Low-dose dexamethasone and thalidomide with higher frequency zoledronic acid (dtZ) for newly diagnosed multiple myeloma

18506

Background: Although dexamethasone (Dex), thalidomide (Thal) and zoledronic acid (Zol) have frequently been combined for the treatment of multiple myeloma (MM), the ideal dosing schedule is unknown. We previously reported that lower doses of Dex and Thal can be effectively combined with high-frequency dosing of Zol (Haematologica 2005). Methods: This “dtZ” regimen - which comprises weekly Dex 20 mg OM for 4 days, Thal 50 mg ON, and 3-weekly Zol 4 mg - resulted in an impressive response rate (RR) of 61.6% and near complete remission (nCR)/complete remission (CR) rate of 7.7% in 26 patients with relapsed/refractory MM. Results: In this present study, we treated 22 newly diagnosed MM patients with “dtZ” and report an even more impressive RR of 100.0% and nCR/CR rate of 20–35%. The median time to response was 1.8 months and median time to maximum response was 2.2 months. The median time to progression (TTP) has not been achieved yet. As expected, low-dose Dex/Thal resulted in lower (18.1%) grade 3 or 4 toxicities. These were all infections; which lead to further dose-reduction of Dex. There were no thromboembolic events, despite the fact that aspirin was not routinely given. Of particular interest, 3- weekly Zol was not associated with any significant decrease in renal function, and none of our patients developed osteonecrosis of the jaw (ONJ). In fact, at the time of writing of this abstract, more than 1,000 doses of Zol had been administered in a 3-weekly fashion to these as well as other patients, and only 1 patient developed ONJ. This patient who had already received greater than 20 doses of Zol healed uneventfully after receiving appropriate outpatient dental treatment, and subsequently received another 8 doses of Zol with no recurrence of ONJ. Conclusion: In conclusion, the Zol-based “dtZ” regimen is potentially a highly-effective and safe frontline regimen for MM. Using Zol every 3 weeks with lower doses of Dex and Thal does not appear to increase the rate or severity of nephrotoxicity or ONJ. Although we do not know exactly why every patient responded to “dtZ”, we speculate that this could be due to a critical balance that has been achieved between the anti-MM, anti-osteoclastic and immunostimulatory effects of the individual drugs of the combination.

No significant financial relationships to disclose.

Decoupling of normal CD40/interleukin-4 immunoglobulin heavy chain switch signal leads to genomic instability in SGH-MM5 and RPMI 8226 multiple myeloma cell lines

The processes mediating genomic instability and clonal evolution are obscure in multiple myeloma (MM). Acquisition of new chromosomal translocations into the switch region of the immunoglobulin heavy chain (IgH) gene (chromosome 14q32) in MM, often heralds transformation to more aggressive disease. Since the combined effects of CD40 plus interleukin-4 (IL-4) mediate IgH isotype class switch recombination (CSR), and this process involves DNA double strand break repair (DSBR), we hypothesized that CD40 and/or IL-4 activation of MM cells could induce abnormal DNA DSBR and lead to genomic instability and clonal evolution. In this study, we show that MM cell lines that are optimally triggered via CD40 and/or IL-4 demonstrate abnormal decoupling of IL-4 signal transduction from CD40. Specifically, CD40 alone was sufficient to trigger maximal growth of tumor cells. We further demonstrate that CD40 triggering induced both DNA DSBs as well as newly acquired karyotypic abnormalities in MM cell lines. Importantly, these observations were accompanied by induction of activation induced cytidine deaminase expression, but not gross apoptosis. These data support the role of abnormal CD40 signal transduction in mediating genomic instability, suggesting a role for the CD40 pathway and intermediates in myelomagenesis and clonal evolution in vivo.

Addition of bortezomib to thalidomide, dexamethasone and zoledronic acid (VTD-Z regimen) significantly improves complete remission rates in patients with relapsed/refractory multiple myeloma

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Background: We previously treated 26 patients with relapsed/refractory multiple myeloma (MM) with thalidomide (Thal), dexamethasone (Dex) and zoledronic acid (Zol); dtZ regimen; and demonstrated an overall response rate of 75.0%. However, the rate immunofixation (IF)-negative complete remissions (CR) was only 7.7%. Recently, the bortezomib (Velcade) has been shown to be effective against MM. In this study, we added bortezomib (Vel) to dtZ (VTD-Z regimen) in a subgroup of patients to determine whether the CR rate can be improved. Methods: A non-randomized, single-arm study was conducted. Consecutive patients (n = 14) who either failed to achieve a partial response (PR) after 3 cycles; or CR after 9 cycles of dtZ were treated with 2 to 11 three-weekly cycles of VTD-Z; comprising: Vel 1.3 mg/m2 on days 1, 4, 8 and 11; Thal 50 mg ON; Dex 20 mg OM on days 1 to 4, 8 to 11, 15 to 18; and Zol 4 mg on day 1. The primary study objective was to determine the maximal response rates (RR). The end-point of the study was maximum response, graded by Bladè’s criteria. Results: Fourteen patients (3 males, 11 females; median age 63.3 years) were studied. Complex karyotypes, including 5 patients with deletion of chromosome 13 (del(13)), were present in 11 patients at diagnosis. The overall RR was 92.9% (13 out of 14), of which 42.9% (6) achieved CR (p < 0.001, chi-squared test). In addition, 21.4% (3) achieved near-CR (nCR), and 28.6% (4) achieved PR. There were no minimal responders (MR) and 1 (7.1%) non-responder (NR). Two patients who achieved CR had del(13). Painful grade 3 peripheral neuropathy was observed in 2 (14.3%) patients. Grade 1 and 2 peripheral neuropathy was observed in another 4 (25.0%) of patients; transient grade 3 thrombocytopenia was observed in 5 (35.7%) patients; and papular rashes were observed in 3 (21.4%) patients. The single NR was the only death that occurred during the period of study. Conclusions: Our study demonstrates that the VTD-Z regimen is exceptionally effective and safe in patients with relapsed/refractory MM. Addition of Vel to dtZ significantly increases the CR rate from 7.7% to 42.9%. These data suggest that combination of these 4 drugs may be at least additive, if not, even synergistic.

No significant financial relationships to disclose.

High-dose therapy followed by autologous haematopoietic stem cell transplantation in multiple myeloma

INTRODUCTION AND OBJECTIVES

The median survival of patients with multiple myeloma (MM) after conventional chemotherapy is 3 years or less. Previous studies have shown that high-dose therapy, supported by haematopoietic stem cell rescue, improves survival of patients with MM. We analysed the outcome of 29 myeloma patients who had autologous haematopoietic stem cell transplantation (AHSCT) in our institution over an 8-year period.

MATERIALS AND METHODS

Between May 1993 and August 2001, 29 patients with MM underwent high-dose therapy followed by unpurged AHSCT. There were 16 male and 13 female patients. The median age of the patients was 52 years (range, 31 to 67 years). All patients had at least a partial remission after initial chemotherapy. The preparative regimen for the AHSCT was melphalan 200 mg/m2 in 25 patients, melphalan-total body irradiation in 1 patient, and busulphan-cyclophosphamide (BuCy) in 3 patients. Twenty-three patients received peripheral blood stem cells (PBSCs) autograft, 3 patients received bone marrow autograft and 3 patients received both.

