Early diagnostic value of Bcl-3 localization in colorectal cancer

Discovery of a small molecule that inhibits Bcl-3-mediated cyclin D1 expression in melanoma cells

Molecular targeted therapy using a drug that suppresses the growth and spread of cancer cells via inhibition of a specific protein is a foundation of precision medicine and treatment. High expression of the proto-oncogene Bcl-3 promotes the proliferation and metastasis of cancer cells originating from tissues such as the colon, prostate, breast, and skin. The development of novel drugs targeting Bcl-3 alone or in combination with other therapies can cure these patients or prolong their survival. As a proof of concept, in the present study, we focused on metastatic melanoma as a model system. High-throughput screening and in vitro experiments identified BCL3ANT as a lead molecule that could interfere with Bcl-3-mediated cyclin D1 expression and cell proliferation and migration in melanoma. In experimental animal models of melanoma, it was demonstrated that the use of a Bcl-3 inhibitor can influence the survival of melanoma cells. Since there are no other inhibitors against Bcl-3 in the clinical pipeline for cancer treatment, this presents a unique opportunity to develop a highly specific drug against malignant melanoma to meet an urgent clinical need.

Multifaceted roles for BCL3 in cancer: a proto-oncogene comes of age

In the early 1990's a group of unrelated genes were identified from the sites of recurring translocations in B-cell lymphomas. Despite sharing the nomenclature 'Bcl', and an association with blood-borne cancer, these genes have unrelated functions. Of these genes, BCL2 is best known as a key cancer target involved in the regulation of caspases and other cell viability mechanisms. BCL3 on the other hand was originally identified as a non-canonical regulator of NF-kB transcription factor pathways - a signaling mechanism associated with important cell outcomes including many of the hallmarks of cancer. Most of the early investigations into BCL3 function have since focused on its role in NF-kB mediated cell proliferation, inflammation/immunity and cancer. However, recent evidence is coming to light that this protein directly interacts with and modulates a number of other signaling pathways including DNA damage repair, WNT/β-catenin, AKT, TGFβ/SMAD3 and STAT3 - all of which have key roles in cancer development, metastatic progression and treatment of solid tumours. Here we review the direct evidence demonstrating BCL3's central role in a transcriptional network of signaling pathways that modulate cancer biology and treatment response in a range of solid tumour types and propose common mechanisms of action of BCL3 which may be exploited in the future to target its oncogenic effects for patient benefit.

BCL3 expression is strongly associated with the occurrence of breast cancer relapse under tamoxifen treatment in a retrospective cohort study

Patients with estrogen receptor positive breast cancer are usually receiving an anti-estrogen therapy by either aromatase inhibitors or selective estrogen receptor mediators such as tamoxifen. Nevertheless, acquired resistance to tamoxifen under treatment frequently hampers therapy. One proposed explanation for this phenomenon is the interaction of the tumor cells with cells of the tumor microenvironment via the Insulin-like growth factor RNA binding protein 5/B-cell lymphoma 3 (IGFBP5/BCL3) axis. Here we investigated whether a high expression of BCL3 either cytoplasmic or nuclear is associated with the occurrence of a relapse under anti-estrogen therapy in patients. Formaldehyde-fixed, paraffin-embedded samples of 180 breast cancer patients were analyzed for BCL3 expression by immunohistochemistry. An immunoreactive score (IRS) was calculated from staining intensity in cytoplasm and nucleus as well as the percentage of positive tumor cells. These scores were correlated with clinico-pathological parameters using cross-tabulation analysis and patients’ relapse free and overall survival by Kaplan–Meier analysis and Cox regression. A tamoxifen-adapted MCF-7 derived cell line was investigated for BCL3 localization by immunofluorescence. The cytosolic BCL3-IRS significantly correlated with the proliferation marker Ki-67, and with the occurrence of a relapse under tamoxifen treatment. Nuclear score correlated only with tamoxifen-relapse. In survival analysis, both scores were highly significant prognostic factors for relapse free, but not for overall survival. This was especially obvious for estrogen receptor positive and HER2/NEU negative cases as well as lobular breast cancer. Tamoxifen-treated, but not aromatase-treated patients had a poor survival when BCL3 scores were high. A tamoxifen adapted cell line exhibited a reduced expression and mainly nuclear localization of BCL3, compared to the parental estrogen receptor positive cell-line MCF-7. Altogether, these data strongly support a function of BCL3 in tamoxifen resistance and its potential use as a predictive biomarker for tamoxifen resistance.

