstitial implant using permanent implant seeds (Rn-222 in eight patients, Au-198 in 62 patients) with or without external radiation. 56 other patients received external irradiation alone and another 14 patients received pre-operative external irradiation plus surgery. 2-year recurrence-free rates were 73% (100% for T1, 76% for T2, 36% for T3 tumours) in the patients who received interstitial implant with or without external radiation and 36% (67% for T1, 48% for T2, 13% for T3 tumours) in the patients treated by external irradiation alone. The incidence of soft-tissue or bone complications requiring long-term treatment was 14%. Based on these findings, it is believed that an interstitial implant using Au-198 grains combined with external beam irradiation is a useful treatment modality for small lesions of the oropharynx.

Squamous cell carcinoma of the maxillary sinus and the oral part of the upper jaw. Comparison of treatment results

The treatment results were compared in 77 patients with maxillary sinus squamous cell carcinoma (MC) and 53 patients with squamous cell carcinoma arising from the oral part of the upper jaw (OC). Both sets of patients received radiotherapy alone, or radiotherapy combined with surgery and/or chemotherapy. Computerized tomography was useful for the definition of the treatment volume. Intraarterial chemotherapy was given in 89 of 130 patients and in these patients the total radiation dose was reduced by about 10 Gy. No difference was found in the 5-year survival rate between the MC (65%) and the OC (66%) groups. The cumulative incidence of local failure was higher in MC (36%) than in OC (26%), whereas the ultimate incidence of neck node metastasis was higher in OC (43%) than in MC patients (18%). Half of the inoperable patients (9/18) were older than 80 years and had contraindications to anaesthesia and major surgery. The local recurrence rate was high in the inoperable MC patients (6/8). Contralateral sinus cancers occurred in 4 patients in the MC group.

Brachytherapy for stage I & II oral tongue cancer: an analysis of past cases focusing on control and complications

An analysis of the therapy used for 370 tongue cancer patients has been made, said patients having been treated by interstitial irradiation alone or by combined external irradiation and brachytherapy (Stage I:90 cases, IIa: 196 cases; and IIb: 84 cases). The neck was followed by close follow-up (304 cases), treated by elective neck irradiation (56 cases), or underwent operation at the time of local recurrence (10 cases). The results have shown that the 5-year survivals for Stages I, IIa, and IIb were 84%, 78%, and 72%, respectively. further, the 5-year primary control was 85% for tumors of the superficial type, 79% for tumors of the exophytic type, and 45% for tumors of the infiltrative type (p < 0.004). In non-electively irradiated patients, a neck metastasis occurred in 31% in Stage I, 41% in Stage IIa, and 51% in Stage IIb. Finally, 110 patients incurred radiation-induced complications (110/291 = 38%) and 11 patients (11/291 = 4%) required a surgical procedure. Brachytherapy for tongue cancer achieved results that are comparable with surgery. The analysis also revealed that the introduction of computer dosimetry and the use of a spacer (a dental guard) in brachytherapy have achieved superior results in the management of a tongue cancer.

Brachytherapy for non-metastatic squamous cell carcinoma of the buccal mucosa. An analysis of forty-five cases treated with permanent implants

An analysis has been undertaken of 45 patients with non-metastatic squamous cell carcinoma of the buccal mucosa treated by permanent 198Au or 222Rn implants and in most cases supplementary external irradiation. Eight patients had T1, 30 had T2, and 7 T3 disease. Of the lesions 21 were located in the buccal mucosal surface, 14 in the retromolar region, and 10 in the bucco-alveolar sulci. Seven of the 45 (16%) died of the disease and the actuarial 5-year survival rate was 81%. No obvious differences were noted in survival rate between different stages of the disease or between different subsites of the primary lesion. There were 6 local recurrences occurring from 3 to 33 months after treatment, and only one of these was salvageable by further radiation therapy. Neck node metastasis occurred in 11 cases from 2 to 34 months after treatment, and 8 of these cases responded successfully to a radical neck dissection or radiotherapy.

