Carboplatin- and cisplatin-induced potentiation of moderate-dose radiation cytotoxicity in human lung cancer cell lines

Composition of Conditioned Media from Radioresistant and Chemoresistant Cancer Cells Reveals miRNA and Other Secretory Factors Implicated in the Development of Resistance

Resistance to chemo- or radiotherapy is the main obstacle to consistent treatment outcomes in oncology patients. A deeper understanding of the mechanisms driving the development of resistance is required. This review focuses on secretory factors derived from chemo- and radioresistant cancer cells, cancer-associated fibroblasts (CAFs), mesenchymal stem cells (MSCs), and cancer stem cells (CSCs) that mediate the development of resistance in unexposed cells. The first line of evidence considers the experiments with conditioned media (CM) from chemo- and radioresistant cells, CAFs, MSCs, and CSCs that elevate resistance upon the ionizing radiation or anti-cancer drug exposure of previously untreated cells. The composition of CM revealed factors such as circular RNAs; interleukins; plasminogen activator inhibitor; and oncosome-shuttled lncRNAs, mRNAs, and miRNAs that aid in cellular communication and transmit signals inducing the chemo- and radioresistance of sensitive cancer cells. Data, demonstrating that radioresistant cancer cells become resistant to anti-neoplastic drug exposure and vice versa, are also discussed. The mechanisms driving the development of cross-resistance between chemotherapy and radiotherapy are highlighted. The secretion of resistance-mediating factors to intercellular fluid and blood brings attention to its diagnostic potential. Highly stable serum miRNA candidates were proposed by several studies as prognostic markers of radioresistance; however, clinical studies are needed to validate their utility. The ability to predict a treatment response with the help of the miRNA resistance status database will help with the selection of an effective therapeutic strategy. The possibility of miRNA-based therapy is currently being investigated with ongoing clinical studies, and such approaches can be used to alleviate resistance in oncology patients.

Role of concurrent chemoradiation on locally advanced unresectable adenoid cystic carcinoma

BACKGROUND/AIMS

Adenoid cystic carcinoma (ACC) is a rare salivary gland tumor characterized by indolence, with a high rate of local recurrence and distant metastasis. This study aimed to investigate the effect of concurrent chemoradiation (CCRT) on locally advanced unresectable ACC.

METHODS

We retrospectively analyzed clinical data from 10 patients with pathologically confirmed ACC of the head and neck who received CCRT with cisplatin in Seoul National University Hospital between 2013 and 2018.

RESULTS

Ten patients with unresectable disease at the time of diagnosis or with positive margins after surgical resection received CCRT with weekly cisplatin. Eight patients (80%) achieved complete remission, of which three later developed distant metastases without local relapse; one patient developed distant metastasis and local relapse. Two patient achieved partial remission without progression. Patients experienced several toxicities, including dry mouth, radiation dermatitis, nausea, and salivary gland inflammation of mostly grade 1 to 2. Only one patient showed grade 3 oral mucositis. Median relapse-free survival was 34.5 months (95% confidence interval, 22.8 months to not reached).

CONCLUSION

CCRT with cisplatin is effective for local control of ACC with manageable toxicity and may be an effective treatment option for locally advanced unresectable ACC.

Efficacy and safety of antitumor agents plus radiotherapy compared with radiotherapy alone for brain metastases from lung cancer

The present study aimed to investigate the efficacy and safety of different therapeutic regimens for brain metastases (BMs) from lung cancer (LC). A total of 13 controlled trials (1,783 cases) involving chemotherapy, tyrosine kinase inhibitors or endostatin plus radiotherapy (combination group) vs. radiotherapy alone group were identified from PubMed. Compared with the radiotherapy alone group, the combination group resulted in a significant benefit for objective response rate (ORR) [risk ratio (RR), 1.38; 95% confidence interval (CI), 1.19–1.60; P<0.0001], notably prolonged the time to central nervous system progression [CNS-TTP; hazard ratio (HR), 0.71; 95% CI, 0.57–0.90; P=0.004] and progression-free survival (PFS; HR, 0.60; 95% CI, 0.44–0.83; P=0.002); however, failed in prolonging the overall survival (OS; HR, 0.80; 95% CI, 0.61–1.05; P=0.11) with a higher overall severe adverse events (AEs, Grade ≥3; RR, 2.57; 95% CI, 1.24–5.35; P=0.01). Notably, subgroup analysis demonstrated that targeted therapy plus radiotherapy possessed a superior OS compared with radiotherapy alone (HR, 0.58; 95% CI, 0.37–0.90; P=0.01) with mild non-hematological toxicity and without severe hematotoxicity. The present study demonstrated that targeted agents plus radiotherapy possessed desirable effects with mild adverse events. Secondary to best, chemoradiotherapy is an alternative option for patients without suitable molecular targets.

