Long non-coding RNA profiling of pediatric Medulloblastoma

Background

Medulloblastoma (MB) is one of the most common malignant cancers in children. MB is primarily classified into four subgroups based on molecular and clinical characteristics as (1) WNT (2) Sonic-hedgehog (SHH) (3) Group 3 (4) Group 4. Molecular characteristics used for MB classification are based on genomic and mRNAs profiles. MB subgroups share genomic and mRNA profiles and require multiple molecular markers for differentiation from each other. Long non-coding RNAs (lncRNAs) are more than 200 nucleotide long RNAs and primarily involve in gene regulation at epigenetic and post-transcriptional levels. LncRNAs have been recognized as diagnostic and prognostic markers in several cancers. However, the lncRNA expression profile of MB is unknown.

Methods

We used the publicly available gene expression datasets for the profiling of lncRNA expression across MB subgroups. Functional analysis of differentially expressed lncRNAs was accomplished by Ingenuity pathway analysis (IPA).

Results

In the current study, we have identified and validated the lncRNA expression profile across pediatric MB subgroups and associated molecular pathways. We have also identified the prognostic significance of lncRNAs and unique lncRNAs associated with each MB subgroup.

Conclusions

Identified lncRNAs can be used as single biomarkers for molecular identification of MB subgroups that warrant further investigation and functional validation.

A Novel Combination Approach Targeting an Enhanced Protein Synthesis Pathway in MYC-driven (Group 3) Medulloblastoma

The MYC oncogene is frequently amplified in patients with medulloblastoma, particularly in group 3 patients, who have the worst prognosis. mTOR signaling-driven deregulated protein synthesis is very common in various cancers, including medulloblastoma, that can promote MYC stabilization. As a transcription factor, MYC itself is further known to regulate transcription of several components of protein synthesis machinery, leading to an enhanced protein synthesis rate and proliferation. Thus, inhibiting enhanced protein synthesis by targeting the MYC and mTOR pathways together may represent a highly relevant strategy for the treatment of MYC-driven medulloblastoma. Here, using siRNA and small-molecule inhibitor approaches, we evaluated the effects of combined inhibition of MYC transcription and mTOR signaling on medulloblastoma cell growth/survival and associated molecular mechanism(s) in MYC-amplified (group 3) medulloblastoma cell lines and xenografts. Combined inhibition of MYC and mTOR synergistically suppressed medulloblastoma cell growth and induced G₁ cell-cycle arrest and apoptosis. Mechanistically, the combined inhibition significantly downregulated the expression levels of key target proteins of MYC and mTOR signaling. Our results with RNA-sequencing revealed that combined inhibition synergistically modulated global gene expression including MYC/mTOR components. In addition, the combination treatment significantly delayed tumor growth and prolonged survival of MYC-amplified medulloblastoma xenografted mice by downregulating expression of MYC and the key downstream components of mTOR signaling, compared with single-agent therapy. Together, our findings demonstrated that dual inhibition of MYC (transcription) and mTOR (translation) of the protein synthesis pathway can be a novel therapeutic approach against MYC-driven medulloblastoma.

Role of protein arginine methyltransferase 5 in group 3 (MYC-driven) Medulloblastoma

BACKGROUND

MYC amplification or overexpression is common in Group 3 medulloblastoma and is associated with the worst prognosis. Recently, protein arginine methyl transferase (PRMT) 5 expression has been closely associated with aberrant MYC function in various cancers, including brain tumors such as glioblastoma. However, the role of PRMT5 and its association with MYC in medulloblastoma have not been explored. Here, we report the role of PRMT5 as a novel regulator of MYC and implicate PRMT5 as a potential therapeutic target in MYC-driven medulloblastoma.

METHODS

Expression and association between PRMT5 and MYC in primary medulloblastoma tumors were investigated using publicly available databases. Expression levels of PRMT5 protein were also examined using medulloblastoma cell lines and primary tumors by western blotting and immunohistochemistry, respectively. Using MYC-driven medulloblastoma cells, we examined the physical interaction between PRMT5 and MYC by co-immunoprecipitation and co-localization experiments. To determine the functional role of PRMT5 in MYC-driven medulloblastoma, PRMT5 was knocked-down in MYC-amplified cells using siRNA and the consequences of knockdown on cell growth and MYC expression/stability were investigated. In vitro therapeutic potential of PRMT5 in medulloblastoma was also evaluated using a small molecule inhibitor, EPZ015666.

RESULTS

We observed overexpression of PRMT5 in MYC-driven primary medulloblastoma tumors and cell lines compared to non-MYC medulloblastoma tumors and adjacent normal tissues. We also found that high expression of PRMT5 is inversely correlated with patient survival. Knockdown of PRMT5 using siRNA in MYC-driven medulloblastoma cells significantly decreased cell growth and MYC expression. Mechanistically, we found that PRMT5 physically associated with MYC by direct protein-protein interaction. In addition, a cycloheximide chase experiment showed that PRMT5 post-translationally regulated MYC stability. In the context of therapeutics, we observed dose-dependent efficacy of PRMT5 inhibitor EPZ015666 in suppressing cell growth and inducing apoptosis in MYC-driven medulloblastoma cells. Further, the expression levels of PRMT5 and MYC protein were downregulated upon EPZ015666 treatment. We also observed a superior efficacy of this inhibitor against MYC-amplified medulloblastoma cells compared to non-MYC-amplified medulloblastoma cells, indicating specificity.

CONCLUSION

Our results reveal the regulation of MYC oncoprotein by PRMT5 and suggest that targeting PRMT5 could be a potential therapeutic strategy for MYC-driven medulloblastoma.

Abstract 1249: The role of PRMT5 in MYC-driven medulloblastoma

Medulloblastoma (MB) is the most common pediatric brain tumor, accounting for about 20% of all brain tumors in children. Children with Group 3 MB (aberrant MYC) show the worst prognosis, with <50% survival. Recently, the role and association of protein arginine methyl transferase (PRMT) 5 have been closely associated with aberrant MYC function in various cancers including other brain tumors such as glioblastoma. However, the role of PRMT5 and its association with MYC in MB have not been explored. Here we provide preliminary data indicating PRMT5 as a novel regulator of MYC and implicating PRMT5 as a potential therapeutic target in MYC-driven MB. Using cell lines, our results showed PRMT5 overexpression in MYC-driven MB compared to non-MYC MB. The results from co-immunoprecipitation experiment in MYC-driven MB cells demonstrated that MYC physically associates with PRMT5 by direct protein-protein interaction. In addition, cycloheximide chase experiment showed that PRMT5 regulates MYC stability. Knockdown of PRMT5 using siRNA in MYC-driven MB cells significantly decreased cell growth and MYC expression. We also tested the therapeutic potential of targeting PRMT5 against MB cell lines using a small molecule inhibitor EPZ015666. We observed a dose-dependent efficacy of EPZ015666 in suppressing cell growth in MYC-driven MB cell lines. We also observed a superior efficacy of this inhibitor against MYC-driven MB cells compared to non-MYC MB cells. Together, our results implicate the regulation of MYC oncoprotein by PRMT5, and suggest that targeting PRMT5 could be a potential therapeutic strategy for MYC-driven MB and other MYC-driven cancers.