The efficacy of radiation therapy for a malignant melanoma in the mucosa of the upper jaw: an analytic study

An analysis has been made of the effect of radiation therapy in 28 patients with a malignant melanoma (Stage I: 18 cases; Stage II: 10 cases) in the mucosa of the upper jaw. Treatment had been provided by one of the following methods: intraoral mold (10 cases), interstitial brachytherapy (two cases), intraoral electron therapy (nine cases), or external irradiation (seven cases). The results have shown that the survival rate for all 28 patients was 25%, and that the survival rate for stage I patients treated by intraoral electron or brachytherapy was 47%. The primary tumor control rate in percentages was 79% (22/28) in all 28 radiotherapy patients; 92% (11/12) for tumors treated by a mold or an interstitial implant; 67% (6/9) for tumors treated by an intraoral cone; and 71% (5/7) for tumors treated by external irradiation with or without surgery. A neck metastasis that was found in 19 patients was treated by surgery, radiotherapy, and/or immunochemotherapy, and the result was successful in nine patients. The major factor in the failure of treatment was a distant, metastatic dissemination. This analysis revealed that radiotherapy has achieved similar or better results than surgery and may be advocated for the management of a localized malignant melanoma in the mucosa of the upper jaw.

Causes of oral tongue cancer treatment failures. Analysis of autopsy cases

Eighty-three autopsy cases of squamous cell carcinoma of the oral tongue were reviewed to identify retrospectively the causes of treatment failure. The cure rate for the primary cancers at autopsy was 48.2% (40 of 83). Regional lymph node metastases were found in 71.1% (59 of 83). Regional metastases and/or juxtaprimary recurrence frequently spread continuously and diffusely, forming bulky neck tumors in 38.6% (32 of 83). The incidence of distant lymph node metastasis (below the clavicle) and hematogenous metastasis was 35.4% (29 of 82) and 58.5% (48 of 82), respectively. The lung was the most common site of hematogenous metastases (52.4%, 43 of 82). Hematogenous metastasis occurred more frequently in the younger age group (less than 40 years of age; P = 0.03). Distant lymph node metastases were identified in the lung hilar, bifurcation, and paratracheal nodes in 89.7% (26 of 29) and had a statistically significant association with lung hematogenous metastasis. Univariate analysis revealed that gross appearance, tumor stage, clinical stage, presence of cervical lymph node metastasis, and interval from N0 to NX were significant predictors of survival time (duration from initial treatment to death). Rupture of the neck vessels was fatal in eight patients (9.6%), and hypercalcemia was seen in six (7.2%). Pulmonary infection was the direct cause of death in 33.7% of patients (28 of 83). Secondary malignant lesions occurred in 22.9% (19 of 83).

Usefulness of 198Au grain implants in the treatment of oral and oropharyngeal cancer

A series of 177 patients with squamous cell carcinoma of the oral cavity and oropharynx were treated with 198Au grain (gold grain) implants. Sites of the lesion included the tongue, mouth floor, buccal mucosa and oropharynx, especially the soft palate and faucial arch. Three-fourths of the patients were treated in combination with prior external beam irradiation. A permanent implant dose (total decay) of 80-90 Gy was given in the form of gold grains alone and in combination with an external dose of no more than 30 Gy, and 60-70 Gy, total decay, was given after an external dose greater than 30 Gy. The 2-year recurrence-free rate was 86.2% in the case of T1N0, 72.6% in T2N0 and 72.2% in T3N0. The difference in the results of implant therapy alone and combined therapy was not significant. Late complications were minimal after grain implantation alone, and when used in combination, less than 70 mCi of grain activity after a 40 Gy external dose did not seem to be a serious hazard with respect to bone damage except in the case of cancer of the mouth floor. Gold grain implants were useful and easily applied under local anesthesia to early or superficial lesions at sites where a rigid linear source could not be used. Exposure of the radiology staff was only 5-10 mrad in the case of the usual 10-15 (50-75 mCi) implant grains.

