High expression of Sam68 in sacral chordomas is associated with worse clinical outcomes

Abstract

Src-associated in mitosis of 68 kDa (Sam68), also known as KHDRBS1 (KH domain-containing, RNA-binding, signal transduction-associated 1), is a member of the signal transduction and activation of RNA family. Previous studies have demonstrated that the aberrant expression of Sam68 is associated with the progression and prognosis of a variety of cancers, but little is known about its expression and role in chordomas, which are rare and aggressive bone neoplasms. In this study, we analyzed 40 tumor tissues and 20 distant normal tissues obtained from 40 patients with sacral chordoma using immunohistochemistry, and observed the expression of Sam68 was significantly upregulated in sacral chordomas compared with normal tissues (P=0.001). A positive correlation between the expression of Sam68 and the cell proliferation index Ki-67 was determined using Spearman's rank correlation test (γ =0.599, P<0.001). In addition, high expression of Sam68 was significantly associated with surrounding muscle invasion (P<0.001). Moreover, Kaplan-Meier curves showed that patients with overexpressed Sam68 had shorter local recurrence-free survival time (P<0.001). Lastly, multivariate analysis indicated that Sam68 is an independent prognostic factor for the local recurrence-free survival of sacral chordomas (hazard ratio =5.929, 95% CI: 1.092-32.188, P=0.039). Our findings suggest the use of Sam68 as a predictor for the recurrence of sacral chordomas.

Keywords: Sam68; prognostic factor; recurrence; sacral chordoma.

Figure 1

Representative expression of Sam68 and Ki-67 and their correlation in sacral chordomas. Notes: (A) Low expression of Sam68; (B) low expression of Ki-67; (C) high expression of Sam68; (D) high expression of Ki-67; (E) negative control. All magnification, ×400. (F) Positive correlation between Sam68 expression and Ki-67 index in sacral chordomas using Spearman’s rank correlation test.

Figure 2

Kaplan–Meier curves of the local recurrence-free survival of patients with sacral chordoma. Notes: (A) Stratified by Sam68 expression; (B) stratified by Ki-67 index; (C) stratified by Sam68/Ki-67 coexpression (low/low and others); (D) stratified by Sam68/Ki-67 coexpression (high/high and others); (E) stratified by tumor stage; (F) stratified by surrounding muscle invasion; (G) stratified by the type of tumor resection. Abbreviations: EA, Enneking appropriate; EI, Enneking inappropriate.

Figure 2

Kaplan–Meier curves of the local recurrence-free survival of patients with sacral chordoma. Notes: (A) Stratified by Sam68 expression; (B) stratified by Ki-67 index; (C) stratified by Sam68/Ki-67 coexpression (low/low and others); (D) stratified by Sam68/Ki-67 coexpression (high/high and others); (E) stratified by tumor stage; (F) stratified by surrounding muscle invasion; (G) stratified by the type of tumor resection. Abbreviations: EA, Enneking appropriate; EI, Enneking inappropriate.

Figure 3

Kaplan–Meier curves of the overall survival of patients with sacral chordoma. Notes: (A) Stratified by tumor stage; (B) stratified by surrounding muscle invasion; (C) stratified by the type of tumor resection. Abbreviations: EA, Enneking appropriate; EI, Enneking inappropriate.