Lack of Ephrin Receptor A1 Is a Favorable Independent Prognostic Factor in Clear Cell Renal Cell Carcinoma

<div><p>The EPH receptor tyrosine kinases and their cell-bound ligands, the ephrins, have been shown to be associated with cancer development and progression. In this study, mRNA and protein expression of the receptors EPHA1 and EPHA2 as well as of their ligand EFNA1 and their prognostic relevance in clear cell renal cell carcinoma was evaluated. Gene expression was measured in 75 cryo-preserved primary tumors and matched non-malignant renal specimens by quantitative PCR. Protein expression was analyzed by immunohistochemistry on tissue microarrays comprising non-malignant, primary tumors and metastatic renal tissues of 241 patients. Gene and protein expression of all three factors was altered in tumor specimens with EPHA1 and EPHA2 being generally diminished in tumors compared to normal renal tissue, whereas EFNA1 was commonly elevated. A positive EPHA1 and EPHA2 protein staining as well as a low EFNA1 protein level were significantly linked to more aggressive tumor features, but only a positive EPHA1 immunoreactivity was significantly associated with poor survival. In subgroup analyses, EPHA1 and EPHA2 protein levels were significantly higher in metastatic than in primary lesions. Patients with EPHA1/EPHA2-positive tumors or with tumors with positive EPHA1 and low EFNA1 immunoreactivity had the shortest survival rates compared to the respective other combinations. In a multivariate model, EPHA1 was an independent prognostic marker for different survival endpoints. In conclusion, an impaired EPH-ephrin signaling could contribute to the pathogenesis and progression of clear cell renal cell carcinoma.</p></div

Differential protein expression of EPHA1, EPHA2 and EFNA1 in primary tumors and subgroups of metastases.

<p>The table beneath each image includes the number of patients and the median staining intensity for each group as well as the p values retrieved by the Mann–Whitney <i>U</i> test. P values highlighted in bold indicate statistically significant differences following corrections for multiple comparisons (n = 5 for each protein) by using the method of Benjamini and Hochberg.</p

Univariate Cox regression analyses for PFS, TSS and OS dependent on clinicopathological parameters and molecular markers.

<p>P values highlighted in bold indicate statistically significant prognostic markers following correction for multiple comparisons (n = 20) by using the method of Benjamini and Hochberg.</p><p>Abbreviations: CI: confidence interval; HR: hazard ratio; n.d.: not determined.</p

Representative images of immunohistochemically determined protein expression in non-malignant renal tissue (Tf) and ccRCC.

<p>The scale bar is 100 µm. Abbreviations: Tf: tumor-free normal kidney specimens.</p

Demographic and clinicopathological characteristics of patients included in the study.

1<p>When no clinical (N0) or pathological (pN0) lymph node metastases were noticed the lymph node status was considered as pN0/N0.</p>2<p>Patients with a time to progression of ≤3 months, distant metastases (M1) or unknown M stage at nephrectomy have been excluded from analysis of progression-free survival.</p

Kaplan-Meier analysis of PFS, TSS and OS of ccRCC patients dependent on protein expression.

<p>The table beneath each Kaplan-Meier curve includes the legend, the number of patients and events in each category as well as the respective median survival times, 5- and 10-year survival rates. P values were calculated by logrank test and then corrected for multiple comparisons (n = 29) by using the method of Benjamini and Hochberg. P values highlighted in bold indicate statistically significant differences. Abbreviations: cum.: cumulative; mo.: months; n.r.: not reached.</p

Kaplan-Meier analysis of PFS, TSS and OS of ccRCC patients dependent on pairwise-combined protein expression.

<p>The table beneath each Kaplan-Meier curve includes the legend, the number of patients and events in each category as well as the respective median survival times, 5- and 10-year survival rates. P values were calculated by logrank test and then corrected for multiple comparisons (n = 29) by using the method of Benjamini and Hochberg. P values highlighted in bold indicate statistically significant differences. Abbreviations: cum.: cumulative; mo.: months; neg.: negative; n.r.: not reached; pos.: positive.</p