Identifying Differentially Expressed Apoptosis Related Genes in Prostate Cancer
Qiang Shao*,
Chao Liu, Yon Cui, Xiaolan Wang
Citation: Shao Q, Liu C, Cui Y, Wang X (2017) Identifying Differentially Expressed Apoptosis Related Genes in Prostate Cancer. J Urol Ren Dis 2017: 138. DOI: 10.29011/2575-7903.000138
1. Abstract
Apoptosis plays a pivotal role in the pathogenesis of cancer. It is important to understand the molecular mechanisms underlying prostate cancer, and how prostate cancer cells evade apoptotic mechanisms. We performed apoptosis related microarray experiments to identify differentially expressed apoptosis related genes in three prostate cancer specimens. Student's t-test and Fisher's exact test were used to compare gene expression between prostate cancer and normal specimens. We identified seven apoptosis related genes that were differentially expressed in prostate cancer. BIK, BAX, BRAF and BNIP3L were up-regulated while CD40, CARD8 and PYCARD were down-regulated. We also found evidence that the apoptosis pathway plays a role in prostate cancer.
2. Keywords:
Apoptosis;
Prostate Cancer; PCR Array
1. Introduction
Apoptosis is a homeostatic cellular process that has been linked to a number of physiological and pathological conditions. It plays a fundamental role in the pathogenesis of several diseases, such as cancer [1]. There are mainly three pathways by which caspases can be activated: intrinsic (or mitochondrial), extrinsic (or death receptor) and intrinsic endoplasmic reticulum pathway [2]. The intrinsic pathway is initiated when internal stimuli such as irreparable genetic damage, hypoxia, extremely high concentrations of cytosolic Ca2+, and severe oxidative stress are present [3]. The extrinsic pathway is initiated when death receptors recruit adapter proteins such as the TNF Receptor-Associated Death Domain (TRADD) and the Fas-Associated Death Domain (FADD) [4]. Either stimulus activates a series of caspases and contributes to typical apoptotic morphological changes. Apoptosis is linked to the elimination of potentially malignant cells, hyperplasia and tumor progression [5]. Therefore, apoptosis and carcinogenesis include: 1) disrupted balance of pro-apoptotic and anti-apoptotic proteins, 2) reduced caspases function and 3) impaired death receptor signaling [6].
Carcinogenesis is complicated and apoptosis plays a role in cancer initiation and progression. Apoptosis is also believed to play an important role in prostate cancer. Therefore, it is important to understand the molecular mechanisms underlying prostate cancer and how prostate cancer cells evade apoptotic mechanisms that give rise to their uncontrolled growth and behavior. This is especially important when prostate cancer progresses to an apoptosis-resistant androgen-independent stage (CRPC, Castration-Resistant Prostate Cancer) [7]. Aim of our study was to perform an apoptosis related microarray study to access to association between apoptosis related genes and prostate cancer.
2. Materials and Methods
2.1. Study Population
We studied three prostate cancer specimens collected from patients who underwent radical prostatectomy at Suzhou Municipal Hospital. All cases were histologically confirmed as prostate adenocarcinoma. The pathological stage of prostate cancer was classified into TNM stage and tumor grade was evaluated by Gleason Score. The ethics committee at Suzhou Municipal Hospital approved this study and all patients provided written informed consent.
2.2. RNA Extraction and cDNA Preparation
We
synthesized cDNA by Reverse Transcription (RT) with Thermoscript™ RT kits (Invitrogen), using random hexamers as
amplification primers. In detail, 2.5 μg of
total RNA, 50 ng of random hexamers and
2.3.
Quantitative
Real-Time PCR Array
Quantitative
real-time PCR (qRT-PCR) was done using an apoptosis PCR Array containing 96
apoptosis-related genes (Super Array Biosciences) (Table
1).
Briefly,
RNA samples were isolated using Trizol reagent. All samples had 260/280 ratios
above 2.0 and 260/230 ratios above 1.7. An equal amount of RNA (2μ/g) was used for reverse transcription using RT2First Strand Kits from Super Array Biosciences.
PCR reactions were done using the RT2
profiler PCR array PAHS-3012 E (Human Apoptosis PCR Array 96 HT) on the
ABI Fast7900 using RT2Real-time SYBR
Green PCR master mix PA-012. The total volume of the PCR reaction was 10μL. The thermocycler parameters were
2.4.
Statistical
analysis
Student's t-test and Fisher's exact test were used to examine gene expression status between prostate cancer and normal tissue. All statistical analyses were 2-sided and performed with SPSS 11.5 (SPSS, Chicago, IL). Statistical significance was set at the 95% level (p-value <0.05).
3. Results
All
the three specimens had localized prostate cancer with pathologic stages that
ranged from T2N
We
observed that 47 apoptosis related genes were over-expressed (fold
changes>1) and 42 genes were under-expressed (fold changes<0). After
performing the Student’s t- test to replicate values for each gene in case and
control groups, we had seven genes BIK(P=0.0103), BAX(P=0.0424),
BRAF(P=0.0448), BNIP
Therefore, we deduced that these seven genes were significantly different between prostate cancer and normal prostate tissue. In addition, this suggests that the genes have different functions in different regions of the same specimens.