The role of B-Cell Lymphoma-3 (BCL-3) in enabling the hallmarks of cancer: implications for the treatment of colorectal carcinogenesis

With its identification as a proto-oncogene in chronic lymphocytic leukaemia and central role in regulating NF-κB signalling, it is perhaps not surprising that there have been an increasing number of studies in recent years investigating the role of BCL-3 (B-Cell Chronic Lymphocytic Leukaemia/Lymphoma-3) in a wide range of human cancers. Importantly, this work has begun to shed light on our mechanistic understanding of the function of BCL-3 in tumour promotion and progression. Here, we summarize the current understanding of BCL-3 function in relation to the characteristics or traits associated with tumourigenesis, termed ‘Hallmarks of Cancer’. With the focus on colorectal cancer, a major cause of cancer related mortality in the UK, we describe the evidence that potentially explains why increased BCL-3 expression is associated with poor prognosis in colorectal cancer. As well as promoting tumour cell proliferation, survival, invasion and metastasis, a key emerging function of this proto-oncogene is the regulation of the tumour response to inflammation. We suggest that BCL-3 represents an exciting new route for targeting the Hallmarks of Cancer; in particular by limiting the impact of the enabling hallmarks of tumour promoting inflammation and cell plasticity. As BCL-3 has been reported to promote the stem-like potential of cancer cells, we suggest that targeting BCL-3 could increase the tumour response to conventional treatment, reduce the chance of relapse and hence improve the prognosis for cancer patients.

BCL‑3 promotes cyclooxygenase‑2/prostaglandin E2 signalling in colorectal cancer

First discovered as an oncogene in leukaemia, recent reports highlight an emerging role for the proto‑oncogene BCL‑3 in solid tumours. Importantly, BCL‑3 expression is upregulated in >30% of colorectal cancer cases and is reported to be associated with a poor prognosis. However, the mechanism by which BCL‑3 regulates tumorigenesis in the large intestine is yet to be fully elucidated. In the present study, it was shown for the first time that knocking down BCL‑3 expression suppressed cyclooxygenase‑2 (COX‑2)/prostaglandin E2 (PGE2) signalling in colorectal cancer cells, a pathway known to drive several of the hallmarks of cancer. RNAi‑mediated suppression of BCL‑3 expression decreased COX‑2 expression in colorectal cancer cells both at the mRNA and protein level. This reduction in COX‑2 expression resulted in a significant and functional reduction (30‑50%) in the quantity of pro‑tumorigenic PGE2 produced by the cancer cells, as shown by enzyme linked immunoassays and medium exchange experiments. In addition, inhibition of BCL‑3 expression also significantly suppressed cytokine‑induced (TNF‑α or IL‑1β) COX‑2 expression. Taken together, the results of the present study identified a novel role for BCL‑3 in colorectal cancer and suggested that expression of BCL‑3 may be a key determinant in the COX‑2‑meditated response to inflammatory cytokines in colorectal tumour cells. These results suggest that targeting BCL‑3 to suppress PGE2 synthesis may represent an alternative or complementary approach to using non‑steroidal anti‑inflammatory drugs [(NSAIDs), which inhibit cyclooxygenase activity and suppress the conversion of arachidonic acid to prostaglandin], for prevention and/or recurrence in PGE2‑driven tumorigenesis.