RESULTS

Treatment-related death occurred in only 2 patients (7%). The median time to neutrophil engraftment was 11 days (range, 8 to 22 days). With a median follow-up period of 18.5 months, the 5-year overall survival (OS) and event-free survival (EFS) rates were 71% and 21%, respectively. The OS was found to be superior to a group of historical controls who were treated with conventional chemotherapy without transplantation (71% vs 19%; P = 0.014).

CONCLUSION

In conclusion, high-dose therapy followed by AHSCT is safe and beneficial for patients with MM.

Treatment of acute promyelocytic leukaemia using a combination of all-trans retinoic acid and chemotherapy

INTRODUCTION

The combination of all-trans retinoic acid (ATRA) with chemotherapy has improved the outcome of acute promyelocytic leukaemia (APL). Effective induction as well as maintenance therapy for APL can be achieved using this combination of anti-leukaemic agents.

MATERIALS AND METHODS

Twenty-four consecutive patients with newly-diagnosed APL were treated with ATRA daily together with either daunorubicin or idarubicin. Therapy with ATRA was continued until complete remission (CR) was achieved; thereafter, patients were treated with 2 cycles of an anthracycline-based consolidation chemotherapy (either daunorubicin or idarubicin). Maintenance therapy was achieved using 5 alternating cycles of low-dose methotrexate (MTX) plus 6-mercaptopurine (6MP) followed by ATRA alone.

RESULTS

Twenty-three out of 24 patients (96%) completed induction therapy and achieved haematological CR (HCR) as well as molecular remission (MR); however, 1 patient (5%) died from retinoic acid syndrome. Twenty-one out of 23 evaluable patients (91%) completed consolidation chemotherapy, and 2 patients (10%) died, 1 from neutropenic sepsis and the other from relapse following non-compliance to therapy. All 21 surviving patients in the present study received maintenance chemotherapy and are still in HCR and MR at a median follow-up of 23 months. The estimated actuarial 2-year overall survival (OS) and event-free survival (EFS) rates were both 84% +/- 9%.

CONCLUSION

The combination of ATRA with an anthracycline is an effective remission-induction therapy for newly-diagnosed APL. Maintenance therapy using alternating cycles of MTX plus 6MP followed by ATRA alone is effective in maintaining CR and MR as well as prolonging the survival of patients with APL.

Ku86 variant expression and function in multiple myeloma cells is associated with increased sensitivity to DNA damage

Ku is a heterodimer of Ku70 and Ku86 that binds to double-stranded DNA breaks (DSBs), activates the catalytic subunit (DNA-PKcs) when DNA is bound, and is essential in DSB repair and V(D)J recombination. Given that abnormalities in Ig gene rearrangement and DNA damage repair are hallmarks of multiple myeloma (MM) cells, we have characterized Ku expression and function in human MM cells. Tumor cells (CD38(+)CD45RA(-)) from 12 of 14 (86%) patients preferentially express a 69-kDa variant of Ku86 (Ku86v). Immunoblotting of whole cell extracts (WCE) from MM patients shows reactivity with Abs targeting Ku86 N terminus (S10B1) but no reactivity with Abs targeting Ku86 C terminus (111), suggesting that Ku86v has a truncated C terminus. EMSA confirmed a truncated C terminus in Ku86v and further demonstrated that Ku86v in MM cells had decreased Ku-DNA end binding activity. Ku86 forms complexes with DNA-PKcs and activates kinase activity, but Ku86v neither binds DNA-PKcs nor activates kinase activity. Furthermore, MM cells with Ku86v have increased sensitivity to irradiation, mitomycin C, and bleomycin compared with patient MM cells or normal bone marrow donor cells with Ku86. Therefore, this study suggests that Ku86v in MM cells may account for decreased DNA repair and increased sensitivity to radiation and chemotherapeutic agents, whereas Ku86 in MM cells confers resistance to DNA damaging agents. Coupled with a recent report that Ku86 activity correlates with resistance to radiation and chemotherapy, these results have implications for the potential role of Ku86 as a novel therapeutic target.

Kaposi's sarcoma-associated herpesvirus gene sequences are detectable at low copy number in primary amyloidosis

Primary amyloidosis (AL), like multiple myeloma (MM), results from a clonal proliferation of plasma cells. Recent detection of Kaposi's sarcoma-associated herpesvirus (KSHV) gene sequences in MM patients, although controversial, suggested that KSHV may also be present in AL. In the present study, we assayed for KSHV gene sequences in patients with primary AL independently in 2 laboratories. Nested polymerase chain reaction (PCR) was performed on DNA isolated from 21 bone marrow (BM) core biopsy samples to amplify orf26 and orf72, 2 regions of the KSHV genome. Eighteen of 21 (86%) BM core biopsy samples were KSHV PCR positive. BM aspirates from 16 of these 21 AL patients were cultured for 4-6 weeks to generate long term bone marrow stromal cells (LT-BMSCs), and 13 of 16 (81%) LT-BMSCs were also KSHV PCR positive. Results in all but 1 sample were consistent in the 2 laboratories. Sequencing of the PCR products in the 2 laboratories confirmed 94-98% and 95-98% homology to the published orf 26 and orf 72 KSHV gene sequences respectively, with interpatient base pair differences. Despite the presence of KSHV gene sequences, only 4/18 (22%) KSHV PCR positive patients demonstrated KSHV lytic antibodies by immunoblot assay. A sensitive assay performed on the BCBL-1 cell line confirmed the presence of KSHV at a very low copy number in AL. PCR using patient specific light chain gene primers also amplified DNA isolated from 2 AL BM core biopsies and 3 AL LT-BMSCs which were KSHV PCR positive, suggesting the presence of clonotypic cells. Our results therefore demonstrate KSHV gene sequences albeit at a very low copy number in the majority of BM core biopsies and LT-BMSCs from AL patients, and serological responses in only a minority of cases. Ongoing studies to identify viral transcripts and gene products will determine the biological relevance of KSHV in AL disease pathogenesis.

Characterization of signaling cascades triggered by human interleukin-6 versus Kaposi's sarcoma-associated herpes virus-encoded viral interleukin 6

Kaposi's sarcoma-associated herpes virus (KSHV) is associated with Kaposi's sarcoma, multicentric Castleman's disease, and body cavity-based lymphomas, settings in which human interleukin-6 (hIL-6) acts as a growth factor. The KSHV open reading frame K2 encodes for viral IL-6 (vIL-6), a protein with 25% amino acid identity to hIL-6, which can promote the growth of hIL-6-dependent cell lines. In the present study, we characterized biological sequelae and signaling cascades triggered by hIL-6 versus vIL-6 in the hIL-6-dependent MH60 and B9 cell lines. Both hIL-6 and vIL-6 induced significant increases (P < 0.01) in DNA synthesis in these cell lines in a dose-dependent fashion. Neutralizing anti-hIL-6 antibody (Ab) inhibited DNA synthesis triggered by hIL-6, without similarly affecting proliferation in response to vIL-6. On the other hand, antimouse IL-6 receptor (mIL-6R) Ab blocked response to vIL-6, but not that to hIL-6. Both hIL-6 and vIL-6 activated gp130, Janus kinase 1, signal transducers and activators of transcription-3, and mitogen-activated protein kinase in both MH60 and B9 cells. Proliferation of these cell lines in response to both hIL-6 and vIL-6 was blocked by PD98059, an inhibitor of MEK1 activation. These data suggest that MEK1 activation mediates the proliferative response to both cytokines. Finally, both hIL-6 and vIL-6 also maintained viability of serum-starved MH60 and B9 cells and blocked dexamethasone-induced apoptosis of MM.1S human myeloma cells. Further characterization of the signaling cascades mediating the growth and antiapoptotic effects of vIL-6 versus hIL-6 may help identify their unique roles in disease pathogenesis in Kaposi's sarcoma and other KSHV-associated neoplasms.

