Improved treatment of a brain-tumor model. Part 1: Advantages of single- over multiple-dose BCNU schedules

Accelerated repopulation as a cause of radiation treatment failure in non-small cell lung cancer: review of current data and future clinical strategies

Despite convincing evidence that the principles of accelerated repopulation would open up additional therapeutic opportunities in the treatment of advanced-stage non-small cell lung cancer, this strategy has been generally underexplored. The implementation of accelerated radiotherapy schedules has been hampered by logistical barriers, concerns about acute toxicity, and the prioritization of integrating concurrent chemotherapy into the standard treatment platform. At present, it is unclear to what extent accelerated fractionation will influence future treatment paradigms in non-small cell lung cancer, although technical advances in radiotherapy, allowing higher dose delivery with reduced toxicity, could permit the development of more convenient and tolerable forms of accelerated schedules.

Scheduling of paclitaxel and gefitinib to inhibit repopulation for optimal treatment of human cancer cells and xenografts that overexpress the epidermal growth factor receptor

PURPOSE

In clinical studies, evaluating the combination of chemotherapy and the epidermal growth factor receptor (EGFR) inhibitor gefitinib, treatments were administered concurrently, despite it being counter-intuitive to give a cytostatic agent concurrent with cycle-active chemotherapy. One strategy to enhance efficacy might be to give the agents sequentially, thus allowing selective inhibition of repopulation of cancer cells between doses of chemotherapy. Here, we evaluate the hypothesis that sequential administration might allow inhibition of repopulation by gefitinib, with tumor cells re-entering cycle to allow sensitivity to subsequent chemotherapy.

METHODS

Sequential and concurrent administration of paclitaxel and gefitinib were studied in vitro and in xenografts using EGFR over-expressing, EGFR-mutant, and EGFR wild-type human cancer cell lines. We evaluated cell cycle distribution and repopulation during treatment.

RESULTS

The sequential use of gefitinib and paclitaxel to treat EGFR over-expressing A431 cells in vitro decreased repopulation compared to chemotherapy alone, and there was greater cell kill compared to concurrent treatment. In contrast, combined treatment led to greater growth delay than use of gefitinib alone for concurrent but not for sequential treatment of mice bearing A431 xenografts; concurrent treatment had greater effects to reduce functional vasculature in the tumors. Conversely, sequential treatment led to greater growth delay than concurrent treatment of EGFR-mutant HCC-827 xenografts that are sensitive to lower doses of gefitinib.

CONCLUSIONS

These studies highlight the importance of considering effects on the cell cycle, and on the solid tumor microenvironment, including tumor vasculature, when scheduling cytostatic and cytotoxic agents in combination.

Repopulation of cancer cells during therapy: an important cause of treatment failure

Radiotherapy and chemotherapy are given in multiple doses, which are spaced out to allow the recovery of normal tissues between treatments. However, surviving cancer cells also proliferate during the intervals between treatments and this process of repopulation is an important cause of treatment failure. Strategies developed to overcome repopulation have improved clinical outcomes, and now new strategies to inhibit repopulation are emerging in parallel with advances in the understanding of underlying biological mechanisms.

alpha-Bisabolol, a nontoxic natural compound, strongly induces apoptosis in glioma cells

In this study, alpha-bisabolol, a sesquiterpene alcohol present in natural essential oil, was found to have a strong time- and dose-dependent cytotoxic effect on human and rat glioma cells. After 24 h of treatment with 2.5-3.5 microM alpha-bisabolol, the viability of these cells was reduced by 50% with respect to untreated cells. Furthermore, the viability of normal rat glial cells was not affected by treatment with alpha-bisabolol at the same concentrations as above. Glioma cells treated with high concentration of alpha-bisabolol (10 microM) resulted in a 100% cell death. Judging from hypo-G1 accumulation, poly(ADP-ribose) polymerase cleavage, and DNA ladder formation, the cytotoxicity triggered by alpha-bisabolol resulted from apoptosis induction. Moreover, the dissipation of mitochondrial-inner transmembrane potential and the release of cytochrome c from mitochondria indicated that, in these glioma cells, apoptosis occurred through an intrinsic pathway. As pointed out by the experimental results, alpha-bisabolol may be considered a novel compound able to inhibit glioma cell growth and survival.