Chromosome aberration frequencies produced by a 70-MeV proton beam

The effectiveness of a 70-MeV proton beam in the induction of chromosome aberrations was studied. We employed peripheral lymphocytes and analyzed the frequencies of dicentrics and rings after irradiation at doses ranging from 0.1 to 8.0 Gy at various depths within a Lucite phantom. The frequency of chromosome aberrations after irradiation with an unmodulated proton beam at 5 mm showed a dose-response relationship similar to that of 60Co gamma rays. However, irradiation at greater depths with the spread-out Bragg peak induced higher aberration frequencies at doses lower than those with gamma rays. Furthermore, the distribution curve of chromosome aberration frequencies as a function of depth was found to be slightly different from the physically measured depth-dose curve. With the spread-out Bragg peak the biological effects were more marked at greater depths, resulting in a distribution of relative biological effectiveness values. The results obtained from chromosome aberration analysis may not be related directly to those for the relationship between dose and cell killing. Slight differences in values for relative biological effectiveness due to the change of dose and site of proton beam irradiation may not be important for practical proton beam therapy, but may be important in the prevention of late radiation injuries.

Prognostic factors in head and neck non-Hodgkin's lymphoma with special reference to serum lactic dehydrogenase and serum copper

An analysis of prognostic variables was performed in a retrospective study of 121 patients with Ann Arbor stage I-II head and neck non-Hodgkin's lymphoma admitted from 1973 to 1988. The overall actuarial 5-year survival rate was 58.8% and the minimum follow-up 15 months. Nine clinical and laboratory parameters were studied, including serum lactic dehydrogenase (LDH) and serum copper (SCL), and subjected to univariate and multivariate analyses. In univariate analysis, histology and LDH were found to be significant prognostic variables. Evaluation by Cox's multivariate proportional hazard model revealed histology, SCL and sex to be of prognostic significance.

Lectin binding in tissues from hydatidiform mole, invasive mole and choriocarcinoma to concanavalin-A, wheat germ agglutinin and peanut agglutinin

A light microscopic analysis of lectin receptors in normal placenta and trophoblastic disease was performed utilizing biotinylated Concanavalin-A (Con-A), wheat germ agglutinin (WGA), and peanut agglutinin (PNA), in conjunction with an avidin-biotin peroxidase complex. Hydatidiform mole, invasive mole and choriocarcinoma exhibited increased receptors to Con-A and WGA compared to normal placenta. Increased reactivity to Con-A and WGA was associated merely with increased growth and proliferation of trophoblasts rather than a malignant transformation. Normal placenta, partial and complete mole generally showed moderate to strong binding with PNA after neuraminidase treatment, while invasive mole and choriocarcinoma (11 of 15 cases) generally showed minimal to absent reaction with PNA. Heterogeneity of PNA binding in choriocarcinoma was manifested by the presence of PNA reactivity in the trophoblast membrane in 2 cases wherein no prior neuraminidase treatment was given. This suggests that in some malignant trophoblasts, there is absence of sialic acid in the terminal cell surface carbohydrate groups resulting in the exposure of N-acetylgalactoseamine.

Discriminant analysis on the treatment results of interstitial radium tongue implants

Discriminant analysis was carried out for 48 tongue cancer patients who were treated with radium single-plane implantation. The 48 patients were grouped into 32 successfully cured without complications, five successfully cured with complications, six successfully cured but requiring additional boost therapy and five with local recurrence. To evaluate the relation between the dose distribution and the local treatment results, the analysis was based on a volume-dose relationship. The functions introduced by this discriminant analysis were linear, and the parameters used were modal dose, average dose and shape factors of histograms. Each group of treatment results had a correction rate of greater than 80%, except for the successfully cured group with ulcers. The discriminant functions were useful as an index to obtain a final clinical treatment result at the early time of implantation, and these functions could be used as a criterion for the optimal treatment of tongue carcinoma. We were also able to recognize the limitation of the actual arrangement of sources in the single-plane implant.