Isolation and characterization of human multiple myeloma cell enriched populations

We developed a simple and rapid method to enrich tumor cells within bone marrow (BM) aspirates from patients with multiple myeloma (MM). Thirty patients with a median of 50% (8-85%) MM cells by morphology and 55% (6--85%) MM cells identified by CD38+CD45-cell surface phenotype were studied. BM mononuclear cells (BMMCs) were isolated by Ficoll Hypaque sedimentation and incubated with a cocktail of mouse monoclonal antibodies (mAbs) directed against CD3 (T cells); CD11b and CD14 (monocytes); CD33 (myeloid cells), CD45 and CD45RA (leucocyte common antigen); CD32 as well as glycophorin A. After the addition of anti-mouse Fc Ig-coated immunomagnetic beads, mAb-bound cells were removed in a magnetic field. The residual cell populations were enriched for MM cells, evidenced by >95% plasma cell morphology and >95% CD38+CD45RA-cell surface phenotype. Since this method requires only two short incubations, cell losses were minimal and the yield of MM cells was therefore high (>95%). Viability of the MM-cell enriched fractions was 99%, and these cells were functional in assays of proliferation, cell cycle analysis and immunoglobulin secretion. This immunomagnetic bead depletion method therefore permits the ready isolation of homogeneous populations of patient MM cells for use in both cellular and molecular studies.

CD40 activation mediates p53-dependent cell cycle regulation in human multiple myeloma cell lines

It has been reported that the activation of multiple myeloma (MM) cells by CD40 induces proliferation, growth arrest, and apoptosis. To determine whether the biologic sequelae of CD40 activation in MM cells depends on p53 function, we identified temperature-sensitive p53 mutations in the RPMI 8226 (tsp53E285K) and the HS Sultan (tsp53Y163H) MM cell lines. These cells were then used as a model system of inducible wtp53-like function because wild-type-like p53 is induced at permissive (30 degrees C) but not at restrictive (37 degrees C) temperatures. Using p21-luciferase reporter assays, we confirmed that CD40 induces p53 transactivation in RPMI 8226 and HS Sultan cells cultured under permissive, but not restrictive, conditions. Furthermore, CD40 activation of these MM cells under permissive, but not restrictive, temperatures increased the expression of p53 and p21 mRNA and protein. Importantly, CD40 activation induced the proliferation of RPMI 8226 and HS Sultan cells at restrictive temperatures and growth arrest and increased subG1 phase cells at permissive temperatures. These data confirmed that CD40 activation might have distinct biologic sequelae in MM cells, depending on their p53 status.

RAFTK/PYK2-dependent and -independent apoptosis in multiple myeloma cells

Related Adhesion Focal Tyrosine Kinase (RAFTK; also known as Pyk2), is a member of the Focal Adhesion Kinase (FAK) subfamily and is activated by TNF alpha, UV light and increases in intracellular calcium levels. However, the function of RAFTK remains largely unknown. Our previous studies demonstrated that treatment with dexamethasone (Dex), ionizing radiation (IR), and anti-Fas mAb induces apoptosis in multiple myeloma (MM) cells. In the present study, we examined the potential role of RAFTK during induction of apoptosis in human MM cells triggered by these three stimuli. Dex-induced apoptosis, in contrast to apoptosis triggered by anti-Fas mAb or IR, is associated with activation of RAFTK. Transient overexpression of RAFTK wild type (RAFTK WT) induces apoptosis, whereas transient overexpression of Kinase inactive RAFTK (RAFTK K-M) blocks Dex-induced apoptosis. In contrast, transient overexpression of RAFTK K-M has no effect on apoptosis triggered by IR or Fas. In Dex-resistant cells, Dex does not trigger either RAFTK activation or apoptosis. Finally, interleukin-6 (IL-6), a known survival factor for MM cells, inhibits both activation of RAFTK and apoptosis of MM.1S cells triggered by Dex. Our studies therefore demonstrate Dex-induced RAFTK-dependent, and IR or Fas induced RAFTK-independent apoptotic signaling cascades in MM cells.

Functional interaction between retinoblastoma protein and stress-activated protein kinase in multiple myeloma cells

Previous studies have demonstrated that gamma-irradiation (IR)-induced apoptosis in multiple myeloma (MM) is associated with activation of stress-activated protein kinase (SAPK). In the present study, we examined the molecules downstream of SAPK/C-Jun N-terminal kinase (JNK), focusing on the role of retinoblastoma protein (Rb) during IR-induced MM cell apoptosis. The results demonstrate that IR activates SAPK/JNK, which associates with Rb both in vivo and in vitro. Far Western blot analysis confirms that SAPK/JNK binds directly to Rb. IR-activated SAPK/JNK phosphorylates Rb, and deletion of the phosphorylation site in the COOH terminus domain of Rb abrogates phosphorylation of Rb by SAPK/JNK. Taken together, our results suggest that Rb is a target protein of SAPK/JNK and that the association of SAPK/JNK and Rb mediates IR-induced apoptosis in MM cells.

Bone marrow and peripheral blood dendritic cells from patients with multiple myeloma are phenotypically and functionally normal despite the detection of Kaposi's sarcoma herpesvirus gene sequences

Multiple myeloma (MM) cells express idiotypic proteins and other tumor-associated antigens which make them ideal targets for novel immunotherapeutic approaches. However, recent reports show the presence of Kaposi's sarcoma herpesvirus (KSHV) gene sequences in bone marrow dendritic cells (BMDCs) in MM, raising concerns regarding their antigen-presenting cell (APC) function. In the present study, we sought to identify the ideal source of DCs from MM patients for use in vaccination approaches. We compared the relative frequency, phenotype, and function of BMDCs or peripheral blood dendritic cells (PBDCs) from MM patients versus normal donors. DCs were derived by culture of mononuclear cells in the presence of granulocyte-macrophage colony-stimulating factor and interleukin-4. The yield as well as the pattern and intensity of Ag (HLA-DR, CD40, CD54, CD80, and CD86) expression were equivalent on DCs from BM or PB of MM patients versus normal donors. Comparison of PBDCs versus BMDCs showed higher surface expression of HLA-DR (P =.01), CD86 (P =. 0003), and CD14 (P =.04) on PBDCs. APC function, assessed using an allogeneic mixed lymphocyte reaction (MLR), demonstrated equivalent T-cell proliferation triggered by MM versus normal DCs. Moreover, no differences in APC function were noted in BMDCs compared with PBDCs. Polymerase chain reaction (PCR) analysis of genomic DNA from both MM patient and normal donor DCs for the 233-bp KSHV gene sequence (KS330233) was negative, but nested PCR to yield a final product of 186 bp internal to KS330233 was positive in 16 of 18 (88.8%) MM BMDCs, 3 of 8 (37.5%) normal BMDCs, 1 of 5 (20%) MM PBDCs, and 2 of 6 (33.3%) normal donor PBDCs. Sequencing of 4 MM patient PCR products showed 96% to 98% homology to the published KSHV gene sequence, with patient specific mutations ruling out PCR artifacts or contamination. In addition, KHSV-specific viral cyclin D (open reading frame [ORF] 72) was amplified in 2 of 5 MM BMDCs, with sequencing of the ORF 72 amplicon revealing 91% and 92% homology to the KSHV viral cyclin D sequence. These sequences again demonstrated patient specific mutations, ruling out contamination. Therefore, our studies show that PB appears to be the preferred source of DCs for use in vaccination strategies due to the ready accessibility and phenotypic profile of PBDCs, as well as the comparable APC function and lower detection rate of KSHV gene sequences compared with BMDCs. Whether active KSHV infection is present and important in the pathophysiology of MM remains unclear; however, our study shows that MMDCs remain functional despite the detection of KSHV gene sequences.

