Abstract WMP19: When Minutes Count: Addition Of Stroke Transfer Coordinator

The treatment of hyper acute ischemic stroke is time critical, requiring a coordinated team response. It is common among primary and comprehensive stroke centers to have a “stroke alert” process, activating physicians, laboratory, radiology, and nursing support. In our center, the stroke alert included activation of a stroke program coordinator during day hours to assist with data gathering and time tracking. A clinical nurse expert would attend stroke alerts as able to on nightshift. At times, there were gaps when no personnel were available, and data was backtracked. In 2021, the use of Viz.AI was implemented. The Viz app allows streamlined communication amongst the treatment team (MD, ED Charge, Bed Capacity, etc.). Information including COVID status, time of Contrast given, imaging studies, and family contact information are exchanged prior to the patient’s arrival. Six Stroke Transfer Coordinators (STC) were hired, whose primary focus was attending stroke alerts, monitoring CT scans through the Viz app, and facilitating the transfer of patients with Large Vessel Occlusion (LVO) for thrombectomy treatment.

Methods: This is a single center retrospective cohort study. Basic demographic data, presence of LVO, time of last known well, time of imaging, time of transfer acceptance, NIHSS, and thrombolysis prior to transfer were recorded. Door-in-door out, door-to-angiogram, and door-to-groin puncture times were also collected. We compared and analyzed data from 12 months prior to implementation of the STC (August 2020-July 2021) to the 12 months post-implementation (August 2021 to July 2022).

Results: Total number of Stroke Alerts (SA) in the pre-STC time period was 1479, with 136 thrombectomy alert. Post-TSC the total number of SA was 1306, with 179 thrombectomy alerts. The mean door-to-intervention time pre-STC was 24 minutes (median=25 minutes). Post implementation of the STC, the mean door-to-intervention time was 17 minutes (median= 12 minutes).

Conclusions: STC’s improved the door-to-intervention time by mean of 7 minutes (median= 13 minutes). When every minute counts in re-establishing brain perfusion, this improvement may lead to better patient outcomes. Further study is necessary.

Increased expression of androgen receptor (AR) and enzymes involved in androgen synthesis in metastatic prostate cancer: Targets for novel personalized therapies

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Background: Androgen receptor (AR) signaling remains active in castration-resistant prostate cancer (CRPC) despite castrate levels of circulating androgens. This is indicated by continuous expression of androgen-responsive genes and is due to mechanisms that include: increased AR expression; AR mutations allowing promiscuous activation by alternative ligands; and increased intratumoral androgen levels, resulting from in situ steroidogenesis. Methods: Gene expression profiles of 30 normal prostate tissue samples, 131 primary prostate carcinomas (PCas) and 16 metastatic PCas, generated using Affymetrix Exon arrays, were interrogated for levels of 40 mRNAs encoding AR, SHBG, 28 enzymes involved in androgen synthesis and 10 enzymes involved in androgen inactivation. For individual tumors, a transcript was considered to be overexpressed or underexpressed when its levels were >2 SDs higher or lower, respectively, than its average levels in normal tissue. Results: Metastatic PCas expressed higher average transcript levels for AR and several steroidogenic enzymes, including SRD5A1 and SRD5A3, than primary PCas and normal prostate tissue. Expression of SRD5A2, CYP3A4, CYP3A5, and CYP3A7 mRNAs was decreased both in primary and metastatic tumors compared to normal prostate tissue. In analysis involving AR and 28 steroidogenic transcripts in individual tumors, all (16/16) metastatic PCas overexpressed at least one transcript (range: 2–14, median: 5 transcripts) compared to normal tissue, while 100/131 (76%) primary PCas overexpressed at least one transcript (range: 2–16, median: 2). Conclusions: Metastatic PCas overexpress AR and several steroidogenic enzymes, while they express lower levels of the androgen-inactivating enzymes CYP3A4, CYP3A5, and CYP3A7. These data highlight the role of AR and the androgen synthetic pathway as a therapeutic target in CRPC. Novel antiandrogens (MDV3100) and CYP17 inhibitors (abiraterone) are already in clinical trials in CRPC. Overexpression of AR or steroidogenic enzymes may serve as a biomarker (e.g. by detection via RT-PCR in circulating tumor cells) to predict for sensitivity to these agents and guide patient selection for participation in clinical trials.