Citation Format: Nagendra K. Chaturvedi, Varun Kesherwani, Matthew J. Kling, Sutapa Ray, Timothy R. McGuire, Shantaram S. Joshi, J. Graham Sharp, Don W. Coulter. The role of PRMT5 in MYC-driven medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1249.

Abstract 5859: Enhanced therapy for MYC-driven medulloblastoma by targeting protein translation pathway

Medulloblastoma is the most frequent pediatric brain tumor of neuroectodermal cerebellar origin. High-risk MB patients with MYC overexpression and amplification usually show an extremely poor clinical outcome responding poorly to current therapies. Recent preclinical studies have revealed that the aberrant activation and interactions of PI3K/AKT/mTOR signaling is frequently associated with MYC-driven MB therapy-resistance. In addition, it is evident that both MYC and mTOR components of the PI3K/AKT/mTOR signaling axis can directly control and share a common translation pathway in increasing protein synthesis by regulating the expression of multiple components of the protein synthesis machinery, including ribosomal proteins and initiation factors of translation. Thus, inhibiting enhanced protein synthesis may represent a highly relevant strategy for the treatment of MYC-driven MB. Therefore, in this study, we investigated the single agents and combined anti-MB efficacies of a recently well-established BRD4 (bromodomain-containing protein 4)/MYC inhibitor JQ1 and PI3K-mTOR dual inhibitor BEZ235. Using four MB cell lines including three MYC amplified cell lines, the in vitro efficacy of this combined approach on cell growth/apoptosis and cell cycle along with associated molecular mechanism(s) were investigated. We used an MTT assay to measure survival and proliferation, flow-cytometric-based propidium-iodide staining to determine the effects of these inhibitors on cell-cycle, Annexin-V analyses to examine the cells undergoing apoptosis following treatments and western blot analyses to determine the expression levels of target molecules. Our results showed that both inhibitors as single agents, significantly decreased MB cell growth and induced apoptosis by targeting the key molecules of the associated pathways. Combined treatment of JQ1 and BEZ235 significantly decreased MB cell growth/survival in a dose-dependent fashion compared to single agent activity. Moreover, JQ1 and BEZ235 alone or combined significantly induced G1 cell-cycle arrest which coincided with decreased expression of cyclin-D1 and increased expression of p21 proteins in MYC-driven MB cells. Mechanistically, the co-treatment of JQ1 and BEZ235 significantly downregulated the expression levels of phosphorylated 4EBP1/p70-S6K (mTOR components) and BRD4/MYC proteins. Together, our findings demonstrate that the combination of JQ1 and BEZ235 showed significant synergistic efficacy against MYC-driven MB, by enhancing the inhibition of protein synthesis (translation) pathway. Initial evidence from this targeted approach, suggests that additional preclinical evaluation is warranted to determine likely clinical utility of targeted therapy for high-risk MB patients.

Citation Format: Nagendra K. Chaturvedi, Don W. Coulter, Matthew J. Kling, Sutapa Ray, Timothy R. McGuire, Shantaram S. Joshi, J. Graham Sharp. Enhanced therapy for MYC-driven medulloblastoma by targeting protein translation pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5859.

Improved therapy for medulloblastoma: targeting hedgehog and PI3K-mTOR signaling pathways in combination with chemotherapy

Aberrant activation and interactions of hedgehog (HH) and PI3K/AKT/mTOR signaling pathways are frequently associated with high-risk medulloblastoma (MB). Thus, combined targeting of the HH and PI3K/AKT/mTOR pathways could be a viable therapeutic strategy to treat high-risk patients. Therefore, we investigated the anti-MB efficacies of combined HH inhibitor Vismodegib and PI3K-mTOR dual-inhibitor BEZ235 together or combined individually with cisplatin against high-risk MB. Using non-MYC- and MYC-amplified cell lines, and a xenograft mouse model, the in vitro and in vivo efficacies of these therapies on cell growth/survival and associated molecular mechanism(s) were investigated. Results showed that combined treatment of Vismodegib and BEZ235 together, or with cisplatin, significantly decreased MB cell growth/survival in a dose-dependent-fashion. Corresponding changes in the expression of targeted molecules following therapy were observed. Results demonstrated that inhibitors not only suppressed MB cell growth/survival when combined, but also significantly enhanced cisplatin-mediated cytotoxicity. Of these combinations, BEZ235 exhibited a significantly greater efficacy in enhancing cisplatin-mediated MB cytotoxicity. Results also demonstrated that the MYC-amplified MB lines showed a higher sensitivity to combined therapies compared to non-MYC-amplified cell lines. Therefore, we tested the efficacy of combined approaches against MYC-amplified MB growing in NSG mice. In vivo results showed that combination of Vismodegib and BEZ235 or their combination with cisplatin, significantly delayed MB tumor growth and increased survival of xenografted mice by targeting HH and mTOR pathways. Thus, our studies lay a foundation for translating these combined therapeutic strategies to the clinical setting to determine their efficacies in high-risk MB patients.

Abstract 4312: Preneoplastic activity of dietary poly unsaturated fatty acid (PUFA) regulation of organ and tissue microenvironments in an iso-caloric pair-fed mouse model

Diets containing omega-3 (ω3) PUFAs have health benefits due to their anti-inflammatory activity and lower risk of chronic conditions including cardiac, autoimmune and neoplastic diseases. This contrasts with ω6 PUFA containing Western diets, which are pro-inflammatory. Balancing the dietary ω6:ω3 ratio has been suggested to have cancer preventive and potentially therapeutic activity; however, the majority of these studies have not differentiated dietary PUFA content from obesity. Herein we examined the effects of the ω6:ω3 ratio in iso-caloric diets that were pair fed. These diets had 35.5% of calories from fat with an ω6:ω3 ratio in the ω6 and ω3 based diets of 42:1 and 1:1 respectively (confirmed by gas chromatography-mass spectrometry) using the liquid, Lieber DeCarli diet and fish oil substituting for 70% of olive oil. The ω3 diet contained eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid at a 3:1 ratio, while the ω6 diet contained linoleic acid as the predominant ω6 PUFA and a low level of the ω3 PUFA, linolenic acid. After establishing female BALB/c mice on these diets, weight gain and diet consumption were monitored for 12 weeks, the mice sacrificed and the dietary effects on mammary gland and hepatic histopathology, leukocyte phenotypes and organ and tissue lipidomics determined. In association with pair feeding there were no differences in diet consumed (ω-3 diet used as baseline) and weight gain between cohorts. The cohort on the ω6 diet had depressed numbers of marrow progenitor cells and increased splenic subcapsular extramedullary hematopoiesis consistent with an inflammatory response, increased hepatocyte lipidosis, hypertrophy and multinucleation and increased hepatic vascularity with thicker intima. The ω-6 dietary cohort also had mammary fat pads (MFPs) with increased adipocytes in the tubular epithelium, stromal cellularity and epithelial tissue density. These mammary gland and hepatic histopathologic changes and subclinical inflammation are consistent with pre-neoplastic lesions and were accompanied by organ specific lipodemic changes. This included significant increases in arachidonic acid (AA) in the plasma, spleen and liver, but not MFPs, of the ω-6 cohort, and a significant increase in EPA and DHA levels in the plasma, spleen, MFPs and liver of the ω-3 cohort. In addition, the liver and MFPs had a significant increase in the ω3 PUFA, docosapentaenoic acid. In summary, our studies demonstrate that the dietary ratio of ω6:ω3, independent of obesity can regulate mammary gland and hepatocyte proliferation and subclinical inflammation in association with significant, organ specific increases in AA levels contributing to microenvironmental preneoplastic hyperplasia.