Accelerated regrowth of non-small-cell lung tumours after induction chemotherapy

Induction chemotherapy of non-small-cell lung cancer (NSCLC) stage III with gemcitabine and cisplatin for downstaging of the tumour with the aim for further treatment with ionising radiation is one of the treatments for lung cancer patients. The purpose of this study was to investigate the influence of the waiting time for radiotherapy, that is, the interval between induction chemotherapy and radiotherapy, on the rate of tumour growth for patients with NSCLC. Interval times between the end of induction chemotherapy and date of diagnostic CT, planning CT and first day of radiotherapy were determined for 23 patients with NSCLC. Increase in gross tumour volume was measured for 18 patients by measuring the dimensions of the primary tumour and lymph node metastases on the diagnostic CT after induction chemotherapy and on the CT used for radiotherapy planning. For each patient, the volume doubling time was calculated from the time interval between the two CTs and ratio of the gross volumes on planning CT and diagnostic CT. The mean time interval between end of chemotherapy and day of diagnostic CT was 16 days, and till first day of radiotherapy 80.3 (range 29 – 141) days. In all, 41% of potentially curable patients became incurable in the waiting period. The ratio of gross tumour volumes of the two CTs ranged from 1.1 to 81.8 and the tumour doubling times ranged from 8.3 to 171 days, with a mean value of 46 days and median value of 29 days. This is far less than the mean doubling time of NSCLC in untreated patients found in the literature. This study shows that in the time interval between the end of induction chemotherapy and the start of radiotherapy rapid tumour progression occurs as a result of accelerated tumour cell proliferation: mean tumour doubling times are much shorter than those in not treated tumours. As a consequence, the gain obtained with induction chemotherapy with regard to volume reduction was lost in the waiting time for radiotherapy. We recommend diminishing the time interval between chemo- and radiotherapy to as short as possible.

Assessment of tumor cell repopulation after chemotherapy for advanced ovarian cancer: pilot study

BACKGROUND

Repopulation of clonogenic tumor cells appears to increase during fractionated radiation treatment and is recognized as an important factor affecting local control. Given the longer intervals between cycles and longer total duration of treatment, the impact of repopulation is likely to be greater after chemotherapy.

METHODS

We assessed tumor cell repopulation with the proliferative marker Ki-67 in 21 patients with ovarian carcinoma who received initial chemotherapy. Paraffin slides were evaluated from the diagnostic biopsy and from tumor obtained at debulking surgery after chemotherapy. Immunohistochemistry using the MIB-1 antibody was performed on the paired samples and analyzed with a digital imaging device linked to a color camera mounted on a transmitted-light microscope. The ratio of Ki-67 positive to all nuclei was used as a proliferative index and compared for pre- and postchemotherapy specimens.

RESULTS

All patients received platinum-based chemotherapy and most showed a response to treatment. The median duration between last chemotherapy and debulking surgery was 33 days (range, 22-50 days). Four (19%) of 21 patients showed an increased proliferative index after chemotherapy, and the remainder showed a decrease (n = 12) or no significant change (n = 5).

CONCLUSIONS

Our results did not suggest an increase in proliferation of tumor cells after this type of chemotherapy in the majority of patients with ovarian cancer.

Repopulation of tumour cells between cycles of chemotherapy: a neglected factor

Repopulation of clonogenic tumour cells during fractionated radiation treatment is recognised as an important factor affecting local control. Given the longer intervals between cycles and longer total duration of treatment, the impact of repopulation is likely to be greater following chemotherapy. Limited data from experimental models suggest that, after chemotherapy, there is a 'lag period', followed by variable but rapid rates of repopulation of tumour cells, possibly accelerating between cycles. Modelling of these properties indicates that after the initial response, accelerated repopulation between cycles can lead to tumour regrowth without any change in the drug sensitivity of the tumour cells. The importance of repopulation may be comparable with that of intrinsic or acquired cellular resistance in determining the effective resistance of tumours to chemotherapy. Biological agents with rapid onset and short duration of action, which can selectively inhibit tumour-cell repopulation, administered between cycles of chemotherapy, might improve the therapeutic index.

