Biology of small cell lung cancer: an overview

Despite disappointing results in the treatment of small cell lung cancer (SCLC), major progress in our understanding of SCLC biology has occurred in the past decade. Advances in the technique for culturing SCLC tumours in vitro have greatly facilitated the study of the biological properties of this tumour. The major progress in our understanding of SCLC includes: 1) the availability of nonspecific biological tumour markers such as neuron-specific enolase (NSE), the BB isoenzyme of creatine phosphokinase (CPKBB), bombesin/gastrin releasing peptide (GRP) and chromogranin A; 2) the generation of monoclonal antibodies raised against the neural and epithelial features of SCLC tumours; 3) the identification of several autocrine growth factors such as bombesin/GRP, insulin-like growth factor (IGF), transferrin and physalaemin; 4) the close study of cytogenetic abnormalities leading to the discovery of a unique chromosomal deletion of the short arm of chromosome 3 (del 3p 14-21), and to changes in oncogenic expression, e.g. c-myc, L-myc and N-myc, accounting for known biological and treatment results. These data suggest that all lung cancers arise from a common stem cell of endodermal origin. The information derived from these biological studies represents the most promising avenue towards new treatment strategies in SCLC.

Immunological and pharmacological removal of small cell lung cancer cells from bone marrow autografts

Autologous bone marrow transplantation is used in small cell lung cancer (SCLC) to reverse the hematological toxicity induced by high dose therapy even though the presence of cancerous cells in the graft is potentially dangerous by reinfusion of the disease along with the hematopoietic stem cells. The present studies were undertaken to examine the effectiveness of anti-SCLC rat monoclonal antibodies LCA1 and LC66 plus human complement combined with a derivative of cyclophosphamide (Asta-Z 7557) for the elimination of cancerous clonogenic cells from the graft. In a series of assays conducted with three SCLC cell lines, used alone or mixed with normal bone marrow cells, the addition of Asta-Z 7557 to two cycles of treatment with monoclonal antibodies plus complement results in a 4- to 5-logarithmic reduction of the clonogenic SCLC cells detectable by limiting dilution analysis. This was superior to either treatment used alone. When normal bone marrow was submitted to the same treatment, a median (range) of 44% (15-77%) of the colony-forming unit, granulocyte-macrophage was recovered. These results suggest that the association of immunological (LCA1 and LC66 plus human complement) and pharmacological (Asta-Z 7557) removal methods is effective for purging metastatic clonogenic cells from bone marrow of SCLC patients and could be considered before autologous bone marrow transplantation.

Carboplatin in association with etoposide and either adriamycin or epirubicin for untreated small cell lung cancer: a dose escalation study of carboplatin. UCL Clinical Oncology Group

A multi-center, open trial was conducted to determine the maximal tolerable dose of carboplatin in combination with conventional doses of both etoposide and an anthracycline for the treatment of previously untreated small cell lung cancer (SCLC) patients. Ninety-five patients [48 with limited disease (LD) and 47 with extensive disease (ED)] received a total of 376 courses of treatment. Carboplatin was given on day 1 at a dose of 250 mg m-2 in 60 courses, 300 mg m-2 in 69, 330 mg m-2 in 236 and 350 mg m-2 in 11, with 120 mg m-2 etoposide on days 1, 3 and 5 and either 40 mg m-2 adriamycin or 60 mg m-2 epirubicin on day 1. Epirubicin was not administered before carboplatin reached the dose of 330 mg m-2. Courses were repeated every 3 weeks. The main toxicity was hematological. The first course of therapy induced a dose-dependent decrease of leucocyte, neutrophil and platelet counts: all patients, except one, who received 350 mg m-2 carboplatin had a neutropenia below 200 microliters-1 and a thrombopenia below 100,000 microliters-1. Three patients died of septicemia. Other toxicities were well tolerated. After three courses, patients were re-staged by performing a mandatory fiberoptic bronchoscopy and a thoracic computed axial tomography (CAT). The overall objective response rate for 86 evaluable patients was 91% (98% for LD) with 21% complete remissions (30% for LD). All 23 hepatic and six brain sites, evaluable after chemotherapy alone, responded.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoclonal antibodies for the in vitro detection of small cell lung cancer metastases in human bone marrow