Citation Format: Saraswoti Khadge, Paul Black, Concetta DiRusso, Geoff Thiele, Lynell W. Klassen, J Graham Sharp, Timothy R. McGuire, Michael J. Duryee, Holly C. Britton, Alicia Dafferner, Jordan Beck, James E. Talmadge. Preneoplastic activity of dietary poly unsaturated fatty acid (PUFA) regulation of organ and tissue microenvironments in an iso-caloric pair-fed mouse model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4312.

Abstract B05: Improved therapy for neuroblastoma using small molecule inhibitors in combination with chemotherapy

Neuroblastoma is the most common pediatric malignancy with poor response to current therapy. The NF-kB/mTOR, hedgehog and PLK1 pathways/molecules are aberrantly expressed and activated in high-risk neuroblastoma, thereby targeting these pathways/molecules is an attractive therapeutic strategy. Therefore, we investigated the efficacy and associated molecular mechanism(s) of NF-kB/mTOR dual inhibitor 13-197, hedgehog inhibitor Vismodegib and PLK1 inhibitor BI2536 alone or in combination with Topotecan against high-risk neuroblastoma in vitro and in vivo. Using three neuroblastoma cell lines, the in vitro efficacy of the inhibitors as single agents or in combination with Topotecan on cell growth and apoptosis along with associated molecular mechanism(s) were investigated. In addition, the combined efficacy of Vismodegib and Topotecan was determined in vivo using a xenograft mouse model. Results showed that 13-197, BI2536 and Vismodegib significantly decreased neuroblastoma cell growth and induced apoptosis by targeting associated pathways and molecules in vitro. The 13-197 and BI2536 as single agents showed similar efficacies and were most potent in inhibiting cell growth and survival of neuroblastoma cells. In combination with Topotecan, BI2536 or Vismodegib further significantly decreased neuroblastoma cell growth/survival and neurospheres formation. Corresponding changes in the expression of targeted molecules following therapy were observed. Together, in vitro data demonstrated that hedgehog pathway inhibitor Vismodegib was most efficacious in potentiating Topotecan-induced antineuroblastoma effects. Therefore, as a next logical step, we tested the combined efficacy of Vismodegib and Topotecan against neuroblastoma in vivo using NOD-SCID Gamma deleted (NSG) mice. Our in vivo results showed that Vismodegib combined with Topotecan significantly (p<0.001) reduced tumor growth and increased survival of xenograft mice compared to single agent activity. This combination not only significantly reduced tumor growth and increased survival of the mice but also significantly enhanced antineuroblastoma efficacy by targeting hedgehog pathway components in neuroblastoma in vivo. Thus our studies lay a foundation for taking this therapeutic strategy to clinical setting to determine their efficacies in high-risk neuroblastoma patients.

Citation Format: Nagendra K. Chaturvedi, McGuire R. Timothy, Don W. Coulter, Ashima Shukla, Erin M. McIntyre, J. Graham Sharp, Shantaram S. Joshi. Improved therapy for neuroblastoma using small molecule inhibitors in combination with chemotherapy. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr B05.

Comparing Biocompatibility of Nanocrystalline Titanium and Titanium-Oxide with Microcrystalline Titanium

Titanium (Ti) is the material of choice for orthopaedic applications because it is biocompatible and encourages osteoblast ingrowth. It was shown that the biocompatibility of Ti metal is due to the presence of a thin native sub-stoichiometric titanium oxide layer which enhances the adsorption of mediating proteins on the surface [1]. The present studies were devised to evaluate the adhesion, survival, and growth of cells on the surface of new engineered nano-crystal films of titanium and titanium oxides and compare them with orthopaedic-grade titanium with microcrystals. The engineered nano-crystal films with hydrophilic properties are produced by employing an ion beam assisted deposition (IBAD) technique. IBAD combines physical vapor deposition with concurrent ion beam bombardment in a high vacuum environment to produce films (with 3 to 70 nm grain size) with superior properties. These films are “stitched” to the artificial orthopaedic implant materials with characteristics that affect the wettability and mechanical properties of the coatings.

To characterize the biocompatibility of these nano-engineered surfaces, we have studied osteoblast function including cell adhesion, growth, and differentiation on different nanostructured samples. Cell responses to surfaces were examined using SAOS-2 osteoblast-like cells. We also studied a correlation between the surface nanostructures and the cell growth by characterizing the SAOS-2 cells with immunofluorescence and measuring the amount alizarin red concentration produced after 7 and 14 days. The number of adherent cells was determined by means of nuclei quantification on the nanocrystalline Ti, TiO2, and microcrystalline Ti and analysis was performed with Image J. Our experimental results indicated that nanocrystalline TiO2 is superior to both nano and microcrystalline Ti in supporting growth, adhesion, and proliferation. Improving the quality of surface oxide, i.e. fabricating stoichiometric oxides as well as nanoengineering the surface topology, is crucial for increasing the biocompatibility of Ti implant materials.

Novel therapy for therapy-resistant mantle cell lymphoma: multipronged approach with targeting of hedgehog signaling

Mantle cell lymphoma (MCL) is one of the most aggressive B-cell lymphomas with a median patient survival of only 5-7 years. The failure of existing therapies is mainly due to disease relapse when therapy-resistant tumor cells remain after chemotherapy. Therefore, development and testing of novel therapeutic strategies to target these therapy-resistant MCL are needed. Here, we developed an in vivo model of therapy-resistant MCL by transplanting a patient-derived MCL cell line (Granta 519) into NOD/SCID mice followed by treatment with combination chemotherapy. Cytomorphologic, immunophenotypic, in vitro and in vivo growth analyses of these therapy-resistant MCL cells confirm their MCL origin and resistance to chemotherapy. Moreover, quantitative real-time PCR revealed the upregulation of GLI transcription factors, which are mediators of the hedgehog signaling pathway, in these therapy-resistant MCL cells. Therefore, we developed an effective therapeutic strategy for resistant MCL by treating the NOD/SCID mice bearing Granta 519 MCL with CHOP chemotherapy to reduce tumor burden combined with GLI-antisense oligonucleotides or bortezomib, a proteosome inhibitor, to target therapy-resistant MCL cells that remained after chemotherapy. This regimen was followed by treatment with MCL-specific cytotoxic T lymphocytes to eliminate all detectable leftover minimal residual disease. Mice treated with this strategy showed a significantly increased survival and decreased tumor burden compared to the mice in all other groups. Such therapeutic strategies that combine chemotherapy with targeted therapy followed by tumor-specific immunotherapy are effective and have excellent potential for clinical application to provide long-term, disease-free survival in MCL patients.