No significant financial relationships to disclose.

Characterization of a reference material for BCR-ABL (M-BCR) mRNA quantitation by real-time amplification assays: towards new standards for gene expression measurements

Monitoring of BCR-ABL transcripts has become established practice in the management of chronic myeloid leukemia. However, nucleic acid amplification techniques are prone to variations which limit the reliability of real-time quantitative PCR (RQ-PCR) for clinical decision making, highlighting the need for standardization of assays and reporting of minimal residual disease (MRD) data. We evaluated a lyophilized preparation of a leukemic cell line (K562) as a potential quality control reagent. This was found to be relatively stable, yielding comparable respective levels of ABL, GUS and BCR-ABL transcripts as determined by RQ-PCR before and after accelerated degradation experiments as well as following 5 years storage at -20 degrees C. Vials of freeze-dried cells were sent at ambient temperature to 22 laboratories on four continents, with RQ-PCR analyses detecting BCR-ABL transcripts at levels comparable to those observed in primary patient samples. Our results suggest that freeze-dried cells can be used as quality control reagents with a range of analytical instrumentations and could enable the development of urgently needed international standards simulating clinically relevant levels of MRD.

Dasatinib (D) in patients (pts) with chronic myelogenous leukemia (CML) in myeloid blast crisis (MBC) who are imatinib-resistant (IM-R) or IM-intolerant (IM-I): Results of the CA180006 ‘START-B’ study

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Background: Dasatinib (D) (BMS-354825) is an oral, multitargeted tyrosine kinase inhibitor of Bcr-Abl and SRC with activity against IM-R cell lines. In a phase I study, there was preliminary evidence that D was active in MBC-CML patients (pts). Methods: START B is an open-label study of D in IM-R or IM-I MBC carried out in 46 sites worldwide. From December 2004 to May 2005, 124 MBC pts were accrued. D was given orally at 70 mg twice a day (BID) with dose escalation to 100 mg BID for poor initial response or dose reductions to 50 mg and 40 mg BID for toxicity. Pts had weekly blood counts and monthly bone marrow evaluations, including cytogenetics. The primary endpoint was confirmed (minimum 4 weeks duration) major hematologic response (MaHR). Results: Data are currently available on the first 74 pts (68 IM-R, 6 IM-I). Median age was 55 years, 55% were male. Other prior therapy included interferon in 55% of pts and bone marrow transplant (BMT) in 12%. Prior IM dose was >600 mg/day in 49% of pts and 47% of pts received IM for > 3 years. At baseline, the WBC count was ≥20 × 103/mm3 in 46%, the platelet count was < 100 × 103/mm3 in 72% of pts and 35% of pts had ≥ 50% bone marrow blasts. Mutations in the BCR-ABL domain were found in 27/63 (43%) pts. Median duration of therapy was 3.5 months. D doses were reduced in 35% pts, temporarily interrupted in 58% pts, and escalated in 41% pts. With a minimum of 6-month follow-up, hematologic response was seen in 39 (53%) pts: confirmed MaHR in 24 (32%) pts, Complete in 18 (24%) and No Evidence of Leukemia in 6 (8%). Major cytogenetic responses were documented in 22 (30%) pts and was complete in 20 (27%). The median time to MaHR was 56 days. There was no loss of response in pts with MaHR; the duration of MaHR ranged from 1.2+ to 7.8+ months. The median PFS had not been reached. Severe myelosuppression was very common. Non-hematologic toxicities were usually mild to moderate. Most common Grade 3–4 toxicities included diarrhea in (7%), pleural effusion (9%), nausea (4%). Peripheral edema was reported in 14% of pts (0% Grade 3–4), and rash in 11% of the pts (0% Grade 3–4). Conclusions: Dasatinib was highly effective in IM-R pts with MBC with durable MaHR. Data on all 124 pts will be presented at the meeting.

