Apoptosis, cancer and cancer therapy

Apoptosis is a specific process that leads to programmed cell death through the activation of an evolutionary conserved intracellular pathway leading to pathognomic cellular changes distinct from cellular necrosis. Apoptosis is essential in the homeostasis of normal tissues of the body, especially those of the gastrointestinal tract, immune system and skin. There is increasing evidence that the processes of neoplastic transformation, progression and metastasis involve alterations in the normal apoptotic pathways. Furthermore, the majority of chemotherapeutic agents as well as radiation utilize the apoptotic pathway to induce cancer cell death. Resistance to standard chemotherapies also seems to be determined by alterations in the apoptotic pathways of cancer cells. Therefore, understanding the signals of apoptosis and the mechanism of apoptosis may allow the development of better chemo- or radiotherapeutic regimens for the treatment of cancer. Finally, components of the apoptotic pathway may represent potential therapeutic targets using gene therapy techniques.     

Apoptosis in cancer

The antiviral activities of sodium dichloroisocyanurate (NaDCC) and a commercial product (Solprogel 2%) against human immunodeficiency virus type 1 (HIV-1) were investigated using a quantitative suspension test method. Solprogel is a compound that contains NaDCC and a biodegradable polymer of acrylic acid. Viral suspensions were prepared containing 3.2 x 10(6) tissue culture infective dose 50 (TCID50) in culture media. Syncytium formation in the MT-2 line and HIV antigen p24 on the supernatant of the cultures were used to determine viral titre. Results indicate that satisfactory disinfection (1000-fold reduction in 5 min) can be achieved using NaDCC and Solprogel at concentrations of 100 and 120 ppm available chlorine, respectively.     

Pharmacogenetics and cancer chemotherapy

Cancer chemotherapy is limited by significant inter-individual variations in responses and toxicities. Such variations are often due to genetic alterations in drug metabolising enzymes (pharmacokinetic polymorphisms) or receptor expression (pharmacodynamic polymorphisms). Pharmacogenetic screening prior to anticancer drug administration may lead to identification of specific populations predisposed to drug toxicity or poor drug responses. The role of polymorphisms in specific enzymes, such as thiopurine S-methyltransferases (TPMT), dihydropyrimidine dehydrogenase (DPD), aldehyde dehydrogenases (ALDH), glutathione S-transferases (GST), uridine diphosphate glucuronosyl-transferases (UGTs) and cytochrome P450 (CYP 450) enzymes in cancer therapy are discussed in this review.     

Small cell lung cancer and chemotherapy

We report a case of a spontaneous pneumothorax in association with a major burn. The pneumothorax remained undetected for 4 days and the patient underwent a 2 h aeromedical transfer which could potentially have been hazardous. We strongly recommend that arterial blood gas analysis is performed before air transport of moderate or severely burned patients. If blood gases are abnormal a chest X-ray should also be performed. In practice a strong case can be made for routinely obtaining a chest X-ray in these patients. In-flight monitoring should include pulse oximetry.     

Pre-operative chemotherapy and radiotherapy in breast cancer

Primary systemic treatment of breast cancer with cytotoxics yields a high response rate and allows conservative surgical procedures in bulky tumours. In order to maximise local control of disease, two innovations were introduced in a pilot study. The first was to identify the good responders after three cycles of chemotherapy and to treat them with three additional cycles. The second was to also give this group of patients a full dose of radiotherapy before surgery with the aim of verifying the rate of pathological complete remissions in view of a possible treatment of breast primary with chemoradiotherapy only. Patients were treated with doxorubicin 60 mg/m2 and cyclophosphamide, 600 mg/m2 both intravenously on day 1, every 21 days for three courses. Partial or complete responders received three more courses followed by radiotherapy (50 Gy plus a 10 Gy boost). The others underwent immediate surgery. A total of 32 patients (median age, 50 years; range 28-69 years); performance status, 0-1; T2 22, T3 8, T4 2) were enrolled and were evaluable for response and side-effects. 9 patients had only three cycles of chemotherapy due to absence of response and 23 patients had six cycles of chemotherapy. Overall, 7 patients had a complete remission, 16 a partial remission and 9 had stable disease, for an overall response rate of 72% (95% confidence interval 53-86%). In the group of patients that completed the programme, two complete pathological remissions were observed and 5 patients had only microfoci of tumour. No toxic death or grade III-IV toxicities were observed. Mild or moderate side-effects included mucositis, nausea/vomiting and leucopenia. In conclusion, our results indicate that the addition of radiotherapy to pre-operative chemotherapy did not significantly enhance the incidence of pathological complete remissions. New primary treatment approaches should be explored in this subset of patients in order to improve outcome.     

The hormonal and chemotherapy of prostatic cancer

Adenocarcinoma of the prostate is one of the most common malignant tumors in adult males. Hormonal therapy is the treatment of choice for patients with systemic disease concerning 80% response rate. Androgen ablation is now the first hormonal manipulation and can be achieved either by means of bilateral orchiectomy or of LH-HR agonist therapy: both are equally effective. Total androgen blockage (association between orchiectomy or LH-RH agonist and non-steroidal anti-androgens) would be reserved for controlled clinical trials only. Estrogens had the same efficacy, but revealed the serious cardio-vascular events. Endocrine therapy does not prolong survival but provides good palliation. Palliation should be given when there is something to palliate. Prostate cancer is usually not recognized as being sensitive to cytotoxic agents. Single agent or combination chemotherapy has not been shown to have a role as first line treatment of disseminated disease and is usually used for hormone refractory disseminated disease.     

