Factor XIIIA variants ³⁴Leu and ⁶⁵⁰Ile demonstrate functional differences for ECM proteins


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Elmena Elfaki1,Aruna Asipu1,Timothy J. Perren2,Alexander F. Markham1,Rashida Anwar1
1University of Leeds,2University of Leeds / Leeds Teaching Hospitals Trust

Abstract

Background

We previously presented data showing Factor XIIIA (FXIIIA) variant 650Ile is associated with shorter overall survival (OS) in epithelial ovarian cancer patients (p=0.008) while FXIIIA 34Leu is associated with improved OS (p=0.0219). Others have reported the 34Leu variant to be associated with improved OS in colorectal and oral cancers. We, therefore, examined the functional capability of these two variants on the ECM proteins fibrinogen, fibronectin, vitronectin and collagen.

Method

FXIIIA protein was expressed in Saccharomyces Cerevisiae. FXIIIA activity was examined using each selected protein and pentylamine-biotin cross-linking assay. FXIIIA antigen was analysed using a sandwich ELISA.

Results

A higher level of activity is seen for both 34Leu and 650Ile variants compared to the Wild Type (WT) on all four proteins examined. 34Leu shows higher activity than 650Ile on all proteins except collagen. For all three FXIIIA variants tested, the highest level of cross-linking is found in Fibronectin, followed by Fibrinogen, vitronectin and finally collagen. Interestingly, when activity is analysed relative to the WT for the four proteins tested 34Leu presents the highest activity on fibronectin (x4.8 higher than WT, range x3.3-x4.8) whereas 650Ile presents the lowest activity on fibronectin (x1.9 higher than WT, range x1.9-x3.4). The opposite is observed for collagen although both 34Leu and 650Ile variants have similar activity on this protein compared to the WT.

FXIIIA Variant

FXIIIA activity (IU/1unit of FXIIIA protein)

Fibrinogen

Fibronectin

Vitronectin

Collagen

34Val_650Val

1.00

(1.00)

2.19

(1.00)

0.62

(1.00)

0.29

(1.00)

34Leu

3.94

(3.94)

10.50

(4.81)

2.25

(3.65)

0.96

(3.29)

650Ile

2.78

(2.78)

4.10

(1.88)

1.48

(2.41)

0.99

(3.40)

             34Val_650Val = Wild Type FXIIIA. Data in parenthesis is FXIIIA activity relative to the WT.

Conclusion

The functional differences observed between the FXIIIA variants for proteins found in the tumour microenvironment could be important in tumour development and warrant further investigation.