Annemarie Larkin

Investigation of MRP‐1 protein and MDR‐1 P‐glycoprotein expression in invasive breast cancer: A prognostic study

The efficacy of breast cancer treatment is limited by the development of resistance to various chemotherapeutic agents. We conducted a retrospective study of the expression of 2 drug resistance efflux pumps, MRP‐1 and MDR‐1 Pgp, in 177 invasive breast carcinomas. Immunohistochemical expression of these proteins was correlated with clinicopathologic characteristics as well as relapse‐free survival (RFS) and overall survival (OS) times. MDR‐1 Pgp was associated strongly with higher histologic grade (grade III). A highly significant association was shown between MDR‐1 Pgp and MRP‐1 expression (p < 0.01), 47.4% of patients expressing both proteins; MRP‐1 was expressed in approximately 61% of patients and MDR‐1, in approximately 66% of patients. No association was shown in the overall group between either MDR‐1 Pgp or MRP‐1 and any of the other clinicopathologic features. Kaplan‐Meier analysis revealed that in a subset of patients with either high‐grade (grade III) stage 1 (node‐negative) or stage 2 (node‐positive) tumours who were treated with surgery followed by adjuvant chemotherapy, MRP‐1 expression in <25% of tumour cells at diagnosis was significantly associated with improved RFS (p < 0.02) and OS (p < 0.02). Using multivariate analysis, MRP‐1 expression in <25% of tumour cells at diagnosis was identified as an independent, significant prognostic factor for RFS (p < 0.01) and OS (p < 0.01) in this patient group but not in other groups. In this subgroup, no significant correlation was observed between expression of MDR‐1 Pgp and MRP‐1. While the number of patients with high‐grade tumours treated with adjuvant chemotherapy was small and further confirmatory research is warranted, it appears that assessment of MRP‐1 expression at diagnosis may offer useful prognostic information in subgroups of patients with stage 1 or stage 2 high‐grade tumours who receive CMF‐based adjuvant chemotherapy. Given the known substrate specificities of MRP‐1, any mechanistic relationship between MRP‐1 expression and CMF resistance remains unclear. No association was shown between MDR‐1 Pgp expression and either RFS or OS time in any subgroup of patients.

RNAi knockdown of Hop (Hsp70/Hsp90 organising protein) decreases invasion via MMP-2 down regulation

We previously identified Hop as over expressed in invasive pancreatic cancer cell lines and malignant tissues of pancreatic cancer patients, suggesting an important role for Hop in the biology of invasive pancreatic cancer. Hop is a co-chaperone protein that binds to both Hsp70/Hsp90. We hypothesised that by targeting Hop, signalling pathways modulating invasion and client protein stabilisation involving Hsp90-dependent complexes may be altered. In this study, we show that Hop knockdown by small interfering (si)RNA reduces the invasion of pancreatic cancer cells, resulting in decreased expression of the downstream target gene, matrix metalloproteinases-2 (MMP-2). Hop in conditioned media co-immunoprecipitates with MMP-2, implicating a possible extracellular function for Hop. Knockdown of Hop expression also reduced expression levels of Hsp90 client proteins, HER2, Bcr-Abl, c-MET and v-Src. Furthermore, Hop is strongly expressed in high grade PanINs compared to lower PanIN grades, displaying differential localisation in invasive ductal pancreatic cancer, indicating that the localisation of Hop is an important factor in pancreatic tumours. Our data suggests that the attenuation of Hop expression inactivates key signal transduction proteins which may decrease the invasiveness of pancreatic cancer cells possibly through the modulation of Hsp90 activity. Therefore, targeting Hop in pancreatic cancer may constitute a viable strategy for targeted cancer therapy.

Expression of multidrug resistance markers ABCB1 (MDR-1/P-gp) and ABCC1 (MRP-1) in renal cell carcinoma

BackgroundRenal cell carcinoma patients respond poorly to conventional chemotherapy, this unresponsiveness may be attributable to multidrug resistance (MDR). The mechanisms of MDR in renal cancer are not fully understood and the specific contribution of ABC transporter proteins which have been implicated in the chemoresistance of various cancers has not been fully defined in this disease.MethodsIn this retrospective study the expression of two of these transporter efflux pumps, namely MDR-1 P-gp (ABCB1) and MRP-1 (ABCC1) were studied by immunohistochemistry in archival material from 95 renal cell carcinoma patients.ResultsIn the first study investigating MDR-1 P-gp and MRP-1 protein expression patterns in renal cell carcinoma patients, high levels of expression of both efflux pumps are observed with 100% of tumours studied showing MDR-1 P-gp and MRP-1 positivity.ConclusionAlthough these findings do not prove a causal role, the high frequency of tumours expressing these efflux pumps suggests that they may be important contributors to the chemoresistance of this tumour type.

