The prognostic utility of the transcription factor SRF in docetaxel-resistant prostate cancer: in-vitro discovery and in-vivo validation

Background

Docetaxel based therapy is one of the first line chemotherapeutic agents for the treatment of metastatic castrate-resistant prostate cancer. However, one of the major obstacles in the treatment of these patients is docetaxel-resistance. Defining the mechanisms of resistance so as to inform subsequent treatment options and combinations represents a challenge for clinicians and scientists.

Previous work by our group has shown complex changes in pro and anti-apoptotic proteins in the development of resistance to docetaxel. Targeting these changes individually does not significantly impact on the resistant phenotype but understanding the central signalling pathways and transcription factors (TFs) which control these could represent a more appropriate therapeutic targeting approach.

Methods

Using a number of docetaxel-resistant sublines of PC-3 cells, we have undertaken a transcriptomic analysis by expression microarray using the Affymetrix Human Gene 1.0 ST Array and in conjunction with bioinformatic analyses undertook to predict dysregulated TFs in docetaxel resistant prostate cancer. The clinical significance of this prediction was ascertained by performing immunohistochemical (IHC) analysis of an identified TF (SRF) in the metastatic sites from men who died of advanced CRPC. Investigation of the functional role of SRF was examined by manipulating SRF using SiRNA in a docetaxel-resistant PC-3 cell line model.

Results

The transcription factors identified include serum response factor (SRF), nuclear factor kappa-B (NFκB), heat shock factor protein 1 (HSF1), testicular receptor 2 & 4 (TR2 &4), vitamin-D and retinoid x receptor (VDR-RXR) and oestrogen-receptor 1 (ESR1), which are predicted to be responsible for the differential gene expression observed in docetaxel-resistance. IHC analysis to quantify nuclear expression of the identified TF SRF correlates with both survival from date of bone metastasis (p = 0.003), survival from androgen independence (p = 0.00002), and overall survival from prostate cancer (p = 0.0044). Functional knockdown of SRF by siRNA demonstrated a reversal of apoptotic resistance to docetaxel treatment in the docetaxel-resistant PC-3 cell line model.

Conclusions

Our results suggest that SRF could aid in treatment stratification of prostate cancer, and may also represent a therapeutic target in the treatment of men afflicted with advanced prostate cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3100-4) contains supplementary material, which is available to authorized users.

Invasive markers identified by gene expression profiling in pancreatic cancer

BACKGROUND

Molecular profiling has proven utility as a diagnostic and predictive tool in clinical oncology. However, a clinically relevant gene expression profile in pancreatic cancer remains elusive.

METHODS

Primary and metastatic pancreatic cancer cell lines (BxPC-3 and AsPC-1), were stimulated with phorbol-12-myristate 13-acetate (PMA), a known inducer of cell invasion. Affymetrix gene expression microarray analysis was performed, comparing gene expression to unstimulated controls. Differential expression was identified using ArrayAssist, and confirmed using quantitative real-time PCR. Bioinformatic analysis was performed using Pathway Studio and GOstat. The derived gene expression was further validated in fresh frozen pancreatic tumour samples. The ability of the derived 3 gene expression markersto differentiate between pancreatic adenocarcinoma (PDAC) and other neoplasms, and its association with clinicopathological variables was examined.

RESULTS

PMA-induced significant changes in cell line gene expression, from which distinctive 3 potential invasive markers were derived. Expression of these genes, uPA, MMP-1 and IL1-R1 was confirmed in human pancreatic tumours, and was found to differentiate PDAC from other pancreatic neoplasms. The expression of IL1-R1 in PDAC is a novel finding. We found that the expression of MMP-1 was associated with high-grade PDAC (p = 0.035, Wilcoxon rank sum).

CONCLUSION

We have identified three potential invasive markers, uPA, MMP-1 and IL1-R1, whose gene expression may differentiate PDAC from other pancreatic neoplasms, and potentially reflect a more invasive phenotype.

The human L1 element: a potential biomarker in cancer prognosis, current status and future directions

The discovery of new biomarkers is a rapidly advancing area in cancer biology. The challenge of biomarker development for broad clinical use requires the translation of lab-based knowledge into clinical practice. The Long Interspersed Nuclear Elements-1 (LINE-1s or L1 elements) are active members of an autonomous family of non-LTR retrotransposons and occupy nearly 17% of the human genome. There is strong experimental evidence that the global hypomethylation of genomic DNA in cancer cells results in the activation of L1s and their expression is detectable at genome, transcriptome and proteome levels in human cancer cells. Thus, human L1s constitute a potential marker for cancer cells. In this review we have attempted to scrutinize L1 expression profiles in clinical cancer studies by undertaking a comprehensive systematic analysis of papers published in the field so far with a view to providing a more complete picture of the detection methods used, improvements achieved and potential future directions. Ultimately, we will try to evaluate the potential of L1s as a molecular marker in cancer detection.

