Expression and prognostic significance of zinc fingers and homeoboxes family members in renal cell carcinoma

Abstract

Zinc fingers and homeoboxes (ZHX) is a transcription repressor family that contains three members; ZHX1, ZHX2, and ZHX3. Although ZHX family members have been associated with the progression of cancer, their values as prognostic factors in cancer patients have been poorly examined. Renal cell carcinoma (RCC) is a highly heterogeneous, aggressive cancer that responds variably to treatment. Thus, prognostic molecular markers are required to evaluate disease progression and to improve the survival. In clear cell RCC (ccRCC), ZHX1 and ZHX3 expression were found to be down-regulated but ZHX2 was up-regulated, and the expressions of ZHX1 and ZHX3 were significantly associated with pathological stage. Furthermore, Kaplan-Meier and multivariate regression analysis showed that reduction in the mRNA expression of ZHX1 was associated with poorer survival. Taken together, the present study shows loss of ZHX1 is correlated with ccRCC progression and suggests it is an independent prognostic marker in ccRCC.

Fig 1. Expressions of ZHX family members and their relationship with clinical stage in ccRCC.

(A) Relative expression levels of ZHX family members in ccRCC compared with those in normal tissues, are presented. Expression values of the three ZHX family members (ZHX1-3) in 70 to 72 tumor (ccRCC) tissues were divided by those of paired non-tumor tissues from the same TCGA cohort. (B) The expression levels of ZHX family members in non-tumor and tumor tissues (both paired and not-paired) are presented as a Box-whisker plot. Significances were calculated using the t-test or the Mann-Whitney U test (ZHX1: p < 0.001, ZHX2: p < 0.001, ZHX3: p < 0.001). (C) ZHX1 (stage I&II: n = 316, stage III&IV: n = 203), ZHX2 (stage I&II: n = 315, stage III&IV: n = 203), and ZHX3 (stage I&II: n = 312, stage III&IV: n = 203) expression levels according to ccRCC stage (stages I-II and III-IV) are represented as a Box-whisker plot. Significances of differences were determined using the t-test or the Mann-Whitney U test (ZHX1: p <0.001, ZHX2: p = 0.136, ZHX3: p <0.001).

Fig 2. Association between the expression levels of ZHX family members and overall survival.

Low expressions of ZHX 1 and 3 were associated with poorer overall survival. Overall survivals for ccRCC patients with low and high expression levels of ZHX family members were represented using Kaplan-Meier curves. Significances of differences were determined using the Log rank test. Left, middle or right three panels present Kaplan-Meier curves for all stages, early stage (I-II) or advanced stage (III-IV) patient group respectively. (A) ZHX1—All stages (low: n = 259, high: n = 260): p = 0.012*, stage I-II (low: n = 140, high: n = 176): p = 0.817, stage III-IV (low: n = 119, high: n = 84): p = 0.047* (B) ZHX2 –All stages (low: n = 259, high: n = 259): p = 0.539, stage I-II (low: n = 162, high: n = 153): p = 0.968, stage III-IV (low: n = 97, high: n = 106): p = 0.640 (C) ZHX3 –All stages (low: n = 257, high: n = 258): p = 0.005*, stage I-II (low: n = 134, high: n = 178): p = 0.049*, stage III-IV (low: n = 123, high: n = 80): 0.837. * p<0.05.

Fig 3. Kaplan-Meier plots of expressions of ZHX family members in subgroup of Hb level.

(A-C) Overall survivals for ccRCC patients in low level and normal and elevated level of Hb based on ZHX1-3 expression (ZHX1—low level of Hb (low: n = 134, high: n = 124): p = 0.408, normal and elevated level of Hb (low: n = 89, high: n = 96): p = 0.007; ZHX2—low level of Hb (low: n = 127, high: n = 131): p = 0.905, normal and elevated level of Hb (low: n = 103, high: n = 81): p = 0.251; ZHX3—low level of Hb (low: n = 128, high: n = 130): p = 0.390, normal and elevated level of Hb (low: n = 100, high: n = 83): p = 0.013). Hb: hemoglobin.