The role of minocycline in the treatment of intracranial 9L glioma

This study was designed to explore the question of whether minocycline, a semisynthetic tetracycline shown to inhibit tumor-induced angiogenesis, could control the growth of the rat intracranial 9L gliosarcoma. Minocycline was tested alone and in combination with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in vivo. Treatment was started at the time of intracranial implantation of 9L gliosarcoma into male Fischer 344 rats, 5 days later, or after tumor resection. Minocycline was delivered locally with a controlled-release polymer or systemically by intraperitoneal injection. Systemic minocycline did not extend survival time. Local treatment with minocycline by a controlled-release polymer implanted at the time of tumor implantation extended median survival time by 530% (p < 0.001) compared to treatment with empty polymer. When treatment was begun 5 days after tumor implantation, minocycline delivered locally or systemically had no effect on survival. However, after tumor resection, treatment with locally delivered minocycline resulted in a 43% increase in median survival time (p < 0.002) compared to treatment with empty polymer. Treatment with a combination of minocycline delivered locally in a controlled-release polymer and systemic BCNU 5 days after tumor implantation resulted in a 93% extension of median survival time compared to BCNU alone (p < 0.002). In contrast, treatment with a combination of systemic minocycline and BCNU did not increase survival time compared to systemic BCNU alone. These results demonstrate that minocycline affects tumor growth when delivered locally and suggest that minocycline may be a clinically effective modulator of intracranial tumor growth when used in combination with a chemotherapeutic agent and surgical resection.

Isolation and preliminary characterization of ACNU-resistant sublines of rat brain tumors in vivo

Two variant cells lines resistant to the nitrosourea derivative ACNU ((1-4-amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride), namely C6/ACNU and 9L/ACNU, were selected in vivo from rat brain tumors. Stable resistance to ACNU proved to be a characteristic of these cell lines, whether they were grown in vivo or in vitro. These cell lines exhibited a different pattern of cross-resistance to a wide range of chemotherapeutic agents with dissimilar chemical structures and mechanisms of action as compared with that of other ACNU-resistant cell lines established in vitro. Distinct cross-resistance was observed in both the C6/ACNU and 9L/ACNU cell lines to chloroethyl-nitrosoureas such as BCNU (carmustine), CCNU (lomustine), and methyl CCNU and, additionally, to vincristine, vinblastine, Adriamycin (doxorubicin), and arabinosylcytosine, but not to bleomycin, methotrexate, cis-platinum, and 5-fluorouracil. This might point to a multifactorial mechanism of drug resistance in ACNU-resistant cell lines derived from rat C6 and 9L brain tumor cells.

Rat glioma cell lines C6 and 9L synthesize type 1 collagen in vitro

Glial cell lines (C6, a glioma and 9L, a gliosarcoma) grown in vitro produce type 1 collagen which is detectable in the extracellular matrix by immunocytochemistry. Northern blot analysis using a cDNA specific for the proalpha2 (I) chain of procollagen indicates the presence of a single transcript with an apparent size of 4.8 kb in the C6 cell line, whereas two transcripts with apparent sizes of 5.8 and 4.8 kb are visualized in the 9L cells. The stimulatory effect of ascorbic acid on collagen production is detectable by a 20-27% increase in the concentration of hydroxyproline in the culture medium from the two glioma cell lines. Therefore these glioma cell lines provide a valuable model system for comparative investigations on the regulation of type 1 collagen synthesis by nonmesenchymal cells of neuroepithelial origin.

Blood flow and blood-to-tissue transport in 9L gliosarcomas: the role of the brain tumor model in drug delivery research