DNA damage response (DDR) pathway engagement in cisplatin radiosensitization of non-small cell lung cancer

Non-small cell lung cancers (NSCLC) are commonly treated with a platinum-based chemotherapy such as cisplatin (CDDP) in combination with ionizing radiation (IR). Although clinical trials have demonstrated that the combination of CDDP and IR appear to be synergistic in terms of therapeutic efficacy, the mechanism of synergism remains largely uncharacterized. We investigated the role of the DNA damage response (DDR) in CDDP radiosensitization using two NSCLC cell lines. Using clonogenic survival assays, we determined that the cooperative cytotoxicity of CDDP and IR treatment is sequence dependent, requiring administration of CDDP prior to IR (CDDP-IR). We identified and interrogated the unique time and agent-dependent activation of the DDR in NSCLC cells treated with cisplatin-IR combination therapy. Compared to treatment with CDDP or IR alone, CDDP-IR combination treatment led to persistence of γH2Ax foci, a marker of DNA double-strand breaks (DSB), for up to 24h after treatment. Interestingly, pharmacologic inhibition of DDR sensor kinases revealed the persistence of γ-H2Ax foci in CDDP-IR treated cells is independent of kinase activation. Taken together, our data suggest that delayed repair of DSBs in NSCLC cells treated with CDDP-IR contributes to CDDP radiosensitization and that alterations of the DDR pathways by inhibition of specific DDR kinases can augment CDDP-IR cytotoxicity by a complementary mechanism.

DNA microarray reveals ZNF195 and SBF1 are potential biomarkers for gemcitabine sensitivity in head and neck squamous cell carcinoma cell lines

Gemcitabine is a potential chemotherapy drug for treatment of head and neck squamous cell carcinoma (HNSCC), however, the poor or partial response of HNSCC patients to gemcitabine demonstrated the urgent need for gemcitabine biomarkers to improve the therapy. In present work, 10 HNSCC cell lines were employed to figure out the biomarkers for gemcitabine sensitivity. The sensitivities of these 10 cell lines to gemcitabine and the basal expression of these cell lines was investigated, the correlation between gemcitabine response (IC50 dose) and gene expression was investigated by Pearson correlation and FDR estimation. The top seven positive genes responsible for gemcitabine sensitivity were validated by qPCR in these 10 HNSCC cell lines, while only two genes (SBF1 and ZNF195) were expression-correlated to gemcitabine response. Furthermore, ZNF195 expression was closely associated with gemcitabine sensitivity in the subsequent independent validation in cell lines from various types of cancer. Our work might provide potential biomarkers for gemcitabine sensitivity in HNSCC and various type of cancer.

Complex cisplatin-double strand break (DSB) lesions directly impair cellular non-homologous end-joining (NHEJ) independent of downstream damage response (DDR) pathways

The treatment for advanced stage non-small cell lung cancer (NSCLC) often includes platinum-based chemotherapy and IR. Cisplatin and IR combination therapy display schedule and dose-dependent synergy, the mechanism of which is not completely understood. In a series of in vitro and cell culture assays in a NSCLC model, we investigated both the downstream and direct treatment and damage effects of cisplatin on NHEJ catalyzed repair of a DNA DSB. The results demonstrate that extracts prepared from cisplatin-treated cells are fully capable of NHEJ catalyzed repair of a DSB using a non-cisplatin-damaged DNA substrate in vitro. Similarly, using two different host cell reactivation assays, treatment of cells prior to transfection of a linear, undamaged reporter plasmid revealed no reduction in NHEJ compared with untreated cells. In contrast, transfection of a linear GFP-reporter plasmid containing site-specific, cisplatin lesions 6-bp from the termini revealed a significant impairment in DSB repair of the cisplatin-damaged DNA substrates in the absence of cellular treatment with cisplatin. Together, these data demonstrate that impaired NHEJ in combined cisplatin-IR treated cells is likely the result of a direct effect of cisplatin-DNA lesions near a DSB and that the indirect cellular effects of cisplatin treatment are not significant contributors to the synergistic cytotoxicity observed with combination cisplatin-IR treatment.

