Evaluation of FAM26F in cancer using immunohistochemistry

Abstract

Calcium (Ca2+) homeostasis is involved in various processes including in immune response and apoptosis. Changes in Ca2+ concentration stimulate various immune responses such as apoptosis through reactive oxygen species (ROS) production, especially in cancer. Calcium ion channels are involved in Ca2+ homeostasis and their expression may vary in cancer since calcium homeostasis and ROS production are reported to be interlinked. Tumor microenvironment studies have shown ROS to be involved in cancer promotion. International Agency for Research on Cancer (IARC) reported cancer fatalities to be 0.11 million in Pakistan hence showing their deadly nature. FAM26F (family with sequence similarity 26, member F) is one such calcium ion channel predicted to be differentially expressed in various cancers. Composed of a single domain Ca_hom_mod, FAM26F is involved in calcium regulation. Previously no attempt has been made to explore the expression of FAM26F in different types of various cancers, and its evolution. This leaves room for both, the investigation of the role of FAM26F in various tumors as well as its phylogenetic study to trace its evolution. The current study aims to answer the questions by 1) conducting immunohistochemical (IHC) analysis to observe the expression of FAM26F in different cancer samples, and 2) by employing a computational-based strategy to scan for the FAM26F domain events, integrating the data with a time-calibrated phylogenetic tree. 1) IHC on formalin fixed- paraffin embedded cancer biopsy samples displayed a varied expression of FAM26F depending on tissue type and cancer grade. A decrease in bladder and breast cancer was seen while an increase in FAM26F expression in renal, prostate, and gastric cancer was seen. 2) The evolutionary analysis identified around 4000 domains, and 14000 domain loss, duplication and loss events along with its Abstract xviii interacting partners. FAM26F evolution as well as the domain events of its interacting partners: Vinculin, Calpain, protein S100-A7, Thioredoxin, Peroxiredoxin and Calmodulin-like protein 5 were analyzed. Duplication events near higher eukaryotes showed its building complexity in function. Patterns of evolutionary events indicated possibility of co-evolution of CALHM6 with its interacting partner, advocating its role in calcium homeostasis and in related processes i.e cancer. Thus both IHC and the phylogenetic approach showed FAM26F to be differentially expressed in cancer