AIRO Breast Cancer Group Best Clinical Practice 2022 Update

Introduction:

Breast cancer is the most common tumor in women and represents the leading cause of cancer death. Radiation therapy plays a key-role in the treatment of all breast cancer stages. Therefore, the adoption of evidence-based treatments is warranted, to ensure equity of access and standardization of care in clinical practice.

Method:

This national document on the highest evidence-based available data was developed and endorsed by the Italian Association of Radiation and Clinical Oncology (AIRO) Breast Cancer Group. We analyzed literature data regarding breast radiation therapy, using the SIGN (Scottish Intercollegiate Guidelines Network) methodology ( www.sign.ac.uk ). Updated findings from the literature were examined, including the highest levels of evidence (meta-analyses, randomized trials, and international guidelines) with a significant impact on clinical practice. The document deals with the role of radiation therapy in the treatment of primary breast cancer, local relapse, and metastatic disease, with focus on diagnosis, staging, local and systemic therapies, and follow up. Information is given on indications, techniques, total doses, and fractionations.

Results:

An extensive literature review from 2013 to 2021 was performed. The work was organized according to a general index of different topics and most chapters included individual questions and, when possible, synoptic and summary tables. Indications for radiation therapy in breast cancer were examined and integrated with other oncological treatments. A total of 50 questions were analyzed and answered. Four large areas of interest were investigated: (1) general strategy (multidisciplinary approach, contraindications, preliminary assessments, staging and management of patients with electronic devices); (2) systemic therapy (primary, adjuvant, in metastatic setting); (3) clinical aspects (invasive, non-invasive and micro-invasive carcinoma; particular situations such as young and elderly patients, breast cancer in males and cancer during pregnancy; follow up with possible acute and late toxicities; loco-regional relapse and metastatic disease); (4) technical aspects (radiation after conservative surgery or mastectomy, indications for boost, lymph node radiotherapy and partial breast irradiation). Appendixes about tumor bed boost and breast and lymph nodes contouring were implemented, including a dedicated web application. The scientific work was reviewed and validated by an expert group of breast cancer key-opinion leaders.

Conclusions:

Optimal breast cancer management requires a multidisciplinary approach sharing therapeutic strategies with the other involved specialists and the patient, within a coordinated and dedicated clinical path. In recent years, the high-level quality radiation therapy has shown a significant impact on local control and survival of breast cancer patients. Therefore, it is necessary to offer and guarantee accurate treatments according to the best standards of evidence-based medicine.

Daily Low-dose Carboplatin and Standard Radiotherapy in Unresectable Head and Neck and Lung Cancers: A Pilot Study

A total of 14 patients with locally advanced and unresectable head and neck (SCCHN) or non small cell lung cancer were treated with a definitive course of radiation therapy with conventional fractionation and 30 mg/m2 carboplatin (CBDCA) given daily as an i.v. infusion during the 1st, 3rd, 5th and 7th weeks of the combined treatment. The planned tumor dose of at least 7000 cGy was reached in all SCCHN patients except 1 (6600 cGy). The 2 NSCLC patients received 6320 and 5980 cGy, respectively. The planned total CBDCA-dose of 600 mg/m2 was administered in all patients. No treatment delays were required in 10 patients. Interruptions for severe mucositis or myelosuppression occurred in 4 patients (28.6%), but in no case did the delay exceed 1 week. Complete response was obtained in 8 patients (57.1%); 7 of the 12 with SCCHN and 1 of the 2 with NSCLC. The other 6 patients achieved a partial response. Granulocytopenia of WHO grade 3 occurred in 1 patient; apart from vomiting and mucositis, toxicities above grade 2 were not observed.

Concomitant Chemotherapy and External Radiotherapy plus Brachytherapy for Locally Advanced Esophageal Cancer Results of a Retrospective Multicenter Study

Aims and Background

In October 1995, the Piedmont AIRO (Italian Society of Radiation Oncology) Group started a multi-institutional study of radiochemotherapy on locally advanced esophageal cancer, characterized by external radiotherapy followed by an intraluminal high dose-rate brachytherapy boost. Most patients were re-evaluated for surgery at the end of the program. The primary aim of the study was to assess efficacy of curative radiochemotherapy regarding overall survival and local control rates. The secondary aim was to evaluate the ability of radiochemotherapy to make resectable lesions previously considered inoperable.

Methods and Study Design

Between January 1996 and March 2000, 75 patients with locally advanced esophageal cancer were enrolled. All were treated with definitive radiotherapy; due to age or high expected toxicity, chemotherapy was employed only in 53 of them. Treatment schedule consisted of 60 Gy external radiotherapy (180 cGy/d, 5 days/week for 7 weeks) concomitant with two 5-day cycles of chemotherapy with cisplatin and fluorouracil (weeks 1 and 5). One or two sessions of 5-7 Gy intraluminal high dose-rate brachytherapy were carried out on patients whose restaging showed a major tumor response. Surgery was performed in 14 patients.

Results

At the end of radiotherapy, dysphagia disappeared in 46/75 cases (61%), and in 20/75 (27%) a significant symptom reduction was recorded. Complete objective response at restaging after radiotherapy was obtained in 33% of patients and a partial response in 53%. At the end of the multimodal treatment program, including esophagectomy, complete responses were 34 (45%); 4 of 14 (28.5%) cases proved to be disease free (pTO) at pathological examination. No G3-G4 toxicity was recorded. Two- and 5-year overall survival rates of all patients were, respectively, 38% and 28%; 2- and 5-year local control rates were, respectively, 35% and 33%. In a subgroup of 20 nonsurgical patients in complete response after radiochemotherapy, the overall survival rate at 3 and 5 years was 65% and the local control rate at 3 and 5 years was 75%. According to multivariate analysis, prognostic factors for survival were Karnofsky index and esophagectomy.

Conclusions

For patients with locally advanced disease, radiochemotherapy showed improved clinical and pathologic tumor response and survival compared to surgery or radiotherapy alone. Intraluminal brachytherapy with a small fraction size allows an increased dose to the tumor without higher toxicity. Esophagectomy following radiochemotherapy could improve survival rates compared to definitive radiochemotherapy, but it is necessary to optimize selection criteria for surgery at the re-evaluation phase.

Senescence-associated secretory phenotype favors the emergence of cancer stem-like cells

The molecular mechanisms underlying cancer resistance remain elusive. One possible explanation is that cancer stem cells (CSCs) elude drug treatment, emerge and reproduce a tumor. Using multiple myeloma as a paradigm, we showed that cancer stem-like cells (CSLCs) appear after genotoxic stress because of their intrinsic properties. However, these properties do not drive the emergence of the CSLCs. Following genotoxic stress, remaining DNA damages lead to a senescence-associated secretory phenotype (SASP). Senescent cells, which are the non-CSLCs, secrete chemokines contributing to the emergence, maintenance and migration of CSLCs. Downregulation of checkpoint protein 2, a key player of SASP, significantly reduced the emergence of CSLCs. Our results unravel a novel molecular mechanism by which SASP might promote malignancy, underlining the dual role of senescence in tumorigenesis. This mechanism, based on mutual cooperation among tumor cells, illustrates how cancer may relapse; its targeting could represent new therapeutic opportunities.