Three rat monoclonal antibodies were selected for the immunodetection of small cell lung cancer metastases in bone marrow and other hematologic samples. By membrane immunofluorescence, they define three distinct surface antigens here termed lung cancer-associated antigens or LCAs. The latter are widely expressed on small cell lung cancer and non-small cell lung cancer cells/cell lines, but not detectable on a variety of normal and transformed bone marrow, blood and lymphoid cells. Anti-LCA1 (IgM) is similar to the many anti-lacto-N-fucopentaose III IgM antibodies rasied against human tumors. In contrast, anti-LCA2 (IgG2b) and anti-LCA3 (IgG2a) define surface proteins of 29, 32, 41 and 98 kilodaltons, respectively, that have not been reported earlier. These three reagents have immunodiagnostic potential, since in combination they label all 49 lung cancer cell lines tested. Their ability to detect lung cancer metastases in patient's bone marrow samples is documented in an accompanying paper.

Immunodetection of small cell lung cancer metastases in bone marrow using three monoclonal antibodies

Detection of bone marrow metastases by indirect immunofluorescence methods was investigated using three monoclonal antibodies (MoAbs) raised against small cell lung cancer (SCLC). These antibodies, designated anti-LCA1, -LCA2 and -LCA3, recognize three different antigens on the surface of SCLC cells. Eighty-four bone marrow samples from 74 different patients were studied. Whereas tumor cells were found in 32 (38%) by MoAb staining, only 10 (12%) were positively identified using conventional morphological methods. Nine out of the morphologically positive specimens showed reactivity with at least two monoclonal antibodies. Among the 32 samples proven positive by immunofluorescence, an important antigenic variability was noted. Anti-LCA1 recognized tumor cells in 62%, anti-LCA2 and anti-LCA3 in 53%. Due to the recognition of bone marrow involvement by fluorescence methods in 26% of the 34 patients classified as limited disease, a new subgroup of limited disease patients was defined whose prognosis remains undetermined. Our results confirm the utility of immunodetection in the diagnosis of SCLC bone marrow metastases and emphasize the advantage of using a panel of MoAbs with different antigenic specificities. Further study is needed to determine the prognostic significance of bone marrow involvement established by immunodetection.

Detection of small cell lung cancer bone marrow metastases by immunofluorescence

It is well known that small cell lung cancer (SCLC) has a high propensity to metastasize to the bone marrow and that such involvement has a prognostic significance. A more accurate detection of these bone marrow metastases is thus mandatory. In this study, we analysed the results of the detection of these metastases using an indirect immunofluorescence test. For this purpose, 3 anti-SCLC rat monoclonal antibodies (MoAbs) specific for 3 different antigens (LCA1, LCA2, LCA3) have been utilized to examine 59 bone marrow samples from patients at time of diagnosis and 20 samples from chemotherapy treated patients. Eight patients had bone marrow clearly involved by morphological analysis. They all had fluorescent cells recognized at immunodetection with at least 2 MoAbs positive for 7 out of the 8 samples. Fifteen samples, negative by morphological analysis, were proven positive by immunofluorescence. In 12 cases, involvement was detected only by 1 MoAb (6 anti-LCA1, 2 anti-LCA2, 4 anti-LCA3). A correlation was found between the number of samples proven positive by morphological analysis and the number of positive MoAbs for these samples (p less than 0.005). Among the bone marrow samples provided by the 32 limited disease patients, LCA positive cells were detected in 9 (28%) compared to 14 out of the 27 (52%) samples from extensive disease patients (p less than 0.05). We concluded that the indirect immunofluorescence with a panel of MoAbs increases the rate of detection of bone marrow SCLC metastases.