We used double-label quantitative autoradiography to measure blood flow (with 131I-iodoantipyrine) and blood-to-tissue transport of 14C-alpha aminoisobutyric acid, AIB) in thirteen 9L gliosarcomas transplanted intracerebrally into Fischer-344 rats. Microscopically, the typical pattern of 9L tumor growth was observed: a solid central tumor mass surrounded by extensive perivascular invasion. The averaged mean whole tumor transfer constant, K, of AIB in the 9L tumors was 33 +/- 15 (+/- SD) microliters/g/min. The averaged mean value of blood flow, F, was 72.2 +/- 27.3 ml/100 g/min. In brain around tumor (BAT), K (13 +/- 4 microliters/g/min) was lower than in the solid tumor, but was still 6-9 times that of tumor-free brain. F in BAT (115.9 +/- 64.6 ml/100 g/min) was comparable to values in tumor-free cortex in the same hemisphere. Values of K and F were used to calculate a net extraction fraction (En) for different regions of brain and tumor. The value of En of AIB in normal cortex was 0.003, in BAT En was 0.02, and in whole tumor the value was 0.09. The delivery of water-soluble compounds in 9L brain tumors is limited by the permeability/surface area characteristics of the tumor capillaries. The properties of blood-to-tissue transport and blood flow of 11 different brain tumor models are compared, and discussed with regard to the choice of brain tumor models for drug delivery research. The 9L brain tumor model is comparable to other transplanted rat brain tumor models, although the extent of tumor cell invasion into BAT makes this model distinctive. However, with regard to blood-to-tissue transport the 9L model differs from autochthonous models and transplanted human glioma models. We discuss guidelines for selecting brain tumor models with which to study the problem of drug delivery to brain tumors.

The chemotherapeutic response of a murine (VM) model of human glioma

Using a cell line derived from the VM spontaneous murine astrocytoma, a reliable in vitro-in vivo model of human malignant glioma has been developed. In this paper we examine the effects of cytotoxic drugs with known activity against other animal brain tumour models and human disease on the in vivo VM model. The drugs BCNU, CCNU and vincristine produced significant volume reduction in tumours growing at a subcutaneous location in syngeneic animals. Procarbazine was ineffective. Similarly, BCNU, CCNU and vincristine produced small but statistically significant increases in survival of VM mice bearing the intracerebral tumour, but procarbazine was again ineffective. The modest, but significant, response of the VM model to the nitrosoureas mimics the human situation more closely than previously described animal models.

Fatal necrotizing encephalopathy complicating treatment of malignant gliomas with intra-arterial BCNU and irradiation: a pathological study

We describe the neuropathologic findings at autopsy in six patients who developed a progressive encephalopathy complicating the treatment of malignant gliomas with combined intra-arterial 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and cerebral irradiation. Four brains were free of tumor and one contained a microscopic focus of residual glioma. In only one case was there evidence of tumor progression. A disseminated process characterized by miliary foci of necrosis with mineralizing axonopathy was present in all cases, restricted to the internal carotid distribution of the perfused hemisphere and involving primarily though not exclusively the white matter, which was diffusely and severely edematous. This was combined in 3 cases with a histologically dissimilar, massive necrotizing leukoencephalopathy indistinguishable from pure radionecrosis. Much of the toxicity of this therapy is mediated by vascular injury, but the disseminated necrotizing lesion probably reflects, at least in part, direct neural damage.

The intraneoplastic chemotherapy in a rat brain tumour model utilizing methotrexate-polymethylmethacrylate-pellets

In an experimental glioma model, using ethylnitrosourea induced and subsequently intracerebrally implanted tumours in BD-IX rats, the effectiveness of intratumoural application of methotrexate (MTX) by stereotactic implantation of polymethylmethacrylate (PMMA) pellets containing MTX, has been studied. Tumour volume 10 days after pellet implantation as well as survival rates of treated, untreated and control animals have been the criteria of the effect of treatment. Tumour volume was significantly smaller in treated compared to untreated animals. The survival rate of untreated to treated animals increased 150 and 233% respectively when compared with the control animals. Thus a positive therapeutic effect of MTX-PMMA pellet implantation in the experimental glioma could be proven. Possible consequences for the treatment of human gliomas are shortly discussed.

In vitro drug sensitivity testing in human gliomas

In vitro drug sensitivity assays have been developed with the goal of predicting the clinical response to chemotherapy. The colony-forming assay, radiolabeled precursor inhibition assay, and microcytotoxicity assay are most commonly used. In retrospective studies, the assays correctly predict clinical response to a chemotherapeutic agent in 50% to 70% of patients and predict clinical resistance in nearly 100% of patients. All of the assays suffer from technical and theoretical problems. In vitro assays depend on cell culture and therefore do not entirely simulate in vivo conditions. Heterogeneity in chemosensitivity is commonly found and can complicate the interpretation of results. Further investigation is needed to determine if these assays will be able to select prospective chemotherapy for patients. The malignant origin of the cells in culture must be verified if meaningful conclusions are to be made.