MiRNA-29a regulates the expression of numerous proteins and reduces the invasiveness and proliferation of human carcinoma cell lines

In this study we have identified a functional role for miR-29a in cancer cell invasion and proliferation. MiRNA expression profiling of human NSCLC cell lines indicated that miR-29a levels were reduced in more invasive cell lines. Exogenous overexpression of miR-29a in both lung and pancreatic cancer cell lines resulted in a significant reduction in the invasion phenotype, as well as in proliferation. 2D DIGE proteomic profiling of cells transfected with pre-miR-29a or anti-miR-29a resulted in the identification of over 100 differentially regulated proteins. The fold change of protein expression was generally modest--in the range 1.2-1.7-fold. Only 14 were predicted computationally to have miR-29a seed sequences in their 3' UTR region. Subsequent studies using siRNA to knock down several candidate proteins from the 2D DIGE experiment identified RAN (a member of the RAS oncogene family) which significantly reduced the invasive capability of a model lung cancer cell line. We conclude that miR-29a has a significant anti-invasive and anti-proliferative effect on lung cancer cells in vitro and functions as an anti-oncomir. This function is likely mediated through the post-transcriptional fine tuning of the cellular levels of several proteins, both directly and indirectly, and in particular we provide some evidence that RAN represents one of these.

TMEM25, REPS2 and Meis 1: favourable prognostic and predictive biomarkers for breast cancer

BACKGROUND/AIMS

A panel of prognostic and predictive biomarkers would contribute to personalized treatment of breast cancer patients. However, many such biomarkers have yet to be identified and evaluated. The aim of this study was to investigate the relevance of 3 such putative biomarkers.

METHODS

TMEM25, REPS2 and Meis 1 expression was investigated by qRT-PCR, in triplicate, in 103 breast tumour biopsies procured in 1993-1994. Normal breast tissue specimens were also analysed for comparative purposes. Univariate and multivariate analyses were used to identify associations between expression of these transcripts as well as patients' clinicopathological and survival data.

RESULTS

TMEM25, REPS2 and Meis 1 transcripts were detected in approximately 52, 78 and 40% of tumour specimens, respectively. Expression of each of the 3 genes was indicative of extended survival times from diagnosis [association between relapse-free survival (RFS) and TMEM25, p = 0.0002; REPS2, p = 0.0287; association between overall survival (OS) and TMEM25, p = 0.001; REPS2, p = 0.0131; Meis 1, p = 0.0255]. Presence of TMEM25 and Meis 1 was associated with oestrogen receptor-positive (TMEM25, p < 0.0005; Meis 1, p = 0.011), lower-grade (TMEM25, p = 0.002; Meis 1, p = 0.001) tumours. Multivariate analysis indicated TMEM25 expression to be an independent prognostic factor for extended RFS (p = 0.011) and OS (p = 0.001). Furthermore, for patients who received adjuvant chemotherapy, significantly longer survival times were achieved if their tumours expressed TMEM25 (OS, p = 0.031; RFS, p = 0.0181) and REPS2 (OS, p = 0.011). While expression of these mRNAs was generally absent from triple-negative breast tumours, statistical significance was not achieved.

CONCLUSION

Our results suggest that TMEM25, REPS2 and Meis 1 mRNAs may be useful members of a panel of favourable prognostic and predictive markers for breast cancer and an understanding of their function may provide useful information about this disease.

Computer Design of a Minimum Vibration Face Milling Cutter Using an Improved Cutting Force Model

An improved cutting force model is integrated in the design of a minimum vibration face milling cutter. The cutting force of a blade is approximated by a rectangular pulse whose height is governed by the blade spacing. Specific examples of a special purpose and a general purpose cutter are given and their performances are evaluated.

Computer Design of a Vibration-Free Face-Milling Cutter

A method is developed to choose the blade spacing for a face-milling cutter that will minimize vibration. When the dynamic frequency response of a machine-tool-workpiece system is known, a special-purpose cutter can be designed to minimize the relative cutter-workpiece vibration for a particular cutting speed. When the dynamic system response is unknown the design method is limited to a general-purpose cutter to avoid resonant excitation over a broad frequency range. A nonlinear least-squares method is used to choose the blade angles for both cases. Experimental results using a general-purpose cutter with unequal blade spacing showed an appreciable reduction in noise and vibration compared to a similar cutter with equal blade spacing.