Concentration of bone marrow progenitor cells by separation on a Percoll gradient using the Haemonetics model 30

To perform an optimal ex vivo bone marrow purge, it is necessary to concentrate the bone marrow progenitor cells and to eliminate both the red blood cells and the polymorphonuclear leucocytes. To achieve this goal which cannot be accomplished by using the Haemonetics model 30 alone, we used the Haemonetics model 30 and a density gradient together in a two-step procedure. In the first step we obtained the buffy coat from original bone marrow grafts and in the second we reintroduced these buffy coats into the Haemonetics bowl followed by Percoll, adjusted to 1.079 g/ml, at 5 ml/min in order to recover the light density mononuclear cells. After this second step, the mean volume of the marrow and the RBC and nucleated cell contaminations were reduced to 9%, 0.96% and 16% of their original values the unseparated bone marrow, respectively. This was far better than the values obtained after the first step (volume: 19%; RBC: 10%; nucleated cells: 54%). The CFU-GM recoveries after the first and second steps were 71% and 70% of the original samples, respectively. The entire procedure lasted between 75 and 150 min. At this time, 17 of the 24 patients whose bone marrow was separated using Percoll gradient in the Haemonetics bowl have been grafted. Thirteen of these 17 patients had an evaluable haematological recovery which was complete and rapid for all but one patient with acute myeloid leukaemia. These results demonstrate that the introduction of a density gradient into the Haemonetics model 30 bowl is possible and effective. The reduction in total volume and cell number permits ex vivo purging, without decreasing the grafting capability.

Detection of small cell lung cancer bone marrow metastases by tumor stem cell assay

Detection of small cell lung cancer (SCLC) bone marrow (BM) metastases has a prognostic implication in itself and a therapeutic interest in the setting of autologous bone marrow transplantation. In a prospective study involving 68 bone marrow samples, we compared SCLC detection results obtained using a tumor stem cell assay and those obtained using conventional morphology by light microscopy. In agar, tumoral cells were stimulated either by Salmon's conditioned medium or by epidermal growth factor (EGF). Tumoral clonogeneic cells were detected in 11 cases, although 7 of these were considered negative when investigated by light microscopy. On the contrary, metastases were detected by morphology in 8 instances where no growing colonies were revealed by tumor stem cell assay. The choice of stimulating factor did not seem critical since the number of colonies was similar in all the cases. We conclude that the tumor stem cell assay is useful in the detection of small cell lung cancer bone marrow metastases, particularly in cases where these metastases have failed to be recognized through light microscopy investigation. However, the sensitivity of this assay is low and should be complemented by other techniques such as immunodetection.

Late intensification chemotherapy with autologous bone marrow transplantation in selected small-cell carcinoma of the lung: a randomized study

A multicentric randomized prospective trial was conducted to test whether late intensification chemotherapy would increase the remission rate, the relapse-free survival, and the survival of small-cell lung cancer patients responding to induction chemotherapy. Autologous bone marrow transplantation was used as support to reduce the duration of the aplasia induced by very high-dose chemotherapy. As induction chemotherapy, 101 patients received, during a period of 5 months, a total dosage of 120 mg/m2 methotrexate, 4.5 mg/m2 vincristine, 1,800 mg/m2 cyclophosphamide, 180 mg/m2 doxorubicin, 160 mg/m2 cisplatin, 750 mg/m2 VP-16-213, and 30 Gy prophylactic cranial irradiation. Forty-five patients, selected for their sensitivity to this induction treatment, were randomized to a last cycle of chemotherapy that combined cyclophosphamide, BCNU, and VP-16-213 either at a conventional dosage of 750 mg/m2 intravenously (IV), 60 mg/m2 IV, and 600 mg/m2 orally or alternatively at a very high dosage of 6 g/m2 IV, 300 mg/m2 IV, and 500 mg/m2 IV, respectively. In the late intensification group, the complete remission rate increased from 39% before randomization to 79% after high-dose chemotherapy. Median relapse-free survivals after randomization for intensified and control chemotherapy groups were 28 and 10 weeks, respectively (P = .002). Median overall survival after induction therapy was 68 weeks for the intensified group compared with 55 weeks for the conventional therapy group (P = .13). Four patients died during intensification. Patients in both groups relapsed at the primary site. It can thus be concluded that late intensification chemotherapy for sensitive small-cell lung cancer increases the complete remission rate and resulted in a statistically significant increase in the relapse-free survival. However, since relapse occurred at the primary site and toxicity was high, overall survival was not significantly improved.