BCL-3 promotes a cancer stem cell phenotype by enhancing β-catenin signalling in colorectal tumour cells

To decrease bowel cancer incidence and improve survival, we need to understand the mechanisms that drive tumorigenesis. Recently, B-cell lymphoma 3 (BCL-3; a key regulator of NF-κB signalling) has been recognised as an important oncogenic player in solid tumours. Although reported to be overexpressed in a subset of colorectal cancers (CRCs), the role of BCL-3 expression in colorectal tumorigenesis remains poorly understood. Despite evidence in the literature that BCL-3 may interact with β-catenin, it is perhaps surprising, given the importance of deregulated Wnt/β-catenin/T-cell factor (TCF) signalling in colorectal carcinogenesis, that the functional significance of this interaction is not known. Here, we show for the first time that BCL-3 acts as a co-activator of β-catenin/TCF-mediated transcriptional activity in CRC cell lines and that this interaction is important for Wnt-regulated intestinal stem cell gene expression. We demonstrate that targeting BCL-3 expression (using RNA interference) reduced β-catenin/TCF-dependent transcription and the expression of intestinal stem cell genes LGR5 and ASCL2. In contrast, the expression of canonical Wnt targets Myc and cyclin D1 remained unchanged. Furthermore, we show that BCL-3 increases the functional stem cell phenotype, as shown by colorectal spheroid and tumoursphere formation in 3D culture conditions. We propose that BCL-3 acts as a driver of the stem cell phenotype in CRC cells, potentially promoting tumour cell plasticity and therapeutic resistance. As recent reports highlight the limitations of directly targeting cancer stem cells (CSCs), we believe that identifying and targeting drivers of stem cell plasticity have significant potential as new therapeutic targets.

This article has an associated First Person interview with the first author of the paper.

Summary: BCL-3 acts as a co-activator of β-catenin/TCF-mediated transcriptional activity, driving a stem-cell-like phenotype in colorectal cancer cells, with implications for tumour cell plasticity and therapeutic resistance.

BCL3 Expression Is a Potential Prognostic and Predictive Biomarker in Acute Myeloid Leukemia of FAB Subtype M2

Although the implication of BCL3 has been disclosed in human chronic lymphocytic leukemia as well as other solid tumors, the diagnostic and prognostic of BCL3 expression in acute myeloid leukemia (AML) remains largely unclear. In this study, we isolated total RNA from bone marrow mononuclear cells collected from 101 de novo AML patients and 27 healthy donors. After reverse transcription, quantitative real-time PCR was performed to detect BCL3 expression level. BCL3 mRNA level was significantly down-regulated in BMMCs of AML patients compared with healthy controls (P = 0.0015). BCL3 was showed a higher level in AML patients with poor-risk karyotypes than that of in patients with favorable/intermediate-risk karyotypes (P = 0.014). ROC analysis demonstrated that BCL3 could effectively differentiate AML patients from normal controls. Among the French-American-British (FAB) subtypes, the frequency of low BCL3 expression in M2 subtypes is significantly higher than that of in the other subtypes M1/M4/M5/M6/M7 (P = 0.006), and mildly lower in myelomonocytic/monocytic subtypes M4/M5 (P = 0.064) than those in M1/M2/M6/M7 subtypes. Chromosome analysis revealed that BCL3^low patients had a remarkably higher frequency of t (8;21) abnormality (P = 0.0047) and lower frequency of normal karyotype (P = 0.0059) than BCL3^high patients. BCL3^high patients showed a significantly higher frequency of FLT3-ITD mutation (P = 0.028) and lower frequency of C-Kit mutation (P = 0.0232) than BCL3^low patients. Although there were no significant differences in complete remission and overall survival between BCL3^low and BCL3^high groups, patients with high BCL3 expression markedly shorter overall survival (OS, P = 0.049), relapse-free survival (RFS, P = 0.027) and disease-free survival (DFS, P = 0.042) in M2 AML than low BCL3 expression patients. Additionally, in AMLs of M2 subtype, high BCL3 expression patients had markedly lower complete remission (CR) rate (P = 0.0317) after the second induction treatment than patients with BCL3 low expression. Thus, these findings indicated that BCL3 appeared as a promising molecular biomarker of pediatric acute myeloid leukemia with unfavorable prognosis.