Engineered Nanostructured Coatings for Enhanced Protein Adsorption and Cell Growth

We designed and produced pure cubic zirconia (ZrO2) ceramic1 coatings by an ion beam assisted deposition (IBAD) with nanostructures comparable to the size of proteins. Our ceramic coatings exhibit high hardness and a zero contact angle with serum. In contrast to hydroxyapatite (HA), nano-engineered zirconia films possess excellent adhesion to all orthopaedic materials. Cell adhesion and proliferation experiments were performed with a bona fide mesenchymal stromal cell line (OMA-AD). Our experimental results indicate that the nano-engineered cubic zirconia is superior in supporting growth, adhesion, and proliferation. Since cell attachment is mediated by adhesive proteins such as fibronectin (FN), to elucidate why cells attach more effectively to our nanostructures, we performed a comparative analysis of adsorption energies of FN fragment using quantum mechanical calculations and Monte Carlo (MC) simulation both on smooth and nanostructured surfaces. We have found that a FN fragment adsorbs significantly stronger on the nanostructured surface than on the smooth surface2.

Searching for Smart Durable Coatings to Promote Bone Marrow Stromal Cell Growth While Preventing Biofilm Formation

There is a great need to develop methods to regulate cellular growth in order to enhance or prevent cell proliferation as needed, to either improve health or prevent disease. In this work we evaluated the adhesion, survival and growth of bone marrow stromal cells on the surface of several new ion beam engineered nano-crystals of ceramic hard coatings such as zirconium, titanium, tantalum and cerium oxides. Cell adhesion and growth on the ceramic coatings were compared to adhesion and growth on a nano-crystalline silver coating which is known to possess antibacterial properties. The initial results of a study to determine the effect of nanocrystalline titanium and silver coating onstaphylococcus aureusbiofilm growth is also discussed.

Human blood and marrow side population stem cell and Stro-1 positive bone marrow stromal cell numbers decline with age, with an increase in quality of surviving stem cells: correlation with cytokines

Hematological deficiencies increase with aging leading to anemias, reduced hematopoietic stress responses and myelodysplasias. This study tested the hypothesis that side population hematopoietic stem cells (SP-HSC) would decrease with aging, correlating with IGF-1 and IL-6 levels and increases in bone marrow fat. Marrow was obtained from the femoral head and trochanteric region of the femur at surgery for total hip replacement (N=100). Whole trabecular marrow samples were ground in a sterile mortar and pestle and cellularity and fat content determined. Marrow and blood mononuclear cells were stained with Hoechst dye and the SP-HSC profiles acquired. Marrow stromal cells (MSC) were enumerated flow cytometrically employing the Stro-1 antibody, and clonally in the colony forming unit fibroblast (CFU-F) assay. Plasma levels of IGF-1 (ng/ml) and IL-6 (pg/ml) were measured by ELISA. SP-HSC in blood and bone marrow decreased with age but the quality of the surviving stem cells increased. MSC decreased non-significantly. IGF-1 levels (mean=30.7, SEM=2) decreased and IL-6 levels (mean=4.4, SEM=1) increased with age as did marrow fat (mean=1.2mmfat/g, SEM=0.04). There were no significant correlations between cytokine levels or fat and SP-HSC numbers. Stem cells appear to be progressively lost with aging and only the highest quality stem cells survive.

Abstract C8: Putative tumor-initiating cell populations in mantle cell lymphoma exhibit microenvironmentally influenced differences in stem cell-like and tumorigenic properties

The presence of subpopulations of cells possessing enhanced tumor formation capabilities has been described in several tissues. These cells have been termed tumor-initiating cells (TICs) or cancer stem cells and have been isolated using various techniques, including the side population (SP), the use of cell surface markers including CD133 and CD44 and aldehyde dehydrogenase activity. We have elected to evaluate the stem cell-like and tumor forming capabilities of SP and CD133+/CD44+ cells in Mantle Cell Lymphoma (MCL), an aggressive and relatively therapy unresponsive form of Non-Hodgkin's Lymphoma. All analyses were conducted in the presence of micro-environmental niche cells (murine stromal 5 cells) or extracellular matrix components (Matrigel) as these factors are known to play an integral role in processes associated with stem cell self-renewal and differentiation. SP cells and CD133+/CD44+ cells were present in Granta 519, an aggressive MCL cell line. The in-vitro technique of the Cobblestone Area Forming Cell (CAFC) assay was utilized to assess the self-renewal capabilities of SP and CD133+/CD44+ cells when the two cell types were cultured in the presence and absence of Matrigel, a mixture of extracellular matrix proteins derived from the Englebreth-Holm murine sarcoma. CAFC assays revealed enhanced self-renewal capabilities for Granta SP cells over non-SP cells, with the addition of Matrigel increasing the self-renewal frequency of SP and non-SP cells by 5.8 and 8.6 fold respectively. Conversely, Granta CD133+/CD44+ and CD133−/CD44− cells possessed similar self-renewal capabilities, with the addition of Matrigel having a negligible effect. When evaluated for chemotherapy resistance, the murine stromal 5 (MS5)-adherent CD133+/CD44+ cells and the non-adherent SP cells were more resistant to hydroxyurea while all MS5-adherent Granta cells were resistant to this agent. In-vivo analyses demonstrated tumor formation of Matrigel mixed SP and non-SP populations but not for Matrigel mixed CD133+/CD44+ or CD133−/CD44− cells. Although micro-metastatic tumors were not detected for SP and non-SP injected mice, flow cytometric analyses identified Granta cells, characterized by CD20 expression, in all murine tissues examined. IL-8, a proangiogenic cytokine implicated in tumor metastasis, may be involved in the metastatic spread of Granta cells as it was significantly present in the supernatants of Granta SP MS5 co-cultures, but was negligible or undetected when non-SP, CD133+/CD44+ and CD133−/CD44− cells were co-cultured with MS5 cells. These studies suggest that the SP phenotype may be a better marker for the isolation of stem-like cells in MCL. Moreover, the micro-environmental components found in Matrigel, rather than cell phenotype differences, appear to play a vital role in the initiation of tumor development by SP and non-SP cells. The tumor micro-environmental niche may therefore be an important target for development of novel therapeutic agents.

Citation Information: Cancer Res 2009;69(23 Suppl):C8.

A comparative evaluation of teaching methods in an introductory neuroscience course for physical therapy students

BACKGROUND

The use of computer-based instruction (CBI) in physical therapy education is growing, but its effectiveness compared to lecture is undefined. This study compared CBI to lecture in an introductory neuroscience course for students in their first year of a 3 year professional program leading to the Doctor of Physical Therapy Degree.

SUBJECTS

Twenty-eight students participated in 2003 and 34 in 2004.

METHODS

A randomized, cross-over design was employed. The course was divided into two sections with an exam after each. Students in one group participated in CBI during the first half of the course and lecture during the second half with the order of participation reversed for the other group. A 6 months post-course review exam was also administered. Exam scores, study time, and student opinions regarding teaching methods were collected after each half of the course. Course development costs for both teaching approaches were also documented.

