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The 11-zinc finger protein CCTC-binding factor (CTCF) employs different sets of zinc fingers to form distinct complexes with varying CTCF- target sequences (CTSs) that mediate the repression or activation of gene expression and the creation of hormone-responsive gene silencers and of diverse vertebrate enhancer-blocking elements (chromatin insulators). To determine how these varying effects would integrate in vivo, we engineered a variety of expression systems to study effects of CTCF on cell growth. Here we show that ectopic expression of CTCF in many cell types inhibits cell clonogenicity by causing profound growth retardation without apoptosis. In asynchronous cultures, the cell-cycle profile of CTCF-expressing cells remained unaltered, which suggested that progression through the cycle was slowed at multiple points. Although conditionally induced CTCF caused the S-phase block, CTCF can also arrest cell division. Viable CTCF-expressing cells could be maintained without dividing for several days. While MYC is the well-characterized CTCF target, the inhibitory effects of CTCF on cell growth could not be ascribed solely to repression of MYC, suggesting that additional CTS-driven genes involved in growth-regulatory circuits, such as p19ARF, are likely to contribute to CTCF-induced growth arrest. These findings indicate that CTCF may regulate cell-cycle progression at multiple steps within the cycle, and add to the growing evidence for the function of CTCF as a tumor suppressor gene.

The cellular protooncogene MYC encodes a nuclear transcription factor that is involved in regulating important cellular functions, including cell cycle progression, differentiation, and apoptosis. Dysregulated MYC expression appears critical to the development of various types of malignancies, and thus factors involved in regulating MYC expression may also play a key role in the pathogenesis of certain cancers. We have cloned one such MYC regulatory factor, termed CTCF, which is a highly evolutionarily conserved-11-zinc finger transcriptional factor possessing multiple DNA sequence specificity. CTCF binds to a number of important regulatory regions within the 5' noncoding sequence of the human MYC oncogene, and it can regulate its transcription in several experimental systems. CTCF mRNA is expressed in cells of multiple different lineages. Enforced ectopic expression of CTCF inhibits cell growth in culture. Southern blot analyses and fluorescence in situ hybridization (FISH) with normal human metaphase chromosomes showed that the human CTCF is a single-copy gene situated at chromosome locus 16q22. Cytogenetic studies have pointed out that chromosome abnormalities (deletions) at this locus frequently occur in many different human malignancies, suggesting the presence of one or more tumor suppressor genes in the region. To narrow down their localization, several loss of heterozygosity (LOH) studies of chromosome arm 16q in sporadic breast and prostate cancers have been carried out to define the most recurrent and smallest region(s) of overlap (SRO) for commonly deleted chromosome arm 16q material. For CTCF to be considered as a candidate tumor suppressor gene associated with tumorigenesis, it should localize within one of the SROs at 16q. Fine-mapping of CTCF has enabled us to assign the CTCF gene to about a 2 centiMorgan (cM) interval of 16q22.1 between the somatic cell hybrid breakpoints CY130(D) and CY4, which is between markers D16S186 (16AC16-101) and D16S496 (AFM214zg5). This relatively small region, containing the CTCF gene, overlaps the most frequently observed SROs for common chromosomal deletions found in sporadic breast and prostate tumors. In one of four analyzed paired DNA samples from primary breast cancer patients, we have detected a tumor-specific rearrangement of CTCF exons encoding the 11-zinc-finger domain. Therefore, taken together with other CTCF properties, localization of CTCF to a narrow cancer-associated chromosome region suggests that CTCF is a novel candidate tumor suppressor gene at 16q22.1.

