In vitro radiobiological parameters of human sarcoma cell lines

Is grid therapy useful for all tumors and every grid block design?

Grid therapy is a treatment technique that has been introduced for patients with advanced bulky tumors. The purpose of this study is to investigate the effect of the radiation sensitivity of the tumors and the design of the grid blocks on the clinical response of grid therapy. The Monte Carlo simulation technique is used to determine the dose distribution through a grid block that was used for a Varian 2100C linear accelerator. From the simulated dose profiles, the therapeutic ratio (TR) and the equivalent uniform dose (EUD) for different types of tumors with respect to their radiation sensitivities were calculated. These calculations were performed using the linear quadratic (LQ) and the Hug-Kellerer (H-K) models. The results of these calculations have been validated by comparison with the clinical responses of 232 patients from different publications, who were treated with grid therapy. These published results for different tumor types were used to examine the correlation between tumor radiosensitivity and the clinical response of grid therapy. Moreover, the influence of grid design on their clinical responses was investigated by using Monte Carlo simulations of grid blocks with different hole diameters and different center-to-center spacing. The results of the theoretical models and clinical data indicated higher clinical responses for the grid therapy on the patients with more radioresistant tumors. The differences between TR values for radioresistant cells and radiosensitive cells at 20 Gy and 10 Gy doses were up to 50% and 30%, respectively. Interestingly, the differences between the TR values with LQ model and H-K model were less than 4%. Moreover, the results from the Monte Carlo studies showed that grid blocks with a hole diameters of 1.0 cm and 1.25 cm may lead to about 19% higher TR relative to the grids with hole diameters smaller than 1.0 cm or larger than 1.25 cm (with 95% confidence interval). In sum-mary, the results of this study indicate that grid therapy is more effective for tumors with radioresistant characteristics than radiosensitive tumors.

Preoperative Radiotherapy for Adult Head and Neck Soft Tissue Sarcoma: Assessment of Wound Complication Rates and Cancer Outcome in a Prospective Series

Combination surgery and radiotherapy (RT) is frequently used in soft tissue sarcoma (STS). Because lower doses and smaller irradiation volumes are possible in preoperative RT (pre-op RT), this approach can be especially valuable in anatomic settings where critical organs are in close proximity to the RT target area. A recent multicenter phase III trial (SR.2 trial of the National Cancer Institute of Canada Clinical Trials Group) comparing pre-op RT against post-op RT for extremity STS has shown significantly higher major wound complication rates (35%) with pre-op RT. We postulated that wound complication rates may be less frequent in the head and neck with better vascularity and wider use of secondary wound reconstruction. Using a prospective database, we identified 40 consecutive patients with head and neck STS treated with pre-op RT (50 Gy) and subsequent (4 to 6 weeks later) resection between 1/89 and 8/99 in a single institution setting. Major wound complications (MWC) were classified by the identical criteria used in the SR.2 trial. Intracranial extension was evident in 5 patients, whereas 50% of the patients had large tumors (> 5 cm). Deep tumor was present in 34 (85%), and 6 (15%) were superficial to fascia. In this series, 31 patients (77.5%) had secondary reconstruction of the acquired soft tissue deficit. The actuarial 2-year local relapse-free rate was 80%, and the metastatic relapse-free rate was 85%. Major wound complications occurred in 8 of 40 patients (20%) within 120 days of surgery according to the SR.2 criteria: secondary wound surgery (3), readmission or prolonged hospital admission for wound care (2), deep packing (0), prolonged dressing changes (2), and invasive procedure for wound care (1). The latter was a minor wound management problem (a single outpatient drainage of a seroma) for the combined rate of 8/20 or 20%. Our findings show that (1) pre-op RT in head and neck STS is associated with lower rates of major wound complications compared to extremity cases; (2) pre-op RT provides high rates of local control in an adverse group of cases of adult head and neck STS; (3) the choice of scheduling of RT should be based on anatomic issues with emphasis on the trade-offs between RT doses and volumes versus wound morbidity for individual patients. This is especially important when tumor may be adjacent to critical head and neck structures which may be protected from the high-dose RT area.

