N-Cadherin Immunoexpression In Patients With Acute Myeloid Leukemia

N-cadherin is a member of the cadherin family which is involved in calcium ion dependent adhesion between cells by interaction with catenin on other cells. In our previous work, we have shown differential patterns of N-cadherin expression in acute myeloid leukemia (AML) cell lines when cultured in traditional 2-dimensional (2-D) culture conditions (over monolayer of stromal cells) compared to 3-D culture conditions.  In addition, we have observed that AML cell lines which are more resistant to chemotherapy in vitro had higher expression of N-cadherin, suggesting potential translational applications to patients with AML.  In order to further examine the role of N-cadherin in AML, we studied patterns of N-cadherin immunoexpression in bone marrow samples taken from patients with untreated AML and compared them to control bone marrow samples.

In this retrospective study, we evaluated bone marrow biopsy specimens of 10 AML patients for N-cadherin expression by immunohistochemistry. Bone marrow biopsy specimens from 10 negative staging lymphoma patients were used as control. Automated Cellular Imaging system (ACIS) was used to quantify and grade N-cadherin immunoexpression in the nucleus as well as in the cytoplasm of evaluated cells. ACIS uses advanced color detection software in order to evaluate N-cadherin positive cells and measure the intensity of staining. Grades of N-cadherin positivity were subclassified as grade 0 (no staining) 1+, 2+, 3+. 10 different areas of each sample were evaluated in order to estimate the median intensity of staining per slide. Student’s t-test was used to compare the generated medians and a P-value of <0.05 was considered statistically significant.

Nuclear N-cadherin staining was graded and compared between bone marrow biopsy specimens of patients with AML and control bone marrow biopsies from patients with negative staging bone marrow examinations for lymphoma.  Interestingly, the percentage of N-cadherin grade 0 (negative) cells was higher in controls than AML samples (54% vs. 37%, p=0. 01). Also, the percentage of grade 1 and grade 2 expressing cells was significantly higher in AML cases compared to controls (grade 1: 39% vs. 29%, p=0.005; grade 2: 21% vs. 13%, p=0.029).  However, there was no statistical difference seen in between AML cases and controls in terms of levels of grade 3 expression. Similarly, cytoplasmic N-cadherin staining was quantified. Grade 0 expressing cells were significantly higher in control samples compared to AML samples (34% vs. 16%, p=0.01). There was no statistical difference seen in terms of levels of grade 1 expression. However, grade 2 and 3 expression levels quantifying the higher levels of N-cadherin expression were significantly higher in bone marrow biopsies from patients with AML versus those from negative staging bone marrows (grade 2: 26% vs. 9%, P=0.01; grade 3:  4% vs. 1%, p=0.04).

Based on these results, we conclude that cytoplasmic N-cadherin expression is significantly increased in AML bone-marrow samples compared to control samples. These results should be further evaluated in the future to determine the prognostic significance of N-cadherin expression in AML.

No relevant conflicts of interest to declare.