The chicken bursa provides a revealing experimental model system which has helped unravel some of the mysteries surrounding induction of neoplasia by retroviruses lacking dominant viral oncogenes. Analysis of this system continues to provide opportunities for further insight into mechanisms underlying some of the essential characteristics of neoplastic change including maturation arrest, prolonged cell survival, and genetic instability. The deregulation of c-myc expression induced by nearby proviral integration appears to initiate preneoplastic change in a specific window of development, i.e., the bursal stem cell. The generation of large numbers of these preneoplastic stem cells, and the ability for further amplification by transplantation technology, may provide an opportunity to address questions such as how and why myc oncogenes produce preneoplastic maturation arrest or why stem cells are selective targets for these effects. Among the unexplained consequences of this preneoplastic state appears to be genetic instability which leads, inevitably, to formation of invasive bursal neoplasms. It is at least conceivable that the observed myc-induced enhancement of the remarkable capacity for apoptotic cell death present in bursal cells plays a role in this instability. DNA strand breakage is a very early feature of bursal cell apoptosis. If such breakage could occur in sublethal form it might provide a mechanism for increased frequency of genetic change (deletions, rearrangement, and recombination). Among the changes that seem required for successful tumor cell growth outside of follicles is the suppression of cell death induced by loss of cell-cell contact which is characteristic of normal and preneoplastic bursal cells. Several genes in the bcl-2 family are potentially important in the modulation of cell death events central to the evolution of these neoplasms. Their role, if any, remains to be established.

Forty-nine patients with severe aplastic anemia, 33 due to unknown cause, 11 drug or chemical related, 2 associated with hepatitis, 1 with paroxysmal nocturnal hemoglobinuria, and 2 possibly associated with Fanconi syndrome did not show recovery after 0.5–96 (median 2) mo of conventional therapy. Twenty-two were infected and 21 were refractory to random platelet transfusions at the time of admission. All were given marrow grafts from HLA-identical siblings. Forty-five were conditioned for grafting by cyclophosphamide (CY), 50 mg/kg on each of 4 successive days, and four by 1000 rad total body irradiation. All were given intermittent methotrexate therapy within the first 100 days of grafting to modify graft-versus-host disease (GVHD). Three patients died from infection too early to evaluate (days 1–8). Forty-six had marrow engraftment. Of these, 20 are surviving with good peripheral blood counts between 186 and 999 days, and 18 have returned to normal activities. Chronic GCHD is a problem in five. Twelve patients died of infection following rejection of the marrow graft. Twelve patients died with bacterial or fungal infections or interstitial pneumonia and active GVHD or soon following resolution of GVHD. Two patients died with marrow engraftment and no GVHD, one with an interstitial, and the other with a bacterial pneumonia. Thirty-six patients who had received random donor blood transfusions were randomly assigned to receive either CY or procarbazine-antithymocyte globulin-CY as conditioning regimens to test whether the incidence of graft rejection could be decreased. There was no difference in the incidence of graft rejection between the two regimens. In 13 patients with rejection, second transplants were attempted either with the original marrow donor (9 patients) or another HLA-identical sibling (4 patients). Three of these transplants were not evaluable, seven were unsuccessful and three were successful with only one of the three surviving for more than 468 days. In conclusion, the long-term survival of 41% of the patients in the present study is similar to that achieved in our first 24 patients, and confirms the importance of marrow transplantation for the treatment of severe aplastic anemia. Marrow graft rejection, GVHD, and infections continue to be the major causes of failure.

Dibromomannitol (DBM) is a new agent for the treatment of chronic granulocytic leukemia. A propsective evaluation of the drug was undertaken in a randomized comparison with busulfan. Forty previously untreated, Philadelphia chromosome-positive cases were treated, with 20 patients in each treatment group. The protocol provided for continuous maintenance therapy after remission induction, with a crossover to the opposite drug in patients who became refractory to the primary agent but are without evidence of blastic tranformation. There were 14 remissions in the DBM group and 15 in those treated with busulfan. The rate of decrease of the elevated leukocyte count was more rapid with DBM, but prolonged disease control off treatment occurred in only three of 14 cases as opposed to nine of fifteen busulfan-treated patients who required a median delay of 12 mo before maintenance could be initiated. Hypoplasia occurred in one DBM patient and two busulfan cases. Following recovery, crossover to the opposite drug in two cases again resulted in hypopllasia. Increased skin pigmentation, amenorrhea, pulmonary fibrosis, and cytologic dysplasia, commonly associated with busulfan adminstration, were also noted with DBM. The median duration of disease control with busulfan was 34 mo and 26 mo with DBM. There was no signigicant difference in the incidence of blastic transformation, and median survival for both groups was 44 mo. DBM appears to be as effective as busulfan in the treatment of the chronic phase of CGL but with a more predictable myelosuppressive action. The principal advantage of busulfan over DBM is the fact that more than half the busulfan-treated patients experienced prolonged disease control off treatment.