RESULTS

There were no statistically significant differences in exam scores between participant groups. CBI students spent less time studying. Student did not distinguish a major preference for either instruction method. Many students preferred that CBI be used as a complementary rather than mutually exclusive instructional method. Lecture-based instruction was much less expensive than CBI.

CONCLUSION

Lecture-based instruction was more cost effective than CBI, but CBI was more time efficient in terms of student learning.

Does the number or quality of pluripotent bone marrow stem cells decrease with age?

In the next 25 years, as the 37 million baby boomers age, we can expect a 400% increase in total joint arthroplasties that will challenge surgeons, the healthcare system, and the scientific community. The burden may be eased if we are able to manipulate side population stem cells and enhance peri-prosthetic bone remodeling thereby reducing the incidence of revisions. Therefore, as a preliminary question, we asked if the number and quality of side population stem cells, with the ability to proliferate into multiple cell lineages for long periods, correlates with age and can be evaluated in peripheral blood. Using flow cytometry we analyzed the quantity and quality of side population stem cells from bone marrow and peripheral blood in 54 patients (20 under 60 years of age, 34 over) undergoing THA. The total side population of stem cells decreased with age, but their long-term repopulating ability (quality) remained constant. The total count of side population stem cells in marrow correlated with the number found in peripheral blood. If these populations can be manipulated, periprosthetic remodeling may be beneficially enhanced.

An ex vivo model of hematopoietic stem cell mobilization

BACKGROUND

Mobilization of hematopoietic stem cells to the circulation facilitates their collection, thereby providing a non-marrow source of these cells for transplantation. Hematopoietic cytokine administration induces mobilization for most, but not all, donors. Because the underlying biology of mobilization is not well understood, improving the process on a rational basis is difficult. The design of an in vitro mobilization model was pursued to facilitate investigations of the process.

METHODS

MS5 murine stromal cell line cells were grown to confluence on microporous transwell membranes. Murine femoral marrow plugs were placed on top of the prepared transwell membranes. The transwells were then seated in wells containing media and hematopoietic growth factors. Cells that were released from the marrow plugs over time and migrated through the stromal layer into the wells were assayed for stem cell/progenitor cell characteristics.

RESULTS

Few or no GM-CSF (progenitors) were found in wells containing media alone or media plus mobilizing cytokines after 24 h. After 120 h, the numbers of cells in the cytokine-containing wells increased, as did the numbers of CD34(+) cells. Cells in the wells at the time progenitor cells were most frequent were shown to include side population (SP) hematopoietic stem cells. After 120 h in the presence of cytokines, cells pooled from the wells were transplanted to lethally irradiated mice. Eighty per cent of the transplanted mice survived 30 days or more, demonstrating that radioprotective stem cells were present in the wells.

DISCUSSION

An ex vivo model has been designed that may aid investigations of the various steps of stem cell mobilization.

Evidence for a qualitative hierarchy within the Hoechst-33342 'side population' (SP) of murine bone marrow cells

In vitro cobblestone area (CA)-forming cell (CAFC) and in vivo (short-term and competitive repopulation) assays demonstrate that a qualitative hierarchy exists within the Hoechst-33342-defined side population (SP) in murine bone marrow (BM). Consistent with and extending previous studies, we demonstrate that (i) hematopoietic activity found in whole BM (WBM) is concentrated within the SP, rather than the non-SP (NSP); and (ii) within the SP, those cells that more strongly efflux the dye (lower SP, LSP) are qualitatively different from those that less strongly efflux the dye (upper SP, USP). Qualitative differences are highlighted by evidence that (i) CA derived from LSP CAFC persist in culture significantly longer than CA derived from USP CAFC; (ii) short-term, multilineage repopulation of lethally irradiated mice by LSP cells is more rapid than that in mice receiving USP, NSP, whole SP (WSP), or WBM cells and (iii) LSP cells out-compete USP cells in the multilineage hematopoietic repopulation of lethally irradiated recipients. These data suggest that LSP cells are of higher quality than USP cells and potentially provide a means by which qualitative changes in primitive hematopoietic progenitors occurring naturally with aging, or clinically as a consequence of therapeutic manipulation, can be assessed.

Promises and pitfalls of stem cell therapy for promotion of bone healing

There is promise in combining stem cells with allogeneic bone matrix to promote bone healing. Murine bone marrow, peripheral blood, and compact bone cells were transplanted ectopically under the kidney capsule in mice, alone or in combination with allogeneic matrix products: powder and putty to determine their bone forming potential in comparison to transplanted femoral bone fragments and long-term cultured bone marrow cells. The end point was the amount of bone formed as determined by quantitative histology. Mononuclear cells from marrow, peripheral blood, or bone alone transplanted under the kidney capsule did not form bone. Mononuclear cell populations did not combine readily with matrix products and there was in vivo migration of the transplanted combinations. Kidney subcapsular transplanted cultured bone marrow cells formed bone in proportion to the culture period, but after 9 weeks, the extent was only 20% by area of that of similarly transplanted femoral bone fragments. An inductive stimulus for bone formation seemed necessary. Osteoprogenitor cells were not detected in significant numbers in blood unless high doses of cytokines were administered. A better definition of the optimal cell populations and manipulations required for promotion of bone healing is needed along with new (transplant) models that allow for cell tracking. Much work remains to overcome current pitfalls in the use of stem cells to promote allograft integration and bone healing.

LEVEL OF EVIDENCE

Therapeutic study, Level V (expert opinion). See the Guidelines for Authors for a complete description of levels of evidence.

Hematopoietic Progenitor Cell Mobilization by Granulocyte Colony-Stimulating Factor and Erythropoietin in the Absence of Matrix Metalloproteinase-9

The use of mobilized hematopoietic progenitor cells (HPC) has largely replaced the use of bone marrow HPC for autologous and allogeneic transplantation; however, the mechanisms of HPC mobilization remain unclear. A better understanding of these mechanisms, may allow the development of improved (potentially more rapid and/or higher yield) HPC mobilization strategies, especially for patients who mobilize poorly using current mobilization protocols. Clinically, granulocyte colony-stimulating factor (G-CSF) is widely used to induce HPC mobilization, and evidence suggests that metalloproteinase enzymes released by activated granulocytes play an important role in the G-CSF-induced HPC mobilization. These enzymes may act to disrupt putative cell-cell and/or cell-extracellular matrix interactions within the hematopoietic microenvironment thereby releasing HPC into the blood. Matrix metalloproteinase-9 (MMP-9) appears to be important for G-CSF-induced mobilization. Using an MMP-9 knock-out (KO) mouse model, we investigated the role of MMP-9 in G-CSF and erythropoietin (EPO)-based HPC mobilization at clinically relevant cytokine doses. There were few hematologic or hematopoietic differences between the wild-type and MMP-9KO mice during steady-state hematopoiesis. When treated subcutaneously with EPO (500 U/kg per day) and G-CSF (15 microg/kg per day) for 5 days and assayed on day 6, similarly increased extramedullary hematopoiesis and numbers of HPC in the spleen and blood were observed for both the wild-type and MMP-9KO mice. These data demonstrate that MMP-9 is not required for EPO + G-CSF mobilization and that alternative mobilization mechanisms must be active at clinically relevant cytokine concentrations.