Wortmannin sensitizes human glioblastoma cell lines carrying mutant and wild type TP53 gene to radiation

The purpose of this paper is to investigate the effect of wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K), on TP53 (formerly known as p53) signal transduction initiated by ionizing radiation and radiosensitization in isogenic derivatives of human glioblastoma cells differing in TP53 status. Wortmannin inhibited the accumulation of TP53 and CDKN1A (formerly known as WAF1) after 6 Gy irradiation in A-172/neo cells bearing wild-type TP53. In A-172/Trp248 cells carrying mutant TP53, X-rays induced no significant accumulation of TP53 and slight increase of CDKN1A. There were, consequently, little differences in the expression of TP53 and CDKN1A between A-172/Trp248 cells exposed to 6 Gy alone and wortmannin plus 6 Gy. However, wortmannin sensitized both A-172/neo and A-172/Trp248 cells to radiation. These studies indicate that wortmannin inhibits TP53 upregulation, but this suppression does not account for the radiosensitization by this drug. These results indicate that inhibitors of PI3K-related kinases may present a new class of radiosensitizers, regardless of the TP53 status of tumor cells.

The local management of soft tissue sarcoma

Soft tissue sarcomas (STS) are rare tumors arising from the connective tissues. STS can arise at any anatomic site, can demonstrate varied behavior and prognosis, and therefore present a formidable challenge in management. The local treatment of STS demands technical complexity in the application of diagnostic tools, including pathology and imaging, as well as treatment approaches, including surgical ablation and reconstruction, radiotherapy, and, in defined cases, chemotherapy. The understanding of the management of these lesions is profoundly dependent on the multidisciplinary setting, where experience has been gained and skills are available to increase the likelihood of a successful result. Several proven options are available for optimal local management, and the choice of approach depends on the prevailing practice and resource profile of the treating center. With modern approaches, the local control rate can be expected to be at least 90% for extremity lesions, which constitute the most common STS. The experience in other anatomic sites is less favorable as a result of a combination of late diagnosis, technically difficult access sites, and possibly less familiarity with these less common presentations. The disappointing results make it all the more important for patients to be referred to a multidisciplinary setting with experience in sarcoma management to maximize the chance of successful local outcome.

Contemporary radiotherapy for soft tissue sarcoma

This review will detail the role of radiotherapy in the management of soft tissue sarcoma. Particular emphasis will be given to its role as an adjuvant to surgical excision for local curative management. The addition of radiotherapy permits a tissue-conserving operation to be performed, which has functional and cosmetic advantages yet produces local control equivalent to more radical surgery alone. The review will consider the historical evolution of treatment up through recent and contemporary practice. The principles of use will be outlined using available evidence and, where this is lacking, it will be acknowledged with suggestions for improvement. Finally, a brief overview of some technical issues about radiotherapy will be provided.

Comparison between the in vitro intrinsic radiation sensitivity of human soft tissue sarcoma and breast cancer cell lines

The purpose of this study is to evaluate the radiation sensitivity of human soft tissue sarcoma cell lines in vitro and to compare with that of human breast carcinoma and glioblastoma cell lines. The intrinsic radiation sensitivity parameters of seven human soft tissue sarcomas and eight breast carcinoma cell lines were investigated in vitro by clonogenic assays for single-dose irradiation under aerobic conditions on cells in exponential phase of growth. The results for sarcoma cell lines showed that the mean surviving fraction at 2 Gy (SF2) was 0.39 (SD +/- 0.09) with a range of 0.24 to 0.53, and the average mean inactivation dose (MID) was 1.92 (SD +/- 0.35) range from 1.36 Gy to 2.49 Gy. These values were not different from that of breast cell lines examined concurrently and using the same experimental methods (mean SF2 0.38, SD +/- 0.09; MID 1.9 Gy, SD +/- 0.37). However radiobiological parameters of nine karyotyped human malignant glioma cell lines determined earlier in this laboratory were significantly higher (mean SF2 0.50 +/- 0.14; mean MID 2.61 +/- 0.60). In conclusion, the data presented here do not support the view that cells of sarcomas show unusual radiation resistance. To the extent that the in vitro determined cellular radiation sensitivity reflects the tumor response in vivo, the success rate for radiation applied against sarcoma and breast carcinoma of comparable size could be similar.

A review of human cell radiosensitivity in vitro

The survival curves of 694 human cell lines irradiated in exponentially growing phase in vitro were collected from the literature. Among them, 271 were derived from tumors, 423 were nontransformed fibroblasts and other normal cell strains from healthy people or people with some genetic disorders. Seventy-six different cell types are identified, and a specific radiosensitivity could be associated with each, using D and surviving fraction at 2 Gy. Technical factors such as culture medium, feeder cells, and scoring method were found to affect intrinsic radiosensitivity. In particular, the cell type is not a discriminating factor when cells are studied in agar. Results obtained with cells irradiated in agar must be used cautiously, depending on how the cells were prepared for the experiments. The use of feeder cells narrows the range of radiosensitivity of human cells. For cells irradiated as monolayer, it was possible to build a scale of radiosensitivity according to cell type, ranging, in terms of D from 0.6 Gy for the most sensitive cell lines to more than 4 Gy for the most resistant. Considering that, in most cases, we could estimate the variation of radiosensitivity within each cell type, our classification among cell types can be used by researchers to place their results in the context of the literature.