Interstitial pneumonia is a major cause of morbidity and mortality following allogeneic marrow transplantation for hematologic malignancy. In this prospective randomized study, 22 of 40 patients received prophylactic adenine arabinoside (Ara-A) at a dose of 5 mg/kg/day administered intravenously on an intermittent schedule. Thirteen episodes of interstitial pneumonia occurred among treated patients, including three cases associated with cytomegalovirus (CMV) in the lung. Ten episodes of interstitial pneumonia were seen in the untreated group, with CMV cultured from five. Surveillance viral cultures were positive from 18 different sites in 12 treated patients compared to 10 sites from 7 patients in the untreated group. No significant toxicity from Ara-A was encountered, and no difference in overall survival between the two groups was detected. Ara-A did not reduce the frequency of interstitial pneumonia or viral isolation from routine cultures.

Human marrow transplantation has resulted in observations of fundamental significance in understanding both aplastic anemia and acute leukemia. For example, the observation that transplanted marrow can grow successfully in patients with aplastic anemia indicates that the disease is due to a defect in the marrow precursor cells and not in the marrow microenvironment. Similarly, the observation of recurrent leukemia in donor cells has important implications. Nonetheless, marrow transplantation is sufficiently established therapeutically to be considered the treatment of choice for patients with severe aplastic anemia, and a realistic alternative for patients with recurrent acute leukemia. We suggest that patients be managed with regard to marrow transplantation according to the general approach outlined in Table 3. Marrow transplantation and histocompatibility typing are available at increasing numbers of institutions throughout the world. More and more patients with either severe aplastic anemia or recurrent acute leukemia should have marrow transplantation available to them when it is indicated as part of optimal management of these no longer hopeless diseases.

Eleven of twenty-four patients with severe aplastic anemia given marrow grafts from HLA-identical siblings between October 1970 and March 1973 are alive with normal marrow function and continued evidence of engraftment 3-5 yr later. Ten have been leading normal lives with no immunosuppressive or other drug therapy since day 100 postgrafting. One has had chronic graft-versus-host disease of the skin which is now slowly improving with no therapy. He returned to full-time employment in the summer of 1975. The long-term well-being of almost half of our initial patients emphasizes the importance of marrow transplantation for the treatment of severe aplastic anemia.

Between January 1973 and February 1975, 77 adults with acute nonlymphoblastic leukemia were treated with a combination of daunorubicin, cytosine arabinoside, 6-thioguanine, prednisone, and vincristine in university-affiliated and private institutions. After 31 patients were treated (regimen 1) the doses of all drugs were significantly increased (regimen 2). Regimes 1 and 2 yielded CR rates of 59% (17 of 29 patients) and 70% (32 of 46 patients) respectively. With regimens 2 the mean number of courses and the median number of days to CR decreased from 3 to 1.4 and from 46 to 29 respectively. Failure to achieve CR was due to persistent leukemia during regimen 1 and fatal infections during regimen 2. With regimen 2 ten of 20 patients (50%) greater than 50 years had CR compared to 22 of 26 patients (85%) less than 50 years. CR rates were similar in community and university institutions.

