The C-Terminal Common to Group 3 POTE's Is a Nucleolar Marker Associated with Cellular Proliferation and Cancer Metastasis
Samantha Redfield, Zelda He, Jinghe Mao, Steven Bigler, Xinchun Zhou. The University of Mississippi Medical Center, Jackson; Tougaloo College, Jackson
Background: The POTEs, encoded by a recently discovered primate-specific gene family, have been reported to be expressed only in normal prostate, ovary, testis, and placenta and in few cancers. Their cellular locations and functions remain unclear. This study was to determine the distribution of POTEs in various benign and malignant tissues and the association with cellular proliferation.
Design: Tissue microarrays made from 204 paraffin blocks from 35 organs/tissues in 8 systems were used for the immunohistochemical (IHC) study of both the C- and N-termini common to group 3 POTEs and Ki-67 and for cytochemical study of argyrophilic nucleolar organizer regions (AgNOR). A combined score, calculated by multiplying area score and intensity score, was used for evaluation. All specimens were divided into 4 groups: normal (86), benign (26), malignant (70), and metastatic (22). Dual indirect fluorescent assay (IFA) was also used to demonstrate the co-localization of N- and C-termini common to groups 3 POTEs in RWPE1, DU-145, PC3, MDA-MB-231, and MCF-7 cells lines.
Results: IHC study showed that the C- and N-termini were separately localized in the nucleolus and cytoplasm, respectively. Both C- and N-termini were positive in 27 benign and 25 malignant tissues and constitutively expressed in benign tissues at low levels in 5 organ systems and at moderate levels in 3 organ systems including the reproductive system. Mean IHC score for the nucleolar C-terminus was significantly increased in malignant versus benign tissues (5.52 vs. 4.01, respectively; p=0.0021), which was similar to that of nuclear Ki-67 (p=<0.0001) in differentiating these two states. There were no significant differences in mean IHC scores for the cytoplasmic N-terminus (p=).20) and nucleolar AgNOR (p=0.81) between benign and malignant states. The C-terminus showed an ability to differentiate metastatic from primary tumors (p=0.0002), whereas, others showed no significant difference in mean IHC score between these two states. A co-localization of fluorescents for cytoplasmic N-terminus, nucleolar C-terminus and nuclear DAPI was also demonstrated by IFA in all 5 cultured cell lines.
Conclusions: This study demonstrated that the C- and N-termini common to the group 3 POTE molecules were separately localized in the nucleolus and in the cytoplasm in many benign and malignant tissues, which could be meaningful in the study of the POTE functions. The C-terminus expressed in nucleoli could be used as a proliferative marker for the progression and metastasis of cancers.
Wednesday, March 21, 2012 9:30 AM
Poster Session V # 260, Wednesday Morning