Cell cycle and apoptosis regulatory protein (CARP)-1 expression in neuroblastoma.

Abstract

9578 Background: Neuroblastoma (NB) is the most common extra-cranial solid tumor in children. The prognosis for patients with high risk NB is still poor. Study of additional prognostic factors will enhance current understanding of the tumor biology and risk stratification. CARP-1 is a recently identified molecule mediating apoptosis signaling by agents like doxorubicin and etoposide. Since these agents are used in the front line treatment of NB, we tested whether CARP-1 expression could be another prognostic factor in NB. Methods: CARP-1 expression was examined by Western blot in a pair of NB cell lines, SK-N-SH and SK-N-SH Dox. We reviewed medical records of patients with NB at Children’s Hospital of Michigan from 2000-2009 and examined CARP-1 expression by immune-histochemistry in the archived, formalin fixed paraffin embedded NB tissues. CARP-1 expression was recorded as positive or negative. Correlation of CARP-1 expression and progression free survival (PFS) was calculated. Results: CARP-1 expression was detected in SK-N-SH but not SK-N-SH Dox, a doxorubicin-resistant derivative of SK-N-SH, suggesting that resistance to doxorubicin is associated with decreased level of CARP-1 expression in NB cells. Of the 30 cases studied, 53 % (16/30) expressed CARP-1. There was no significant difference in N-myc amplification status (13% vs.14%, p=0.3), or proportion of unfavorable Shimada histology (60% vs. 64%, p=0.5) between CARP-1 positive vs. negative groups. Twenty three percent (7/22) patients progressed or relapsed, including 2/16 (13%) in CARP-1 positive group vs. 5/14 (36%) in CARP-1 negative group (p=0.1). There was no significant difference in the PFS at 1 year (94% vs.79%, p=0.2) and 3 year (86% vs.71%, p=0.2) between CARP-1 positive vs. negative groups. Conclusions: CARP-1 expression was decreased in doxorubicin resistant NB cell line. CARP-1 expression was detected in approximately half (53%) of NB tumors. Patients with NB who expressed CARP-1 showed trend towards better 1- & 3-year PFS as compared to those who did not express CARP-1, however, the results are not statistically significant which could be due to the small sample size. Further study with a larger number of patients is warranted to clarify these findings.