Comparison of the combined action of oxaliplatin or cisplatin and radiation in cervical and lung cancer cells

BACKGROUND AND PURPOSE

To test the combined effects of oxaliplatin and radiation versus cisplatin and radiation using human cervical and lung cancer cell lines.

MATERIAL AND METHODS

CaSki cervical cancer cells, and A549 lung cancer cells were cultured under standard conditions. Cells were treated with escalating doses of gamma-irradiation (0-6 Gy), and with oxali- and cisplatin for 2 h or 24 h, or a combination of both. Cell survival was measured by a colony-forming assay. Survival curves were fitted to the data using the linear quadratic model. Sensitizer enhancement ratios (SER) were calculated at the 37% survival level, and isobologram analysis was applied to test for the drug-radiation interactions.

RESULTS

Oxaliplatin as well as cisplatin alone were cytotoxic in both cell lines. In CaSki cells, oxaliplatin and cisplatin significantly increased radiation toxicity. In A549 cells no increase of radiation toxicity was observed after treatment with cisplatin, however, isobologram analysis revealed supra-additive interaction between oxaliplatin and radiation in A549 cells.

CONCLUSION

Oxaliplatin had the same effectiveness on tumor cells as cisplatin and induced enhanced radiation toxicity in lung cancer cells, where cisplatin was not able to achieve radiosensitization.

Effect of treatment schedule on the interaction of Cisplatin and radiation in human lung cancer cells

This study was designed to determine the effects of the treatment schedule on the interaction between cisplatin and radiation. Cells of a human squamous cell lung cancer cell line were treated with cisplatin and radiation using three treatment protocols: 1-h exposure to cisplatin immediately followed by irradiation (A), 4-day continuous exposure to cisplatin immediately followed by irradiation (B), and 1-h exposure to cisplatin followed by irradiation after a 4-day interval (C). The interactions were assessed by isobologram, cell cycle distribution and apoptosis. The combination resulted in a additive effect in every protocol. Cell cycle accumulation at G(2)/M phase before irradiation was observed in Protocols B and C, whereas no cell cycle shift in the limited time course was noted in Protocol A. Although a 4-day continuous exposure to cisplatin and a 1-h exposure to cisplatin followed by a 4-day interval before irradiation caused significantly increased apoptosis, an additional increase in apoptosis after irradiation was not observed in Protocols B and C, whereas Protocol A showed an additional increase. Despite a cell cycle shift favoring radiation sensitivity, the drug-radiation interactions in Protocols B and C were additive, possibly because of negative effects including induction of a durable G(2)/M-phase arrest and suppression of apoptosis by cisplatin.

Phase II trial of docetaxel, cisplatin and fluorouracil followed by carboplatin and radiotherapy in locally advanced oesophageal cancer

This study was performed to assess the efficacy and safety of docetaxel, cisplatin and fluorouracil combination in patients with unresectable locally advanced oesophageal squamous cell carcinoma. Treatment consisted of docetaxel 60 mg m⁻², cisplatin 75 mg m⁻² on day 1 and fluorouracil 750 mg m⁻² day⁻¹ on days 2–5, repeated every 3 weeks for three cycles, followed by carboplatin 100 mg m⁻² week⁻¹ for 5 weeks and concurrent radiotherapy (45 Gy in 25 fractions, 5 days week⁻¹). After radiotherapy, eligible patients either underwent an oesophagectomy or received high dose rate endoluminal brachytherapy (HDR-EBT). Thirty-one out of 37 enrolled patients completed the planned chemotherapy and 30 completed chemoradiation. After completion of chemotherapy, 49% (95% CI: 32.2–66.2) had a clinical response. Twelve patients (32%) underwent a resection, which was radical in 60% (postoperative mortality: 0%). A pathological complete response was documented in four patients (11% of enrolled, 30% of resected). The median survival was 10.8 months (95% CI: 8.1–12.4), and the 1- and 2-year survival rates were 35.1 and 18.9%, respectively. Grade 3–4 toxicities were neutropoenia 32%, anaemia 11%, non-neutropoenic infections 18%, diarrhoea 6% and oesophagitis 5%. Nine patients (24%) developed a tracheo-oesophageal fistula during treatment. Even if the addition of docetaxel to cisplatin and 5-fluorouracil (5-FU) seems to be more active than the cisplatin and 5-FU combination, an incremental improvement in survival is not seen, and the toxicity observed in this study population is of concern. In order to improve the prognosis of these patients, new drugs, combinations and strategies with a better therapeutic index need to be identified.

