Association of PAX5 expression with clinical outcome in patients with TaT1 transitional cell carcinoma of the bladder

Homeobox Gene Expression Dysregulation as Potential Diagnostic and Prognostic Biomarkers in Bladder Cancer

Homeobox genes serve as master regulatory transcription factors that regulate gene expression during embryogenesis. A homeobox gene may have either tumor-promoting or tumor-suppressive properties depending on the specific organ or cell lineage where it is expressed. The dysregulation of homeobox genes has been reported in various human cancers, including bladder cancer. The dysregulated expression of homeobox genes has been associated with bladder cancer clinical outcomes. Although bladder cancer has high risk of tumor recurrence and progression, it is highly challenging for clinicians to accurately predict the risk of tumor recurrence and progression at the initial point of diagnosis. Cystoscopy is the routine surveillance method used to detect tumor recurrence. However, the procedure causes significant discomfort and pain that results in poor surveillance follow-up amongst patients. Therefore, the development of reliable non-invasive biomarkers for the early detection and monitoring of bladder cancer is crucial. This review provides a comprehensive overview of the diagnostic and prognostic potential of homeobox gene expression dysregulation in bladder cancer.

Transactivation of PTGS2 by PAX5 signaling potentiates cisplatin resistance in muscle-invasive bladder cancer cells

Cisplatin (CDDP)-based systematic chemotherapy remains the mainstay of treatment for muscle-invasive bladder cancer (MIBC). However, acquired resistance to CDDP, a multifactorial process governed by an array of signals acting at different levels, is the major problem in BC treatment. Here, we report for the first time that, expression of Paired-box gene 5 (PAX5), a B-cell essential transcription factor, was significantly induced in CDDP-resistant BC tissues and in experimentally-induced CDDP-resistant BC cells. Inhibition of PAX5 expression by shRNA treatment effectively improved CDDP sensitivity in BC cells, whereas overexpression of PAX5 potentiated CDDP resistance through supporting BC cell survival. Mechanistically, using luciferase reporter and chromatin immunoprecipitation assays, we identified prostaglandin-endoperoxide synthase 2 (PTGS2, also called COX2), a potent enzyme responsible for prostanoids formation and inflammatory response, as the direct down-stream target of PAX5. PAX5 exerted its oncogenic function during the pathogenesis of CDDP resistance via stimulation of PTGS2 transcription. These observations collectively suggest that dysregulation of PAX5/PTGS2 cascade plays a causal role in the induction of CDDP resistance and gene silencing approaches targeting this pathway may therefore provide a novel therapeutic strategy for overcoming CDDP resistance in BC.

Spleen-specific isoforms of Pax5 and Ataxin-7 as potential proteomic markers of lymphoma-affected spleen

The splenomegaly, enlargement of spleen, has been observed in several diseases. It has been intended to evaluate histochemical alterations, spleen-specific enzymatic and proteomic markers during splenomegaly, and lympho-proliferative disorders from spleen of mice bearing Dalton's lymphoma. The higher expression of c-fos, c-jun, and MAPK testifies proliferation of lymphocytes. The lower expression of Pax5, higher expression of CD3, and the presence of additional form of Zap-70 suggest hypertrophy of follicles and splenomegaly influenced by weak B-cell receptor-mediated signaling, but activated T-cell receptor-mediated signaling. Simultaneously, lower levels of SOD, NDR2, and MIB2 and higher expression levels of Ataxin-7 and LDH also suggest impact of stress either as a cause or effect of cell proliferation. Spleen-specific isoform of Pax5, NDR2, MIB2, and Ataxin-7 can be considered as spleen-specific unique molecular markers for the evaluation of splenomegaly and lympho-proliferative disorders.

Biomarkers in bladder cancer: translational and clinical implications

Bladder cancer is associated with high recurrence and mortality rates. These tumors show vast heterogeneity reflected by diverse morphologic manifestations and various molecular alterations associated with these disease phenotypes. Biomarkers that prospectively evaluate disease aggressiveness, progression risk, probability of recurrence and overall prognosis would improve patient care. Integration of molecular markers with conventional pathologic staging of bladder cancers may refine clinical decision making for the selection of adjuvant and salvage therapy. In the past decade, numerous bladder cancer biomarkers have been identified, including various tumor suppressor genes, oncogenes, growth factors, growth factor receptors, hormone receptors, proliferation and apoptosis markers, cell adhesion molecules, stromal factors, and oncoproteins. Recognition of two distinct pathways for urothelial carcinogenesis represents a major advance in the understanding and management of this disease. Nomograms for combining results from multiple biomarkers have been proposed to increase the accuracy of clinical predictions. The scope of this review is to summarize the major biomarker findings that may have translational and clinical implications.