Detection of Kaposi's sarcoma herpesvirus DNA sequences in multiple myeloma bone marrow stromal cells

Whether Kaposi's sarcoma herpesvirus (KSHV) is associated with multiple myeloma (MM) remains controversial. We assayed for KSHV DNA sequences in long-term bone marrow stromal cells (BMSCs) from 26 patients with MM and 4 normal donors. Polymerase chain reaction (PCR) using primers which amplify a KSHV gene sequence to yield a 233-bp fragment (KS330233 within open reading frame 26) was negative in all cases. Aliquots of these PCR products were used as templates in subsequent nested PCR, with primers that amplify a 186-bp product internal to KS330233. BMSCs from 24 of 26 (92%) patients with MM and 1 of 4 normal donors were KSHV PCR+. DNA sequence analyses showed interpatient specific mutations (2 to 3 bp). Both Southern blot and sequence analyses confirmed the specificity of PCR results. The presence of the KSHV gene sequences was further confirmed by amplifying T 1.1 (open reading frame [ORF] K7) and viral cyclin D (ORF 72), two other domains within the KSHV genome. Immunohistochemical studies of KSHV PCR+ MM BMSCs demonstrate expression of dendritic cell (DC) lineage markers (CD68, CD83, and fascin). Serological studies for the presence of KSHV lytic or latent antibodies were performed using sera from 53 MM patients, 12 normal donors, and 5 human immunodeficiency virus (HIV)/KSHV+ patients. No lytic or latent antibodies were present in sera from either MM patients or normal donors. Taken together, these findings show that KSHV DNA sequences are detectable in BMSCs from the majority of MM patients, but that serologic responses to KSHV are not present. Ongoing studies are defining whether the lack of antibody response is caused by the absence of ongoing infection, the presence of a novel viral strain associated with MM, or underlying immunodeficiency in these patients.

Restoration of p16INK4A protein induces myogenic differentiation in RD rhabdomyosarcoma cells

p16INK4A (p16) tumour suppressor induces growth arrest by inhibiting function of cyclin-dependent kinase (CDK)4 and CDK6. Homozygous p16 gene deletion is frequent in primary rhabdomyosarcoma (RMS) cells as well as derived cell lines. To confirm the significance of p16 gene deletion in tumour biology of RMS, a temperature-sensitive p16 mutant (E119G) gene was retrovirally transfected into the human RMS cell line RD, which has homozygous gene deletion of p16 gene. Decrease from 40 degrees C (restrictive) to 34 degrees C (permissive) culture temperature reduced CDK6-associated kinase activity and induced G1 growth arrest. Moreover, RD-p16 cells cultured under permissive condition demonstrated differentiated morphology coupled with expressions of myogenin and myosin light chain. These suggest that deletion of p16 gene may not only facilitate growth but also inhibit the myogenic differentiation of RD RMS cells.

Muc-1 core protein is expressed on multiple myeloma cells and is induced by dexamethasone

Monoclonal antibodies (MoAbs) that selectively identify Muc-1 core protein (MoAbs DF3-P, VU-4H5) determinants were used to identify the Muc-1 glycoform present on 7 multiple myeloma (MM) cell lines, 5 MM patient plasma cells, 12 MM patient B cells, as well as 32 non-MM cell lines and normal hematopoietic cells. Flow cytometry studies demonstrated that all MM cell lines, MM patient plasma cells, and MM patient B cells expressed Muc-1 core protein epitopes. Circulating B cells from 4 normal donors also expressed Muc-1 core protein. In contrast, Muc-1 core protein was absent on 28 of 32 non-MM neoplastic cell lines, 17 of which expressed Muc-1. Splenic and tonsillar B cells, CD34(+) stem cells, resting T cells, and bone marrow plasma cells obtained from normal donors both lacked Muc-1 glycoforms. We next studied the effects of estrogen, progesterone, and glucocorticoid receptor agonists and antagonists on Muc-1 expression, because consensus sequences for the response elements of these steroids are present on the Muc-1 gene promoter. These studies showed that dexamethasone (Dex) induced Muc-1 expression on MM cell lines, as determined by both flow cytometry and Western blot analyses. Dex also induced upregulation of Muc-1 on prostate and ovarian cancer cell lines. Time and dose-response studies demonstrated that Dex induced maximal cell surface Muc-1 expression by 24 hours at concentrations of 10(-8) mol/L. Dex induced Muc-1 upregulation could be blocked with a 10-fold excess of the glucocorticoid receptor antagonist RU486, confirming that Dex was acting via the glucocorticoid receptor. No changes in Muc-1 expression were observed on MM cells treated with estrogen and progesterone receptor agonists and antagonists or with RU486. These studies provide the framework for targeting Muc-1 core protein in vaccination and serotherapy trials in MM. In addition, the finding that Muc-1 expression on MM cells can be augmented by Dex at pharmacologically achievable levels suggests their potential utility in enhancing treatments targeting Muc-1 in MM.

Adenovirus vector-based purging of multiple myeloma cells

Adenoviruses are efficient gene delivery agents for a variety of neoplasms. In the present study, we have investigated the use of adenoviruses for the delivery of the thymidine kinase (tk) gene into multiple myeloma (MM) cells. We first demonstrated that MM cell lines and MM patient cells express both adenovirus receptors as well as the DF3/MUC1 protein, thus providing a rationale for using adenoviruses to selectively deliver genes under the control of the DF3 promoter. By using an adenoviral construct containing beta-galactosidase (beta-gal) gene driven by the DF3 promoter (Ad. DF3-betagal), we demonstrate greater than 80% transduction efficiency in OCI-My5 and RPMI 8226 MM cell lines at a multiplicity of infection of 1 to 100. Importantly, transduction with the tk gene driven by the DF3 promoter (Ad.DF3-tk) followed by treatment with 50 micromol/L ganciclovir (GCV) purged >/=6 log of contaminating OCI-My5 and RPMI 8226 MM cells within bone marrow mononuclear cells. In contrast, normal human hematopoietic progenitor cell number was unaffected under these conditions. Selectivity of DF3/MUC1 promoter was further confirmed, because Ad.DF3-betagal or Ad.DF3-tk did not transduce MUC1-negative HeLa cervical carcinoma cells. In addition, GCV treatment of Ad.DF3-tk-transduced RPMI 8226 MM cells did not induce a significant bystander effect. These findings demonstrate that transduction with Ad vectors using a tumor-selective promoter provides a highly efficient and selective approach for the ex vivo purging of MM cells.