Alternative NF-κB signaling promotes colorectal tumorigenesis through transcriptionally upregulating Bcl-3

Multiple studies have shown that chronic inflammation is closely related to the occurrence and development of colorectal cancer (CRC). Classical NF-κB signaling, the key factor in controlling inflammation, has been found to be of great importance to CRC development. However, the role of alternative NF-κB signaling in CRC is still elusive. Here, we found aberrant constitutive activation of alternative NF-κB signaling both in CRC tissue and CRC cells. Knockdown of RelB downregulates c-Myc and upregulates p27^Kip1 protein level, which inhibits CRC cell proliferation and retards CRC xenograft growth. Conversely, overexpression of RelB increases proliferation of CRC cells. In addition, we revealed a significant correlation between Bcl-3 and RelB in CRC tissues. The expression of RelB was consistent with the expression of Bcl-3 and the phosphorylation of Bcl-3 downstream proteins p-Akt (S473) and p-GSK3β (S9). Bcl-3 overexpression can restore the phenotype changes caused by RelB knockdown. Importantly, we demonstrated that alternative NF-κB transcriptional factor (p52:RelB) can directly bind to the promoter region of Bcl-3 gene and upregulate its transcription. Moreover, the expression of RelB, NF-κB2 p52, and Bcl-3 was associated with poor survival of CRC patients. Taken together, these results represent that alternative NF-κB signaling may function as an oncogenic driver in CRC, and also provide new ideas and research directions for the pathogenesis, prevention, and treatment of other inflammatory-related diseases.

Immunohistochemical assessment of Survivin and Bcl3 expression as potential biomarkers for NF-κB activation in the Barrett metaplasia-dysplasia-adenocarcinoma sequence

Non-dysplastic Barrett's oesophagus (NDBE) occurs as a consequence of an inflammatory response triggered through prolonged gastro-oesophageal reflux and it may precede the development of oesophageal adenocarcinoma. NF-κB activation as a result of the inflammatory response has been shown in NDBE, but the possible mechanism involved in the process is unknown. The aim of this study was to assess, using immunohistochemistry, Survivin and Bcl3 expression as potential biomarkers for NF-κB activation along the oesophageal metaplasia-dysplasia-adenocarcinoma sequence. Survivin is an NF-κB-inducible anti-apoptotic protein, and Bcl3 is a negative regulator of NF-κB. There was progressive upregulation of Survivin expression along the oesophageal metaplasia-dysplasia-adenocarcinoma sequence. Bcl3 expression was upregulated in non-dysplastic Barrett's oesophagus, low-grade, high-grade dysplasia and oesophageal adenocarcinoma when compared to squamous group. The study shows the differential expression of Bcl3 between the squamous and Barrett's stage, suggesting that Bcl3 could be a surrogate marker for early event involving constitutive NF-κB activation. In addition, the study suggests that NF-κB activation may infer resistance to apoptosis through the expression of anti-apoptotic genes such as Survivin, which showed progressive increase in expression throughout the oesophageal metaplasia-dysplasia-adenocarcinoma sequence. This ability to avoid apoptosis may underlie the persistence and malignant predisposition of Barrett's metaplasia.

Potentiating the effects of radiotherapy in rectal cancer: the role of aspirin, statins and metformin as adjuncts to therapy

BACKGROUND

Complete tumour response (pCR) to neo-adjuvant chemo-radiotherapy for rectal cancer is associated with a reduction in local recurrence and improved disease-free and overall survival, but is achieved in only 20-30% of patients. Drug repurposing for anti-cancer treatments is gaining momentum, but the potential of such drugs as adjuncts, to increase tumour response to chemo-radiotherapy in rectal cancer, is only just beginning to be recognised.

METHODS

A systematic literature search was conducted and all studies investigating the use of drugs to enhance response to neo-adjuvant radiation in rectal cancer were included. 2137 studies were identified and following review 12 studies were extracted for full text review, 9 studies were included in the final analysis.

RESULTS

The use of statins or aspirin during neo-adjuvant therapy was associated with a significantly higher rate of tumour downstaging. Statins were identified as a significant predictor of pCR and aspirin users had a greater 5-year progression-free survival and overall survival. Metformin use was associated with a significantly higher overall and disease-free survival, in a subset of diabetic patients.

CONCLUSIONS

Aspirin, metformin and statins are associated with increased downstaging of rectal tumours and thus may have a role as adjuncts to neoadjuvant treatment, highlighting a clear need for prospective randomised controlled trials to determine their true impact on tumour response and overall survival.