[A study on the role of DNA methylation within hCG and hPL genes in trophoblastic disease]

It has been shown that the extent of methylation of cytocine in DNA is inversely correlated with gene expression in many cases. The DNAs extracted from placental tissue, hydatidiform mole and choriocarcinoma tissue were examined to see whether the extent of cytocine methylation is correlated to the gene expression of placental peptide hormones and the transformation of trophoblast. First of all we measured the amount of methylated cytocine per total DNA with HPLC. We then examined cytocine methylation in hCG alpha,beta and hPL genes using methylation sensitive (Hha I, Hpa II) and non sensitive (Msp I) restriction enzymes and molecular hybridization. During pregnancy the total amount of methylated cytocine measured with HPLC increases gradually from 0.72 mol.% at first trimester to 0.92 mol.% at term. The DNA of WBC showed a higher level of methylated cytocine than placental DNA. The extent of DNA methylation in the peptide hormone genes increases during placental development. Hypomethylation in the hCG alpha gene was also seen in molar tissue which expresses a high amount of hCG. Therefore it is inversely correlated that gene expression of hCG alpha,beta and the extent of DNA cytocine methylation. Furthermore some restriction polymorphisms were observed with Msp I in hCG alpha and hPL genes which might be related to malignant transformation of the trophoblast.

[Selective augmentation of cellular hCG alpha mRNA levels and immunoreactive hCG alpha secretion by 17 beta-estradiol in the normal placenta]

In order to elucidate a possible self-regulation for hCG synthesis in placenta, effects of estradiol on hCG production and secretion were evaluated by culturing early placental tissue in the presence or absence of estradiol. The cellular level of mRNAs encoding hCG (alpha, beta) and hPL were estimated by mean grain count per syncytial nucleus on the placental sections hybridized in situ with labeled cDNA probes corresponding to these mRNAs. Immunoreactive hCG, hCG alpha and hPL in the media and explanted tissues were measured by the homologous RIAs. Addition of estradiol at concentration of 1 approximately 10 ng/ml into the medium caused an increase in the cellular levels of hCG alpha mRNA after 24-hour cultured, and exhibited significant increases in immunoreactive hCG alpha levels in the media and explanted tissues after 72-hour culture. The addition of estradiol neither affected the cellular levels of mRNA encoding hCG beta and hPL nor immunoreactive hCG and hPL levels in the media and tissues. The appropriated concentration of estradiol (1 approximately 10 ng/ml) used in above experiments was found to be similar to the tissue concentration in normal placenta. These findings suggest that the physiological concentration of estradiol selectively stimulates hCG alpha synthesis and secretion by normal placenta. Thus, estradiol in placenta may be a factor responsible for the increase of hCG alpha in maternal serum and placental tissue with the progress of gestation.

A comparative study of dose distribution of a high-energy electron beam and chromosome aberration frequencies

Electron beam therapy is usually employed for the treatment of tumours located at or near the surface of the body, because the electron beam gives a high dose near the surface, but falls off rapidly with increasing depth beyond the level of the 80% depth dose. Isodose curves for radiotherapy have been obtained using physical methods, but have rarely been investigated on the basis of living human cells. In the present study, lymphocyte chromosome analysis was employed as a biological dosemeter for comparison with the isodose curve measured physically. The peripheral blood was exposed to a 14 MeV electron beam in a plastic tube set in a specially made test-tube stand immersed in a water tank. The chromosome aberration frequencies induced by irradiation of about 95% of peak dose at a depth of 31 mm were found to be higher in value than those induced at a depth of 17 mm where the peak dose had been determined physically. Three gray of irradiation given to whole blood in the presence of contrast medium gave rise to a slight enhancement of radiation-induced chromosome aberration frequencies in the lymphocytes exposed at a depth of 17 mm, but a slight decrease at 31 mm.