Characterization of a New Monoclonal Antibody Against PAX5/BASP in 1525 Paraffin-embedded Human and Animal Tissue Samples

INTRODUCTION

We describe the newly generated DAK-PAX5 monoclonal antibody raised against a fixation-resistant epitope of the human PAX5/BSAP molecule.

MATERIALS AND METHODS

Following Western-blot, absorption, and chess-board titration tests, and optimization of antigen-retrieval and detection methods, DAK-Pax5 was used in parallel with a reference antibody (clone 24) on tissue micro-arrays (TMAs) constructed from normal human and animal tissues and from hematologic and nonhematologic human malignancies. Such TMAs were also tested with an anti-PAX2 antibody.

RESULTS

DAK-Pax5 reacted with normal human and animal B-cells and with 460/473 B-cell non-Hodgkin lymphomas (B-NHLs). All plasmacytomas/plasmablastic tumors (n=13) and T/NK-cell neoplasms (n=264) turned out consistently negative as did acute myelogenous leukaemias (n=19) except 2 carrying t(8;21). Positivity was found in 6/6 and 155/169 lymphocyte predominant and classical HLs, respectively, although the staining intensity varied through cases. Among 521 nonhematologic malignancies, DAK-Pax5 reacted with 22/399 carcinomas (4/11 neuroendocrine, 2/4 Merkel-cell, 4/21 prostatic, 1/11 urothelial, 1/26 renal, 2/12 cervical squamous-cell, 3/13 ovarian, and 5/75 colonic). When compared with clone 24, DAK-Pax5 produced a stronger positivity in most if not all B-NHLs and HLs. No cross-reactivity with the anti-PAX2 antibody was recorded.

DISCUSSION

DAK-Pax5 represents a new reliable tool for diagnostics and research.

PAX5 expression in nonhematopoietic tissues. Reappraisal of previous studies

The Pax gene family encodes transcription factors with similar structures but distinctive roles in development and with limited expression in adult tissues. Reexpression of PAX proteins is frequently observed in human cancers, reflecting recapitulation of embryologic or developmental function. Defining expression of PAX family members is important in the immunohistochemical differential diagnosis of cancer, understanding oncogenesis, and defining targets for therapy. Immunostaining for PAX5 has become a commonly used technique in differential diagnosis of B-lineage hematologic malignancies. In seeking to define the range and degree of expression of PAX5 in nonhematologic pediatric cancers by immunohistochemical analysis with the anti-PAX5 monoclonal antibody routinely used in research and diagnosis, we observed strong immunostaining in a number of malignant tissues, including Wilms tumor. The pattern of expression of PAX5 in Wilms tumor was found to be identical to that of PAX2, raising the possibility of antibody cross-reactivity. This was subsequently confirmed by Western blotting and immunostaining of transfected cells and quantitative reverse transcriptase-polymerase chain reaction. Since the same PAX5 monoclonal antibody has been used consistently in the literature, these findings indicate a need for reappraisal of published PAX5 immunostaining results.

Development of cellular immune responses against PAX5, a novel target for cancer immunotherapy

PAX5 is a member of the PAX family of developmental transcription factors with an important role in B-cell development. Its expression in normal adult tissue is limited to the hemopoietic system, but it is aberrantly expressed in a number of solid cancers and leukemias where it functions as an oncogene. We therefore hypothesized that anti-PAX5 immune responses could be used to target a number of malignancies without significant toxicity. We screened PAX5 peptides for the ability to bind HLA-A2 and identified a novel sequence, TLPGYPPHV (referred to as TLP). CTL lines against TLP were generated from peripheral blood of five normal HLA-A2-positive blood donors and showed specific HLA-A2-restricted killing against PAX5-expressing target cells. We generated high-avidity CTL clones from these lines capable of killing cells pulsed with <1 nmol/L of TLP and killing a range of PAX5-expressing malignant cell lines. I.v. injection of an anti-PAX5 CTL clone into immunodeficient mice bearing s.c. human tumors resulted in specific growth inhibition of PAX5-expressing tumors. This knowledge can be used for the therapeutic generation of CTL lines or the cloning of high-avidity T-cell receptor genes for use in adoptive immunotherapy.

Expression of the endothelin axis in noninvasive and superficially invasive bladder cancer: relation to clinicopathologic and molecular prognostic parameters

BACKGROUND

The endothelin (ET) axis plays a role in cancer biology and plays a potential role as a target for molecular therapy in urogenital tumours. Alterations of several proteins of the ET axis were detected in invasive bladder cancer.

