Management of mantle cell lymphoma: key challenges and next steps.

Mantle cell lymphoma (MCL) is regarded as an aggressive lymphoid malignancy that exhibits varied clinical behavior and prognoses, reflecting the biologic heterogeneity of the disease. In most cases, patients with MCL achieve a shorter median survival compared with more common B-cell lymphomas, such as follicular lymphoma, and are less likely to achieve a durable response with chemotherapy. Currently, there is no defined standard of care for patients with MCL. Rituximab-containing immunochemotherapy strategies are commonly used, but the addition of rituximab to conventional induction chemotherapy has produced suboptimal responses that are relatively short-lived and have not resulted in a survival advantage. Further intensification of the chemotherapy component, including autologous stem cell transplantation, has increased response and survival rates but has not proven to be curative while being associated with higher toxicity. Clearly, there is a need for developing novel agents and strategies that will improve clinical outcomes for patients with MCL. Targeted therapies and new cytotoxic agents are showing great promise and may have a role in maintenance and/or initial therapy. This summary highlights current challenges in the management of MCL, and outlines expert perspectives, key questions, and future directions. For the third consecutive year, a panel of global experts in MCL assembled to deliberate on topical issues in MCL including advances in pathobiology, strategies for risk-adapted therapy, front-line treatment options, consolidation approaches, and novel therapeutic strategies. The proceedings of this workshop, held December 3, 2009 in New Orleans, LA, are summarized here. It must be emphasized that this synopsis is not meant to serve as an exhaustive review of MCL biology and management, but is a distillation of the expert discussions, highlighting key questions and future directions identified.

Chronic lymphocytic leukemia: new concepts for future therapy.

Over the past several years, we have witnessed rapid advances in our understanding of the biology and treatment of chronic lymphocytic leukemia (CLL). New prognostic factors have been characterized that help identify patients at high risk of rapid disease progression, refractoriness to treatment, and short overall survival (OS). These advances have led to a significant paradigm shift in the management of CLL. Novel therapeutic strategies, including combinations of monoclonal antibodies with conventional chemotherapy, have dramatically improved response rates, remission duration, and recently, OS. However, these benefits do not appear to extend to certain patient subsets, especially those with unfavorable clinical or cytogenetic risk factors. The majority of patients with CLL will invariably relapse following first-line therapy and can acquire high-risk genetic abnormalities. Repeated treatment leads to eventual therapeutic refractoriness and shortened survival compared with age-matched healthy individuals. Several novel agents and strategies, including next-generation anti-CD20 monoclonal antibodies, the alkylating agent bendamustine, the immunomodulatory agent lenalidomide, the cyclin-dependent kinase inhibitor flavopiridol, and small-molecule Bcl2 inhibitors, are currently under clinical investigation as novel agents that will hopefully improve treatment outcomes for CLL. Though allogeneic stem cell transplantation offers curative potential, it also presents clinical challenges in terms of patient appropriateness, donor availability, and timing. The merits and challenges of incorporating these treatment modalities into the treatment algorithm for patients with CLL, as discussed by a panel of experts in CLL, are outlined in this article.

Forced expression of MMP9 rescues the loss of angiogenesis and abrogates metastasis of pancreatic tumors triggered by the absence of host SPARC.

Pancreatic adenocarcinoma is characterized by desmoplasia, local invasion, and metastasis. These features are regulated in part by MMP9 and SPARC. To explore the interaction of SPARC and MMP9 in cancer, we first established orthotopic pancreatic tumors in SPARC-null and wild-type mice with the murine pancreatic adenocarcinoma cell line, PAN02. MMP9 expression was higher in tumors from wild-type compared to SPARC-null mice. Coincident with lower MMP9 expression, tumors grown in SPARC-null mice were significantly larger, had decreased ECM deposition and reduced microvessel density compared to wild-type controls. In addition, metastasis was enhanced in the absence of host SPARC. Therefore, we next analyzed the orthotopic tumor growth of PAN02 cells transduced with MMP9 or a control empty vector. Forced expression of MMP9 by the PAN02 cells resulted in larger tumors in both wild-type and SPARC-null animals compared to empty vector controls and further diminished ECM deposition. Importantly, forced expression of MMP9 within the tumor reversed the decrease in angiogenesis and abrogated the metastatic potential displayed by control tumors grown in SPARC-null mice. Finally, contrary to the in vivo results, MMP9 increased cell migration in vitro, which was blocked by the addition of SPARC. These results suggest that SPARC and MMP9 interact to regulate many stages of tumor progression including ECM deposition, angiogenesis and metastasis.