Malignant gliomas of the brain. A retrospective study

A retrospective study of 72 consecutive and nonrandomized patients with malignant glial tumors is presented. The influence of age, sex, location of tumor, initial presenting symptoms, symptomatic preoperative interval, reoperation, extent of tumor removal, histological subtype of tumor, lymphocyte infiltration, and different treatments upon survival time has been evaluated and statistically analyzed. Age was inversely associated with survival with a strong statistical significance (p = 0.0001). Headache was the most common (67%) initial symptom; aphasia and seizure were both present in 45.3% of patients. Initial presenting symptoms had no effect upon survival. Parietal lobe and lymphocyte infiltration had marginally negative effects upon survival (p = 0.097 and p = 0.10 respectively). The amount of tumor removal was marginally associated with an improved survival (p = 0.07). Radiation therapy was strongly associated with an improved survival time (p = 0.0007). The addition of chemotherapy did not affect the survival (perhaps reflecting the small number of patients and inadequate chemotherapy). There was an obvious beneficial effect of reoperation upon survival time, if the patient lived and underwent reoperation later than 16 months after the initial operation (slow-growing tumor). Although median and mean survival times (10 and 20.34 months respectively, SD 7.45 months) were similar to most series reported, our rates of survival (20%, 12.5%, and 7.5% at 2, 3, and 5 years, respectively) were notably higher.

Intraarterial 1,3-bis(2-chloroethyl)-1-nitrosourea chemotherapy for the treatment of malignant gliomas of the brain: a preliminary report

In a clinical trial, 10 patients with malignant gliomas underwent partial resection of their tumors and were treated by intraarterial 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) chemotherapy. The drug was given at least 1 month after the completion of postoperative radiotherapy in total doses of 270-280 mg/m2 in two sessions separated by a 48-hour interval (the two sessions with interval were equal to one course). This therapy was repeated every 8-10 weeks. Four patients had three courses and the other six patients had two courses of chemotherapy. This therapy was the only antitumor chemotherapy for this group of patients. Our preliminary results demonstrate the safety of this new procedure and suggest that intraarterial BCNU chemotherapy may be more effective, and has a better tolerance and less toxicity, than intravenous BCNU chemotherapy. Furthermore, it was demonstrated that, in the case of one patient, higher antitumor activity resulted from intraarterial BCNU chemotherapy as compared to intravenous BCNU therapy.

Intra-arterial BCNU chemotherapy for treatment of malignant gliomas of the central nervous system

Because of the rapid systemic clearance of BCNU (1,3-bis-(2-chloroethyl)-1-nitrosourea), intra-arterial administration should provide a substantial advantage over intravenous administration for the treatment of malignant gliomas. Thirty-six patients were treated with BCNU every 6 to 8 weeks, either by transfemoral catheterization of the internal carotid or vertebral artery or through a fully implantable intracarotid drug delivery system, beginning with a dose of 200 mg/sq m body surface area. Twelve patients with Grade III or IV astrocytomas were treated after partial resection of the tumor without prior radiation therapy. After two to seven cycles of chemotherapy, nine patients showed a decrease in tumor size and surrounding edema on contrast-enhanced computerized tomography scans. In the nine responders, median duration of chemotherapy response from the time of operation was 25 weeks (range 12 to more than 91 weeks). The median duration of survival in the 12 patients was 54 weeks (range 21 to more than 156 weeks), with an 18-month survival rate of 42%. Twenty-four patients with recurrent Grade I to IV astrocytomas, whose resection and irradiation therapy had failed, received two to eight courses of intra-arterial BCNU therapy. Seventeen of these had a response or were stable for a median of 20 weeks (range 6 to more than 66 weeks). The catheterization procedure is safe, with no immediate complication in 111 infusions of BCNU. A delayed complication in nine patients has been unilateral loss of vision secondary to a retinal vasculitis. The frequency of visual loss decreased after the concentration of the ethanol diluent was lowered.