Molecular mechanisms of resistance and toxicity associated with platinating agents

Platinating agents, including cisplatin, carboplatin, and oxaliplatin, have been used clinically for nearly 30years as part of the treatment of many types of cancers, including head and neck, testicular, ovarian, cervical, lung, colorectal and relapsed lymphoma. The cytotoxic lesion of platinating agents is thought to be the platinum intrastrand crosslink that forms on DNA, although treatment activates a number of signal transduction pathways. Treatment with these agents is characterized by resistance, both acquired and intrinsic. This resistance can be caused by a number of cellular adaptations, including reduced uptake, inactivation by glutathione and other anti-oxidants, and increased levels of DNA repair or DNA tolerance. Here we investigate the pathways that treatment with platinating agents activate, the mechanisms of resistance, potential candidate genes involved in the development of resistance, and associated clinical toxicities. Although the purpose of this review is to provide an overview of cisplatin, carboplatin, and oxaliplatin, we have focused primarily on preclinical data that has clinical relevance generated over the past five years.

Cutaneous reactions to chemotherapy and their management

International data from 2002 report 10.9 million new cases of cancer and 6.7 million cancer deaths. Chemotherapy is an essential component in the multidisciplinary management of most cancers. Cutaneous reactions to chemotherapeutics are common and may contribute significantly to the morbidity, and rarely to the mortality, of patients undergoing such treatments. Recognition and management of these reactions is important to provide optimal care. This article aims to present the most common cutaneous reactions to frequently used chemotherapies and provides management guidelines. A MEDLINE search from 1966 through June 2005 was conducted to identify reports of common cutaneous toxicities with systemic chemotherapy and their appropriate management. An analysis of our literature search is presented in review form outlining common chemotherapy-related cutaneous reactions and their management, as well as the chemotherapeutics responsible for the cutaneous toxicity. Chemotherapy-related cutaneous toxicity includes generalized rashes such as the spectrum between erythema multiforme and toxic epidermal necrolysis, and site-specific toxicity such as mucositis, alopecia, nail changes, extravasation reactions, or hand-foot syndrome. Most of the toxicity is reversible with chemotherapy dose reductions or delays. Certain toxicities can be effectively treated or prevented, allowing optimal delivery of chemotherapy (e.g. premedications to prevent hypersensitivity, prophylactic mouthwashes to prevent mucositis). Newer non-chemotherapeutic targeted therapies such as epidermal growth factor receptor inhibitors (e.g. gefitinib, cetuximab) may also be associated with cutaneous toxicity and can be distressing for patients. Recent data suggest that skin toxicity associated with these agents may correlate with efficacy. Cutaneous toxicity occurs frequently with chemotherapy and non-chemotherapeutic biologic therapies. Early recognition and treatment of the toxicity facilitates good symptom control, prevents treatment-related morbidity, and allows continuation of anti-cancer therapy.

Phase I study of cisplatin and irinotecan combined with concurrent hyperfractionated accelerated thoracic radiotherapy for locally advanced non-small cell lung carcinoma

BACKGROUND

Irinotecan, when combined with cisplatin, is an effective treatment for advanced non-small cell lung cancer (NSCLC). This constitutes a rationale for conducting a phase I study of chemoradiotherapy including this combination for locally advanced NSCLC.

PATIENTS AND METHODS

Patients with locally advanced NSCLC and a performance status of 0 or 1 were eligible. The protocol consisted of escalating doses of irinotecan on days 1 and 15, and daily low-dose cisplatin (6 mg/m(2) daily for a total dose of 120 mg/m(2)) combined with concurrent hyperfractionated accelerated thoracic irradiation (1.5 Gy twice daily for a total dose of 60 Gy).

RESULTS

The maximum tolerable dose was 50 mg/m(2) of irinotecan, and the dose-limiting toxicity was esophagitis. Tumor response was observed in 50% of cases, and the median survival time of the 12 patients enrolled was 10.1 months, including two patients with 5-year disease-free survival. A pharmacokinetics study demonstrated an accumulation of total platinum, but not of free platinum, during the 26-day treatment period.