Differential modulation of chorionic gonadotropin (CG) subunit messenger ribonucleic acid levels and CG secretion by progesterone in normal placenta and choriocarcinoma cultured in vitro

The ability of progesterone to modulate the production and secretion of human CG (hCG) in both normal placenta and choriocarcinoma was compared by culturing explants of each trophoblastic tissue in the presence or absence of progesterone. The cellular level of messenger RNAs (mRNAs) encoding hCG alpha, hCG beta, and human placental lactogen (hPL) were quantitatively estimated by mean grain count per syncytial nucleus on the tissue sections hybridized in situ with labeled complementary DNA probes corresponding to these mRNAs. Immunoreactive hCG, hCG alpha, and hCG beta in the media and explanted tissues were measured by the homologous RIAs, and hPL was assayed by hPL-RIA kit. Addition of progesterone at concentrations of 5-20 micrograms/ml into the culture of normal early placenta caused a decrease in the cellular levels of hCG alpha mRNA and hCG beta mRNA after a 24-h culture, and exhibited a decline in immunoreactive hCG and hCG alpha levels released into the media together with a decrease in immunoreactive hCG alpha and hCG beta levels in the explanted tissues after a 48-h culture. The addition of progesterone neither affected the cellular levels of hPL mRNA nor immunoreactive hPL levels in the media and tissues. On the other hand, addition of 17 beta-estradiol at concentrations similar to those used with progesterone did not alter the levels of immunoreactive hCG and hCG alpha in the media or explanted placental tissues, while lower concentrations (1-10 ng/ml) of 17 beta-estradiol caused an increase in immunoreactive hCG alpha levels in the media and cultured tissues. These findings suggest that the suppressive effect observed with progesterone is not likely to be a toxic effect of steroid, but is rather selective on hCG production and secretion by normal placenta. Thus, progesterone may be a factor responsible for the inhibitory regulation of hCG production and secretion by normal placenta. However, in contrast to normal placenta, the choriocarcinoma culture in vitro did not respond to progesterone. The steroid was without significant effect on the cellular levels of hCG alpha mRNA and hCG beta mRNA, and on the levels of immunoreactive hCG and hCG alpha in the media and explanted tissues. These results suggest that the inhibitory regulation of hCG production and secretion in choriocarcinoma is different from that in normal early placenta.

[Selective inhibition of synthesis and secretion of hCG by progesterone and its correlation with hCG (alpha, beta) mRNA levels]

In order to elucidate the inhibitory regulation of hCG synthesis, the dynamics of the synthesis and secretion of hCG was investigated by culturing explants of trophoblastic tissues from early placenta and choriocarcinoma in the presence and absence of progesterone, and these results were then compared to those of hPL. The dynamics of mRNAs encoding hCG (alpha, beta) and hPL was assessed by grain counts in the tissue sections hybridized in situ with labelled cDNA probes corresponding to these mRNAs. In the control culture of early placenta, hCG, hCG alpha and hPL in the medium showed marked increases compared to the initial tissue levels, whereas hCG, hCG alpha and immunoreactive hCG beta in the tissue explants remained constant. Progesterone suppressed the secretion of hCG and hCG alpha by placental tissue after 48-hour culture in a dose-response manner and simultaneously decreased the tissue level of immunoreactive hCG beta. However, neither hPL secretion nor hPL tissue level were decreased by progesterone. The in situ hybridization revealed that grain counts for hCG alpha-mRNA and hCG beta-mRNA in the sections prepared from placenta cultured with progesterone were decreased compared to those prepared without progesterone, whereas grain counts for hPL-mRNA remained unchanged. In culture of explants from chorio-carcinoma, no inhibition of synthesis and secretion of hCG by progesterone was found. From these results it will be concluded that progesterone inhibits hCG synthesis through the inhibition of hCG alpha-mRNA and hCG beta-mRNA accumulation and that regulation of hCG synthesis in choriocarcinoma is different from that in the normal placenta.