4. Discussion
We
conducted this study in order to determine mRNA transcription levels of
apoptosis related genes using a quantitative real-time RT-PCR method. An
apoptosis PCR Array contains premiere global apoptosis-related genes and we were
able to detect all targeted genes in one procedure. PCR reactions were performed
using the RT2 profiler PCR array PAHS-3012 E which has been used in
many studies [8-10]. We successfully
detected seven differentially expressed genes using an apoptosis PCR Array. The
BIK gene shares a critical BH3 domain with other death-promoting proteins, such
as BID, BAK, BAD and BAX [11], and is
associated with apoptosis repressors Bcl-X (L) or Bcl-2 suppresses death-promoting
activity [12-15] reported that the expression level
of BIK was up-regulated in prostate cancer compared with normal tissue ranging
from 1.28 to 2.42-fold. As a likely target for anti-apoptosis, over-expression
of BIK changed the apoptosis pathway for prostate tissue. The BAX gene shares the
same BH3 domain with the BIK gene and it has a similar function when it is associated
with BAX-Bcl-X (L) as BIK does [15-17] reported
similar results of BAX over-expression in prostate cancer tissues. The BNIP
BIK,
BAX and BNIP
The
CD40 gene was previously named the TNF Receptor Super Family Member 5(TNFRSF5).
This receptor has been found to be essential in mediating a broad variety of
immune and inflammatory responses [22]. In the apoptosis
pathway, CD40-mediated cell survival proceeds through NF-Kappa B (NFKB) dependent
up-regulation of Bcl-2 family members [23]. In
our data, CD40 was 3.19-fold under-expressed in prostate cancer. This result is
similar to that reported by [15-17,20]. PYCARD
(also named TMS1 and ASC) mediates the apoptosis pathway and is involved in
activation of the mitochondrial apoptotic pathway and promotes
caspase-8-dependent proteolytic maturation of BID independently of FADD in
certain cell types [24]. It also mediates
mitochondrial translocation of BAX and activates BAX-dependent apoptosis
coupled to activation of caspase-9, -2 and -3 [25,26]
reported that a direct role for aberrant methylation of the TMS1 gene in the
progression of breast and gastric cancer involving down-regulation of the pro-apoptotic
TMS1 gene. We observed that PYCARD was under-expressed in our samples. This
finding confirms what other studies have reported [15-20].
Furthermore, growing tumors of transplanted human cancer cells in nude mice
were eradicated by the activation of endogenous ASC in the tumor cells,
irrespective of the form of cell death. Thus, ASC mediates distinct forms of
cell death in different cell types, and is a promising target for cancer
therapy [27]. CARD8 shares the same
C-terminal Caspase-Recruitment Domain (CARD) with PYCARD. Both PYCARD and CARD8
mediate apoptosis involved in NFKB and pro-Caspase-1 activation [28] reported CARD8 under-expression at 1.04-fold in
prostate cancer which was similar with our result. We have a limitation on this
study that the sample is few. When this study began we collected few radical
prostatectomy sample and when the PCR-array conducted some samples were not
preserved well and ruled out of the test. We still thought although the samples
are not big enough the outcome may be useful for identifying apoptosis related
genes in prostate cancer.
As
a premiere global profiling platform, our experimental method is convenient. On
the other hand, a main disadvantage was that we did not detect all of the genes
using the combined platform. This study identified seven apoptosis related
genes differentially expressed between normal prostate and prostate cancer
tissue and revealed that the apoptosis pathway plays a role in prostate cancer.
Although we only studied three prostate cancer specimens, all of our outcomes
could be confirmed by other various studies. We will focus future work on the
seven genes and seven protein expression in different prostate cell lines.
Moreover, we will try to study the regulation, initiation and progression of
the seven genes in prostate cancer.
This
study was supported by two Suzhou Science and Technology Foundation
Grant–Leading Project for
Medical
Science (Nos SYSD2014114) and LCZX201511) and (SS201652).
Figure 1: Fold-change in
apoptosis related genes expression scatter plot in prostate cancer.
Figure 2: Magnificent
expression of seven apoptosis related genes.
|
Case 1 |
Case 2 |
Case 3 |
Age (year) |
64 |
67 |
70 |
PSA (ng/ml) |
8.2 |
6.5 |
10.1 |
cStage |
T2a |
T2a |
T2b |
pStage (TNM) |
T2N0M0 |
T2N0M0 |
T3N0M0 |
Gleason score |
4+3 |
3+4 |
4+4 |
Note: cStage: clinical stage; pStage: pathlogical stage
Table 1: Characteristics of prostate cancer patients.
|
Case(Ct) |
Con(Ct) |
Case(2^-ΔCt) |
Con(2^-ΔCt) |
P value |
Fold regulation |
BAX |
3.78 |
4.42 |
7.30E-02 |
4.70E-02 |
0.0424 |
1.55 |
BIK |
6.48 |
7.25 |
1.10E-03 |
6.60E-03 |
0.0103 |
1.7 |
BNIP3L |
4.34 |
4.82 |
4.90E-05 |
3.50E-02 |
0.0394 |
1.39 |
BRAF |
9.59 |
10.36 |
1.30E-03 |
7.60E-04 |
0.0448 |
1.71 |
CARD8 |
10.75 |
10.18 |
5.80E-04 |
8.60E-04 |
0.0472 |
-1.48 |
CD40 |
5.76 |
4.08 |
1.90E-02 |
5.90E-02 |
0.0116 |
-3.19 |
PYCARD |
4.58 |
3.45 |
4.20E-02 |
9.10E-02 |
0.0277 |
-2.19 |
Note: Fold regulation value>1 means up-regulation, value<0 means down-regulation
Table 2: Expression analysis of apoptosis related genes in prostate cancer.
3.
Karp
G (2013) Cell and molecular biology: Concepts and experiments. New Jersey: John
Wiley and Sons 2013: 659-661.
4.
Schneider P and Tschopp J (2000)
Apoptosis induced by death receptors. Pharm Acta Helv 74: 281-286.
6.
Wong RS (2011) Apoptosis
in cancer: from pathogenesis to treatment. J Exp Clin Cancer Res 30: 87.