CONCLUSION

The recommended dose for phase II studies was determined.

Cisplatin-mediated DNA double-strand breaks in replicating but not in quiescent cells of the yeast Saccharomyces cerevisiae

DNA double-strand breaks (DSBs) are formed during the processing of DNA interstrand crosslinks in replicating yeast and Chinese hamster cells exposed to DNA crosslinkers such as psoralen plus UVA or nitrogen mustard. They were also detected in human cells after treatment with photoactivated psoralen or mitomycin C. In contrast, no DSBs were observed after exposure of Chinese hamster cells to cisplatin, another crosslinking agent widely used for the therapy of various cancers, challenging a common role for DSBs in the processing of DNA interstrand crosslinks. Here we report for the first time that cisplatin-mediated DSBs are induced in replicating but not quiescent cells of the yeast Saccharomyces cerevisiae. When the main pathway of repair of DSBs is inhibited, these breaks accumulate in replicating cells. Thus it appears that DNA interstrand crosslinks induced by different crosslinking agents, including cisplatin, are processed yielding DSBs as an intermediate lesion. In stationary cells, however, removal of DNA interstrand crosslinks after cisplatin treatment occurs without the formation of DSBs. These findings point to an altered mode of processing of cisplatin-DNA adducts in replicating versus quiescent cells.

Cisplatin sensitizes cancer cells to ionizing radiation via inhibition of nonhomologous end joining

The combination of cisplatin and ionizing radiation (IR) treatment represents a common modality for treating a variety of cancers. These two agents provide considerable synergy during treatment, although the mechanism of this synergy remains largely undefined. We have investigated the mechanism of cisplatin sensitization to IR using a combination of in vitro and in vivo experiments. A clear synergistic interaction between cisplatin and IR is observed in cells proficient in nonhomologous end joining (NHEJ) catalyzed repair of DNA double-strand breaks (DSB). In contrast, no interaction between cisplatin and IR is observed in NHEJ-deficient cells. Reconstituted in vitro NHEJ assays revealed that a site-specific cisplatin-DNA lesion near the terminus results in complete abrogation of NHEJ catalyzed repair of the DSB. These data show that the cisplatin-IR synergistic interaction requires the DNA-dependent protein kinase-dependent NHEJ pathway for joining of DNA DSBs, and the presence of a cisplatin lesion on the DNA blocks this pathway. In the absence of a functional NHEJ pathway, although the cells are hypersensitive to IR, there is no synergistic interaction with cisplatin.

A randomised phase III study of palliative radiation with concomitant carboplatin for brain metastases from non-small cell carcinoma of the lung

PURPOSE

To determine if the addition of carboplatin chemotherapy to whole brain irradiation improves response and survival in patients with brain metastases from non-small cell lung cancer (NSCLC).

PATIENTS AND METHODS

Forty-two patients with brain metastases from NSCLC and performance status ECOG 0-2 were randomised to receive either whole brain radiotherapy (WBRT) alone (20Gy in five fractions) or the same radiotherapy plus concomitant carboplatin (70 mg/m(2) intravenously for 5 days).

RESULTS

The median survival was 4.4 months in the radiotherapy alone (RT) arm and 3.7 months in the combined treatment (RTC) arm (P = 0.64). The objective response rates of 10% on the RT arm and 29% on the RTC arm were not significantly different (P = 0.24). The trial was closed early because of poor accrual.

CONCLUSIONS

Although no firm conclusions can be made regarding the efficacy of the combined treatment, this prospective study highlights the poor objective response rates and relatively poor symptom control despite standard treatment of brain metastases from NSCLC.

Continuously infused carboplatin used as radiosensitizer in locally unresectable non-small-cell lung cancer: a multicenter phase III study

PURPOSE

To determine the radiosensitizing effect of prolonged exposure of carboplatin in patients with locally unresectable non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Patients with histologically proven NSCLC, performance score <2, weight loss <10%, and normal organ functions were randomized between carboplatin 840 mg/m2 administered continuously during 6 weeks of radiotherapy or thoracic radiotherapy alone (both 60 Gy). Toxicity was evaluated with National Cancer Institute Common Toxicity Criteria (NCI CTC) and the Radiation Therapy Oncology Group (RTOG) criteria. Quality of life was measured with European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30/LC13 questionnaires.