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Interferon-alpha induces dendritic cell differentiation of CML mononuclear cells in vitro and in vivo

The ability of interferon-alpha (IFN-alpha) to induce dendritic cell (DC) differentiation in chronic myeloid leukemia (CML) was evaluated. Peripheral blood mononuclear cells from CML patients cultured with IFN-alpha and granulocyte-macrophage colony-stimulating factor (GM-CSF) developed a dendritic morphology. Fluorescence in situ hybridization demonstrated that the DCs harbored the bcr/abl translocation. The DCs prepared with IFN-alpha/GM-CSF expressed significantly higher levels of class I and II HLA than those grown in interleukin-4 (IL-4) and GM-CSF. The DCs prepared from newly diagnosed CML patients using IFN-alpha/GM-CSF expressed immunoregulatory proteins at levels comparable to normal DCs. In contrast, DCs cultured from CML patients who did not achieve a cytogenetic response to IFN-alpha expressed significantly lower levels of class I HLA, CD40, CD54, CD80 and CD86 than normal DCs. The expression of CD86 by CML DCs was enhanced when they were cultured with IFN-alpha/IL-4/GM-CSF, or when IFN-alpha/GM-CSF-treated cells were induced to mature by CD40 ligand. The DCs from IFN-alpha failures were less stimulatory than normal DCs in the allogeneic mixed leukocyte reaction. CML patients who had a cytogenetic response to IFN-alpha initially had low numbers of bone marrow DCs that increased significantly with treatment, while nonresponders had more prevalent DCs at baseline that showed no consistent change with treatment. Therefore, IFN-alpha can induce DC differentiation from CML progenitor cells both in vitro and in vivo. The therapeutic activity of IFN-alpha in CML may be due to its ability to stimulate the generation of DCs that can present CML-specific antigens. Resistance to IFN-alpha may result when DC differentiation becomes impaired.

An inhibitor of mTOR reduces neoplasia and normalizes p70/S6 kinase activity in Pten+/- mice

PTEN phosphatase acts as a tumor suppressor by negatively regulating the phosphoinositide 3-kinase (PI3K) signaling pathway. It is unclear which downstream components of this pathway are necessary for oncogenic transformation. In this report we show that transformed cells of PTEN(+/-) mice have elevated levels of phosphorylated Akt and activated p70/S6 kinase associated with an increase in proliferation. Pharmacological inactivation of mTOR/RAFT/FRAP reduced neoplastic proliferation, tumor size, and p70/S6 kinase activity, but did not affect the status of Akt. These data suggest that p70/S6K and possibly other targets of mTOR contribute significantly to tumor development and that inhibition of these proteins may be therapeutic for cancer patients with deranged PI3K signaling.

Transplantation of IL-2-mobilized autologous peripheral blood progenitor cells for adults with acute myelogenous leukemia in first remission

In order to improve leukemia-free survival we evaluated the feasibility and efficacy of autologous transplantation of interleukin-2 (IL-2)-mobilized peripheral blood progenitor cells for adult patients with acute myelogenous leukemia in first remission. Forty-nine consecutive patients (median age 49, range 21-70) with acute myelogenous leukemia in first remission were enrolled on a study of high-dose cytarabine/mitoxantrone consolidation chemotherapy with post-recovery IL-2 used as a method of in vivo purging for the purpose of autologous peripheral blood progenitor cell transplantation. A median of 2.08 x 10(6) CD34+ peripheral blood progenitor cells/kg were infused 1 day after preparative conditioning with 11.25 Gy total body irradiation and cyclophosphamide (120 mg/kg). Forty-one patients received myeloablative chemoradiotherapy followed by the infusion of IL-2-mobilized autologous peripheral blood progenitor cells. The median times to both neutrophil and platelet recovery were 16 days (range, 2-43) and 23 days (8-318+ days), respectively. Twenty-seven patients remain alive with 24 in continued first complete remission. Median remission duration for all eligible patients is 8 months, and actuarial leukemia-free survival is 49+/-15%. The actuarial risk of relapse is 43+/-16%. Toxicity of autologous peripheral blood progenitor cell transplant included treatment-related death in three patients and serious organ toxicity in 12. Advanced age was a negative prognostic factor for leukemia-free survival. Results were compared to an age-matched historical control treated with autologous transplantation of chemotherapy-mobilized progenitor cells; no significant difference in favor of IL-2 mobilization could be demonstrated. Our results demonstrate that autologous transplantation of IL-2-mobilized peripheral blood progenitor cells is feasible in an unselected population of adult patients with acute myelogenous leukemia in first remission with minimal toxicity but no clear evidence of benefit in leukemia-free survival.