Differential Expression of Fourteen Proteins between Uveal Melanoma from Patients Who Subsequently Developed Distant Metastases versus Those Who Did Not

PURPOSE To compare the proteomic profiles of two categories of primary uveal melanoma tissue samples; those from patients who have subsequently developed metastatic disease and those who have not. METHODS Two-dimensional difference gel electrophoresis (2D DIGE) was performed on 25 uveal melanoma tissue specimens (minimum follow-up of 7 years) comparing nine uveal melanoma tumors from patients who developed metastatic disease and 16 from those who did not. Most of the tumors which metastasized also exhibited chromosome 3 monosomy. Selected differentially expressed proteins were further followed up by immunohistochemistry and functional validation in vitro using siRNA. RESULTS Proteomic analysis revealed 14 statistically significant differentially expressed proteins, with nine showing increased expression (PDIA3, VIM/HEXA, SELENBP1, ENO1, CAPZA1, ERP29, TPI1, PARK7, and FABP3) and five showing decreased expression (EIF2S, PSMA3, RPSA, TUBB, and TUBA1B) in uveal melanomas that subsequently metastasized compared with those that did not. Immunohistochemical analysis was performed for six of the differentially expressed proteins and gave similar results to the 2D DIGE study for two of these proteins, fatty acid-binding protein, heart-type (FABP3) and triosephosphate isomerase (TPI1). siRNA knockdown in the 92.1 uveal melanoma cell line confirmed a functional role for FABP3 and TPI1 in invasion in vitro. CONCLUSIONS Proteomic analysis identified proteins differentially expressed in uveal melanoma that will subsequently metastasize, some of which appear to have a functional role in invasion. These results may contribute to better predictive tests (along with genetic analysis) and to the identification of new therapeutic targets.

MDR-1, but not MDR-3 gene expression, is associated with unmutated IgVH genes and poor prognosis chromosomal aberrations in chronic lymphocytic leukemia.

Two P-glycoprotein (P-gp) genes, MDR-1 (ABCB1) and MDR-3 (ABCB4), have been identified in humans. This study was designed to investigate whether associations exist between expression of MDR-1 and MDR-3 P-gp and other markers of poor prognosis and/or prior exposure to therapeutic agents in chronic lymphocytic leukemia (CLL). IgVH mutational status, gene usage, CD38 positivity, FISH analysis and clinical information were available on all patients. Twenty-one of 101 patients tested showed MDR-3 P-gp positivity. Associations with markers of poor prognosis or prior chemotherapy did not reach statistical significance, but MDR-3 P-gp positive patients had significantly shorter survivals than MDR-3 P-gp negative patients. MDR-1 P-gp expression (18/25) showed a strong association with unmutated IgVH genes and adverse prognosis cytogenetics (p = 0.015, p = 0.014, respectively), but was independent of prior exposure to chemotherapeutic agents. These results suggest a role for MDR-1 and MDR-3 in chemoresistant disease. This study highlights the value of determining MDR phenotype in CLL patients prior to treatment, to allow the design of novel drug regimens containing agents that reverse MDR function.

Membrane transport proteins in human melanoma: associations with tumour aggressiveness and metastasis.

Background:Malignant melanoma, generally described as incurable, is notoriously refractory to chemotherapy. The mechanisms contributing to this have not yet been defined and the contributions of drug efflux pumps, implicated in chemo-resistance of many other cancer types, have not been extensively investigated in melanoma.Methods:In this study, expression of multi-drug resistant (MDR1/P-gp and MRP-1) proteins was examined, by immunohistochemistry, in archival specimens from 134 melanoma patients. This included 92 primary tumours and 42 metastases.Results:On assessing all specimens, MRP-1 and MDR1/P-gp expression was found to be common, with the majority (81%) of melanomas expressing at least one of these efflux pumps. Although there is significant association between expression of these pumps (P=0.007), MRP-1 was found to be the predominant (67% of cases) form detected. χ2 analysis showed significant associations between expression of MRP-1 and/or MDR1/P-gp and the aggressive nature of this disease specifically increased Breslows depth, Clarks level and spread to lymph nodes. This association with aggressiveness and spread is further supported by the observation that a significantly higher percentage of metastases, than primary tumours, express MRP-1 (91% vs 57%; P<0.0001) and MDR1/P-gp (74% vs 50%; P=0.010).Conclusion:The predominant expression of these pumps and, in particular, MRP-1 suggests that they may be important contributors to the inherent aggressive and resistant nature of malignant melanoma.