Anti-estrogens induce apoptosis of multiple myeloma cells

Previous studies have suggested that multiple myeloma (MM) cells express estrogen receptors (ER). In the present study, we characterized the effects of estrogen agonists and antagonists (anti-estrogens [AE]) on growth of MM cell lines and MM patient cells. In addition to antagonizing estrogen binding to ER, AE can trigger apoptosis. Hence, we also determined whether estrogens or AE altered MM cell survival. Immunoblotting showed that ER-alpha is expressed in 4 of 5 MM cell lines (ARH-77, RPMI 8226, S6B45, and U266, but not OCI-My-5 cells), as well as in freshly isolated MM cells from 3 of 3 patients. 17beta-estradiol (E2) did not significantly alter proliferation of MM cell lines or MM patient cells. In contrast, two structurally distinct AE, tamoxifen (TAM) and ICI 182,780 (ICI), significantly inhibited the proliferation of all 5 MM cell lines and MM cells from 2 of 2 patients (IC50, 2 to 4 micromol/L). Proliferation of these cell lines was also inhibited by the hydroxylated TAM derivative, 4-hydroxytamoxifen (4HTAM), although this derivative was less potent than TAM (IC50, 3 to 25 micromol/L). In contrast, the dehalogenated TAM derivative toremifene (TOR) did not inhibit MM cell proliferation. We next examined the effects of these agents on MM cell survival. TAM, ICI, and, to a lesser extent, 4HTAM and TOR triggered apoptosis in both ER-alpha-positive as well as ER-alpha-negative MM cell lines and patient MM cells, evidenced both by fluorescence-activated cell sorting (FACS) analysis using propidium iodide staining and the TUNEL assay. TAM-induced growth inhibition and apoptosis of ER-alpha-positive S6B45 MM cells was not blocked by coculture with excess E2. TAM-induced apoptosis of S6B45 MM cells was also unaffected by addition of exogenous interleukin-6. Importantly, both the inhibition of MM cell proliferation and the induction of MM cell apoptosis were achieved at concentrations of TAM (0.5 and 5.0 micromol/L) that did not significantly alter in vitro growth of normal hematopoietic progenitor cells. Similar plasma levels of TAM have been achieved using high-dose oral TAM therapy, with an acceptable toxicity profile. These studies therefore provide the rationale for trials to define the utility of AE therapy in MM.

MDM2 protein overexpression inhibits apoptosis of TF-1 granulocyte-macrophage colony-stimulating factor-dependent acute myeloblastic leukemia cells

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a growth factor for acute myeloblastic leukemia (AML) cells. Murine double minute 2 (MDM2) oncoprotein, a potent inhibitor of wild-type p53 (wtp53), can function both to induce cell proliferation and enhance cell survival, and is frequently overexpressed in leukemias. Therefore, we focused on the importance of MDM2 protein in GM-CSF-dependent versus GM-CSF- independent growth of AML cells. The TF-1 AML cell line, which has both wtp53 and mutant p53 genes, showed GM-CSF-dependent growth; deprivation of GM-CSF resulted in G1 growth arrest and apoptosis. MDM2 mRNA and protein were highly expressed in proliferating TF-1 cells in the presence of GM-CSF and decreased significantly with deprivation of GM-CSF. In contrast, p53 protein increased with GM-CSF deprivation. Ectopic overexpression of MDM2 in TF-1 AML cells conferred resistance to GM-CSF deprivation, and is associated with decreased p53 protein expression. Moreover, a variant of TF-1 cells that grows in a GM-CSF-independent fashion also expressed high levels of MDM2 and low levels of p53. These results suggest that GM-CSF-independent growth of AML cells is associated with overexpression of MDM2 protein and related modulation of p53 expression.

The 86-kD subunit of Ku autoantigen mediates homotypic and heterotypic adhesion of multiple myeloma cells

Previous studies have shown that triggering multiple myeloma (MM) cells via CD40 induces IL-6-mediated autocrine growth as well as increased expression of cell surface adhesion molecules including CD11a, CD11b, CD11c, and CD18. In this study, we generated the 5E2 mAb which targets an antigen that is induced upon CD40 ligand (CD40L) activation of MM cells. Immunofluorescence, immunoprecipitation, and protein sequencing studies identified the target antigen of 5E2 mAb as the 86-kD subunit of the Ku autoantigen. We demonstrate that increased cell surface expression of Ku on CD40L-treated cells is due to migration of Ku from the cytoplasm to the cell surface membrane. Moreover, cell surface Ku on CD40L-treated MM cells mediates homotypic adhesion of tumor cells, as well as heterotypic adhesion of tumor cells to bone marrow stromal cells and to human fibronectin; and 5E2 mAb abrogates IL-6 secretion triggered by tumor cell adherence to bone marrow stromal cells. These data suggest that CD40L treatment induces a shift of Ku from the cytoplasm to the cell surface, and are the first to show that Ku functions as an adhesion molecule. They further suggest that cell surface Ku may play a role in both autocrine and paracrine IL-6-mediated MM cell growth and survival.

Cytochrome c-dependent and -independent induction of apoptosis in multiple myeloma cells

Cytochrome c is a mitochondrial protein that induces apoptosis when accumulated in the cytosol in response to diverse stress inducers. This protein has also been shown to cause apoptosis when added to cell free extracts. In this report, we studied the role of cytochrome c (cyto-c) in dexamethasone (Dex), anti-Fas monoclonal antibody (mAb), and ionizing radiation-induced apoptosis in multiple myeloma cells. The results demonstrate that ionizing radiation-induced apoptosis is associated with an increase in cytosolic cyto-c levels, whereas apoptosis induced by Dex or anti-Fas mAb has no detectable effect on cyto-c release. By contrast, caspase-3 was activated in response to all of these agents. Thus, our findings suggest that Dex or anti-Fas mAb-induced apoptosis is not accompanied by cyto-c release and that there are at least two different pathways leading to activation of caspases and induction of apoptosis in multiple myeloma cells that can be distinguished by accumulation of cytosolic cyto-c.

p16INK4A promotes differentiation and inhibits apoptosis of JKB acute lymphoblastic leukemia cells

Homozygous p16(INK4A) (p16) gene deletion is frequent in primary tumor cells from acute lymphoblastic leukemia (ALL), suggesting that loss of p16 may be an important precursor to transformation in ALL. We have previously described JKB, a human ALL cell line, that contains homozygous deletion of the p16 gene. Because ectopic expression of p16 suppresses cell growth, we created a temperature sensitive p16 mutant to develop a system for inducible p16 function in human ALL. JKB cells were transfected either with a p16 gene mutated at position 119 (E119G) to confer temperature sensitivity (JKB p16MT) or with control vector. The percentage of cells in G1 phase was similar in JKB control cells or in JKB p16MT cells cultured at restrictive conditions (40 degrees C). However, with lowering of temperature from 40 degrees C to permissive conditions (31 degrees C), the percentage of JKB p16MT cells in G1 phase and binding of p16 to CDK4 and CDK6 increased, with associated decreases in CDK4 and CDK6 kinase activities, and dephosphorylation of retinoblastoma protein (pRB). Culture of JKB p16MT cells at 31 degrees C for >/=3 days irreversibly inhibited growth. Moreover, JKB p16MT cells cultured under these permissive conditions showed a less transformed morphology and more differentiated phenotype than did these cells cultured under restrictive temperatures. Finally, dexamethasone (Dex) induced apoptosis of JKB p16MT cells cultured at 40 degrees C, but did not trigger death of these cells cultured at 31 degrees C. These results suggest that deletion of p16 gene in JKB human ALL cells is associated with dysregulated growth of less differentiated tumor cells, which nonetheless remain susceptible to apoptosis triggered by Dex.