Conservative surgery and adjuvant radiation therapy in the management of adult soft tissue sarcoma of the extremities: clinical and radiobiological results

PURPOSE

The outcome of adult patients with soft tissue sarcoma of the extremities treated with conservative surgery and adjuvant irradiation was evaluated to (a) determine the appropriate treatment volume and radiation dosage in the postoperative setting, and (b) correlate in vitro radiobiological parameters obtained prior to therapy with clinical outcome.

METHODS AND MATERIALS

Sixty-four consecutive adult patients with soft tissue sarcoma of the extremities (40 lower, 24 upper) who underwent conservative surgery and adjuvant irradiation 7 preoperative, 50 postoperative, 7 perioperative) between 1978 and 1991 were reviewed. The initial radiation field margin surrounding the tumor bed/scar was retrospectively analyzed in all postoperative patients. Initial field margins were < 5 cm in 12 patients, 5-9.9 cm in 32 and > or = 10 cm in 6. Patients with negative pathological margins were initially treated with traditional postoperative doses (64-66 Gy); however, in later years the postoperative dose was reduced to 60 Gy. Thirteen cell lines were established prior to definite therapy, and radiobiological parameters (multitarget and linear-quadratic) were obtained and correlated with outcome.

RESULTS

Postoperative patients treated with an initial field margin of < 5 cm had a 5-year local control of 30.4% vs. 93.2% in patients treated with an initial margin of > or = 5 cm (p = 0.0003). Five-year local control rates were similar in patients treated with initial field margins of 5-9.9 cm (91.6%) compared with those treated with > or = 10 cm margins (100%) (p = 0.49). While postoperative patients receiving < 60 Gy had a worse local control than those receiving > or = 60 Gy (p = 0.08), no difference was seen in local control between patients receiving less than traditional postoperative doses (60-63.9 Gy) (74.4% vs. those receiving 64-66 Gy (87.0%) (p = 0.5). The local control of patients treated in the later years of the study, with strict attention to surgical and radiotherapeutic technique, was 87.6%. Severe late sequelae were more frequent in patients treated with doses > or = 63 Gy compared to patients treated with lower doses (23.1% vs. 0%) (p < 0.05). Mean values for Do, alpha, beta, D, n and SF2 obtained from the 13 cell lines were 115.7, 0.66, 0.029, 2.15, 0.262, respectively. Four of the 13 cell lines established prior to therapy ultimately failed locally. The radiobiological parameters of these cell lines were similar to the other nine cell lines in terms of radiosensitivity.

CONCLUSIONS

Our data confirm the importance of maintaining an initial field margin of at least 5 cm around the tumor bed/scar in the postoperative setting. No benefit was seen with the use of margins > or = 10 cm. In addition, patients undergoing wide local excision with negative margins can be treated with lower than traditional postoperative doses (60 Gy) without compromising local control and with fewer chronic sequelae. Finally, it does not appear that inherent tumor cell sensitivity is a major determinant of local failure following radiation therapy and conservative surgery in soft tissue sarcoma.

Role of radiation in the management of adult patients with sarcoma of soft tissue

Radiation in moderate dose levels, viz. 60-65 Gy at 2 Gy/fraction, administered in combination with conservative surgery, yields local control frequencies at least comparable to those achieved by radical resectional surgery alone. The clinical interest in this management strategy is the reduction in the scope of the resection and a consequent gain in cosmetic and functional status. This combined approach is favored for sarcomas so situated that resection with wide margin, > or = 2 cm at the most narrow, cannot be realized unless there is a clinically important loss in function. Where radical surgery is planned, there must be great care in assessment of the probability of achieving good margins. The patient is ill served if there is radical surgery and then, because of close margins, postoperative radiation is required. There appears to be clinical gain for the patient with a large sarcoma by administering the radiation preoperatively. Advantages include smaller treatment volume and higher local control rates. The management of the surgical wound in the irradiated patient is discussed. Also, brief consideration is given to current use of brachytherapy, high linear energy transfer (LET) radiation, and combination of radiation and chemotherapy.