A phase I study of vinblastine tryptophan ester

Vinblastine tryptophan ester (VTrpE) is a new vinca alkaloid derivative that achieves antitumor activity in a large variety of animal models. In this phase I study the drug was given as an i.v. injection over 5 min, once a week or once every 2 weeks. Twenty patients with advanced cancer were entered in this trial. The doses ranged from 2.5 mg/m2 to 35 mg/m2. Myelosuppression is the dose-limiting toxicity, with the risk of leukopenia being more serious than that of thrombocytopenia, but the myelosuppression is always reversible. Neurotoxicity, well documented when other vinca alkaloid derivatives are used, is insignificant. Two cases of disease stabilization have been observed in patients with non-small cell lung cancer. For VTrpE, a dose schedule of 30 mg/m2 per week may be recommended for phase II studies in non-small cell lung cancer.

Leukocyte membrane proteins in chronic lymphocytic leukemia, as studied by two-dimensional gel electrophoresis

We evaluated protein expression in leukocytes from 20 patients with chronic lymphocytic leukemia (CLL), including one with the rare T-cell form of the disease. To identify proteins that potentially could be used to characterize leukemia or as candidates for new markers of differentiation, we studied cell and membrane extracts from these leukemic cells. We used immune precipitation and extraction of integral membrane proteins with Triton X-114 to identify known proteins on the surface of these cells. Extraction with Triton X-114 in the presence of protease inhibitors yielded reproducible membrane extracts, which we examined by two-dimensional gel electrophoresis. Of the approximately 2000 proteins or protein subunits so resolved from cell lysates and the 450 from membrane extracts of leukocytes from patients with T- and B-cell CLL, we were able to identify spots corresponding to the proteins designated by the OKT.4 and OKT.10 antibodies, the human class I and II histocompatibility antigens, beta 2-microglobulin, and surface IgM. We also defined sets of proteins that are characteristically expressed on the membranes of leukemic T or B cells, some of which correspond to previously defined markers of normal leukocyte subpopulations.

Leukocyte membrane proteins in chronic lymphocytic leukemia, as studied by two-dimensional gel electrophoresis

We evaluated protein expression in leukocytes from 20 patients with chronic lymphocytic leukemia (CLL), including one with the rare T-cell form of the disease. To identify proteins that potentially could be used to characterize leukemia or as candidates for new markers of differentiation, we studied cell and membrane extracts from these leukemic cells. We used immune precipitation and extraction of integral membrane proteins with Triton X-114 to identify known proteins on the surface of these cells. Extraction with Triton X-114 in the presence of protease inhibitors yielded reproducible membrane extracts, which we examined by two-dimensional gel electrophoresis. Of the approximately 2000 proteins or protein subunits so resolved from cell lysates and the 450 from membrane extracts of leukocytes from patients with T- and B-cell CLL, we were able to identify spots corresponding to the proteins designated by the OKT.4 and OKT.10 antibodies, the human class I and II histocompatibility antigens, beta 2-microglobulin, and surface IgM. We also defined sets of proteins that are characteristically expressed on the membranes of leukemic T or B cells, some of which correspond to previously defined markers of normal leukocyte subpopulations.