Characterization of p16(INK4A) expression in multiple myeloma and plasma cell leukemia

Loss of p16(INK4A) (p16) expression is frequently associated with the development of epithelial and lymphoid malignancies. However, the frequency and significance of p16 abnormalities in multiple myeloma (MM) and the more aggressive phase of plasma cell leukemia (PCL) have not been well defined. Accordingly, the goal of this study was to define the expression and function of p16 in fresh samples of MM and PCL. We found that p16 protein was highly expressed in primary MM cells, although it was undetectable in fresh samples of PCL. Additionally, p16 protein was also absent in four of four MM-derived cell lines. To determine the mechanism for p16 underexpression in PCL and MM-derived cell lines, we performed PCR analysis to evaluate both gene deletion and the presence of methylation. Interestingly, the p16 gene was present and methylated in all patient PCL cells and MM cell lines, whereas it was unmethylated in patient MM cells and normal B cells. Furthermore, treatment with the demethylating agent 5-deoxyazacytidine or p16 retrofection restored p16 protein expression and induced G1 growth arrest in patient PCL cells and MM cell lines. These results suggest that inactivation of the p16 gene by methylation may be associated with decreased growth control and the development of PCL in a subset of patients with MM.

Role of CDK4 and p16INK4A in interleukin-6-mediated growth of multiple myeloma

Interleukin-6 (IL-6) promotes growth of human multiple myeloma (MM) cells via phosphorylation of retinoblastoma protein (pRB). We therefore examined the kinetics of cyclin-dependent kinase 4 (CDK4), p16INK4A, and pRB activation during IL-6-mediated patient MM cell growth compared with growth of IL-6 unresponsive patient plasma cell leukemia (PCL) cells. CDK4 protein was more strongly expressed in PCL cells than in MM cells. On the other hand, p16 protein was present in MM cells but undetectable in PCL cells. Interestingly, IL-6 induced peak proliferation of MM cells at days 1-3, with a return to baseline levels of DNA synthesis by days 6-9 in spite of replenishing IL-6. In these cells, IL-6 triggered a sustained increase in CDK4 by day 1 and a gradual increase in p16 to day 9. The progressive increase in p16 without further increments in CDK4 resulted in a shift from cyclin D2-CDK4/CDK6 binding at days 1-3 to p16-CDK4/CDK6 complex formation at days 6-9. Both phosphorylated pRB and dephosphorylated pRB were present initially in patient MM cells; IL-6 triggered a shift to phosphorylated pRB and G1 to S transition at days 1-3, with return to baseline levels of dephosphorylated pRB and related G1 growth arrest by day 9. No similar changes in CDK4, p16, or cell cycle profile were observed in IL-6 nonresponsive PCL cells. Our data therefore suggest a feedback mechanism in IL-6-mediated MM cell growth which is absent in IL-6 nonresponsive PCL cells.

IL-6 triggers cell growth via the Ras-dependent mitogen-activated protein kinase cascade

IL-6 mediates growth of some human multiple myeloma (MM) cells and IL-6-dependent cell lines. Although three IL-6 signaling pathways (STAT1, STAT3, and Ras-dependent MAPK cascade) have been reported, cascades mediating IL-6-triggered growth of MM cells and cell lines are not defined. In this study, we therefore characterized IL-6 signaling cascades in MM cell lines, MM patient cells, and IL-6-dependent B9 cells to determine which pathway mediates IL-6-dependent growth. IL-6 induced phosphorylation of JAK kinases and gp130, regardless of the proliferative response of MM cells to this growth factor. Accordingly, we next examined downstream IL-6 signaling via the STAT3, STAT1, and Ras-dependent mitogen-activated protein kinase (MAPK) cascades. IL-6 triggered phosphorylation of STAT1 and/or STAT3 in MM cells independent of their proliferative response to IL-6. In contrast, IL-6 induced phosphorylation of Shc and its association with Sos1, as well as phosphorylation of MAPK, only in MM cells and B9 cells that proliferated in response to IL-6. Moreover, MAPK antisense, but not sense, oligonucleotide inhibited IL-6-induced proliferation of these cells. These data suggest that STAT1 and/or STAT3 activation may occur independently of the proliferative response to IL-6, and that activation of the MAPK cascade is an important distal pathway for IL-6-mediated growth.

MDM2 protein overexpression promotes proliferation and survival of multiple myeloma cells

The murine double minute 2 (MDM2) protein facilitates G1 to S phase transition by activation of E2F-1 and can enhance cell survival by suppressing wild-type p53 (wtp53) function. In this study, we examined MDM2 expression and function in multiple myeloma (MM) cells. MDM2 is strongly and constitutively expressed in MM cell lines (ARH-77, RPMI 8226, and OCI-My5) and in the cells of plasma cell leukemia (PCL) patients, but is not expressed in normal bone marrow mononuclear cells (BM MNCs). Treatment of MM cells with MDM2 antisense, but not sense, nonsense, or scrambled, oligodeoxyribonucleotides (ODNs) decreased DNA synthesis and cell viability; it also induced G1 growth arrest, as evidenced by propidium iodide (PI) staining and induction of retinoblastoma protein (pRB) to E2F-1 binding. Moreover, inhibition of MDM2 using antisense ODNs also triggered MM cell apoptosis as evidenced by acridine orange-ethidium bromide staining. We next studied the association of MDM2 with wtp53 and/or mutant p53 (mtp53), E2F-1, CDK4, and p21. MDM2 constitutively binds to E2F-1 in all MM cells, to both wtp53 and mtp53, and to p21 in tumor cells lacking p53. These data suggest that MDM2 may enhance cell-cycle progression in MM cells both by activating E2F-1 and by downregulating cell-cycle inhibitory proteins (wtp53 and p21). Overexpression of MDM2 may therefore contribute to both growth and survival of MM cells, suggesting the potential utility of treatment strategies targeting MDM2 in MM.

IL-6 triggers cell growth via the Ras-dependent mitogen-activated protein kinase cascade

IL-6 mediates growth of some human multiple myeloma (MM) cells and IL-6-dependent cell lines. Although three IL-6 signaling pathways (STAT1, STAT3, and Ras-dependent MAPK cascade) have been reported, cascades mediating IL-6-triggered growth of MM cells and cell lines are not defined. In this study, we therefore characterized IL-6 signaling cascades in MM cell lines, MM patient cells, and IL-6-dependent B9 cells to determine which pathway mediates IL-6-dependent growth. IL-6 induced phosphorylation of JAK kinases and gp130, regardless of the proliferative response of MM cells to this growth factor. Accordingly, we next examined downstream IL-6 signaling via the STAT3, STAT1, and Ras-dependent mitogen-activated protein kinase (MAPK) cascades. IL-6 triggered phosphorylation of STAT1 and/or STAT3 in MM cells independent of their proliferative response to IL-6. In contrast, IL-6 induced phosphorylation of Shc and its association with Sos1, as well as phosphorylation of MAPK, only in MM cells and B9 cells that proliferated in response to IL-6. Moreover, MAPK antisense, but not sense, oligonucleotide inhibited IL-6-induced proliferation of these cells. These data suggest that STAT1 and/or STAT3 activation may occur independently of the proliferative response to IL-6, and that activation of the MAPK cascade is an important distal pathway for IL-6-mediated growth.

