1. EMT inducing transcription factor SIP1: a predictive biomarker of colorectal cancer survival and recurrence?
A Patel, R Sreekumar, R Bhome, KA Moutasim, J Wigley, JN Primrose, E Sayan, A Mirnezami
Introduction
Colorectal carcinoma (CRC) is the second commonest cancers in the UK1. Metastases are the
main reason for CRC related mortality2. Currently, there are no biomarkers of occult CRC metastasis. Epithelial mesenchymal transition (EMT) is a phylogenically conserved trans-differentiation program known to drive cancer spread by inducing formation of highly invasive and motile cancer cells3,4. Identifying and targeting this pool of tumour cells is a major challenge in cancer research. SIP1 belongs to the Zhfx1 family of EMT-inducing transcription factors5. SIP1 expression and functional consequences are yet to be studied in the setting of CRC. Thus we investigated SIP1 expression CRC patients and highlight its potential as a prognostic biomarker.
FIGURE 1: Epithelial cells demonstrate increased motility and invasiveness when EMT is activated. Consequently these cells manifest a mesenchymal phenotype
Impact of SIP1 expression on patient survival as emulated by Kaplan Meier method FIGURE 3: Impact of SIP1 expression on patient survival as emulated by KM method. (A) Overall survival rate (log rank , p=0.001) (B) DFS rate (log rank , p=0.001) (C) CSS rate (log rank12.237, p=0.0001) (D) Local recurrence (log rank 9.132, p=0.03) (E) Distal recurrence (log rank , p=0.01)
Kaplan-Meier (survival analysis by log rank test, demonstrated SIP1 expression is associated with poor overall survival (log rank=10.525, P=0.001, Figure A), decreased DFS (log rank=17.968, P=0.001, Figure B) and CSS (log rank=12.237, P=0.0001, Figure C).
Early mortality in SIP1 expressing patients was due to disease recurrence after surgical intervention (Figure D and E).
Mean DFS was 51 months (95% CI: –58.438) in SIP1 positive patients, compared to 68 months (95% CI: –71.862) in SIP1 negative (log rank=10.525, P=0.001).
Mean CSS for SIP1 positive vs SIP1 negative patients was 55 (95% CI: –61.764) vs. 68 months (95% CI: –72.575) respectively (log rank=12.237, P=0.0001).
Independent prognostic marker for CSS and DFS
TABLE 2: Multivariate Analysis by Cox proportional hazard regression Model
SIP1 expression has been identified as am independent prognostic marker for both cohorts, predicting DFS and CSS
Nuclear SIP1 positivity is an independent prognostic biomarker for CSS and DFS in CRC. Stratifying CRC patients according to SIP1 expression may have profound translational effect on patient prognosis and management in future years. To facilitate progression of the role of SIP1 as a biomarker to a prospective study, and potentially randomised clinical trial in the future, external validation using an independent patient cohort is now required.
Lee J M et al. J Cell Biol 2006;172:
Methods
A prospective database of 228 patients undergoing surgical resection for CRC containing demographic, pathological and clinical outcomes was collated. Immunohistochemistry (IHC) was undertaken and scored by two independent pathologists. SIP1 positivity and its association with clinicopathological outcomes and survival were calculated using Chi-Squared and Kaplan–Meier methods respectively. Cox proportional hazard regression model was used to undertake multivariable analysis for Disease free (DFS) and Cancer specific survival (CSS).
Results
FIGURE 2: Differential SIP1 scoring – Present of nuclei SIP1 staining = positive. Absence of nuclei SIP1 staining = negative
46% (105/228) of our CRC cases were scored SIP1 positive by two independent pathologist.
Patient Clinicopathological Outcomes
TABLE 1: (Right) Clinicopathological correlation with SIP1 expression in CRC patients
To clarify the correlation between SIP1 expression and carcinogenesis of CRC, the clinicopathological variables between SIP1 expression patterns were compared.
Clinicopathological correlations by Pearson’s Chi2 and Fishers Exact Tests revealed positive expression of SIP1 statistically correlated with; >TNM stage (P=0.024) >Metastasis at diagnosis (P=0.023) >Lymph node involvement (P=0.015) >Tumour stage (P=0.036).
a= Pearsons Chi2 Test b= Fishers Exact Test
Characteristic
Risk Ratio
95% confidence interval
p- value
Cancer Specific Survival
SIP1 positive
3.193
0.002
Disease Free Survival
3.464
1.773 – 6.764
0.0001
Characteristic
Total no.
SIP1 low expression
SIP1 high expression
p- value
T Stage I
0.036 a II 60 37 23
III
158 72 83 IV  0
TNM Score 44 20 24
0.024 b
106 58 48 68 21
 Lymph Node Involvement
Absent
144 
83 
61 
0.015 a
Present 27 41 77
Metastasis at diagnosis
196
107 89
0.023 a 16 4 12
Tumour Size (mm)
<50
141 75 66
0.656a
 >50
 77
 37
 40
Conclusion and future work
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5. Kalluri R and Weinberg RA, The basics of Epithelial mesenchymal transition, Journal of Clinical Investigations, 2009;(119):