Forty-six previously untreated patients with advanced aggressive non-Hodgkin's (34 poorly differentiated and mixed diffuse, 8 histiocytic and 4 undifferentiated) were treated with a 3 phase combined modality program employing cyclophosphamide (C), hydroxyl-daunomycin (H), vincristine (O), prednisone (P), procarbazine (P) [CHOP(P)] combination chemotherapy in an initial induction phase, radiotherapy and nonmarrow toxic chemotherapy as a second consolidation phase, followed by a third phase of CHOP(P) chemotherapy for four more cycles. Long-term maintenance therapy was not given. High dose involved field radiation in phase II was limited to volumes encompasing less than 50% of the marrow bearing skeleton. The large majority of patients (82%) had such widespread involvement that this limitation precluded the use of local radiation and were treated instead with a mean of 132 rad of fractionated total body irradiation (TBI). Thirty-eight patients (83%) achieved complete remission. Twenty-nine (66%) of the 44 patients evaluable for follow-up, and 22 (61%) of the 36 patients receiving TBI, remain alive in complete remission for observation periods of up to 26 months.

More than 4,500 breeding female chickens of nine inbred lines maintained under specific-pathogen-free conditions to approximately 500 days of age were studied. Routine monitoring and special assays indicated that they were free of infection by exogenous viruses of the leukosis-sarcoma and the reticuloendotheliosis groups. Some birds were maintained free of Marek's disease (MD) virus infection in plastic isolators, and others were maintained in conventional chicken houses and vaccinated with the herpesvirus of turkeys to prevent the lesions of MD. Ten birds bearing lymphoid tumors were observed in two sublines of one line of chickens known to produce embryos that spontaneously produce Rous-associated virus, type 0 (RAV-O), an endogenous virus of the chicken. Four tumors were found in chickens of one subline maintained free of MD virus infection in isolators. These tumors did not involve the bursa and had some histologic features different from those typical of lymphoid leukosis. Six tumors were found in chickens of the other subline that were vaccinated to prevent MD; these tumors involved the bursa and were typical of lymphoid leukosis but not MD. These results suggest that two types of tumors may have been observed. The fact that DNA extracted from both types of tumors did not contain exogenous lymphoid leukosis virus sequences confirms the virologic evidence that exogenous viruses were not involved. The fact that endogenous viral sequences were not increased in copy number suggests that the endogenous virus RAV-O did not directly induce the tumors. Two birds with tumors not involving the bursa were found alive, and transplantable lymphoid tumors were developed. These tumors were of T-cell origin rather than of bursa cell origin as would be expected of lymphoid leukosis. These are the first reported lymphoid tumors that have been observed in the absence of known exogenous tumor virus infection in chickens. Our evidence suggests that the endogenous virus RAV-O did not play a primary role in the induction of these tumors.

This report summarizes the experience with 25 patients who received a second marrow transplant. The marrow donor for the first transplant was an identical twin in four cases and a sibling matched at the major histocompatibility complex in 21 instances. The donor for the second transplant was the same as the first except for three patients whose second donor was another matched sibling. Nine patients with aplastic anemia rejected their first graft. Four of these patients were prepared for the second graft with a regimen of procarbazine and antithymocyte globulin (ATG) followed by cyclophosphamide or total body irradiation and were successfully regrafted. One rejected the second graft, two died of septicemia and one is alive and well 10 months after the second graft. Twelve patients with hematologic malignancy had a recurrence of disease after the first transplant. Despite preparation for the second graft with a variety of intensive chemotherapeutic regimens, the five patients who did not succumb to infection showed an early recurrence of disease. Four patients with hematologic malignancy had a failure of the first graft for unknown reasons, possibly related to the administration of ATG or methotrexate. One patient prepared for the second graft with procarbazine and ATG showed evidence of engraftment but died of infection. Two out of three patients given no additional preparation were successfully grafted. One died of recurrent central nervous system leukemia after 18 months and one is alive and well 26 months after the second graft.