Cyclin D1 mediates resistance to apoptosis through upregulation of molecular chaperones and consequent redistribution of cell death regulators

Cyclin D1 is a key regulator of cell proliferation. It also controls other aspects of the cell fate, such as cellular senescence, apoptosis and tumourigenesis. We used B-lymphoid cell lines producing cyclin D1 to investigate the role of this protein in B-cell lymphomas and leukaemias. Constitutive low levels of cyclin D1 had no effect per se on cell proliferation, but conferred resistance to various apoptotic stimuli in B cells. Activation of the pro-apoptotic protein, Bax, was reduced and mitochondrial permeabilization and phosphatidylserine exposure following cytokine withdrawal were delayed in cyclin D1-producing cells. Proteomic analysis showed that the presence of cyclin D1 led to intracellular accumulation of various molecular chaperones. The chaperone, heat shock protein (Hsp)70, bound to both Bax and the mitochondrial apoptosis inducing factor following cytokine withdrawal, and impeded inhibitors of kappaB (IkappaB)-mediated inhibition of nuclear factor-kappaB anti-apoptotic signalling. Impairment of Hsp70 activity--using a pharmacological Hsp inhibitor or transfecting cells with an Hsp70-blocking antibody--restored the cellular response to mitochondrial apoptosis triggering. Thus, constitutive de-novo cyclin D1 production in B cells delays commitment to apoptosis by inducing Hsp70 chaperoning activity on pre- and post-mitochondrial pro-apoptotic factors.

No BCL-2 protein over expression but BCL-2/IgH rearrangements in B cells of patients with persistent polyclonal B-cell lymphocytosis

INTRODUCTION

Persistent polyclonal B-cell lymphocytosis is a rare hematological disorder, characterized by a chronic, stable and absolute polyclonal lymphocytosis, the presence of binucleated lymphocytes, a polyclonal increase in serum IgM immunoglobulin and clonal cytogenetic abnormalities involving chromosome 3. For explaining the expansion of B-lymphocytes pool in PPBL, an association with cigarette smoking and/or chronic Epstein-Barr virus infection have been suggested but both hypotheses have been ruled out.

MATERIALS AND METHODS

We studied the presence of BCL-2/IgH rearrangements in a series of eight PPBL patients (seven females and one male) by a nested polymerase chain reaction (PCR), targeting the Major Breakpoint Region in BCL-2 locus and we explored the BCL-2 protein expression by Western blot.

RESULTS

We demonstrated: (a) the constant presence of BCL-2/IgH rearrangements in eight out of eight DNA samples, (b) multiple rearrangements in three out of eight cases and, (c) normal BCL-2 protein expression, as compared to BCL-2 level in B-lymphocytes from healthy population.

CONCLUSION

Despite the presence of BCL-2/IgH rearrangements, the accumulation of B lymphocytes in PPBL is not related to an overexpression of BCL-2 protein.

Cyclin D1 expression in patients with multiple myeloma

INTRODUCTION

Chromosomal abnormalities are detected in 50 to 70% of patients with multiple myeloma (MM). By conventional cytogenetic analysis, a t(11;14)(q13;q32) is observed at a frequency of 3 to 14%.

MATERIALS AND METHODS

To demonstrate a cyclin D1 expression in MM patients or MM cell lines, 14 patients with multiple myeloma (MM) and nine human multiple myeloma cell lines (HMCL) were screened by a competitive RT-PCR and/or Northern blot analysis for cyclin D1 expression. Furthermore, we screened 10 MM patients with FISH to demonstrate a relationship between the cyclin D1 expression and the presence of the t(11;14).

RESULTS

Five HMCL had a cyclin D1 overexpression: three of them had a t(11;14)(q13;q32) and two had extra copies of chromosome 11. A cyclin D1 expression was found at diagnosis in seven out of 14 untreated MM patients (50%). Out of 14 MM patients, FISH studies were performed in 10 patients. A t(11;14) was detected in three out of 10 patients and extra copies of chromosome 11 were found in two additional patients.

CONCLUSION

Cyclin D1 expression is a common event in MM patients (50%) and is associated either with a t(11;14)(q13;q32) or extra copies of chromosome 11. The prognostic role of the cyclin D1 expression and the level of this expression, as compared to other B-cell chronic lymphoproliferative disorders such as mantle cell lymphoma or hairy cell leukemia, remains to be determined in the pathogenesis of multiple myeloma.

Upstream mediators of the Fas apoptotic transduction pathway are defective in B-chronic lymphocytic leukemia

Data concerning the presence and the functionality of Fas receptor in malignant B-cells are controversial. We have analyzed Fas molecules on B-cells from patients with B-chronic lymphocytic leukemia (B-CLL) cells. We observed a large variability, both of percentage of Fas-positive cells and of intensity of Fas level. Fas triggering was inefficient in inducing apoptosis whatever the number of Fas-positive B-cells, the amount of Fas receptors. B-cells were also resistant to etoposide treatment, but able to undergo apoptosis after dexamethasone treatment. We suggest that the Fas apoptotic pathway is altered in B-CLL patients at the initial step(s) of apoptotic machinery.

Ectopic expression of cyclin D1 impairs the proliferation and enhances the apoptosis of a murine lymphoid cell line

Cyclin D1, a key regulator of the cell cycle, acts as an oncogene when over-expressed in several types of cancer. In some B-chronic lymphoproliferative disorders, the over-expression of cyclin D1 protein is thought to confer a proliferative phenotype. We have generated BaF3 pro-B cell derivatives in which cyclin D1 can be induced rapidly and reversibly in a dose-dependent manner by the hormone muristerone A. When non-expressing clones displayed the same proliferative capacity as the parental cell line, in the sub-clones, a moderate induction of cyclin D1 lengthened the proliferation rate. The over-expression of cyclin D1 had the same effects on cell proliferation but also led ultimately to cell death by apoptosis. The induction of cyclin D1 in growth factor-deprived cells as well as in anticancer drug-treated cells also reinforced the magnitude of apoptosis. Thus, the expression of cyclin D1 in lymphoid cells does not confer a proliferative advantage but rather alters the response of cells towards apoptotic stimuli in a p53-independent manner.