Mutations in the mitotic check point gene, MAD1L1, in human cancers

Aneuploidy is a characteristic of the majority of human cancers, and recent studies suggest that defects of mitotic checkpoints play a role in carcinogenesis. MAD1L1 is a checkpoint gene, and its dysfunction is associated with chromosomal instability. Rare mutations of this gene have been reported in colon and lung cancers. We examined a total of 44 cell lines (hematopoietic, prostate, osteosarcoma, breast, glioblastoma and lung) and 133 fresh cancer cells (hematopoietic, prostate, breast and glioblastoma) for alterations of MAD1L1 by RT-PCR-SSCP and nucleotide sequencing. Eight mutations consisting of missense, nonsense and frameshift mutations were found, together with a number of nucleotide polymorphisms. All the alterations in cell lines were heterozygous. Frequency of mutations was relatively high in prostate cancer (2/7 cell lines and 2/33 tumor specimens). We placed a mutant truncated MAD1L1, found in a lymphoma sample, into HOS, Ht161 and SJSA cell lines and found that it was less inhibitory than wild type MAD1L1 at decreasing cell proliferation. Co-expression experiments showed that the mutant form had a dominant-negative effect. Furthermore, this mutant impaired the mitotic checkpoint as shown by decreased mitotic indices in HOS cells expressing mutant MAD1L1 after culture with the microtubule-disrupting agent, nocodazole. Our results suggest a pathogenic role of MAD1L1 mutations in various types of human cancer.

Development of an animal model for prostate cancer cell metastasis to adult human bone

BACKGROUND

Prostate cancer metastases to bone are associated with significant morbidity and mortality. Presently, there is little known about the biological interaction between prostate cancer cells and bone. Development of an animal model using adult human bone will enhance our ability to study the biology of prostate cancer metastasis to bone.

METHODS

Bone was harvested from patients undergoing total joint arthroplasty and implanted in the hindlimbs of pre-treated SCID mice. Two months after bone implantation 4 x 104 prostate cancer cells (PC-3 or LAPC-4) were injected near the bone implantation site. The animals were sacrificed approximately 8 to 12 weeks after the injections of the cells. Complete histological analysis including immunostaining was performed.

RESULTS

Both the PC-3 and LAPC-4 prostate cancer cells homed to the human bone implant, specifically the reconstituted bone marrow cavity. Analysis of the bone-tumor interaction after injection of PC-3 cells revealed strong labeling for PTHrP, TNF alpha and IL-6, consistent with osteoclast recruitment and osteoclast activity. These cells also were positively stained for CK18. After cellular injection of LAPC-4 cells, there was strong labeling for TNF alpha, IL-6, and IL-1 (osteoclast recruitment and osteolytic activity). PTHrP staining was also noted. The bone cells were strongly stained for osteocalcin, and the tumor cells for PSA.

CONCLUSIONS

These data suggest that the tumor cells may induce an osteolytic response to enhance their ability to metastasize to bone. This animal model allows us to study the biologic interaction between prostate cancer cells and human bone and may enhance our understanding of the events associated with prostate cancer metastasis to bone.

Cooperative assembly of androgen receptor into a nucleoprotein complex that regulates the prostate-specific antigen enhancer

Prostate cancer is characterized by elevated serum levels of prostate-specific antigen (PSA). PSA gene expression is controlled by an androgen-responsive transcriptional enhancer. Our study suggests that formation of a nucleoprotein complex, encompassing 170 base pairs of enhancer DNA, mediates androgen-responsive PSA enhancer activity. The complex is assembled by cooperative binding of androgen receptor to at least four tandem, nonconsensus androgen response elements (AREs). Systematic mutagenesis of the AREs demonstrated that they act synergistically to stimulate androgen receptor-responsive gene expression. We discuss a mechanism whereby a combination of high androgen receptor levels in the prostate and low affinity AREs contribute to the cell type specificity and activity of the enhancer.

