Spontaneous remission in a patient with chronic myeloid leukaemia

Chronic myelogenous leukemia as a paradigm of early cancer and possible curative strategies

The chronological history of the important discoveries leading to our present understanding of the essential clinical, biological, biochemical, and molecular features of chronic myelogenous leukemia (CML) are first reviewed, focusing in particular on abnormalities that are responsible for the massive myeloid expansion. CML is an excellent target for the development of selective treatment because of its highly consistent genetic abnormality and qualitatively different fusion gene product, p210(bcr-abl). It is likely that the multiple signaling pathways dysregulated by p210(bcr-abl) are sufficient to explain all the initial manifestations of the chronic phase of the disease, although understanding of the circuitry is still very incomplete. Evidence is presented that the signaling pathways that are constitutively activated in CML stem cells and primitive progenitors cooperate with cytokines to increase the proportion of stem cells that are activated and thereby increase recruitment into the committed progenitor cell pool, and that this increased activation is probably the primary cause of the massive myeloid expansion in CML. The cooperative interactions between Bcr-Abl and cytokine-activated pathways interfere with the synergistic interactions between multiple cytokines that are normally required for the activation of stem cells, while at the same time causing numerous subtle biochemical and functional abnormalities in the later progenitors and precursor cells. The committed CML progenitors have discordant maturation and reduced proliferative capacity compared to normal committed progenitors, and like them, are destined to die after a limited number of divisions. Thus, the primary goal of any curative strategy must be to eliminate all Philadelphia positive (Ph+) primitive cells that are capable of symmetric division and thereby able to expand the Ph+ stem cell pool and recreate the disease. Several highly potent and moderately selective inhibitors of Bcr-Abl kinase have recently been discovered that are capable of killing the majority of actively proliferating early CML progenitors with minimal effects on normal progenitors. However, like their normal counterparts, most of the CML primitive stem cells are quiescent at any given time and are relatively invulnerable to the Bcr-Abl kinase inhibitors as well as other drugs. We propose that survival of dormant Ph+ stem cells may be the most important reason for the inability to cure the disease during initial treatment, while resistance to the inhibitors and other drugs becomes increasingly important later. An outline of a possible curative strategy is presented that attempts to take advantage of the subtle differences in the proliferative behavior of normal and Ph+ stem cells and the newly discovered selective inhibitors of Bcr-Abl. Leukemia (2003) 17, 1211-1262. doi:10.1038/sj.leu.2402912

Concurrent mediastinal B cell lymphoma and chronic myeloid leukemia with an unusually favorable response to chemotherapy

A 67-year-old Chinese woman presented with mediastinal B cell lymphoma in 1992 with incidental leukocytosis. Bone marrow and peripheral blood findings confirmed the diagnosis of chronic myeloid leukemia (CML). After combination chemotherapy and radiotherapy for lymphoma, her peripheral blood counts remained normal, and she refused further treatment for nearly six years. Frank hematologic relapse occurred in 1998 and low dose hydroxyurea was used, which was stopped after six months owing to cytopenia. She remained well without treatment at 12-year follow up. Retrospective Southern blot analysis confirmed BCR gene rearrangement in marrow in 1992 and 1998, but not in the lymphoma or the latest peripheral blood. Fluorescence in-situ hybridzation analysis showed no Philadelphia chromosome positive (Ph+) cells in the peripheral blood at last (FISH) follow-up, but BCR/ABL remained detectable. The relevance of the concomitant occurrence of CML and lymphoma and the unusually favorable response of CML to chemotherapy to the pathogenesis of CML is discussed.

Busulfan-induced loss of Ph chromosome in chronic myeloid leukemia

We report a 44-yr-old female with Philadelphia chromosome positive chronic myeloid leukemia who was initially treated with busulfan, and clinical remission has been achieved. After 4 yr, low-dose busulfan therapy was started again and induced bone marrow aplasia. The patient spontaneously has recovered from aplasia, and complete cytogenetic remission with loss of Ph+ chromosome in bone marrow has been achieved. However, reverse-transcription-polymerase chain reaction analysis showed presence of the bcr-abl transcript in bone marrow.

Direct evidence that leukemic cells present HLA-associated immunogenic peptides derived from the BCR-ABL b3a2 fusion protein

The BCR-ABL oncogene is central in the pathogenesis of chronic myeloid leukemia (CML). Here, tandem nanospray mass spectrometry was used to demonstrate cell surface HLA-associated expression of the BCR-ABL peptide KQSSKALQR on class I-negative CML cells transfected with HLA-A*0301, and on primary CML cells from HLA-A3-positive patients. These patients mounted a cytotoxic T-lymphocyte response to KQSSKALQR that also killed autologous CML cells, and tetramer staining demonstrated the presence of circulating KQSSKALQR-specific T cells. The findings are the first demonstration that CML cells express HLA-associated leukemia-specific immunogenic peptides and provide a sound basis for immunization studies against BCR-ABL.

BCR-ABL fusion peptides and cytotoxic T cells in chronic myeloid leukaemia

The BCR-ABL gene that arises in chronic myeloid leukaemia (CML) is a neoantigen. Peptides derived from the BCR-ABL fusion junction may therefore be immunogenic, if appropriately presented to the immune system. This article reviews data demonstrating that certain junctional peptides will bind to HLA molecules, and that these peptides will elicit specific T-lymphocyte responses in vitro, in both normal subjects and in CML patients. The clinical relevance of these observations is discussed.

Spontaneous loss of Ph chromosome with maintenance of clonal hemopoiesis in an untreated patient with myeloproliferative disease and a long survival

The unusual case of myeloproliferative disease described here is characterized by the following features: (1) a clinically completely silent course for 11 years without splenomegaly, marrow fibrosis, or cellular morphologic alterations; (2) the presence, at the onset, of a Philadelphia (Ph) chromosome without DNA breakpoints in the M-bcr region; (3) the spontaneous loss of detectable Ph-positive cells, 5 years after the first finding of leukocytosis, in the absence of any therapy; (4) the maintenance of the clonal nature of hematopoiesis, as revealed by the PGK X-linked inactivation pattern, in the absence of the Ph chromosome; and (5) a biphasic trend in the levels of leukocytes, red cells, and platelets during the years of observation.

Detection of residual BCR/ABL transcripts in chronic myeloid leukaemia patients in complete remission using the polymerase chain reaction and nested primers

We sought evidence of BCR/ABL transcripts in the peripheral blood of nine CML patients in complete clinical and cytogenetic remission after treatment by bone marrow transplantation (BMT) or interferon and in one patient who entered spontaneous remission. Six patients were investigated at different times during their follow-up. We compared results obtained with the polymerase chain reaction (PCR) using (a) a single-stage PCR comprising 30 cycles of amplification with selected oligomers, and (b) a two-stage procedure in which the reaction product from the first stage was subjected to a further 30 cycles with nested amplimers. Special care was taken to assess contamination, including for each patient simultaneous co-extraction of a negative control. Blood cells from all patients showed no evidence of BCR/ABL transcripts in the one-stage PCR but 9/17 specimens were positive in the two-stage procedure. Patients in complete remission for a long time (greater than 2 years) appeared negative. These results serve in part to explain the discordant findings reported in other studies and emphasize the importance of carefully selecting the technical conditions most likely to give results that are prognostically relevant for individual patients.