RESULTS

One-hundred and sixty patients were included. Pathologically confirmed persistent tumor was present in 53% of patients in the combination arm versus 58% in the radiotherapy alone arm (P=0.5). Median survival in the combination arm was 11.8 [95% confidence interval (CI) 9.3-14.2] months and in the radiotherapy alone arm 11.7 (95% CI 8.1-15.5) months; progression-free survival was not different between arms [6.8 and 7.5 months, respectively (P=0.28)]. Acute toxicity was mild, late toxicity was radiation-induced cardiomyopathy (three patients) and pulmonary fibrosis (five patients). Quality of life was not different between arms, but in all measured patients cough and dyspnea improved, pain became less, and slight paresthesia developed 3 months after treatment.

CONCLUSION

Addition of continuously administered carboplatin as radiosensitizer for locally unresectable NSCLC does not improve local tumor control or overall survival.

Expression of apoptosis-related proteins and morphological changes in a rat tumor model of human small cell lung cancer prior to and after treatment with radiotherapy, carboplatin, or combined treatment

PURPOSE

In order to understand the apoptosis pathway in tumor cells, differences in cell morphology and expression of apoptosis-related proteins induced by radiation and/or chemotherapy, were investigated in a rat double tumor model comparing cisplatin-sensitive and -resistant human small cell lung cancer tumors.

METHODS

The cisplatin-sensitive human small cell lung cancer cell line (GLC4) and its cisplatin-resistant subline (GLC4-CDDP) were each injected subcutaneously in a different hind limb of the rat. After 15-17 days, radiation (10 Gy), carboplatin (25 mg/kg, intraperitoneal), combined treatment, or no treatment was administered. In combined treatment, carboplatin was administered 24 h before radiation. Tumors were removed and fixed 72 h after carboplatin or 48 h after radiation. Paraffin-embedded slides were stained with hematoxylin/eosin for morphology. Expression of the apoptosis-related proteins p53, p21, Rb, bcl-2, bax, c-myc, Fas and Fas-L was assessed immunohistochemically.

RESULTS

In the GLC4 tumor, carboplatin treatment increased tumor cell size, tumor cell size heterogeneity, and number of apoptotic tumor cells. After radiation and combined treatment, these changes were more pronounced and multinuclear giant cells were observed. In GLC4-CDDP tumors, minimal changes were detected after carboplatin. Following radiation slight increases in tumor cell size, tumor cell size heterogeneity and number of apoptotic tumor cells were observed. No multinuclear giant cells were seen. After combined treatment, GLC4-CDDP showed cellular changes comparable to those in GLC4 cells after radiation or combined treatment, but no giant cells were observed. Untreated, both tumors were equally positive for p53, bax, Fas, Fas-L, c-myc and negative for Rb. Contrary to GLC4, untreated GLC4-CDDP tumors showed no p21 and bcl-2 expression. After combined treatment, an increase in number of bcl-2 positive cells was found in GLC4-CDDP tumors. No p21 was induced in GLC4-CDDP by any treatment modality. In GLC4 tumors, p21 was induced by radiation alone. No further changes in protein expression were induced by any treatment in GLC4 tumors.

CONCLUSION

Following therapy, morphological changes in cell size and cell size heterogeneity were more pronounced in GLC4 than in GLC4-CDDP tumors. However, morphological changes in GLC4-CCDP tumors after treatment indicate that carboplatin plus radiotherapy may be effective also in cisplatin resistant tumor cells. An increase in p21 in GLC4 after radiation might facilitate apoptosis. The increase in number of Bcl-2 positive cells after combined treatment and the consistently negative p21 status after any treatment in GLC4-CDDP may protect these tumor cells from apoptosis as a part of their resistance mechanism to cisplatin.

Sensitivity to ionizing radiation and chemotherapeutic agents in gemcitabine-resistant human tumor cell lines

PURPOSE

To determine cross-resistance to anti-tumor treatments in 2',2'difluorodeoxycytidine (dFdC, gemcitabine)-resistant human tumor cells.

METHODS AND MATERIALS

Human lung carcinoma cells SW-1573 (SWp) were made resistant to dFdC (SWg). Sensitivity to cisplatin (cDDP), paclitaxel, 5-fluorouracil (5-FU), methotrexate (MTX), cytarabine (ara-C), and dFdC was measured by a proliferation assay. Radiosensitivity and radioenhancement by dFdC of this cell panel and the human ovarian carcinoma cell line A2780 and its dFdC-resistant variant AG6000 were determined by clonogenic assay. Bivariate flowcytometry was performed to study cell cycle changes.