Transplantation of autologous peripheral blood progenitor cells procured after high-dose cytarabine-based consolidation chemotherapy for adults with secondary acute myelogenous leukemia in first remission

Patients with acute myelogenous leukemia secondary to an antecedent hematologic disturbance or cytotoxic chemotherapy are considered to have a very low likelihood of leukemia-free survival regardless of the form of post-remission therapy. The purpose of this study is to evaluate, on the basis of intention to treat, the feasibility and efficacy of high-dose cytarabine/anthracycline consolidation chemotherapy followed by autologous transplantation of chemotherapy/rHuG-CSF-mobilized peripheral blood progenitor cells for seventeen adult patients (median age 63, range 27 to 68) with secondary acute myelogenous leukemia in first remission. Ten eligible patients underwent autologous transplantation of peripheral blood progenitor cells procured following high-dose cytarabine/mitoxantrone consolidation chemotherapy used as a method of in vivo purging. A median of 5 collections (range 2 to 13) were required to procure a median of 9.27 x 10(8) total mononuclear cells/kg (range 2.35 to 21.44 x 10(8) per kg). The median number of CD34-positive progenitor cells was 1.18 x 10(6) kg (range 0.34 to 30.9 x 10(6) kg). After preparative conditioning with 11.25 Gy total body radiation and cyclophosphamide (120 mg/kg) and autologous transplantation, the median time to neutrophil and platelet recovery were 18 days (range 12 to 29 days) and 25 days (range 8 to 158+ days), respectively. After a median follow-up for surviving patients of 33.4 months (range 7.5 to 54 months), 9 of 17 patients (53%) remain alive with 7 in continued first remission. The median remission duration is 13 months (3 to 53 months) and actuarial leukemia-free survival at 3 years is 51+/-25%. Toxicity of autologous peripheral blood progenitor cell transplant included serious liver and pulmonary toxicity in 2 and 1 patient, respectively. Our results demonstrate that a postremission program of high-dose cytarabine-based consolidation chemotherapy followed by autologous transplantation of chemotherapy-mobilized peripheral blood progenitor cells is feasible for patients with secondary acute myelogenous leukemia producing prolonged leukemia-free survival with minimal toxicity.

Interleukin-6-induced inhibition of multiple myeloma cell apoptosis: support for the hypothesis that protection is mediated via inhibition of the JNK/SAPK pathway

The mechanism by which interleukin-6 (IL-6) protects multiple myeloma (MM) plasma cells from apoptosis induced by anti-fas antibodies and dexamethasone was studied. Anti-apoptotic concentrations of IL-6 had no effect on cell-cycle distribution or activation of RAF-1 or ERK in dexamethasone- or anti-fas-treated 8226 and UCLA #1 MM cell lines. However, IL-6-dependent protection of viability correlated with an inhibition of dexamethasone- and anti-fas-induced activation of jun kinase (JNK) and AP-1 transactivation. To test the hypothesis that cytokine-induced protection was mediated through inhibition of JNK/c-jun, we also inhibited c-jun function in 8226 cells via introduction of a mutant dominant negative c-jun construct. Mutant c-jun-containing MM cells were also resistant to anti-fas-induced apoptosis but were significantly more sensitive to dexamethasone-induced apoptosis. These results support the notion that IL-6 protects MM cells against anti-fas through its inhibitory effects on JNK/c-jun but indicate protection against dexamethasone occurs through separate, yet unknown pathways.

Transplantation of autologous peripheral blood progenitor cells procured after high-dose cytarabine-based consolidation chemotherapy for adults with acute myelogenous leukemia in first remission

The purpose of the study was to evaluate the feasibility and efficacy of high-dose cytarabine-anthracycline consolidation chemotherapy followed by autologous transplantation of chemotherapy/rHuG-CSF-mobilized peripheral blood progenitor cells for adult patients with acute myelogenous leukemia in first remission. Fifty-nine consecutive patients (median age 45, range 18-69) with acute myelogenous leukemia in first remission were enrolled on a study of high-dose cytarabine-mitoxantrone consolidation chemotherapy used as a method of in vivo purging for the purpose of autologous peripheral blood progenitor cell transplantation. A median of 7 x 10(8) peripheral blood mononuclear cells/kg were infused 1 day after preparative conditioning with 11.25 Gy total body irradiation and cyclophosphamide (120 mg/kg). Forty-six patients received myeloablative chemo-radiotherapy followed by the infusion of chemotherapy/rHu-G-CSF-mobilized autologous peripheral blood progenitor cells. The median time to both neutrophil and platelet recovery from transplant was 15 days (range, 11-36 and 5-253+ days, respectively). After a median follow-up of 27 months, 31 patients remain alive with 27 in complete remission. Median remission duration for all eligible patients is 12 months, and actuarial leukemia-free survival at 3 years is 42 +/- 14%. The actuarial risk of relapse is 54 +/- 15%. Toxicity of autologous peripheral blood progenitor cell transplant included treatment-related death in two patients and grade III/IV organ toxicity in six. Advanced age was a negative prognostic factor for leukemia-free survival. Our results demonstrate that autologous transplantation of chemotherapy-mobilized peripheral blood progenitor cells is feasible in an unselected population of adult patients with acute myelogenous leukemia in first remission producing improved leukemia-free survival with minimal toxicity.