Tumor-associated antigen, TA-4, in the monitoring of the effects of therapy for squamous cell carcinoma of the uterine cervix. Serial determinations and tissue localization

The level of tumor-associated antigen (TA-4) was determined in the serum and tumor tissue of patients with squamous cell carcinoma of the cervix by radioimmunoassay and immunoperoxidase techniques. Using an arbitrary limit of 2.5 ng/ml of serum, positive values were observed in 5.5% of healthy controls and 53.6% of patients with cervical squamous carcinoma. The mean value and incidence of elevation of serum TA-4 increased significantly with advancing disease stage. There was, however, no significant increase in serum TA-4 in the early stages of disease. Elevated TA-4 in serum rapidly fell to normal within 72 hours after radical surgery, but remained elevated if complete excision could not be performed. In case of radiotherapy, TA-4 levels in serum and tumor tissue often increased during the administration of the initial 2000 rad, and subsequently declined after the administration of a total of more than 4000 rad. The decline of serum TA-4 to normal observed during radiotherapy was found to be closely correlated with the disappearance of viable cancer cells in histopathologic specimens from the cervix. Immunohistochemical TA-4 staining was present in large cell nonkeratinizing carcinoma, but not in small cell nonkeratinizing carcinoma. These results indicate that the expression of TA-4 antigen in cervical squamous carcinoma is related to differentiation of the tumor cells and that serum TA-4 determination, despite its limitation for early diagnosis, provides a potential means for monitoring the effects of individual therapy for cervical squamous cell carcinoma.

Linkage of human chorionic gonadotrophin and placental lactogen biosynthesis to trophoblast differentiation and tumorigenesis

Normal trophoblast of the human placenta elaborates at least two major protein hormones, chorionic gonadotrophin (hCG) and placental lactogen (hPL). Molar and choriocarcinoma tissues characteristically synthesize large amounts of hCG and hPL. To examine the role of trophoblast differentiation in the expression of the hCG and hPL genes, we studied the cytological distribution of their mRNAs in tissue sections of human hydatidiform mole and choriocarcinoma by in situ hybridization. Histologically, these tissues are in different stages of cellular differentiation. In normal placenta, hCG alpha/beta mRNA can be localized to some cytotrophoblasts and primarily to the syncytium, whereas hPL mRNA appears only in the syncytial layer. In hydatidiform mole, which still retains placental villous morphology, the hPL gene and hCG alpha and beta genes are expressed but are poorly localized because of the admixture of cyto- and syncytiotrophoblasts. By contrast, choriocarcinoma, which is devoid of placental villous pattern but in which the cyto- and syncytiotrophoblast-like components are distinguishable, expresses hCG alpha and beta in the syncytial-like areas but little, if any, hPL. These results suggest that a certain level of trophoblast differentiation, such as villous formation, is associated with hPL expression, while the hCG alpha gene and the hCG beta gene can be expressed in more disorganized tissues which contain cytotrophoblastic elements.

[Molecular biological analysis of the DNA in trophoblastic disease--with special reference to genetic information of hPL and hCG(alpha, beta)]

Genomic DNAs extracted from normal placenta, while blood cells, hydatidiform mole and choriocarcinoma were examined to see if they had the same coding structure for hPL, hCG alpha and hCG beta using each of the complementary DNAs. The restriction analysis of these genomic DNAs showed the same pattern even for the DNA of choriocarcinoma that transcribed no hPL mRNA but a relatively high level of hCG(alpha,beta)mRNA. We considered that during trophoblastic malignant transformation, neither the gene deletion for hPL nor the gene amplification for hCG occurred. Moreover, the genomic DNA sequence in hCG alpha gene has polymorphic restriction sites designated as R+/- and H+/-. Using these polymorphisms, we confirmed the hypothesis that a hydatidiform mole develops from an androgenetic origin. We also observed that it is possible that a hydatidiform mole having R- and H+ homozygous DNA may develop into a choriocarcinoma. These observation suggested that some intervening sequence between these polymorphic sites is related to the tumorigenesis of choriocarcinoma.