Cells Derived from the Circulation Contribute to the Repair of Lung Injury

Bone marrow (stem/progenitor) cells have been shown to "differentiate" into cells in multiple tissues, including lung. A low number of hematopoietic stem/progenitor cells also circulate in peripheral blood. The physiologic roles of these cells are still uncertain. This study was designed to test, using parabiotic mice that were joined surgically, whether stem/progenitor cells in blood contributed to the regeneration of lung after injury. Parabiotic mice were generated surgically by joining green fluorescent protein transgenic mice and wild-type littermates. These mice developed a common circulation (approximately 50% green cells in blood) by 2 weeks after surgery. The wild-type mouse was either uninjured or lethally irradiated or received intratracheal elastase or the combination of radiation with intratracheal elastase injection. Radiation or the combination of radiation with elastase significantly increased the proportion of bright green cells in the lungs of the wild-type mice. Morphologically, interstitial monocytes/macrophages, subepithelial fibroblast-like interstitial cells, and additionally type I alveolar epithelial cells immunostained for green fluorescent protein in wild-type mice. Approximately 5 to 20% of lung fibroblasts primary cultured from injured wild-type mice were green fluorescent protein expressing cells, indicating their blood derivation. This study demonstrates that stem/progenitor cells in blood contribute to the repair of lung injury in irradiated mice.

Transplanted BM and BM side population cells contribute progeny to the lung and liver in irradiated mice

BACKGROUND

BM cells have been shown to give rise to progeny of various cell lineages, including cells in lung and liver. This investigation evaluated whether purified BM mononuclear cells and side population (SP) cells that have hematopoietic stem-cell activity also had this property; whether a TBI preparative regimen was necessary for engraftment; and where BM-derived cells were engrafted.

METHODS

Either 1-3 million BM mononuclear cells or 2000 BM SP cells from transgenic enhanced green fluorescent protein-expressing (EGFP) mice were transplanted i.v. to unirradiated or 7-9.5 Gy irradiated recipients.

RESULTS

Flow cytometric analysis showed that lung cells (mean 45%, range 4-70%) and liver cells (mean 4%, range 0.4-8.3%) from irradiated, but not unirradiated recipients, were EGFP donor-derived. Similar results were obtained transplanting BM mononuclear cells or SP cells. Morphologically, donor-derived cells in the lung were primarily monocytes and macrophages. Additionally, lung fibroblasts and Type I, but not Type II, alveolar cells and rare cells in the bronchial epithelium were donor BM derived. In the liver, Kupffer cells, inflammatory cells and small clusters of hepatocytes, but not bile duct cells, were donor-derived.

DISCUSSION

BM mononuclear and SP cells generated progeny in some compartments of the lung and liver, but only in TBI recipients. Stem cells in BM can contribute to repair of tissue injury in some compartments, but not to the same extent in the lung and liver.

Lung Cells Transplanted to Irradiated Recipients Generate Lymphohematopoietic Progeny

Bone marrow (stem) cells can differentiate into cells in multiple tissues, including lung. Conversely, there are reports that cells of nonhematopoietic tissues (brain, muscle) can give rise to lymphohematopoietic cells. Here we show that the lung contains cells capable of giving rise to lymphohematopoietic cells when transplanted to irradiated recipients. Whole lung cell suspensions, lung side population (SP) cells, and CD45(+/-) lung cells obtained from male transgenic enhanced green fluorescent protein-expressing mice were transplanted intravenously to total body irradiated female mice. Green fluorescent cells were recovered from the circulation and phenotyped for their expression of lymphohematopoietic markers (CD3, CD4, CD8, B220, Gr-1, and Mac-1). Lung SP cells were composed of heterogeneous populations and had less ability to give rise to lymphohematopoietic cells than did bone marrow SP cells. Furthermore, the ability of cells from the lung of aged mice to generate lymphohematopoietic progeny was equivalent to that of cells from young mice. Cells from lung with radioprotective and lymphohematopoietic reconstituting abilities were CD45(+). CD45(+) cells in the lung cells have lymphohematopoietic stem/progenitor cell characteristics, and this has implications for cell or gene therapy applications.

Effect of prior therapy and bone marrow metastases on progenitor cell content of blood stem cell harvests in breast cancer patients

This study was designed to examine the relationship of prior therapy, bone marrow metastases, mobilization, and blood progenitor/stem cell (BSC) collection in breast cancer patients. Cells were collected from 19 breast cancer patients during steady state (nonmobilized group) and from 69 breast cancer patients after cytokine administration (mobilized group). Characteristics of the patients were compared with the cells obtained. A significant inverse association was found between the number of chemotherapy regimens the patients had received prior to BSC collection and the mononuclear cell (MNC) count of the product per liter of blood processed (LBP) with apheresis (P = .0006) and the granulocyte monocyte/macrophage colony-forming cell (GM-CFC) numbers per LBP (P = .0002). This association was evident in both mobilized and nonmobilized patients. Similar results were seen in those 25 patients who had received prior radiation therapy (MNC/LBP, P = .0003; GM-CFC/LBP, P = .0004). Patients in both the mobilized and nonmobilized groups with marrow metastases at the time of collection also had significantly lower levels of MNC/LBP (P = .0039) and GM-CFC/LBP (P = .0001) than did those without marrow metastases. The findings suggest that prior administration of radiation therapy and/or chemotherapy and the presence of marrow metastases all negatively impacted the collection of mobilized and nonmobilized progenitor cells from breast cancer patients. The mechanisms of this impact are not understood.

Plasma from poorly mobilizing human subjects inhibits cytokine-induced murine blood stem-cell mobilization

BACKGROUND

Cytokine-induced mobilization of hematopoietic stem/progenitor cells to the circulation facilitates efficient harvest of blood stem cells by leukapheresis. Up to 30% of autologous, and 10-20% of allogeneic blood stem-cell donors respond poorly to mobilizing cytokines and preliminary studies implicated a circulating inhibitor of mobilization.

METHODS

In this study, plasma from 11 allogeneic and 23 autologous stem cell donors was assayed for inhibition of mobilization in mice.

RESULTS

There were significant correlations between CD34(+) cells collected/kg human donor weight and spleen weight, CD34(+) CD45(+) cells, GMCFC and HPP-CFC per spleen in murine recipients of these plasma samples. Overall, there was a positive association between transforming growth factor beta (TGF-beta) levels and CD34(+) cells per liter of blood processed (LBP). However, when arbitrarily segregated into good versus poor mobilizers, based on less or greater than 15 million CD34(+) cells collected per LBP, the majority (64%) of normal donors were good mobilizers. The majority of the poor mobilizers (83%) were patients. For a subset of 12 individuals whose plasma strongly inhibited mobilization in the mouse, a significant positive correlation of the extent of inhibition with TGF-beta levels was found. For 11 individuals whose plasma, based on colony assays, enhanced mobilization when injected into mice, no correlation with TGF-beta levels was evident.