Circadian chemotherapy in cancer patients

Continuous infusion of 5-FU at night was performed for four patients: three had liver metastasis (one with gastric cancer and two with rectal cancer) and one had local recurrence of rectal cancer. The chemotherapy schedule was 400 mg/m2/day 5-FU intraarterial or intravenous infusion from 6:00 p.m. to 6:00 a.m. for five days repeated every 3 weeks. There were one complete response, two partial responses and one with no change. It is expected that the chemotherapy of 5-FU at night will result in a high efficacy and lower toxicity.     

Adjuvant chemotherapy of breast cancer

Numerous randomized trials have been conducted in an attempt to demonstrate the role of adjuvant chemotherapy in localized operable breast cancer. A major meta-analysis has demonstrated its effectiveness in certain indications. These trials show that only long-term combination chemotherapy has an undeniable efficacy. The reference protocol is the classical CMF combining cyclophosphamid, methotrexate and 5 fluoro-uracil. Efficacy is clear for patients under 50 years of age. After this age, tamoxifen is effective. There does not appear to be any benefit from prolonging chemotherapy over 6 months. The meta-analysis has not however answered all the questions raised by adjuvant chemotherapy. Should chemotherapy be used in N-forms? What is the effect of treatment in patients over 65? What is the optimal treatment duration? Is there a dose-efficacy relationship? What is the relative effect of chemotherapy versus radiotherapy? Does perioperative chemotherapy add any benefit? What should be the relative roles of hormone therapy and chemotherapy? Is castration as effective as chemotherapy before menopause and tamoxifen after menopause? Currently, only partial answers to these questions have been obtained and many remaining problems will only be solved by the results of controlled trials currently under way.     

Electropermeabilization in bladder cancer chemotherapy

PURPOSE: Electropermeabilization has been used for the introduction of genes into cells. Using this technique, we introduced the cytotoxic drug bleomycin (BLM) into cells and examined whether the technique might be useful for the treatment of bladder cancer. MATERIALS AND METHODS: For electropermeabilization in vitro, we used YTS-1 cells, a human transitional cell carcinoma line. Aliquots of cell suspension were mixed with a solution of BLM and immediately exposed to electric pulses. A high-power pulse generator was used to supply square-shaped pulses of 1250 V/cm (100 micros, eight pulses). After a 2-h post-shock incubation, cells were washed and incubated for one further hour. Then the concentration of BLM in the cells was measured using a bioassay. For electropermeabilization of tissue, we used normal male Wistar rats. The bladder was exposed and 10 mg/kg BLM was injected into the caudal vein. A series of eight pulses with a time constant of 100 micros at an electric field intensity of 1000 V/cm was applied. The bladder, liver and lungs were extracted 1 h later and prepared for quantification of the BLM concentration using the bioassay. RESULTS: Electrotreated cells contained significantly higher concentrations of BLM than nonelectrotreated cells. The concentration of BLM 1 h after electrotreatment in bladder tissue was 2.7 times higher than that in nonelectrotreated bladder tissue. CONCLUSION: The electropermeabilization technique has the potential to serve as a new and effective modality for the treatment of bladder cancer.     

Head and neck cancer: guidelines for chemotherapy

Head and neck cancer is estimated to be one of the most prevalent cancers in the world. This tumour type accounts for 5% of all new cancer cases in the US and Europe each year. Patients with locally recurrent or metastatic squamous cell carcinoma of the head and neck have a poor prognosis, with a median duration of survival between 4 and 6 months. During the past few years, screening for potentially active new compounds, new associations and new modalities of chemotherapy administration have had some degree of success. Clinical investigations have also focused on the addition of chemotherapy to locoregional treatment for patients with locally advanced disease. Induction chemotherapy or concomitant chemo- and radiation therapy can result in high response rates, and reduced incidence of distant metastases. However, there is no clear demonstration of any benefit from the addition of chemotherapy to locoregional therapy on overall survival in patients with resectable disease. In patients with resectable laryngeal or hypopharyngeal cancer, chemotherapy combined with radiotherapy can be considered as a standard treatment option for larynx preservation, keeping total laryngectomy reserved for salvage therapy. In patients with unresectable head and neck cancer, simultaneous chemoradiotherapy has been shown to improve locoregional control and survival, at the cost of greater toxicity. Outside clinical trials, this approach can also be considered as a standard therapy for unresectable disease.     

Adjuvant systemic chemotherapy in colon cancer

The prognosis for patients with cancer of the colon is dubious. An intendedly curative colon resection is performed in two-thirds of these patients, but half of them will subsequently die from metastatic disease. Randomized trials of adjuvant therapy with fluorouracil in combination with levamisole or leucovorin have shown significant benefit in terms of increased disease-free survival and overall survival. In 1990 adjuvant treatment was recommended as routine therapy in high risk patients in USA. A number of European countries are routinely treating high risk patients with Dukes' C coloncarcinoma. The recommendations are based on results from several cooperative trials reviewed in this article. Treatment related toxicity accelerates with increasing age but was acceptable in the reviewed trials. Adjuvant therapy is widely accepted as an important supplement to surgery in high risk patients. A Conference on the results and experiences now available should take place in the near future in order to establish a national consensus on adjuvant chemotherapy in Denmark. Patients with resected Dukes' C coloncarcinoma should receive adjuvant chemotherapy including 5-fluorouracil and leucovorin. Randomized trials are needed to establish the most effective regimens but "no-treatment" controls are no longer ethically acceptable.