OBJECTIVES

To examine the potential role of the expression of ET axis proteins compared to other prognostic parameters (kinase inhibitor 67 [Ki-67], tumour protein 53 [TP53], and fibroblast growth factor receptor 3 gene [FGFR3] mutations) in noninvasive and invasive bladder cancer.

DESIGN, SETTING, AND PARTICIPANTS

Tissue microarrays from 154 consecutive patients with pTa-pT2 urothelial bladder cancer were immunohistochemically stained for endothelin 1 (ET-1), endothelin A and B receptors (ET(A)R, ET(B)R), TP53, and Ki-67. FGFR3 mutations were detected by SNaPshot analysis.

MEASUREMENTS

The results were correlated with clinicopathologic parameters and disease-specific survival, overall survival, and recurrence-free survival.

RESULTS AND LIMITATIONS

Proteins of the ET axis were frequently expressed in bladder cancer (ET-1 in 62% of tumours, ET(A)R in 93% of tumours, and ET(B)R in 84% of tumours). ET-1 expression was strongly correlated with tumour stage (p=0.015), histologic grade (p=0.008), and low proliferation status (p=0.003). ET(A)R immunostaining was only associated with low proliferation status (p=0.015). Kaplan-Meier survival analysis showed a significantly longer overall survival for patients with ET-1-expressing tumours (p=0.007). A significantly longer disease-free survival was found in patients with ET(A)R-expressing tumours (p=0.040), whereas ET(B)R expression was significantly correlated to a longer disease-free survival only in subgroups of patients with multifocal tumours (p=0.031), low proliferation index (Ki-67 ≤10; p=0.050), low TP53 expression (≤10; p=0.018), and tumours with an FGFR3 mutation (p=0.026). In the global model for recurrence-free survival, only high-grade (p=0.048) and negative ET(A)R immunoreactivity (p=0.048) were correlated with poor prognosis.

CONCLUSIONS

In addition to other factors, particularly age at diagnosis and growth pattern, lack of ET-1 expression may be an independent negative prognostic factor for the overall-survival probability of bladder cancer patients. Lack of ET(A)R expression may be an independent negative marker for recurrence-free survival.

Diagnostic uses of Pax5 immunohistochemistry

Pax5, or B-cell-specific activator protein, is a nuclear protein in the paired-box containing (PAX) family of transcription factors involved in control of organ development and tissue differentiation. Pax5 is mostly expressed in B lymphocytes and B-cell lymphomas, although recent data have shown expression in the developing central nervous system, some neuroendocrine tumors, and occasional myeloid leukemias. Pax5 immunohistochemistry shows robust nuclear staining, and has become a valuable tool in the diagnosis and subclassification of lymphomas. Pax5 staining is positive in most Hodgkin and B-cell non-Hodgkin lymphomas, and also precursor B-cell lymphoblastic neoplasms. Plasma cell neoplasms, multiple myeloma, and plasmablastic lymphomas typically are negative. T-cell lymphomas are, to date, consistently negative. Recently, Pax5 expression has been described in the majority of small cell carcinomas and Merkel cell carcinomas. Rare cases of Pax5 expression in other carcinomas have been reported. With these exceptions, Pax5 immunohistochemistry is fairly specific for B-cell lineage and is a valuable addition to the armamentarium of markers available for lymphoma subtyping.

Rare expression of BSAP (PAX-5) in mature T-cell lymphomas

Lineage determination in lymphomas is based on the assessment of lineage-specific markers, such as the B-cell-specific activator protein of the paired box family (BSAP, PAX-5) for the B-cell lineage. BSAP is thought to be expressed exclusively in B cells from the pro-B- to the mature B-cell stage and then silenced in plasma cells. BSAP has oncogenic potential and experimental evidence shows that the T-cell lineage is prone to this effect. Herein, we report on a BSAP-positive peripheral T-cell lymphoma with monoclonal T-cell receptor gamma-gene rearrangement. To assess the relative frequency of BSAP expression in mature T-cell lymphomas, we constructed and examined a tissue microarray consisting of 43 angioimmunoblastic T-cell lymphomas and peripheral T-cell lymphomas and detected no additional BSAP-positive cases. To conclude, BSAP can probably contribute to T-cell lymphomagenesis not only in vitro, but also in vivo. It is rarely expressed in peripheral T-cell lymphoma, thus its detection on lymphoid malignancies cannot be considered definitively lineage specific.