DISCUSSION

Elevated plasma TGF-beta levels in some stem-cell donors may be associated with poor stem-cell mobilization. It remains to be determined whether elevation of TGF-beta levels is a cause of, or a compensatory response to, poor mobilization.

Occult tumor cells detected in autologous blood stem cell harvests have no impact on 5 year outcomes for breast cancer patients with 4-9 positive nodes treated with adjuvant high-dose therapy and stem cell transplantation

Breast cancer cells have been detected in autologous blood stem cell collections of early stage breast cancer patients, but their clinical significance is undefined. From October 1993 to August 1998, 32 consecutive Stage II breast cancer patients with 4-9-positive nodes underwent stem cell apheresis. The patients were treated with cyclophosphamide 1.75 gm/m(2), etoposide 400 mg/m(2) and cisplatin 50 mg/m(2) daily for 3 days, followed by infusion of the autologous cells. Cytospins of cells from each apheresis collections and from an aliquot of three pooled collections were examined for cytokeratin expression using an immunocytochemical assay. The cells were considered positive for tumor if at least one cell with tumor morphology stained positively for cytokeratin. Negative aliquots were confirmed with RT-PCR. Six patients (19%) had positive collections. In total, 24 patients (75%) were disease free a median of 61 (30-86) months after transplant. Eight patients relapsed at a median of 17 (8-27) months after transplant. Four of the disease-free patients and two of the relapsed patients had positive apheresis collections. There was no significant correlation between the presence of detectable tumor cells in the graft product and outcome.

The whys and hows of hematopoietic progenitor and stem cell mobilization

Intentional mobilization of hematopoietic/stem cells into the circulation has improved the efficiency of their collection. Transplantation of mobilized blood stem cells to patients with marrow aplasia results in a faster pace of hematopoietic recovery than transplantation of marrow-derived stem cells. Autologous and allogeneic hematopoietic stem cell transplantation are increasingly performed with blood-derived cells. Donors of both autologous and allogeneic blood stem cells do not always respond well to therapies designed to produce mobilization. Autologous donors may respond poorly as a result of myelotoxic damage inflicted by prior antitumor therapy, but this explanation is not valid for allogeneic donors. The mechanism(s) involved in the process of mobilization are incompletely understood. Until these mechanisms are elucidated, methods to improve mobilization vigor on a rational basis will not be obvious. In the meanwhile, clinical observations may provide some hints regarding the whys and hows of mobilization and permit incremental improvements in this process.

Elevated transforming growth factor beta levels in the plasma of cytokine-treated cancer patients and normal allogeneic stem cell donors

BACKGROUND

Allogeneic blood stem-cell donors demonstrate more vigorous mobilization of CD34(+) cells to the circulation in response to cytokine administration than do autologous donors. Transforming growth factor (TGF-beta1) has been implicated as a mobilization inhibitor. A study was designed to determine whether plasma TGF-beta1 levels are elevated in cytokine-mobilized autologous cancer donors compared with cytokine-mobilized normal donors.

METHODS

Plasma collected from 29 autologous cancer donors and 33 normal allogeneic stem-cell donors following administration of mobilizing cytokines just prior to the first collection was assayed for TGF-beta1 using a sandwich-type ELISA. Plasma from three volunteers not treated with cytokine was also analyzed. Comparisons were made using the Student's t test on log-transformed data.

RESULTS

Average TGF-beta1 levels in the plasma of cancer patients were significantly higher than in allogeneic stem-cell donors (4.4 ng/mL versus 7.2 ng/mL; p = 0.038). The allogeneic donors required fewer collections to harvest greater numbers of CD34(+) cells and colony-forming unit granulocyte-macrophage (CFU-GM) than autologous donors. Plasma from three untreated volunteers had mean TGF-beta1 levels of 0.36 ng/mL, with all three levels below the 25th percentile for allogeneic donors and the 5th percentile for cancer patients.

DISCUSSION

Cytokine administration was associated with increased plasma TGF-beta1 levels. The levels were higher in cancer patients being mobilized for stem-cell collection than in allogeneic blood stem-cell donors. These differences could underlie the increased number of apheresis procedures required to harvest autologous graft products from cancer patients.

A murine model of bone marrow micrometastasis in breast cancer

Bone marrow (BM) is one of the most common sites and often the first clinical indication of metastatic progression of breast cancer. Multivariate analyses have shown that the presence of cytokeratin positive tumor cells in the marrow of women with newly diagnosed stage I, II or III breast cancer is an independent predictor of survival. The objective of this study was to develop an orthotopic model of spontaneous BM metastasis to facilitate studies of this process. A murine mammary adenocarcinoma cell line, Clone 66, was transduced with the neomycin resistance gene (Cl66neo) and injected orthotopically into female Balb/c mice. Polymerase chain reaction (PCR) for the neo gene performed on BM cells harvested from tumor bearing mice demonstrated as few as 10(2) injected tumor cells produced BM micrometastases at 4 weeks postinjection. Small foci of tumor cells were identified in the mammary fatpad (mfp) without gross evidence of primary tumors. Higher doses of tumor cells produced BM micrometastases, detectable by PCR, at one week post-injection. Constructs containing green fluorescent protein (GFP) and the neomycin resistance gene (neo) were also transduced into Clone 66 cells (Cl66-GFPneo) and injected into the mfp. GFP transduced tumor cells were identified in multiple tissues in addition to BM by flow cytometric analysis (FACS) but less 13% of the animals developed gross metastases. This model is a clinically relevant tool for the analysis of organ specificity of metastasis.

Report of the Tumor Evaluation Committee workshops at ISHAGE 2001

Multiple factors impact polymerase chain reaction (PCR) detection of tumor cells ranging from the fundamental, such as selection of targets for amplification, to the practical, including the timing of sample processing, granulocyte contamination and anticoagulant used. Much more work, including standardization studies, remains to be performed. Tumor enrichment can be achieved either by positive selection, generally by use of antibodies or by depletion of (CD45(+)) hematopoietic cells. Both approaches work and each has advantages and disadvantages. Enriched tumor cells can be further analyzed for expression of prognostic markers. A future area of emphasis should be to establish a dialogue between practitioners of tumor detection and developers of new therapies who are in search of surrogate markers of outcomes.

Intensive immunoablation and autologous blood stem cell transplantation in patients with refractory rheumatoid arthritis: the University of Nebraska experience

Two patients with severe rheumatoid arthritis (RA) were treated with high dose chemotherapy and autologous blood stem cell transplantation. Hematopoietic stem cells mobilized readily with cyclophosphamide and granulocyte-colony stimulating factor. Both patients achieved an American College of Rheumatology (ACR) 50% response before starting high dose therapy. The transplantation regimen included 200 mg/kg cyclophosphamide and 6 doses of equine antithymocyte globulin. Transplantation was well tolerated and both patients recovered neutrophils on day 7 post-transplant. At one month post-transplant both patients had an ACR response of 80%. Both individuals relapsed at 6 months and responded well to a combination of disease modifying antirheumatic drugs that was previously ineffective. At 12 months ACR responses were 80% and 60%, respectively. The first patient developed a flare at 18 months when she was found to be hypothyroid; she regained an 80% ACR response at 24 months with therapy of hypothyroidism. The second patient progressed relentlessly 15 months post-transplant. Immunological reconstitution showed a continuous inversion of the ratio of CD4 and CD8 lymphocytes with a predominant expansion of memory T cells.