Segregation patterns of polymorphic restriction sites of the gene encoding the alpha subunit of human chorionic gonadotropin in trophoblastic disease

The gene encoding the alpha subunit of human chorionic gonadotropin contains at least two polymorphic sites in its 3' flanking region detected by restriction enzymes HindIII and EcoRI. We used these polymorphic sites as markers of tissue genotype in normal placenta, hydatidiform mole, choriocarcinoma, and peripheral leukocytes. As expected, inheritance patterns of most hydatidiform moles showed only a paternal genetic contribution. However, one uncommon DNA polymorphism pattern, homozygosity for the absence of the EcoRI site and the presence of the HindIII site, predominated in choriocarcinoma. Thus, our results suggest that moles which have this uncommon polymorphism pattern appear particularly likely to develop into choriocarcinoma.

[Cytological localization of hPL, hCG, and mRNA in chorionic tissue using in situ hybridization]

The human trophoblast elaborates at least two major hormones, hPL and hCG(alpha, beta). To clarify the mechanism of biosynthesis and the gene expression of hPL and hCG(alpha, beta), the specific mRNA should be examined. We here studied the cytological distribution of these mRNAs in trophoblastic tissue of normal placenta, hydatidiform mole and choriocarcinoma by in situ hybridization using complementary DNAs(cDNA) corresponding to hPL and hCG alpha, beta-subunit. mRNAs for hPL and hCG alpha, beta were primarily observed on syncytiorophoblasts excepting some cytotrophoblasts which contain the signals for hCG alpha mRNA and probably beta mRNA. Therefore, we came to the conclusion that hPL and hCG were synthesized mainly in syncytiotrophoblasts. AT the same time, we believe that the gene expression of hCG alpha and probably hCG beta begins before transformation from cyto- to syncytiotrophoblast, while that of hPL appears later in well differentiated syncytiotrophoblasts. On the other hand, in choriocarcinoma hPL mRNA was not observed while many signals for hCG alpha, beta mRNA were localized in syncytiotrophoblastic cells. In other words, the hPL gene was not expressed in choriocarcinoma because of the blocking of trophoblastic differentiation. The data presented here show that the gene expression of hPL and hCG alpha, beta is closely related to trophoblastic differentiation and/or dedifferentiation (tumoregenesis).

The role of trophoblast differentiation in the control of the hCG and hPL genes

Normal trophoblast of the human placenta elaborates at least two major protein hormones, hCG and hPL. Molar and choriocarcinoma tissues characteristically synthesize large amounts of hCG and small quantities of hPL. To examine the role of trophoblast differentiation in the expression of the hCG and hPL genes, we studied the cytological distribution of their mRNAs in tissue sections of human hydatidiform mole and choriocarcinoma by in situ hybridization. Histologically, these tissues are in different stages of cellular differentiation. In normal placenta, hCG alpha and hCG beta mRNAs can be localized to some cytotrophoblasts and primarily to the syncytium, whereas hPL mRNA appears only in the syncytial layer. In hydatidiform mole, which still retains placental villous morphology, the hPL gene and hCG alpha and hCG beta genes are expressed but are poorly localized because of the admixture of cyto- and syncytiotrophoblasts. By contrast, choriocarcinoma, which is devoid of placental villous pattern but in which the cyto- and syncytiotrophoblast-like components are distinguishable, expresses hCG alpha and hCG beta in the syncytial-like areas but little, if any, hPL. These results suggest that a certain level of trophoblast differentiation, such as villus formation, is associated with hPL expression, while the hCG alpha gene and the hCG beta gene can be expressed in more disorganized tissues which contain cytotrophoblastic elements.