Pharmacological delta1- and delta2-opioid receptor subtypes in the human neuroblastoma cell line SK-N-BE: no evidence for distinct molecular entities

The two pharmacological delta-opioid receptor subtypes, delta1 and delta2, have been defined on the basis of pharmacological tools but remain to be characterized at the molecular level, since only a single cDNA has been cloned. The present study aimed to investigate the pharmacological properties of delta1- and delta2-opioid subtypes expressed in the human neuroblastoma cell line SK-N-BE and to characterize their putative corresponding mRNAs. Binding experiments using "selective" delta1- and delta2-opioid agonists and antagonists revealed the presence of two binding sites, demonstrating the presence of these delta1-opioid subtypes as they were previously described. The activation of these pharmacological subtypes by the selective agonists induced the incorporation of [alpha-(32)P]azidoanilide-GTP into Galpha(i2)/Galpha(0) subunits with the same efficiency and potency and inhibited adenosine 3', 5'-cyclic monophosphate (cAMP) accumulation with similar efficiency, while their sustained activation for 15 min induced a cross-desensitization. The "selective" delta1 and delta2 antagonists, 7-benzylidenenaltrexone and naltrindole benzofuran, respectively, were found to be as potent in blocking the inhibition of cAMP accumulation induced by both [D-Pen(2,5)]enkephalin and Tyr-D-Ala-Phe-Asp-Val-Val-Gly-NH(2). The possibility that delta-opioid subtypes could arise from alternative splicing was ruled out by reverse transcription-polymerase chain reaction (RT-PCR) experiments and the sequencing of PCR products, which revealed the presence of a single transcript encoding for the delta-opioid receptor. Different possibilities which could account for the delta-opioid receptor heterogeneity observed in the SN-N-BE cell line are discussed.

Early and sequential recruitment of apoptotic effectors after focal permanent ischemia in mice

In experimental models of cerebral ischemia, cells within the damaged territory die by necrosis and by apoptosis that contributes to the expansion of the insult. Apoptotic machinery mobilizes intracellular processes such as induction of Bcl-2 family members, activation of the proteolytic cascade including the caspases, and cleavage of caspase substrates, such as poly(ADP-ribose) polymerase or PARP. Mitochondria play a pivotal role in controlling apoptosis by releasing cytochrome c and modulating redox state, both under the regulation of manganese superoxide dismutase (Mn SOD) via superoxide anion detoxification. The implication and the kinetics of such events in apoptosis induced after focal permanent ischemia in mice remains to be studied. In a paradigm of ischemic insult induced by occlusion of the middle cerebral artery (MCAO) in mice, we showed by immunohistochemistry a constitutive expression of caspase-3 that is enhanced after MCAO in neurons localized within the infarcted zone. As a function of time intervals after MCAO, the cytochrome c amount increased in the cytosolic fraction of ischemic cortical extracts. The kinetics of the release was in concordance with the expression of caspase-3 and the subsequent cleavage of PARP appearing before the internucleosomal fragmentation of DNA, the ultimate step of apoptosis. When the apoptotic markers progressively appeared, no changes of Mn SOD activity or Mn SOD expression were detected after MCAO. We can therefore speculate that the recruitment of Mn SOD did not participate per se in the release of cytochrome c elicited after permanent focal ischemia.

Transcriptional and post-transcriptional mechanisms induce cyclin-D1 over-expression in B-chronic lymphoproliferative disorders

Cyclin D1 participates in cell-cycle control, in the progression through the G(1) phase and in the transition from the G(1) to the S phase. The CCND1 locus, located in 11q13, is amplified and cyclin-D1 protein is over-expressed in a wide range of human solid tumors. In some B-lymphoid malignancies, the t(11;14)(q13;q32) translocation joins the Ig heavy-chain locus to the CCND1 locus and leads to cyclin-D1 over-expression. In this study, a series of 127 patients presenting a B-chronic lymphoproliferative disorder (B-CLPD) was analyzed using a competitive RT-PCR designed to detect cyclin-D1-mRNA over-expression. Cyclin-D1 mRNA was expressed in patients with mantle-cell lymphoma (MCL; 10/10), hairy-cell leukemia (HCL; 3/5), B-chronic lymphoid leukemia (B-CLL; 4/111) and B large-cell lymphoma (BLCL; 1/1). Densitometric analysis of RT-PCR products and Western-blot autoradiograms, in addition to cytogenetic data, indicated that activation of the cyclin-D1 gene occurred independently of the t(11;14)(q13;q32) translocation in patients with HCL. Indeed, a normal-sized protein of 36 kDa exhibiting a level incompatible with gene activation by a translocation mechanism was detected in lymphoid cells with a normal karyotype. Moreover, we found a discrepancy between cyclin-D1 mRNA and protein levels in MCL and B-CLL, which suggested that some regulatory mechanisms acting at a post-transcriptional level persist in tumor cells.

Overproduction of Cu/Zn-superoxide dismutase or Bcl-2 prevents the brain mitochondrial respiratory dysfunction induced by glutathione depletion

Recent work has focused attention on the role of oxidative stress in various acute and chronic neurodegenerative diseases. Low concentrations of the powerful antioxidant glutathione (GSH) and impaired brain energy metabolism, particularly in the substantia nigra, are key features of Parkinson's disease (PD). The main goal of this study was to better characterize the deleterious effects of brain GSH depletion on mitochondrial function. We depleted GSH in the brains of newborn wild-type (WT) and transgenic (Tg) mice overproducing either human Cu/Zn-superoxide dismutase (h-CuZnSOD) or human Bcl2 (h-Bcl-2), by subcutaneous injection of l-buthionine sulfoximine (BSO), a specific inhibitor of gamma-glutamylcysteine synthetase. GSH was 97% depleted in brain homogenates and 90% depleted in brain mitochondria for both WT and Tg mice. This depletion of brain GSH led to a decrease in the activity of the GSH-dependent antioxidant enzyme glutathione peroxidase, both in WT and in Tg animals. BSO treatment decreased the activities of respiratory complexes I, II, and IV in the brain homogenates of WT mice. BSO-treated h-CuZnSOD or h-Bcl-2 Tg mice had no respiratory chain deficiencies. Thus, brain GSH depletion leads to the impairment of mitochondrial respiratory chain activity. The protection of mitochondrial respiratory function by overproduction of Bcl-2 may result from a decrease in the generation of reactive oxygen species (ROS) or lipid peroxidation. The protection of mitochondria by overproduction of CuZnSOD is consistent with the involvement of superoxide or superoxide-derived ROS in the mitochondrial dysfunction caused by brain GSH depletion. This study demonstrates that the antioxidant balance is critical for maintenance of brain mitochondrial function, and its disruption may contribute to the pathogenesis of PD.