New insights in biology and current therapeutic options for patients with chronic myelogenous leukemia

BACKGROUND AND OBJECTIVE

From the discovery of the Ph-chromosome, there has been an extraordinary progress in our understanding of chronic myeloid leukemia (CML). During the last three decades, new findings arising from dissection of the genetic abnormalities at a molecular level have received the most attention, but there have also been important new observations arising from studies of the biologic behaviour of normal and leukemic stem cells and, more recently, from clinical investigations. In this review we first report the most important observations relevant to understanding the oncogenic potential of the BCR-ABL chimeric gene, and the behaviour and the relationships of normal and leukemic stem cells. From a clinical point of view, allogeneic stem cell transplantation is the only procedure able to cure CML. The main issues are: who can receive this procedure, and when and how it can be given. The situation is more complex in unrelated transplants. In patients without HLA compatible donors, many large trials in different countries have demonstrated that interferon alpha therapy is indicated and effective in the majority of patients. On the other hand, autologous stem cell transplantation is still an experimental procedure. These aspects will be analyzed in detail and, at the end, a therapeutic algorithm of a possible approach to the patients with untreated CML is provided.

EVIDENCE AND INFORMATION SOURCES

The method used for preparing this review was an informal consensus development. All the authors of the present review have been working in the field of chronic myeloid leukemia, and have contributed original papers in peer-reviewed journals. In addition, the material examined in the present review includes articles and abstracts published in journals covered by the Science Citation Index and Medline.

STATE OF ART AND PERSPECTIVES

The oncogenic potential of BCR-ABL has been demonstrated in a number of in vitro and in vivo model systems. Current research efforts are focused on defining the mechanism by which BCR-ABL transforms primary hematopoietic cells. The fact that BCR-ABL contains tyrosine residues, an SH2 domain, an SH3 domain, and proline-rich sequences raises the possibility of multiple protein-protein interactions. Indeed, BCR-ABL is reported to bind and/or phosphorylate more than 20 proteins. The insights into the signal transduction pathways activated by BCR-ABL will hopefully provide a new basis for the treatment of CML patients. Clinical evidence of the existence of a transplantable CML stem cell population has recently been extended to xenogeneic recipients of transplanted CML cells and by retroviral marking to autograft recipients. The potential of using immunodeficient mice as recipients of CML stem cells to create an in vivo model of chronic phase CML should be invaluable for testing novel therapies designed to eliminate residual disease in the patient. Current therapeutic options include conventional chemotherapy, IFN-a and allogeneic stem cell transplantation as established procedures, and autografting as an experimental procedure. While IFN-a as a first line therapy does not seem to jeopardize further treatments, autografting, according to the Genoa approach or other procedures, i.e. Ph-positive cells collected at diagnosis without mobilization therapy, raises the question of an ideal sequential strategy in the management of CML patients. There seems to be a general agreement that a patient less than 50 years old, with an HLA identical sibling, should receive an allogeneic stem cell transplant. This approach should be offered also to younger patients (< or = 40 years) who are able to find an unrelated matched donor. Since it seems that the normal hematopoietic reservoir declines with time, it may be desiderable to mobilize and collect peripheral stem cells in order to store Ph-negative progenitors as soon after diagnosis as possible when the WBC count has been controlled by hydroxyurea while searchin

Genotoxic drugs induce interaction of the c-Abl tyrosine kinase and the tumor suppressor protein p53