RESULTS

In the SWg, a complete deoxycytidine kinase (dCK) deficiency was found on mRNA and protein level. This was accompanied by a 10-fold decrease in dCK activity which resulted in the >1000-fold resistance to dFdC. Sensitivity to other anti-tumor drugs was not altered, except for ara-C (>100-fold resistance). Radiosensitivity was not altered in the dFdC-resistant cell lines SWg and AG6000. High concentrations (50-100 microM dFdC) induced radioenhancement in the dFdC-resistant cell lines similar to the radioenhancement obtained at lower concentrations (10 nM dFdC) in the parental lines. An early S-phase arrest was found in all cell lines after dFdC treatment where radioenhancement was achieved.

CONCLUSIONS

In the dFdC-resistant lung tumor cell line SWg, the deficiency in dCK is related to the resistance to dFdC and ara-C. No cross-resistance was observed to other anti-tumor drugs used for the treatment in lung cancer. Sensitivity to ionizing radiation was not altered in two different dFdC-resistant cell lines. Resistance to dFdC does not eliminate the ability of dFdC to sensitize cells to radiation.

Clinical application of intensity-modulated radiotherapy for locally advanced cervical cancer

Intensity-modulated radiotherapy (IMRT) offers technical advantages over conventional external beam radiotherapy (CXRT) that might prove clinically advantageous in the management of gynecologic malignancies. Especially in the case of locally advanced cervical cancer, IMRT provides an opportunity to improve the therapeutic ratio by allowing a selective combination of normal tissue dose reduction and/or concomitant integrated boost dose to the tumor. The clinical and biologic rationale for IMRT in this setting is presented here, and pertinent technical considerations such as the delineation of relevant clinical and planning target volumes are discussed. The capacity for IMRT-mediated normal tissue sparing is illustrated by example and review of the literature. Furthermore, for a small cohort of patients with locally advanced or recurrent cervical cancer treated with concomitant integrated boost IMRT and concurrent chemotherapy, preliminary clinical observations of toxicity and tumor response are presented. Concomitant integrated boost IMRT appears clinically tolerable and efficacious in this setting, and formal clinical investigation is warranted as a means of exploiting the fraction-size dependence of radiosensitizers in common clinical use.

Enhancement of radiation effects by combined docetaxel and carboplatin treatment in vitro

This study was designed to evaluate the combination of docetaxel (Taxotere) and carboplatin for radiopotentiation in vitro. H460 human lung carcinoma cells were treated with docetaxel (or paclitaxel) for 1 h and rinsed. After 24 h, the cells were treated with carboplatin for 1 h, irradiated, and colony forming ability was assesed. Using various doses of docetaxel with 100 microM carboplatin, the dose enhancement ratio (D.E.R.) for drugs only was 1.26. When 25 nM docetaxel was used with various doses of radiation, the radiation D.E.R. was 1.41. With all three agents combined, and after normalization for combined drug effects, the radiation D.E.R. was 1.55. Similar values were obtained using paclitaxel with these agents. Significant redistribution of cells into the radiosensitive G2/M phase was observed using a dose of paclitaxel (750 nM), which also caused radiation enhancement. However, an equally cytotoxic dose of docetaxel (25 nM) did not result in any cell cycle redistribution; this phenomenon was only observed at higher doses. This study shows that the combination of docetaxel and carboplatin enhance the effects of radiation in vitro more effectively than either drug seperately. In addition, our data show that the mechanism of radiopotentiation by docetaxel probably does not involve a G2/M block in H460 cells.

A randomised phase III study of accelerated or standard fraction radiotherapy with or without concurrent carboplatin in inoperable non-small cell lung cancer: final report of an Australian multi-centre trial

PURPOSE

To investigate the effects separately and together of (a) shortening overall treatment time and (b) giving concurrent carboplatin in patients having radical radiotherapy for inoperable non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Between April 1989 and May 1995, 204 patients with medically inoperable or technically unresectable NSCLC localised to the primary site and regional lymph nodes were randomised to receive one of four treatments using a 2 x 2 factorial design: standard radiotherapy, 60 Gy in 30 fractions in 6 weeks (R6); accelerated radiotherapy, 60 Gy in 30 fractions in 3 weeks (R3); standard radiotherapy as in R6 with carboplatin 70 mg/m2/day for 5 days during weeks 1 and 5 of radiotherapy (R6C); accelerated radiotherapy as in R3 with carboplatin 70 mg/m2/day for 5 days during week 1 of radiotherapy (R3C).