Reduction of ischemic damage in NGF-transgenic mice: correlation with enhancement of antioxidant enzyme activities

If permanent focal ischemia is induced by middle cerebral artery occlusion (MCAO), neurons within the infarcted territory die by necrosis and apoptosis (or programmed cell death). We have previously shown, using a mouse strain transgenic (tg) for the nerve growth factor (NGF) gene, that tg mice have consistently smaller infarcted areas than wild-type (wt) animals, correlated with upregulated NGF synthesis and impaired apoptotic cell death. We studied, in wt and tg mice subjected to MCAO, the activities of several antioxidant enzymes and the synthesis of the proteins of the Bcl-2 family. Our results show that the antiapoptotic Bcl-2 protein and glutathione peroxidase are recruited after MCAO. NGF-tg mice also had an intrinsic resistance to oxidative stress because their basal copper zinc superoxide dismutase (SOD) and glutathione transferase activities were high. Additionally, manganese SOD activity increased in NGF-tg mice after MCAO, correlating strongly with the resistance of these mice to apoptosis.

In vitro evaluation of B-CLL cells apoptotic responses to irradiation

Defective apoptosis is a mechanism which could possibly explain B chronic lymphocytic leukemia (B-CLL) cell accumulation. Differences in evolution and prognosis of B-CLL patients may be due to heterogeneity in apoptotic cell death. We studied the apoptotic response to in vitro gamma radiation of blood mononuclear cells from 18 untreated B-CLL patients. In cells irradiated with 2, 4 or 8 Gy and then cultured for 20 hours, the percentage of trypan blue excluding (viable) cells was not modified (>92%). An apoptotic response to irradiation was detected in the majority of the patients, but the individual percentage of apoptotic cells varied widely (8 to 81% after 8 Gy irradiation) in individual cases. The flow cytometric analysis of nick-end DNA labeling demonstrated a dose effect of irradiation, particularly in patients with an apoptotic response of over 20%. In the future, a valuable clue to the selection of irradiation regimens for B-CLL patients may be the investigation of correlations between in vitro radiation-induced apoptosis and the in vivo response to radiation therapy.

Detection by the comet assay of apoptosis induced in lymphoid cell lines after growth factor deprivation

Dysregulation of apoptosis contributes to various diseases such as neurodegenerative or aging disorders, autoimmune syndromes or cancers. Numerous experimental paradigms have been explored to characterize molecular and cellular modulators of apoptosis. Similarly, numerous techniques have been described for detecting and/or quantifying accurately cells committed to apoptosis. Besides the conventional techniques, we describe in this report that the comet assay, which detects DNA single- and double-strand breaks in situ, at the cellular level, is relevant for the characterization of apoptotic cells. The comet assay is very sensitive and detects DNA fragmentation occurring in the apoptotic process as early as exposure of phosphatidylserine residues on the outer leaflet. Thus the comet assay can be used for the recognition of apoptosis that follows the death signal caused, for example, by genotoxic stress as well as lack of survival signal as in growth factor deprivation.

Recruitment of several neuroprotective pathways after permanent focal ischemia in mice

After an ischemic episode induced by the electrocoagulation of the left middle cerebral artery (MCA) in mouse, neurons within the damaged territory die either by an apoptotic or by a necrotic process. Most of the cortical neurons within the ischemic area display both morphological and biochemical signs of programmed cell death: nuclear condensation, DNA degradation, formation of apoptotic bodies, and glutathione depletion. In fact, apoptosis essentially contributes to the expansion of the ischemic lesion and the maximum of damaged territory is reached 24 h postocclusion. Several potentially neuroprotective pathways have been evidenced in different experimental models of ischemia including the activation of antioxidant enzyme activities and/or the recruitment of neurotrophic as well as antiapoptotic factors. In our model of permanent focal ischemia induced by MCA occlusion, we measured the temporal synthesis of nerve growth factor (NGF) and examined the status of antioxidant enzymes as well as Bcl-2 antiapoptotic product. We detected in both cortices a transient increase of NGF which peaks at 6 h. Moreover, we reported that glutathione peroxidase is recruited with a time course which parallels NGF synthesis. Finally, we observed the induction of Bcl-2 in safe neurons; this may represent a self-protective response against ischemia-induced apoptosis. We provide evidence that in a model of permanent focal ischemia, several neuroprotective pathways could be coactivated.

Reduction of cortical infarction and impairment of apoptosis in NGF-transgenic mice subjected to permanent focal ischemia

The neuroprotective potential of the nerve growth factor (NGF) against permanent ischemic brain damage has been investigated in vivo using NGF-transgenic (tg) mice. The expression of the transgene is driven by part of the promoter of the proto-oncogene c-fos, which belongs to the first set of genes activated after brain ischemic insult. Wild-type (wt) mice and tg mice were subjected to permanent focal ischemia induced by electrocoagulation of the middle cerebral artery. Twenty four hours (h) after the ischemic shock, when compared to wt, tg mice displayed a 40% reduction of the infarcted area, which lasted up to 1 week. However, infarcted brain areas were similar in wt and tg mice within the first hours post-occlusion, indicating that NGF acted to block the progression of neuronal damage. Kinetics of NGF synthesis assessed by ELISA was in good agreement with the observed neuroprotective effect, since NGF content peaked 6 h post-ischemia. This was further correlated with the time-course of c-Fos immunoreactivity, detectable only from 6 h post-ischemia. The neuroprotective effect of NGF involved the impairment of apoptotic cell death, as evidenced by a marked decrease of the number of apoptotic profiles inside the ischemic zone in tg mice. These results underline the potential of c-fos-NGF-tg mice to study in vivo the molecular and cellular mechanisms of the NGF-induced neuroprotective effect against ischemic damage.

Influence of debris and aggregates on image cytometry DNA measurement of archival tumors

OBJECTIVE

To investigate, for seven samples, the influence of unwanted elements (e.g., remains of erythrocyte cell membranes, sliced nuclei, damaged nuclei and aggregates) on image cytometry DNA ploidy measurements.

STUDY DESIGN

Two normal reference tissues (brain and breast), one breast cancer and four brain tumors were studied. For each sample, the influence of the different classes of debris on DNA ploidy histograms and indices was evaluated.

RESULTS

The influence differs regarding each class of debris and the index to be evaluated.

CONCLUSION

Strict and precise elimination of debris and aggregates is required. Moreover, strategies and efforts that must be applied to automated elimination of these unwanted elements must be a direct function of the bias they introduce into DNA ploidy measurements.

c-Jun and cyclin D1 proteins as mediators of neuronal death after a focal ischaemic insult

c-Jun, a transcriptional activator, as well as cyclin D1, a key regulator of the cell cycle, have been described in vitro as mediators of programmed neuronal death. After trophic factor deprivation, the activation of c-jun and cyclin D1 genes is considered as a necessary step within the cellular machinery that leads to cell death. We show here that both c-Jun and cyclin D1 proteins are present in neurones within the infarcted area after experimental cerebral ischaemia in the mouse. Since their presence was associated with DNA fragmentation revealed by the TUNEL procedure, we propose that c-Jun and cyclin D1 are involved in the process of neuronal death.