Radiosensitivity in vitro of human soft tissue sarcoma cell lines and skin fibroblasts derived from the same patients

Skin fibroblast cell strains and tumour cell lines were established from 12 patients with various types of soft tissue neoplasms, and radiation survival curve parameters were measured in vitro. Soft tissue sarcoma cells were consistently more sensitive to X-irradiation than fibroblasts isolated from the same patient, and were also more sensitive as a group than cell lines derived from 34 other human tumours. There was a general correlation in radiosensitivity between fibroblasts and tumour cells derived from the same patient, indicating that some component of tumour cell sensitivity may relate to genetic factors in the host. Such genetic factors, however, do not explain all of the heterogeneity in tumour cell response. The response of soft tissue sarcoma in vivo may be dependent on complex radiomodifying factors other than inherent radiation sensitivity, thus making it difficult to predict clinical outcome by use of assays which use survival of irradiated tumour cell lines in vitro as an endpoint.

Mechanisms of X-ray-mediated protooncogene c-jun expression in radiation-induced human sarcoma cell lines

c-jun is a protooncogene associated with neoplastic transformation and is transcriptionally induced by ionizing radiation. To examine the possible mechanisms of radiation-induced c-jun transcription, we analyzed RNA from human tumor cell lines RIT-3 and STSAR-5 following x-irradiation in the presence of protein kinase inhibitors, or the absence of serum and calcium. Protooncogene c-jun expression increased several fold following irradiation of these radiation-induced human sarcoma cell lines. The expression of c-jun was not altered following irradiation in conditioned medium containing serum as compared to that of cells in serum free medium. Depletion of PKC by prolonged TPA treatment resulted in inhibition of c-jun expression. In addition, nonspecific protein kinase inhibitors, staurosporin and H7 attenuated c-jun expression, whereas the analogue of ATP (sangivamycin) did not. Furthermore, the selective inhibitor of cAMP dependent protein kinase HA 1004 did not alter radiation-mediated c-jun induction. These data indicate that ionizing radiation exposure results in c-jun induction which is dependent upon the activation of PKC. Protein kinase C activation and the subsequent expression of the protooncogene c-jun by ionizing radiation may further define the molecular mechanisms of radiation-induced neoplastic transformation.

High dose hyperfractionated radiotherapy in the treatment of extremity soft tissue sarcomas

A hyperfractionated radiotherapy schedule has been evaluated in the treatment of 29 adults with limb or limb girdle soft tissue sarcomas. The objective was to increase the total administered dose and possibly improve local control, without increasing late normal tissue damage. Twice daily 1.25 Gy fractions (with a minimum interval of 6 h) have been given over 5 to 6 weeks to 12 patients pre-operatively, 10 post-operatively and 7 palliatively. Five patients received 62.5 Gy in 5 weeks pre-operatively and 3 palliatively. Nineteen of the remaining 21 patients received 75 Gy in 6 weeks with a field size reduction after 5 weeks. Sixteen of 29 tumours were situated in the thigh and only 2 were in the upper limb. Twenty were of high grade. The mean tumour size of those treated radically was 13.1 cm (range 5 to 40 cm). Sixteen patients (76%) given 75 Gy developed moderate or severe skin erythema maximal at 5 weeks. Despite the large field sizes used (mean phase one of 34.5 cm, and phase two of 22.8 cm) only 2 patients failed to complete the planned treatment because of the severity of these reactions. Two other patients developed partial wound breakdowns after the end of treatment--both healing spontaneously. Fourteen patients developed an area of moist desquamation--11 mild, 2 moderate and one severe. There have been four late wound breakdowns requiring surgical intervention; all have since healed well. The median follow up is short at 556 days. Ten of 19 evaluable patients have developed moderate/severe induration, 5/19 mild and 4/19 none.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiation-induced DNA double-strand break frequencies in human squamous cell carcinoma cell lines of different radiation sensitivities

DNA neutral (pH 9.6) filter elution was used to measure radiation-induced DNA double-strand break (dsb) frequencies in eight human squamous cell carcinoma cell lines with radiosensitivities (D0) ranging from 1.07 to 2.66 Gy and D values ranging from 1.46 to 4.08 Gy. The elution profiles of unirradiated samples from more radiosensitive cell lines were all steeper in slope than the profiles from resistant cells. The shapes of the dsb induction curves were curvilinear and there was some variability from cell line to cell line in the dose-response for the induction of DNA dsb after exposures to 5-100 Gy 60Co gamma-rays. There was no relation between the shapes of the survival curves and the shapes of the dose-responses for the induction of DNA dsb. At low doses (5-25 Gy), three out of four of the more sensitive cell lines (D less than 2.5 Gy) had larger initial break frequencies than the more resistant lines (D greater than 3.0 Gy). Although the low-dose (5-25 Gy) elution results were variable, they do suggest that DNA neutral elution will detect differences between sensitive and resistant tumour cells in initial DNA dsb frequencies.