Understanding the mechanisms of FHIT inactivation in cervical cancer for biomarker development.

OBJECTIVE: Loss of the fragile histidine triad (Fhit) protein has been documented in cervical cancer and dysplasia. The goal of this study was to confirm the utility of homozygous deletions, aberrant methylation, and immunohistochemical evaluations of FHIT as functionally relevant determinants of FHIT expression. METHODS: We studied matched DNA, RNA, and protein from nine early-passage cervical cancer cell lines. DNA markers spanning FHIT were used to examine the extent of homozygous deletions for each cell line. 5 CpG island methylation of FHIT was investigated by methylation-specific polymerase chain reaction (PCR) assays. FHIT transcripts were characterized by reverse transcriptase (RT)-PCR. Western blot analysis and immunohistochemistry were performed to characterize Fhit protein expression. RESULTS: Homozygous deletions were found in six of nine cervical cancer cell lines, but only one had homozygous deletions involving an exon. All nine lines had both methylated and unmethylated alleles according to methylation-specific PCR. Loss of wild-type FHIT transcripts were found in five of nine lines. By western blot analysis, Fhit protein expression was lost in five of nine lines, producing an exact correlation with RT-PCR results. Immunohistochemical staining was concordant with Fhit protein expression by western blotting in eight of nine cell lines. CONCLUSION: A perfect correlation was found between FHIT mRNA expression and western blot analysis. Assays for Fhit protein expression and large FHIT homozygous deletions are representative biomarkers of Fhit expression. By contrast, the aberrant methylation assay is not concordant with FHIT gene expression, and we suggest caution in its use as a functionally relevant biomarker for cervical cancer.

Enhanced growth of pancreatic tumors in SPARC-null mice is associated with decreased deposition of extracellular matrix and reduced tumor cell apoptosis.

SPARC, a matricellular glycoprotein, modulates cellular interaction with the extracellular matrix (ECM). Tumor growth and metastasis occur in the context of the ECM, the levels and deposition of which are controlled in part by SPARC. Tumor-derived SPARC is reported to stimulate or retard tumor progression depending on the tumor type, whereas the function of host-derived SPARC in tumorigenesis has not been explored fully. To evaluate the function of endogenous SPARC, we have examined the growth of pancreatic tumors in SPARC-null (SP(-/-)) mice and their wild-type (SP(+/+)) counterparts. Mouse pancreatic adenocarcinoma cells injected s.c. grew significantly faster in SP(-/-) mice than cells injected into SP(+/+) animals, with mean tumor weights at sacrifice of 0.415 +/- 0.08 and 0.086 +/- 0.03 g (P < 0.01), respectively. Lack of endogenous SPARC resulted in decreased collagen deposition and fiber formation, alterations in the distribution of tumor-infiltrating macrophages, and decreased tumor cell apoptosis. There was no difference in microvessel density of tumors from SP(-/-) or SP(+/+) mice. However, tumors grown in SP(-/-) had a lower percentage of blood vessels that expressed smooth muscle alpha-actin, a marker of pericytes. These data reflect the importance of ECM deposition in regulating tumor growth and demonstrate that host-derived SPARC is a critical factor in the response of host tissue to tumorigenesis.

Genomic organization and mapping of the gene encoding the PP2A B56gamma regulatory subunit.

Protein phosphatase 2A (PP2A) is a major serine/threonine phosphatase that regulates a wide variety of cellular processes. The enzymatic activity and intracellular localization of PP2A are determined by three distinct families of cellular regulatory subunits (B, B'', and B''). The B' subunit, also known as B56, is the most diverse, consisting of five isoforms (alpha, beta, gamma, delta, and epsilon). The gene encoding B56gamma has been designated as PPP2R5C and encodes three differentially spliced variants: B56gamma1, -gamma2, and -gamma3. However, conflicting chromosomal loci have been reported in human genomic databases. The original cytogenetic mapping placed the gene on chromosome 3p21.3, whereas subsequent studies using radiation hybrid analysis localized PPP2R5C to chromosome 14q. In this study, by radiation hybrid mapping, FISH analysis, BAC clone sequencing, and RT-PCR analysis, we show that the functional gene PPP2R5C exists at 14q32.2 and gives rise to three splicing variants, B56gamma1, -gamma2, and -gamma3, whereas a nonfunctional B56gamma1 pseudogene, PPP2R5CP, is present at 3p21.3. We also report the genomic organization of both the functional gene and the pseudogene.