The function of the c-Abl protein tyrosine kinase is unknown. The present studies demonstrate that the antimetabolite 1-beta-D-arabinofuranosylcytosine (ara-C) induces binding of c-Abl and p53. Ara-C treatment of cells that express wild type or a dominant negative, kinase-inactive c-Abl(K-R) was associated with formation of c-Abl-p53 complexes and increased expression of the cyclin-dependent kinase (Cdk) inhibitor p21. However, down-regulation of Cdk2 by ara-C was found in cells expressing wild type c-Abl and not in cells expressing c-Abl(K-R) or those deficient in p53. Similar findings were obtained following treatment of cells with the alkylating agent methyl methanesulfonate (MMS). Cells that express the c-Abl dominant negative or are null for c-Abl exhibited partial abrogation of Cdk2 down-regulation and G1 arrest in response to MMS exposure. Cells lacking the c-abl gene also responded to ara-C and MMS with increases in p53 levels and induction of p21. These findings indicate that the cellular response to certain genotoxic drugs involves binding of c-Abl to p53 and down-regulation of Cdk2 by a c-Abl kinase/p53-dependent mechanism.

Role for c-Abl tyrosine kinase in growth arrest response to DNA damage

The c-Abl protein tyrosine kinase is activated by certain DNA-damaging agents, and its overexpression causes arrest in the G1 phase of the cell cycle by a mechanism dependent on the tumour-suppressor protein p53 (refs 2-4). Here we investigate the possible role of c-Abl in growth arrest induced by DNA damage. Transient transfection experiments using wild-type or inactivated c-Abl show that both induce expression of p21, an effector of p53, but only wild-type c-Abl downregulates the activity of the cyclin-dependent kinase Cdk2 and causes growth arrest. Exposure to ionizing radiation of cells that stably express active or inactive c-Abl is associated with induction of c-Abl/p53 complexes and p21 expression. However, cells expressing the dominant-negative c-Abl mutant and cells lacking the c-abl gene are impaired in their ability to downregulate Cdk2 or undergo G1 arrest in response to ionizing radiation. We also show that expression of c-Abl kinase in p21(-1-), but not in p53(-1-), cells results in downregulation of Cdk2. Our results suggest that c-Abl kinase contributes to the regulation of growth arrest induced by ionizing radiation by a p53-dependent, p21-independent mechanism.

In vitro modulation of the invasive and metastatic potentials of human renal cell carcinoma by interleukin-2 and/or interferon-alpha gene transfer

BACKGROUND

Continuous local delivery of interleukin-2 (IL-2) and interferon-alpha (IFN-alpha) via gene transfer appears to be more effective than systemic therapy in preventing the growth of human renal cell carcinoma (RCC) in vitro and in vivo. To understand further if cytokine-gene transfection of RCC could alter certain cellular properties that are associated with the invasive and metastatic potentials of tumor, the authors characterized six cell lines that produce IL-2 and/or IFN-alpha in their expression of intercellular adhesion molecule-1 (ICAM-1) and CD44; binding affinity to extracellular matrix (ECM) components (fibronectin, laminin, type IV collagen, and vitronectin); and preference in forming homotypic aggregation and mRNA levels of c-myc, epidermal growth factor receptor (EGF-R), tumor transforming growth factor-beta (TGF-beta) and type IV collagenase. These six lines were compared with control vector transfected parental R11 line.

METHODS

The expression of ICAM-1 and CD44 was determined by fluorescence-activated cell sorter (FACS) analysis, the tumor cell binding affinity to ECM components was measured by cell attachment assay, the degree of homotypic aggregation was quantified by cell aggregation assay, and the mRNA levels of c-myc, EGF-R, TGF-beta, and collagenase were analyzed by a quantitative polymerase chain reaction analysis.

RESULTS

Both IL-2-gene- and IFN-alpha-gene-modified R11 exhibited enhanced expression of ICAM-1, suppression of CD44, and decreased binding affinity to ECM components, when compared with the R11-control vector. All cytokine-producing tumor lines showed a decreased preference to form homotypic aggregation. Interferon-alpha gene transfer downregulated c-myc, EGF-R, and type IV collagenase mRNA expression, whereas only the higher producers of IL-2 downregulated TGF-beta mRNA expression. Exogenous IL-2 and/or IFN-alpha treatment of a IFN-alpha-resistant RCC enhanced both HLA class I antigen and ICAM-1 expression and suppressed CD44 expression, but had no effect on tumor growth rate.

CONCLUSIONS

The local production of high concentrations of IL-2 and IFN-a at the tumor site may directly alter tumor properties associated with invasive and metastatic phenotypes of RCC. Interleukin-2 and/or IFN-alpha gene therapy may be an effective strategy for treatment of patients with advanced renal cancer.