Oligonucleotide enhanced cytotoxicity of Idarubicin for lymphoma cells

Oligonucleotides offer the potential to manipulate gene expression in targeted cells which might be exploitable for therapeutic benefit. The effects of combining a phosphorothioate oligonucleotide OL(1) p53, which transiently down-regulates p53 levels, with an anthracycline, Idarubicin, on the growth of wild-type p53 WMN gene-expressing lymphoma cells was evaluated. Fluorescent OL(1) p53, was used to demonstrate oligonucleotide uptake and retention by the WMN cells. Uptake was maximal at 24 hours and compared to baseline (0 hours) increasing apoptotic cells were evident in WMN cells treated with OL(1) (1 microM) alone and in combination with Idarubicin (0.2 nM) for 24 to 48 hours. In cells treated with OL(1) p53 and Idarubicin, truncated p53 message of a predicted 201 base pair length based on RNAase H cleavage of the OL(1) p53-p53 mRNA heteroduplex was detected after 7 hours of incubation. The message for p53 was transiently downregulated as detected by RT-PCR analysis at 24 hours, and protein levels transiently reduced at 36 hours, as shown by a quantitative Western blot. Corresponding to these events, the growth of WMN cells ceased after 48 hours in the concurrent presence of OL(1) p53 and Idarubicin and, the lymphoma cells were dead after 72 hours. No reduction in hematopoietic colony forming cell capacity of similarly treated hematopoietic progenitor cells harvested from cytokine-mobilized blood by apheresis was observed. Therefore, synergistic cytotoxicity of Idarubicin for lymphoma cells treated with an oligonucleotide targeting p53 message was demonstrated at oligonucleotide and Idarubicin concentrations which were minimally toxic to hematopoietic progenitor cells. This approach offers new opportunities for purging of lymphoma cells from hematopoietic harvests and systemic lymphoma therapy.

Progenitor and lymphoma cells in blood stem cell harvests: impact on survival following transplantation

This study evaluated whether cytokine-induced blood stem cell mobilization also mobilized lymphoma cells and whether lymphoma cell mobilization affected outcome post autologous blood stem cell transplant. Blood stem cell collections from 26 non-Hodgkin's lymphoma (NHL) patients harvested during steady-state (non-mobilized) and from 35 NHL patients harvested after cytokine administration (mobilized) were studied. The harvests were cultured and molecularly evaluated for clonal markers of the primary lymphoma. All patients underwent high-dose chemotherapy and autologous transplantation. Graft products from mobilized patients were more likely to contain lymphoma than graft products from non-mobilized patients (37% vs 19%) but this difference was not significant (P = 0.16). In a multivariate analysis, lymphoma contamination was not associated with patient age, gender, tumor grade, prior radiotherapy, duration of prior chemotherapy, mononuclear cell count, or the number of aphereses performed to obtain the product. Heavily pre-treated patients were less likely to have lymphoma-contaminated harvests (P = 0.064). Lymphoma contamination was positively associated with the number of progenitor cells collected (P = 0.047). In multivariate analyses, the only significant independent predictor of lymphoma contamination was the number of mononuclear cells collected (P = 0.031). Lymphoma contamination of transplanted apheresis products had no apparent impact on event-free and overall survival.

Circulating factors may be responsible for murine strain-specific responses to mobilizing cytokines

OBJECTIVE

To determine if circulating factors influence strain-specific responses to administration of hematopoietic stem-cell mobilizing cytokines, a murine model was employed.

METHODS

Plasma aliquots from intact DBA2, Balb/c, and C57Bl/6 mice were injected into intact Balb/c mice prior to delivery of mobilizing cytokines. Control Balb/c mice were injected with mobilizing cytokines alone. Plasma from hemi-body irradiated Balb/c mice, known to inhibit mobilization, was also injected into Balb/c mice. Twenty-four hours later, spleen cells were harvested and assayed for granulocyte-macrophage colony-forming cells (GM-CFC) and high-proliferative-potential colony-forming cells (HPP-CFC). Simultaneously harvested blood aliquots were assayed for CD45(+)/CD34(+) cells using flow cytometric techniques.

RESULTS

Mice receiving plasma from any source demonstrated significant inhibition of mobilization of HPP-CFC and GM-CFC to the spleen as compared to mobilized controls; for HPP-CFC, plasma from C57Bl/6 mice was more inhibitory than plasma from Balb/c (p = 0.001) or from DBA2 mice (p = 0.01), while for GM-CFC, plasma from C57Bl/6 mice was more inhibitory than Balb/c plasma but not more inhibitory than DBA2 plasma. Mice injected with plasma from previously irradiated Balb/c mice exhibited the expected HPP-CFC and GM-CFC mobilization inhibition, which was not statistically different from the inhibition seen in animals that received C57Bl/6 plasma. Mobilization of CD34(+)/CD45(+) cells to the blood also appeared to be inhibited by pretreatment with C57Bl/6 plasma, but not DBA2 plasma.

CONCLUSION

These data suggest that strain-specific patterns of mobilization may be influenced by a circulating mobilization inhibitor(s).

VLA-4 mediated adhesion to bone marrow stromal cells confers chemoresistance to adherent lymphoma cells

The mechanisms of maintenance of residual lymphoma in bone marrow during chemotherapy are currently not well understood. Previous studies have shown that primary lymphoma cells obtained from histologically negative bone marrow of non-Hodgkin's lymphoma (NHL) patients grew in long-term bone marrow cultures primarily in association with bone marrow stromal cells. Furthermore, the interaction of NHL patient cells with bone marrow stromal cells inhibited their spontaneous apoptosis. The current studies were designed to characterize the components of the heterotypic interaction between lymphoma cells and bone marrow stromal cells as well as to probe the consequences of this interaction as it pertains to the potential survival of minimal numbers of lymphoma cells during chemotherapy. Cellular adhesion assays performed in the presence of either neutralizing antibodies to VCAM- or the alpha and beta subunit of VLA-4 resulted in >95%, 82% and 35% inhibition of lymphoma cell line adhesion to the bone marrow stromal line MS-5, respectively. Modulation of VLA-4 affinity by the 8A2 antibody resulted in enhanced secondary adhesion at 24 and 72 hours to either cellular fibronectin (65% and 65%) or MS-5 cells (60% and 55%), superceding levels obtained using untreated lymphoma cells (<20%). The bone marrow stromal cells induced a chemoprotective effect for adherent lymphoma cells over a 3-log dose range of vincristine, resulting in a 2-log increase in the ED50 at day 6 of culture. The failure of glutaraldehyde fixed stromal cells to induce a chemoprotective effect demonstrated that viable bone marrow stromal cells were necessary. Similarly, lymphoma/stromal cell conditioned medium also failed to provide a survival advantage. These data demonstrated that viable bone marrow stromal cells possessed the ability to actively inhibit the apoptotic pathways of intimately adherent lymphoma cells and this potentially contributes to their survival during chemotherapy.