RESULTS

The estimated median survival of all randomised patients was 15.7 months and estimated 2-year survival was 31%. The longest survival was seen in patients randomised to R6C (median 20.3 months, 41% surviving at 2 years) but there were no statistically significant differences between treatment arms or treatment factors (carboplatin versus no carboplatin, accelerated versus conventional radiotherapy). Haematological toxicity was significantly greater in patients treated with carboplatin and oesophageal toxicity was significantly greater and more protracted in patients treated with accelerated radiotherapy.

CONCLUSIONS

This study failed to show a significant survival advantage for any of the treatment arms or factors. Halving overall treatment time resulted in significantly greater oesophageal toxicity with no suggestion of a survival advantage.

Radiopotentiation by the oral platinum agent, JM216: role of repair inhibition

PURPOSE

To test for in vitro radiopotentiation by the orally-administered platinum (IV) complex, JM216; to compare these results to cisplatin and carboplatin; and to investigate whether the mechanism of radiopotentiation involves repair inhibition of radiation-induced DNA damage.

METHODS AND MATERIALS

H460 human lung carcinoma cells were incubated with the drugs for 1 h at 37 degrees C, irradiated at room temperature, and returned to 37 degrees C for 20 min. Cells were then rinsed and colony forming ability was assessed. Wild-type V79 Chinese hamster cells and radiosensitive, DNA repair-deficient mutant cells (XR-V15B) were also studied along with H460 cells. Ku86 cDNA, which encodes part of a protein involved in DNA repair, was transfected into XR-V15B cells as previously described. The effect of JM216 on sublethal damage repair (SLDR) was also assessed using split-dose recovery.

RESULTS

Using equally cytotoxic doses of JM216, cisplatin, and carboplatin, the radiation dose enhancement ratios (DER) were 1.39, 1.31, and 1.20, respectively; the DER with 20 microM JM216 was 1.57. JM216 (20 microM) did not significantly change the final slope of radiation survival curves, but greatly reduced the survival curve shoulder. V79 cells also showed radioenhancement using 20 microM JM216, but no enhancement occurred using XR-V15B cells. Transfection of Ku86 cDNA into XR-V15B cells restored radiopotentiation by JM216 to wild-type V79 levels. In addition, 20 microM JM216 completely inhibited sublethal damage repair in H460 cells.

CONCLUSION

Our results show that JM216 can potentiate the effects of radiation in human lung cancer cells, and that the mechanism of this effect is probably inhibition of DNA repair by JM216.

Radiosensitization with carboplatin for patients with unresectable stage III non-small-cell lung cancer: a phase III trial of the Cancer and Leukemia Group B and the Eastern Cooperative Oncology Group

PURPOSE

To determine whether the administration of carboplatin concurrently with radiation treatment improves survival in patients with inoperable stage III non-small-cell lung cancer.

PATIENTS AND METHODS

Two hundred eighty-three patients with inoperable stage III non-small-cell lung cancer were entered onto a randomized trial by the Cancer and Leukemia Group B and the Eastern Cooperative Oncology Group. Randomization was performed before initiation of any therapy. All patients received an induction chemotherapy program with vinblastine and cisplatin for 5 weeks, followed by 6,000 cGy of radiation therapy over 6 weeks. One hundred thirty-seven patients were randomized to this therapy regimen alone; 146 patients were randomized to receive carboplatin at 100 mg/m2/wk concurrent with the radiation therapy.

RESULTS

The complete response was 18% with concurrent carboplatin versus 10% with radiotherapy alone (P = .101). There was no difference with respect to failure-free survival (10% with carboplatin and 9% with radiotherapy alone) or overall survival (13% with carboplatin and 10% with radiotherapy alone) at 4 years. In patients not receiving carboplatin, the relapse rate was 69% within the field of radiation and 53% in the boost volume. In patients receiving carboplatin, the relapse rate was 59% within the field of radiation and 43% in the boost volume. Patients with cancers more than 70 cm2 in size had significantly poorer survival (P = .01).

CONCLUSION

Carboplatin at the dose and schedule used did not significantly impact on disease control or survival. The relapse rate within the chest remained more than 50%. More effective regimens will be required to impact on local disease control and survival.