Lipospermine-mediated gene transfer technique into murine cultured cortical cells

In order to transfer exogenous DNA into embryonic cortical cells, we have chosen a transfection technique using a synthetic lipospermine (dipalmitoylphosphatidylethanolamylspermine, DPPES) which complexes DNA molecules and allows their penetration into the intracellular compartment. The procedure was optimized after testing several parameters: DPPES/DNA ratio, incubation time, kinetics of transgene expression, and growth medium. The protocol was achieved by following the expression of the E. coli LacZ reporter gene under the control of the cytomegalovirus promoter. The lipopolyamine-mediated transfection is efficient for terminally differentiated cells, since we routinely obtained transfection efficiencies of 30% for neurons.

Radiation therapy and chemotherapy in the conservative treatment of carcinoma of the anal canal: survival and late morbidity in a series of 25 patients

Combined radiation therapy and chemotherapy have been reported to produce a high incidence of complete regression of epithelial cancer of the anal canal. Our group has treated 25 patients since June 1986. Treatment included chemotherapy (first period: Mitomycin C + 5-Fluorouracil; second period: Carboplatin + 5-Fluorouracil) and simultaneous whole-pelvis irradiation (50.40 Gy). Our results confirm that radiochemotherapy can achieve good local control: all patients were in complete clinical remission three months after the completion of combined therapy. Seven, patients developed recurrences; the actuarial survival rate was 78.5% and the disease free survival rate 67%. Acute toxicity was tolerable, but a relatively high number of patients exhibited chronic treatment-related symptoms. In order to reduce late side effects, other studies are necessary to explore if, in patients with small tumors, less extensive locoregional treatment can be effective without reducing the survival rate.

Apoptotic death in cortical neurons of mice subjected to focal ischemia

Permanent focal cortical ischemia was induced in mice by electrocoagulation of the middle cerebral artery. At different time intervals after the injury, the volume of infarction was assessed together with an analysis of neuronal death. Morphological studies of ischemic brains and detection of nucleosomal DNA ladder within ipsilateral cortices might implicate a component of this neuronal loss to apoptosis as well as necrosis. Furthermore, we used the TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling) procedure to detect in situ DNA fragmentation. The localization and the proportion of apoptotic cells in the ischemic mouse brain would indicate that apoptosis contributes largely to the cellular loss induced by cerebral ischemia.

[The combined radiochemotherapy of inoperable esophageal neoplasms: a feasibility study]

January, 1994, through January, 1995, eighteen patients (17 men; median age: 59.9, range: 32-73) with biopsy-proved squamous cell carcinoma (n = 15), adenocarcinoma (n = 2) or undifferentiated carcinoma (n = 1) of the esophagus were treated with concurrent chemo-radiotherapy. All patients had inoperable lesions for unresectable disease (11 patients) or concomitant illness (7 patients); median Karnofsky score was 70 (range: 60-80). According to the 1988 American Joint Committee on Cancer Staging system, one patient was graded as Stage IIA (T2N0 + oropharyngeal cancer T4N1), two Stage IIB (T2N1), twelve Stage III (8 T3N1, 1 T4N0, 3 T4N1) and three Stage IV (2 T3N0M1, 1 T4N0M1). Treatment consisted of two courses of chemotherapy by cisplatin (75 mg/m2 i.v. on days 1 and 29) and 5-FU (1000 mg/m2/24 hours by continuous infusion from days 1 to 4 and from days 29 to 32) along with one course of concomitant radiotherapy at 45 Gy (1.8 Gy per fraction, one fraction per day and 5 fractions a week). After 15-30 days, the patients were treated with a boost dose of 7 Gy by high-dose-rate intraluminal brachytherapy. All patients are assessable for toxicity and seventeen for response. The combined treatment was generally well tolerated, with only one case of WHO grade III toxicity (thrombocytopenia). Eight of the eighteen patients had a complete response (47%); four a partial response (24%); four a minimal response (24%) and one showed stable disease (5%). Only one patient developed local progression, and four distant metastases. All the eight patients with CR are alive without local recurrence (two distant metastases) with a mean follow-up of 6 months. This treatment regimen provides good local tumor resolution with no major toxicity. The value of this study protocol will be determined by the rate of long-term survivors.

Isolation of new oncogenic forms of the murine c-fms gene

The c-fms gene encodes the receptor for the macrophage colony-stimulating factor, which plays a key role in the proliferation and differentiation of cells of the myelomonocytic lineage. In order to study the effects of overexpression of the macrophage colony-stimulating factor receptor in hematopoietic cells, a Harvey sarcoma virus-derived retroviral vector containing the murine c-fms cDNA was pseudotyped with Friend murine leukemia virus and inoculated into newborn DBA/2 mice. This viral complex induced monoclonal or oligoclonal leukemias with a shorter latency than that for Friend murine leukemia virus alone. Unexpectedly, 60% of the integrated fms proviruses had deletions at the 5' end of the c-fms gene. Sequence analysis of seven mutant proviruses indicated that the deletions always included the c-fms ligand binding domain and either occurred within the c-fms sequences, leaving the fms open reading frame unchanged, or joined VL30 sequences located at the 5' end of the parental retroviral vector to internal c-fms sequences, resulting in truncated fms proteins devoid of the canonical signal peptide. In contrast to all tyrosine kinase receptors transduced in retroviruses, no helper gag- or env-derived sequences were fused to the rearranged fms sequences. Viral supernatants isolated from hematopoietic tumors with viruses with deletions were able to transform NIH 3T3 cells as efficiently as parental fms virus, indicating that deletions resulted in constitutive activation of the c-fms gene. These oncogenic variants differ from those transduced in the Suzan McDonough strain of feline sarcoma viruses (L. Donner, L. A. Fedele, C. F. Garon, S. J. Anderson, and C. J. Sherr, J. Virol. 41:489-500, 1982). The high rate of c-fms rearrangement and its relevance in the occurrence of hematopoietic tumors are discussed.

Cycloheximide and actinomycin D block the toxic effect of glutamic acid on PC12 cells

Programmed cell death is considered to play a key role during development and also during physiopathological events such as neurodegenerative diseases and ischaemia. We have recently shown in PC12 cells that glutamate induces a progressive cytotoxicity which is only visible 8-10 h after incubation with glutamate for at least 4-6 h. We now present evidence that the toxic action of glutamate may correspond to programmed cell death because it is blocked by either actinomycin D or cycloheximide. This effect, however, may not be due to apoptosis since it is not blocked by aurintricarboxylic acid, a non-specific inhibitor of endonucleases, and neither chromatin condensation nor DNA fragmentation or liberation is seen after glutamate treatment.

