Identifying New Therapeutic Targets for Endometrial Cancer Treatment

The Female Reproductive System and Cancer

The female reproductive system is composed of the reproductive tract, which includes the ovaries, fallopian tubes, uterus, vagina, vulva, and the mammary glands, which are important secondary reproductive organs. The functional maintenance of the female reproductive system organs is controlled by the interplay of pituitary and ovarian hormones like estrogen and progesterone.

By far the most common disease affecting the female reproductive system is endometrial carcinoma (EC), also called uterine cancer. The American Cancer Society estimates there will be over 65,000 new cases of cancer of the uterus in the United States in 2020. EC originates in the layer of cells that form the lining (endometrium) of the uterus where an embryo implantation and placenta development occurs.

Check out the LIfeline® catalog for cell types from the female reproductive system:

• Uterine Smooth Muscle Cells
• Fallopian Tube Epithelial Cells
• Vaginal Epithelial Cells
• Endometrial (Uterine) Epithelial Cells
• Uterine Fibroblasts
• Cervical Epithelial Cells
• Normal Human Mammary Epithelial Cells – Female

Having normal cell type controls is integral for oncological studies so that changes in the genomic and proteomic expression profiles in cancer cells can be qualified. A previous blog detailed the use of Lifeline’s Normal Human Endometrial (Uterine) Epithelial Cells (HEuECs) as normal controls for EC research. Here, we look at a new publication from April 2020 by Liu and Colleagues, who sought to understand the role of circular RNA in EC disease progression, which also utilized HEuECs cultured in ReproLife™ Media as control cells in comparison studies.

The Function of Circular RNA in Endometrial Carcinoma Pathogenesis

Research indicates that non-coding RNAs, which can be divided into circular non-coding RNAs (circRNAs) and linear ncRNAs, have important roles in biological processes like cellular differentiation, tissue homeostasis, and in the development of cancer and other diseases. Next-generation sequencing of circular RNA (circRNA) revealed differential expression of circRNA between cancers and normal tissues indicating that these circRNAs could be used as biomarkers or molecular targets for cancer diagnosis and treatment.

Recent studies with genome-wide sequencing determined that hsa_circ_0001610, a circular RNA derived from tumor necrosis factor receptor superfamily member 21 (TNFRSF21), was highly upregulated in grade 3 EC compared to adjacent non-cancerous endometrial tissue. TNFRSF21 is involved in activation of cell apoptosis pathways. The authors sought to study the role of circTNFRSF21 in EC pathogenesis using Lifeline’s HEuECs as normal in vitro control cells in comparison studies with 4 EC cell lines (HEC1-A, HEC1-B, AN3CA, and Ishikawa).

The two main mechanisms by which circular RNAs can affect tissue homeostasis is through competition with its own pre-mRNA splicing, which alters mRNA production and functions as a sponge for microRNA (miRNA) by binding to and affecting miRNA-targeted gene expression.

siRNA knockdown of circTNFRSF21 in EC cell lines showed upregulation of TNFRSF21 mRNA and protein expression, confirming its ability to modulate the function of its own mRNA. Additionally, the researchers were able to link the high expression circTNFRSF21 in EC cells to rapid proliferation and in vivo tumor formation. Taken together, high expression of circTNFRSF21 in EC cells not only inhibits cell apoptosis pathways regulated by TNFRSF21 but also promotes rapid cell growth, which culminates in EC tumor formation and disease progression.

Next, Lui and Colleagues looked at the effect of circTNFRSF21 as a sponge for miRNAs. Bioinformatics analysis revealed miR-1227 as a potential target of circTNFRSF21-miRNA. Knockdown and overexpression assays showed that circTNFRSF21 could bind to and inhibit miR-1227 activity. Commonly, miRNAs impair mRNA stability, which in turn affects protein synthesis. As was the case here, miR-1227 binds to MAPK13 inhibiting its expression and subsequent ATF2 activation. The MAPK13/ATF2 pathway is implicated in EC cell proliferation as evidenced by CRISPR/Cas9 knockdown experiments.

In effect, the presence of circTNFRSF21 blocked the activity of miR-1227 and almost completely restored both MAPK13 expression and ATF2 activity impaired by miR-1227, resulting in EC cell growth and proliferation. This new evidence implicates the circTNFRSF21-miR1227- MAPK13/ATF2 pathway in EC disease progression and thus, the researchers are hopeful that these molecules could be new therapeutic targets for late-stage EC treatment.

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