Radiobiological characterization of head and neck and sarcoma cells derived from patients prior to radiotherapy

The radiobiological parameters of 33 tumor cell lines were studied in biopsy samples obtained from patients prior to radiotherapy. Epithelial tumor cells derived from head and neck cancer patients were more radioresistant than tumor cell lines derived from patients with sarcoma regardless of method of analysis. The presence of radioresistant tumor cell lines was associated with local failure in some patients. However, the presence of radiosensitive tumor cells did not necessarily predict local control. Our data suggest radiocurability is complex and inherent radiobiological parameters of tumor cells may be only one factor in radiotherapy outcome.

The interaction between recombinant human tumor necrosis factor and radiation in 13 human tumor cell lines

Tumor necrosis factor (TNF) was cytotoxic at concentrations of 10 to 1000 units/ml to 12 of 14 human tumor cell lines. Synergistic or additive cell killing between TNF and radiation was observed in 7 of 10 tumor cell lines, while independent tumor cell killing by each agent occurred in two tumor cell lines. The maximum synergistic effect was observed when TNF was added 4-12 hr prior to irradiation. This interaction was absent when TNF was added after irradiation. TNF also reduced potentially lethal damage repair in 3 of 5 cell lines tested. Possible mechanisms of interaction of TNF and X rays including induction of hydroxyl radicals and subsequent DNA damage by TNF and radiation are discussed.

Mean inactivation dose (D). A critical analysis of a neglected parameter in radiotherapy

By predicting treatment outcome to radiotherapy from in vitro radiobiological parameters, not only individual patient treatments can be tailored, but also new promising treatment protocols can be tried in patients in whom unfavorable outcome is predicted. In this respect, choosing the right parameter can be very important. Unlike D0 and N which provide information of the distal part of the survival curve, mean inactivation dose (D) estimates overall radiosensitivity. However, the parameters reflecting the response at the clinically relevant low-dose region are neglected in the literature. In a literature survey of 98 papers in which survival curves or D0/N were used, only in 2D was used. In 21 papers the D0/N values were important in drawing conclusions. By calculating D in 3 of these 21 papers, we show that the conclusion drawn may be altered with the use of D. The importance of 'low-dose-region-parameters' is reviewed.

Increased tumor necrosis factor alpha mRNA after cellular exposure to ionizing radiation

We report that tumor necrosis factor alpha (TNF-alpha) mRNA is increased after treatment with x-rays in certain human sarcoma cells. An increase in TNF-alpha mRNA is accompanied by the increased production of TNF-alpha protein. TNF-alpha enhances radiation lethality in both TNF-alpha-producing and -nonproducing tumor cells. These data suggest that, in addition to the direct cytotoxic effects of x-rays, production of TNF-alpha may add to radiation lethality through autocrine and paracrine mechanisms. Combinations of TNF-alpha and therapeutic radiation may be useful in clinical cancer therapy.

Radiobiological characterization of 53 human tumor cell lines

We investigated the in vitro radiobiological survival parameters of 53 human tumor cell lines studied in exponential growth. Epithelial cell lines derived from 24 patients with head and neck carcinoma, 15 patients with ovarian carcinoma, and mesenchymal tumor cell lines derived from 14 patients with bone and soft tissue sarcomas were studied. Survival data are analyzed using the multi-target and linear quadratic models. The head and neck and ovarian carcinoma tumor cell lines were more radioresistant as measured by D0, D, and alpha parameters, compared with the bone and soft-tissue sarcoma lines. The radiobiological parameters of tumor cell lines reported herein are similar to parameters of tumor cell lines derived from head and neck and soft tissue sarcoma patients presently being followed for clinical outcome following radiotherapy in our clinic.

Radioresistant tumor cell lines derived from head and neck radiation failures

We studied the in vitro radiobiological parameters of 16 human head and neck squamous cell carcinoma tumor cell lines cultured from patients who suffered local failure after a curative course of radiotherapy. The radiobiological parameters determined included D0, n, and D. When compared with in vitro radiobiological parameters of tumor cells cultured from head and neck cancer patients prior to radiotherapy, human sarcoma cell lines, and normal human diploid fibroblasts studied in our laboratory (as well as other human tumor cell lines reported in the literature), tumor cells derived from radiotherapy failures on average are resistant to the cytotoxic effects of ionizing radiation.