Growth arrest and terminal differentiation of leukemic myelomonocytic cells induced through ligation of surface CD23 antigen

Acute myelogenous leukemia (AML) cells express CD23 surface antigen after in vitro treatment with various cytokines, including interleukin-4 (IL-4) and interferon gamma. Subsequent ligation of CD23 by specific monoclonal antibody (MoAb) induces substantial morphologic and functional modifications in these cells. In the present study, we investigated the role of CD23 in the proliferation and the maturation of leukemic cells from AML patients or the U937 cell line. CD23+ cell treatment with CD23 MoAb inhibited the proliferation of leukemic cells. This correlated with their terminal differentiation after 7 to 9 days incubation because they (1) definitively lost their growth capacity; (2) adhered to culture flasks and became monocyte/macrophage-like; and (3) expressed mature monocyte markers including nonspecific esterases. Intracellular mechanism of this antitumoral effect was then analyzed in U937 cells. Induction of high-density surface CD23 expression by IL-4 or granulocyte-macrophage colony-stimulating factor coincided with a transient decrease of U937 cell proliferation. CD23 ligation during this low-proliferative phase induced a rapid activation of L-arginine-dependent pathway and the intracellular accumulation of cyclic guanosine monophosphate and cyclic adenosine monophosphate (cAMP). Induction of these early messengers was followed by the activation of nuclear factor-kB transcription factor and the modulation of proto-oncogene expression by U937 cells. Whereas U937 cell treatment with IL-4 decreased c-fos/c-jun expression, CD23 MoAb reinduced c-fos/c-jun and promoted the expression of cell maturation-associated proto-oncogenes junB and c-fms, during the first 24 hours. Both IL-4 and CD23 MoAb downregulated the expression of c-myb. CD23 ligation also induced the production of TNF alpha by U937 cells. Inhibitors of cAMP and nitric oxide reversed CD23-mediated modification in U937 cells. These data evidence the ability of CD23 surface antigen to mediate terminal differentiation of early leukemic myelomonocytic cells.

[RAdio-chemo-surgical combined treatment of non-small cell lung carcinoma N2]

As yet, no optimal treatment for stage-IIIA non-small-cell lung cancer (NSCLC) has been established. Particularly, in the patients with stage-IIIA N2 disease, surgical resection for cure is limited to few selected patients. Of late, a number of studies have suggested that such treatment modalities as chemotherapy, radiotherapy and surgery might be combined to improve treatment efficacy. Based on these conclusions, a cooperative study for N2 NSCLC patients was performed. Treatment included continuous CDDP infusion (6 mg/m2/day) and concomitant irradiation. Fifteen patients were examined. After neoadjuvant treatment, 4 patients were found to have unresectable lesions for local disease progression or metastasis. Eleven patients underwent complete resection (73% resectability). Follow-up ranged 6 to 32 months: 6 patients are now free from relapse (respectively at 31, 28, 23, 14, 12 and 3 months) and 1 is alive with adrenal gland metastasis. Overall and disease-free survival rates are 40.6% and 31.5%, respectively. Our preliminary results indicated that this protocol is well tolerated. Resectability was good and tumor sterilization rate was satisfying (complete T and N sterilization in 6 cases, sterilization of either T or N in 3 cases). The patients with non-adenocarcinoma histology exhibited better local control and prognosis than those with histologic diagnosis of adenocarcinoma.

Expression of functional beta-platelet-derived growth factor receptors on hematopoietic cell lines

The beta-type receptor of platelet-derived growth factor (beta PDGFR) is a class III transmembrane receptor with tyrosine kinase activity. The beta PDGFR gene is located on mouse chromosome 18 close to the c-fms gene which codes for the colony stimulating factor-1 receptor (CSF-1R). We previously reported that in a high percentage of myeloblastic leukemias induced by the Friend helper murine leukemia virus (F-MuLV), proviruses were integrated in the first intron of the c-fms gene leading to an enhanced expression of c-fms mRNA. Since activation by proviral insertion can act at long distance, we studied beta PDGF receptor gene expression in murine myeloblastic leukemias. This gene was found to be frequently expressed but the level of beta PDGF receptor mRNA was weak and not related to proviral activation. High affinity binding sites were expressed on myeloblastic cells and ligand binding induced cell proliferation. To determine whether beta PDGFR expression is a common feature in hematopoietic cells, we tested cell lines belonging to other hematopoietic lineages. We found that multipotent stem and mast cell lines also expressed the beta PDGF receptor gene. This suggests that PDGF, known as a mitogen for connective tissue cells, could also play a role in normal hematopoiesis.

Results of chemotherapy plus external reirradiation in the treatment of locally advanced recurrences of nasopharyngeal carcinoma

Between 1982 and 1991, 16 patients with recurrent cancer of the nasopharynx were treated with chemotherapy (CT) and radiotherapy (RT). All patients had received prior RT (45-69, 30 Gy). According to rTNM there were three rT2, one rT3 and 12 rT4. 5 patients were N1. Reirradiation (12-46 Gy, mean: 28) started 3-4 weeks after CT (2-6 cycles of different combinations), but 2 cases involved concomitant therapy. Out of 16 patients 7 had complete response (CR) (43.7%), 7 partial response and 2 no response. Statistically significant prognostic factors for obtaining CR were time of relapse and response to initial CT. Median duration of CR was 22+ months (9-64+). Failures at primary site occurred in 3 patients, 2/2 of those receiving CT without platinum compounds and 1/5 of other ones, with statistically significant difference in local recurrence free-survival between the two groups. Two- and 3-year actuarial overall survival were 28% and 10%. Rates of disease-free survival were 17% and 8%, respectively. The acute toxicity was generally mild. No central nervous system damage or radiation-induced myelitis were observed in survivors.