Dexamethasone induces apoptosis of multiple myeloma cells in a JNK/SAP kinase independent mechanism

The stress-activated protein kinases (SAPKs), also known as c-Jun amino-terminal kinases (JNKs), are activated in response to diverse stimuli including DNA damage, heat shock, interleukin-1, tumor necrosis factor-alpha and Fas. Although all these inducers cause apoptosis, whether SAPK/JNK activation is required for apoptosis is controversial. In this study, we demonstrate that ionizing radiation (IR) and dexamethasone (Dex) induce apoptosis in multiple myeloma (MM) derived cell lines, as well as in patient cells. IR-induced apoptosis is associated with activation of SAPK/JNK and p38 kinase, in contrast to Dex-induced apoptosis, which is not associated with activation of stress kinases. Moreover, Dex-induced apoptosis is associated with a significant decrease in the activities of mitogen activated protein kinase (MAPK) and p70S6K, whereas IR-treatment does not alter the activity of these kinases. Both IR and Dex induce poly (ADP ribose) polymerase (PARP) cleavage, a signature event of apoptosis. Finally, interleukin-6 (IL-6) inhibits Dex-induced apoptosis, downregulation of MAP and p70S6K growth kinases and PARP cleavage; in contrast, IL-6 does not inhibit IR-induced apoptosis, activation of SAPK/JNK, and PARP cleavage. Taken together, our findings suggest that SAPK/JNK activation is not required for apoptosis in MM cells, and that there are at least two distinct apoptotic signaling pathways: (i) SAPK/JNK-associated, which is induced by IR and unaffected by IL-6; and (ii) SAPK/JNK-independent, which is induced by Dex, associated with downregulation of MAPK and p70S6K and inhibited by IL-6.

The development of a model for the homing of multiple myeloma cells to human bone marrow

Prior in vitro studies have suggested a role of adhesion molecules, bone marrow stromal cells (BMSCs), and cytokines in the regulation of human multiple myeloma (MM) cell growth and survival. Although in vivo models have been developed in severe combined immunodeficient (SCID) mice that support the growth of human MM within the murine BM microenvironment, these xenograft models do not permit a study of the role of adhesion proteins in human MM cell-human BMSC interactions. We therefore established an in vivo model of human MM using SCID mice implanted with bilateral human fetal bone grafts (SCID-hu mice). For the initial tumor innoculum, human MM derived cell lines (1 x 10(4) or 5 x 10(4) ARH-77, OCI-My5, U-266, or RPMI-8226 cells) were injected directly into the BM cavity of the left bone implants in irradiated SCID-hu mice. MM cells engrafted and proliferated in the left human fetal bone implants within SCID-hu mice as early as 4 weeks after injection of as few as 1 x 10(4) MM cells. To determine whether homing of tumor cells occurred, animals were observed for up to 12 weeks after injection and killed to examine for tumor in the right bone implants. Of great interest, metastases to the right bone implants were observed at 12 weeks after the injection of 5 x 10(4) MM cells, without spread of human MM cells to murine BM. Human MM cells were identified on the basis of characteristic histology and monoclonal human Ig. Importantly, monoclonal human Ig and human interleukin-6 (IL-6), but not human IL-1beta or tumor necrosis factor-alpha, were detectable in sera of SCID-hu mice injected with MM cells. In addition, specific monoclonal Ig light chain deposition was evident within renal tubules. This in vivo model of human MM provides for the first time a means for identifying adhesion molecules that are responsible for specific homing of human MM cells to the human, as opposed to murine, BM microenvironment. Moreover, induction of human IL-6 suggests the possibility that regulation of MM cell growth by this cytokine might also be investigated using this in vivo model.

Interleukin-6 overcomes p21WAF1 upregulation and G1 growth arrest induced by dexamethasone and interferon-gamma in multiple myeloma cells

Interleukin-6 (IL-6) is a growth factor for multiple myeloma (MM) cells and can inhibit MM cell apoptosis. Our recent studies show that IL-6 facilitates MM cell growth via phosphorylation of retinoblastoma protein (pRB); however, the effects of IL-6 on those cyclins, cyclin-dependent kinases (CDKs), and CDK inhibitors (CDIs) that are known to regulate phosphorylation of pRB have not been defined in MM cells. In the present report, we cultured MM cell lines and patient cells with IL-6 and/or dexamethasone (Dex) and characterized changes in cell cycle; expression and association of cyclins, CDKs, and CDIs; and phosphorylation of pRB. Dex induced G1 growth arrest in MM cells, whereas IL-6 facilitated G1 to S phase transition; moreover, the effect of Dex was blocked by IL-6. p21WAF1 (p21) protein was constitutively expressed in the majority of MM cells independent of the status of p53. Its expression was upregulated by Dex and downregulated by IL-6; again, IL-6 inhibited the increase in p21 triggered by Dex. These alterations in p21 expression in MM cells were associated with changes in p21 binding to CDK2, CDK4, and CDK6; CDK2, CDK4, and CDK6 kinase activities; and phosphorylation of pRB. In contrast, expression of G1 cell cycle regulatory proteins, including p27KIP1, cyclin D2, and cyclin E, was not altered in MM cells cultured with Dex and/or IL-6. Finally, interferon-gamma (IFN-gamma) also induced G1 growth arrest and upregulated p21 protein expression; as with Dex, affects of IFN-gamma were inhibited by IL-6. Our results therefore show that changes in cell cycle distribution in MM cells triggered by Dex, IL-6, and IFN-gamma correlate with changes in p21 protein expression and implicate p21 in the coupling of Dex-, IL-6-, and IFN-gamma-related signals to G1 cell cycle regulation in MM cells.

Blockade of mitogen-activated protein kinase cascade signaling in interleukin 6-independent multiple myeloma cells

Interleukin 6 (IL-6) is a growth factor for multiple myeloma (MM) cells, yet not all MM cell lines or patient cells require IL-6 for their growth. It is well known that IL-6 activates the signal transducers and activators of transcription (stat) 1-stat3 heterodimer, stat3 homodimer, and Ras-dependent mitogen-activated protein kinase (MAPK) cascades in multiple cell systems. We have shown previously that the MAPK pathway is an important pathway for IL-6-mediated MM cell growth. In this study, we delineate the pattern of upstream MAPK cascade activation in IL-6-responsive B9 cells and in IL-6-nonresponsive U266, OCI-My5, and RPMI8226 MM cells to define sites of blockade of this pathway associated with loss of responsiveness to IL-6. In B9 cells, IL-6 triggered the following in sequence: gp130 phosphorylation, gp130-to-protein tyrosine phosphatase 1D (PTP1D) binding, PTP1D phosphorylation, PTP1D complex formation with Grb2-Son of sevenless 1 (Sos1), and Sos1 phosphorylation. gp130 phosphorylation, gp130-to-PTP1D binding, PTP1D phosphorylation, and PTP1D-to-Grb2 binding are also induced by IL-6 in all IL-6-independent MM cell lines studied. However, Grb2 is not associated with Sos1, and neither Grb2-to-Sos1 binding nor Sos1 phosphorylation is triggered by IL-6 in OCI-My5 MM cells. On the other hand, Grb2 and Sos1 are associated constitutively in U266 and RPMI8226 MM cells, but phosphorylation of Sos1 is not induced by IL-6. These data suggest that lack of Sos1 activation is associated with loss of IL-6 responsiveness in MM cell lines that grow independently of IL-6.