MDR1 expression is associated with adverse survival in melanoma of the uveal tract

Metastatic uveal melanoma is profoundly chemoresistant and has a very poor outcome. We have previously shown that the MDR1 gene and its gene product P-glycoprotein (P-gp), which are known to cause drug resistance in cancer cells, are expressed in ocular melanoma. Overexpression of MDR1 has been associated with a poor survival in some tumor types treated by chemotherapy and in some untreated tumours. To assess whether MDR1 expression is of prognostic value in uveal melanoma, we evaluated the expression of MDR1 by immunohistochemistry in 108 cases. Three semiquantitative grades were used to evaluate positive staining. We detected MDR1 expression in 80% of cases; 28% showed grade I staining; 30%, grade II staining; and 22%, grade III staining. There was a statistically significant association (P=.004) between MDR1 expression by tumor cells and shorter survival times (n=96), which was most striking at grade III levels of expression. Multivariate analysis showed that MDR1 expression is an independent prognostic indicator of poor survival. We conclude that (1) MDR1 may be involved in chemoresistance and tumor propagation in primary uveal melanoma, and (2) increasing levels of expression are prognostically significant and may prove a useful marker of tumor invasiveness, independent of established prognostic factors.

Influence of multidrug resistance and drug transport proteins on chemotherapy drug metabolism

Introduction: Chemotherapy involving the use of anticancer drugs remains an important strategy in the overall management of patients with metastatic cancer. Acquisition of multidrug resistance remains a major impediment to successful chemotherapy. Drug transporters in cell membranes and intracellular drug metabolizing enzymes contribute to the resistance phenotype and determine the pharmacokinetics of anticancer drugs in the body. Areas covered: ATP-binding cassette (ABC) transporters mediate the transport of endogenous metabolites and xenobiotics including cytotoxic drugs out of cells. Solute carrier (SLC) transporters mediate the influx of cytotoxic drugs into cells. This review focuses on the substrate interaction of these transporters, on their biology and what role they play together with drug metabolizing enzymes in eliminating therapeutic drugs from cells. Expert opinion: The majority of anticancer drugs are substrates for the ABC transporter and SLC transporter families. Together, these proteins have the ability to control the influx and the efflux of structurally unrelated chemotherapeutic drugs, thereby modulating the intracellular drug concentration. These interactions have important clinical implications for chemotherapy because ultimately they determine therapeutic efficacy, disease progression/relapse and the success or failure of patient treatment.

Elevated levels of 14-3-3 proteins, serotonin, gamma enolase and pyruvate kinase identified in clinical samples from patients diagnosed with colorectal cancer

BACKGROUND Colorectal cancer (CRC), a heterogeneous disease that is common in both men and women, continues to be one of the predominant cancers worldwide. Lifestyle, diet, environmental factors and gene defects all contribute towards CRC development risk. Therefore, the identification of novel biomarkers to aid in the management of CRC is crucial. The aim of the present study was to identify candidate biomarkers for CRC, and to develop a better understanding of their role in tumourogenesis. METHODS In this study, both plasma and tissue samples from patients diagnosed with CRC, together with non-malignant and normal controls were examined using mass spectrometry based proteomics and metabolomics approaches. RESULTS It was established that the level of several biomolecules, including serotonin, gamma enolase, pyruvate kinase and members of the 14-3-3 family of proteins, showed statistically significant changes when comparing malignant versus non-malignant patient samples, with a distinct pattern emerging mirroring cancer cell energy production. CONCLUSION The diagnosis and management of CRC could be enhanced by the discovery and validation of new candidate biomarkers, as found in this study, aimed at facilitating early detection and/or patient stratification together with providing information on the complex behaviour of cancer cells.

Identification and functional validation of RAD23B as a potential protein in human breast cancer progression.

Identification of protein targets that play a role in breast cancer invasion may help to understand the rapid progression of cancer and may lead to the development of new biomarkers for the disease. In this study, we compared two highly invasive and two poorly invasive breast cancer cell lines using comparative label-free LC-MS profiling in order to identify differentially expressed proteins that may be linked to the invasive phenotype in vitro. Forty-five proteins were found to be upregulated, and 34 proteins, downregulated. UV excision repair protein RAD23 homologue B (RAD23B) was found among the downregulated proteins in highly invasive breast cancer cell lines. In poorly invasive breast cancer cell lines, siRNA-mediated downregulation of RAD23B subsequently led to an increase in invasion and adhesion in vitro. Immunohistochemistry analysis of 164 specimens of invasive breast cancer showed that having a high percentage (>80%) of RAD23B positive nuclei was significantly associated with histopathological grades 1 and 2 breast cancer and with low mitotic activity. In addition, a high staining intensity for RAD23B in the cytoplasm was significantly associated with histopathological grade 3 breast cancer. This study suggests a potential role of RAD23B in breast cancer progression and may further imply a tumor suppressor role of nuclear RAD23B in breast cancer.