Cooperation between structural elements in hormono-regulated transcription from the mouse mammary tumor virus promoter

The mouse mammary tumor virus (MMTV) promoter is under the control of several types of regulatory agents. The proximal promoter within the long terminal repeat (LTR), from -200 to the CAP site and its regulation by steroid hormones have been extensively studied. However the precise role of sequences located upstream of this region remain unclear. We have constructed MMTV LTR deletion mutants coupled to the luciferase reporter gene and assayed their activities after transient transfection into transformed mammary epithelial cells (34i) and immortalized fibroblasts (NIH-3T3). In the absence of hormone, the MMTV promoter is almost silent, and deletions in the LTR have no significant effect on basal activity. In the presence of hormone, deletions spanning from the 5'-end to -455 have only slight effects on luciferase levels. In contrast, deletion of the region spanning from -450 to -201 leads to a dramatic decrease in transcription. A substantial decrease, more marked in 34i cells, is also clear when 90bp between -290 and -201 are deleted. At least one element cooperating positively with the glucocorticoid response element (GRE) is present between -223 and -201, as supported by the results of substitution mutation experiments. In 34i cell line, dexamethasone stimulates the MMTV LTR transcriptional activity to a level comparable to that of SV40. In contrast, in NIH-3T3 cells, MMTV promoter inducibility is weak. This results from a glucocorticoid receptor content 10-fold lower in NIH-3T3 cells than in 34i cells. Transfection of a glucocorticoid receptor expression plasmid allows recovery of a high inducibility of the MMTV promoter. This was true with all the MMTV LTR mutants studied here and suggests that NIH-3T3 cells possess all the factors necessary to cooperate with the steroid hormone in order to achieve a high transcriptional activity.

[5- and 10-year survival in carcinomas of the oral cavity (T1-2/N0-1) treated with external radiotherapy alone or associated with surgery and/or chemotherapy]

The authors report their results on the treatment of 211 T1-2/N0-1 carcinoma of the oral cavity treated with radiotherapy alone or associated with surgery and/or chemotherapy. Five- and ten-year survival rates are respectively 48 and 37%. Two groups were recognized: one with a better prognosis (T1 gum and cheek) and another with a poor prognosis (T2-N1 mobile tongue and floor of the mouth).

Rearrangements of the Pim-1, c-myc, and p53 genes in Friend helper virus-induced mouse erythroleukemias

The Friend helper leukemia virus (F-MuLV) induces in mice leukemias of the erythroid, lymphoid, and myeloblastic lineages. Erythroleukemic cell DNAs were examined for genetic alterations at loci described as common proviral integration regions in MuLV-induced myeloid or lymphoid leukemias or in Friend complex-induced erythroleukemias. No alteration of the Fim-1, Fim-2, Fim-3, pvt-1, and Spi-1 loci were detected in 17 erythroleukemias, p53 gene rearrangement was observed in 6 (30%) erythroleukemias and was always associated with a loss of the germ line allele. Interestingly, genetic alterations were also detected at two loci, c-myc and Pim-1, previously described as common provirus integration regions in T lymphoid leukemias. Rearrangements of these two genes were often associated with p53 gene alteration within the same tumor.

Role of chromatin structure in transcriptional regulation of MMTV LTR hormone-dependent promoter

Studies of chromatin structure were performed in mouse fibroblast cell lines containing Bovine Papilloma Virus (BPV) based artificial minichromosomes containing Mouse Mammary Tumor Virus (MMTV) Long Terminal Repeat (LTR), a retroviral promoter regulated by glucocorticoids, driving the transcription of v-Ha-ras. These minichromosomes fractionate with the "active chromatin", indicating an association of the minichromosomes with components of the "nuclear matrix". Two regions of the minichromosomes upstream and downstream of v-Ha-ras are involved in this interaction. MMTV LTR promoter is associated with nucleosomes precisely positioned on the DNA sequences. Hormonal activation is accompanied by a structural change of the nucleosome associated with the hormone response elements (HREs). This structural change can be visualized by the appearance of a hormono-dependent DNaseI hypersensitive site. Anti-hormones, even when able to promote a strong binding of the receptor to the nucleus, are unable to induce the chromatin structural change. The strong association of the hormone-receptor complex with the nucleus is necessary to induce the DNaseI hypersensitive site and to maintain the transcription, but is not necessary for DNaseI hypersensitivity maintenance. This suggests a double role for the hormone-receptor complex: 1) induction of a chromatin rearrangement and 2) transcriptional transactivation.

The human homologues of Fim1, Fim2/c-Fms, and Fim3, three retroviral integration regions involved in mouse myeloblastic leukemias, are respectively located on chromosomes 6p23, 5q33, and 3q27

Three mouse genomic domains, Fim1, Fim2, and Fim3, were previously described as proviral integration regions frequently involved in the early stages of myeloblastic leukemogenesis induced in vivo or in vitro by the Friend murine leukemia virus. Fim2 was identified as the 5' end of the c-Fms protooncogene, which encodes the receptor of the macrophage colony stimulating factor (Csflr). The functions of Fim1 and Fim3 are not yet known, but these regions are highly conserved among different species. To examine whether these regions could correspond to known human loci involved in genetic alterations specific to some human leukemias, we undertook their chromosomal mapping. The localization of FIM2/c-FMS on 5q33 was confirmed. FIM1 and FIM3 were localized on human chromosomes 6p22.3-p23 and 3q27 respectively. Interestingly, translocations involving these two regions have been described in various hematopoietic malignancies: the t(6;9)(p23;q34) in acute nonlymphocytic leukemias and the 3q26-q28 translocations in a large variety of leukemias.

Early involvement of the fim-2 and fim-3 regions in mouse myeloblastic leukemogenesis

Retroviruses lacking oncogenes induce tumors or leukemias after a long latency which generally exceeds several months. Cellular transformation most probably results from the activation of cellular oncogenes or putative proto-oncogenes due to proviral integration. Several genetic changes are likely to be necessary for the appearance of fully malignant cells. However, the sequence of genetic changes initiating and leading to malignant transformation is difficult to study since, in most experimental conditions, the only accessible cells are fully transformed cells. We have previously described an in vitro model of murine myeloblastic leukemogenesis during which several successive steps leading to fully malignant and transplantable cells have been identified. This in vitro transformation process develops over approximately a 1-year period. In this paper, we demonstrate that frequent cellular DNA rearrangements due to proviral integrations in specific regions occur early in the myeloblastic transformation process and remain stable throughout the in vitro leukemogenesis, and in tumors derived from in vitro fully transformed myeloblasts.

Fim-1, Fim-2/c-fms, and Fim-3, three common integration sites of Friend murine leukemia virus in myeloblastic leukemias, map to mouse chromosomes 13, 18, and 3, respectively

Three common proviral integration sites, Fim-1, Fim-2/c-fms, and Fim-3, have been described in mouse myeloid leukemias induced by the Friend murine leukemia virus. The nature and function of Fim-1 and Fim-3 are still unknown since no transcript from these loci has been detected so far. To identify these two loci, we undertook their chromosomal localization using restriction fragment length polymorphism detected between C57BL/6 mice and the wild-derived inbred strain of Mus spretus. Using interspecific backcross analysis, we mapped Fim-1 to mouse chromosome 13 and Fim-3 to mouse chromosome 3. Interestingly, Fim-3 is tightly linked to Evi-1, another common integration site of ecotropic virus involved in another model of mouse myeloid leukemogenesis. Fim-2 spans the 5' end of the c-fms gene, which encodes for the macrophage-colony-stimulating factor receptor. We located the c-fms gene on the D band of chromosome 18 by in situ hybridization.