Interaction of tumor and host cells with adhesion and extracellular matrix molecules in the development of multiple myeloma

Adhesion molecules play an important role in the growth regulation and migration of multiple myeloma (MM) cells. They mediate homing of MM cells to the bone marrow and MM cell to bone marrow stromal cell adhesion, with resultant interleukin-6 related autocrine and paracine growth and antiapoptotic affects. Their pattern of expression on tumor cells correlates with the development of plasma cell leukemia or extramedullary disease. Clinically, expression of adhesion molecules on tumor cells or in the serum has already shown prognostic utility. Finally, since adhesion molecules are involved at multiple steps in the pathogenesis of MM, therapeutic studies may target these molecules.

Interleukin-6 inhibits Fas-induced apoptosis and stress-activated protein kinase activation in multiple myeloma cells

Fas belongs to the family of type-1 membrane proteins that transduce apoptotic signals. In the present studies, we characterized signaling during Fas-induced apoptosis in RPMI-8226 and IM-9 multiple myeloma (MM) derived cell lines as well as patient plasma cell leukemia cells. Treatment with anti-Fas (7C11) monoclonal antibody (MoAb) induced apoptosis, evidenced by internucleosomal DNA fragmentation and propidium iodide staining, and was associated with increased expression of c-jun early response gene. We also show that anti-Fas MoAb treatment is associated with activation of stress-activated protein kinase (SAPK) and p38 mitogen-activated protein kinase (MAPK); however, no detectable increase in extracellular signal-regulated kinases (ERK1 and ERK2) activity was observed. Because interleukin-6 (IL-6) is a growth factor for MM cells and inhibits apoptosis induced by dexamethasone and serum starvation, we examined whether IL-6 affects anti-Fas MoAb-induced apoptosis and activation of SAPK or p38 MAPK in MM cells. Culture of MM cells with IL-6 before treatment with anti-Fas MoAb significantly reduced both DNA fragmentation and activation of SAPK, without altering induction of p38 MAPK activity. These results therefore suggest that anti-Fas MoAb-induced apoptosis in MM cells is associated with activation of SAPK, and that IL-6 may both inhibit apoptosis and modulate SAPK activity.

A novel pre-B acute lymphoblastic leukemia cell line with chromosomal translocation between p16(INK4A)/p15(INK4B) tumor suppressor and immunoglobulin heavy chain genes: TGFbeta/IL-7 inhibitory signaling mechanism

p16 INK4A and/or p15 INK4B genes are frequently deleted in leukemias and other cancers. We have established a novel pre-B acute lymphoblastic leukemia (ALL) cell line (JKB2) with a chromosomal translocation between 9p2l and 14q32, on which p16INK4A/p15INK4B and heavy chain immunoglobulin (Ig) genes, respectively, are located. Homozygous deletions of P16INK4A/p15INK4B genes in JKB2 cells were confirmed by polymerase chain reaction, and their protein products were not detectable by Western blotting. Therefore JKB2 is the first example of an immunoglobulin heavy chain translocation associated with deletions of these genes. In JKB2 cells, cyclin-dependent kinase(CDK)4 and CDK6 formed complexes with cyclin D, due to the lack of p16, triggering phosphorylation of retinoblastoma protein (pRB) and continuous cell proliferation. Moreover, the growth of JKB2 cells was partially inhibited by TGF beta or IL-7, accompanied by decreased CDK4 and CDK6 expression, increased p2l and p27 expression, decreased p27 binding to CDK4/CDK6, and increased binding of p27 to CDK2. In addition, IL-7 both inhibited proliferation and induced differentiation of JKB2 cells. These studies suggest that a t(9;14)(p21;q32) chromosomal translocation can result in deletion of both p16 INK4A and p15 INK4B genes in pre-B ALL, and that the JKB2 cell line therefore provides a model for the study of leukemogenesis related to abnormalities in chromosome 9p2l. Moreover, they suggest that TGF-beta can, suppress JKB2 cell growth in a p15-independent mechanism.

Interleukin-6 promotes multiple myeloma cell growth via phosphorylation of retinoblastoma protein

Interleukin-6 (IL-6) mediates autocrine and paracrine growth of multiple myeloma (MM) cells and inhibits tumor cell apoptosis. Abnormalities of retinoblastoma protein (pRB) and mutations of RB gene have been reported in up to 70% of MM patients and 80% of MM-derived cell lines. Because dephosphorylated (activated) pRB blocks transition from G1 to S phase of the cell cycle whereas phosphorylated (inactivated) pRB releases this growth arrest, we characterized the role of pRB in IL-6-mediated MM cell growth. Both phosphorylated and dephosphorylated pRB were expressed in all serum-starved MM patient cells and MM-derived cell lines, but pRB was predominantly in its phosphorylated form. In MM cells that proliferated in response to IL-6, exogenous IL-6 downregulated dephosphorylated pRB and decreased dephosphorylated pRB-E2F complexes. Importantly, culture of MM cells with RB antisense, but not RB sense, oligonucleotide (ODN) triggered IL-6 secretion and proliferation in MM cells; however, proliferation was only partially inhibited by neutralizing anti-IL-6 monoclonal antibody (MoAb). In contrast to MM cells, normal splenic B cells express dephosphorylated pRB. Although CD40 ligand (CD40L) triggers a shift from dephosphorylated to phosphorylated pRB and proliferation of B cells, the addition of exogenous IL-6 to CD40L-treated B cells does not alter either pRB or proliferation, as observed in MM cells. These results suggest that phosphorylated pRB is constitutively expressed in MM cells and that IL-6 further shifts pRB from its dephosphorylated to its phosphorylated form, thereby promoting MM cell growth via two mechanisms; by decreasing the amount of E2F bound by dephosphorylated pRB due to reduced dephosphorylated pRB, thereby releasing growth arrest; and by upregulating IL-6 secretion by MM cells and related IL-6-mediated autocrine tumor cell growth.

Haemophagocytosis in bone marrow aspirate--a review of the clinical course of 10 cases

The clinical course of 10 cases where marrow aspirate showed features of haemophagocytosis was reviewed. Eight of these had a fulminant clinical course characterized by high fever, constitutional symptoms, wasting, hepatosplenomegaly with liver dysfunction, sometimes lymphadenopathy, progressive pancytopenia and coagulopathy, like that described as 'malignant histiocytosis' in the past. The remaining 2 cases did not have this classical clinical syndrome. Among the former 8 cases, 4 of them had high-grade lymphoma, 3 of whom were confirmed to be peripheral T cell lymphoma. Three of the remaining 4 had suspicious lymphomatous infiltrate on marrow trephine. In every case an extensive search for viral etiology by serology was negative. The 2 cases which did not have fulminant clinical feature were found to have lymphoma of the diffuse large cell and Ki-1 anaplastic type, respectively. A review of the literature reveal that most cases with haemophagocytic syndrome have a fulminant clinical course and are peripheral T cell lymphoma, which generally has a poor prognosis. In our study, the 8 cases with the classical haemophagocytic syndrome had a median survival of 24 days and a long-term survival of 37.5% at 28 months. Prompt initiation of chemotherapy is a life-saving measure and the only chance of achieving a long-term survival in patients with haemophagocytic syndrome if the underlying lymphoma can be diagnosed early.

Acute traumatic tetraplegia during pregnancy

A case of acute traumatic tetraplegia during pregnancy resulting in maternal death is presented, and problems of management are discussed. Difficulties experienced by the mother were intractable urinary tract infection and respiratory insufficiency; those in the neonate were prematurity and the effects of drugs administered to the mother.