Frequent involvement of the fim-3 region in Friend murine leukemia virus-induced mouse myeloblastic leukemias

fim-3 is a new proviral integration region involved in 23% (16 of 68) of Friend murine leukemia virus-induced myeloblastic leukemias. This region is distinct from 20 oncogenes and from putative oncogenes tested so far. Proviruses are integrated in a 16-kilobase region, always in the same orientation. No RNA expression of fim-3 was detected.

Frequent c-fms activation by proviral insertion in mouse myeloblastic leukaemias

Retroviruses lacking oncogenes can induce tumours in animals, and the tumour cells are frequently found to contain proviral DNA inserted next to a proto-oncogene, which is thus placed under the regulatory control of the retroviral long terminal repeat (LTR). This altered regulation leads to overexpression of the proto-oncogene, which presumably contributes to the growth properties of the tumour cells. fim-2 has been described as a retroviral integration site frequently and specifically involved in murine myeloblastic leukaemias induced in vivo or in vitro by the replication-competent Friend murine leukaemia virus (F-MuLV). Here we report that fim-2 spans the 5'-end of the murine proto-oncogene c-fms, known to code for a transmembrane glycoprotein with tyrosine kinase activity probably identical to the receptor of the haemopoietic growth factor, monocyte-macrophage colony-stimulating factor (M-CSF or CSF-1). Proviral integration in the fim-2 region results in a high expression of a normal sized c-fms messenger RNA. We also observe that some tumours have lost the fim-2/c-fms germ line allele. These results provide the first evidence for the presumed involvement of c-fms in myelomonocytic leukaemias.

Hemolytic anemia and erythroleukemia, two distinct pathogenic effects of Friend MuLV: mapping of the effects to different regions of the viral genome

Two different pathogenic effects of the Friend ecotropic murine leukemia virus (F-MuLV) were distinguished by serial examinations of hematocrits and reticulocyte counts of IRW mice inoculated as newborns. F-MuLV induced hemolytic anemia with increased levels of erythropoiesis, which was detectable as early as 13 days of age, whereas blocked erythroid differentiation, associated with erythroleukemia, was apparent only after 30 days of age. Using strains of Friend-MuLV with different virulences, we constructed recombinant viruses that allowed us to map the hemolytic effect and the ability to induce rapid erythroleukemia to different regions of the viral genome. Moreover, the ability of the virus to induce rapid erythroleukemia appeared to be independent of the presence of severe early hemolytic anemia.

fim-1 and fim-2: two new integration regions of Friend murine leukemia virus in myeloblastic leukemias

The Friend helper murine leukemia virus (F-MuLV) induces in mice a high percentage of myeloblastic leukemias. Myeloblastic transformation is also observed after in vitro infection of long-term bone marrow cultures. To investigate the molecular events leading to the generation of myeloblastic leukemias, we first screened a panel of leukemic cells for rearrangement or amplification of known oncogenes or previously described specific integration sites. No modification of these genes was observed. Therefore, we searched for common integration sites by constructing a genomic library from a myeloblastic cell line harboring only five integrated proviruses. This library was screened with a virus-specific probe, and virus-host cellular junction fragments were subcloned. Two flanking cellular sequences corresponding to two different integrated proviruses were used to analyze additional myeloblastic leukemias. The first probe detected rearrangements in 2 of 42 myeloblastic leukemias, and the second probe detected rearrangements in 6 of 42. We demonstrated that, in each case, the rearrangement was the result of F-MuLV integration, with all proviruses in the same orientation and clustering in a region less than 3 kilobases long. The two regions, named fim-1 and fim-2, were different from 15 oncogenes tested. Rearrangements of these two regions were found in F-MuLV-induced myeloblastic leukemias but not in 20 lymphoid or erythroid leukemias induced by the same virus.

Long-term culture of bone marrow-derived preleukemic cells from F-MuLV-infected mice

The replication-competent Friend leukemia virus (F-MuLV) induces leukemias involving three hematopoietic lineages after a latent period of several months. In an attempt to elucidate the early events of the leukemogenic process, we looked for a method allowing the isolation and the long term in vitro maintenance of preleukemic cells. When established as long-term cultures according to the technique described by Dexter et al, bone marrow cells obtained from 7/7 apparently healthy F-MuLV-infected preleukemic mice led to the accumulation of immature myeloblastic cells, and to the generation of permanent myeloblastic cell lines, which in most cases further became tumorigenic in preirradiated recipient animals. The delays required to obtain cell lines were shorter when the duration of the in vivo infection was longer, suggesting that these cells were committed into the leukemogenic pathway before their transfer into culture flasks. The myelomonocytic preleukemic cells exhibited normal sensitivity to purified preparations of CSFs, but acquired the capacity to grow in the absence of exogenous CSF stimulation. Examination of integrated provirus copies demonstrated that the preleukemic cell proliferation involved a single or a few clones which may progress in vitro from a preleukemic to a fully malignant stage without major modifications of the integrated provirus copies.

Monoclonal proliferation of Friend murine leukemia virus-transformed myeloblastic cells occurs early in the leukemogenic process

Integrated Friend murine leukemia virus copies were analyzed by the Southern blotting procedure in myeloblastic cell lines obtained after in vitro infection of long-term mouse bone marrow cultures. Several steps leading to the generation of malignant myeloblastic cells after a long latency period were observed in the evolution of infected cultures. Shortly after infection, a random distribution of integrated provirus copies was observed in the DNA of normally differentiating myeloid cells. In contrast, a distinct pattern of integrated Friend murine leukemia virus copies was evident in the first non-differentiating immature myeloblastic cells appearing in cultures, suggesting a monoclonal origin of these cells. For each cell line, characteristic hybridizing fragments were conserved during the 1-year culture period necessary for the acquisition of tumorigenic properties and were also observed in tumors grafted in vivo. We can conclude that monoclonality is effective very early in the myeloid transformation process, as soon as the precursor cells are blocked in their differentiation.

Multistep virus-induced leukemogenesis in vitro: description of a model specifying three steps within the myeloblastic malignant process

A helper-independent Friend leukemia virus was used to infect bone marrow cultures. This virus induces myeloblastic leukemia in mice after a long latency period. Infection of the bone marrow cultures resulted in the in vitro production of myeloblastic leukemogenesis after a long latency period. Three steps were observed in the evolution of the infected cultures, and permanent cell lines were derived at each step. This allowed us to individualize three successive events in the course of the myeloblastic transformation: (i) an abnormal responsiveness to the physiological hormone granulo-macrophagic colony-stimulating factor, (ii) the acquisition of growth autonomy, and (iii) the acquisition of in vivo tumorigenicity.