MCM10 expression is linked to cervical cancer aggressiveness

Abstract

Cervical cancer screening is a challenge mainly in developing countries. In developed countries, both incidence and mortality rates have been decreasing due to well organized screening programs. One of the potential biomarkers being exploited are the minichromosome maintenance proteins (MCMs), which show both specificity and sensitivity. MCM2-7 are involved in DNA replication initiation and elongation, and the MCM subunits are highly expressed in malignant tissues. Unlike other MCMs, MCM10, which is not part of the core helicase complex, is a critical determinant of origin activation and its levels are limiting in cancer cells. In this study, we performed bioinformatic analysis on the expression profile of all DNA replication associated MCM proteins in cervical cancer. MCM10 showed a relatively higher expression profile compared to the other MCMs. The mRNA expression levels of the MCMs were significantly increased in tumour tissues compared to normal, and MCM10 showed a fold change of 3.4. In order to understand if MCM10 is associated with the aggressiveness of cervical cancer, we looked into the mRNA expression pattern of MCM10 in three cervical cancer cell lines and one normal cervical cell line. MCM10 expression was significantly higher in the case of the more aggressive cancer cell line HeLa compared to controls. MCM10, therefore, can serve as a prominent biomarker for cancer progression and thus aid in early detection to control the spread of cancer cells. Our results show that MCM10 expression levels in cervical cancer cell lines are associated with cancer aggressiveness, demonstrating its clinical significance.

Keywords: DNA replication; cancer aggressiveness; cervical cancer; immunocytochemistry; minichromosome maintenance protein 10; origin firing; qRT-PCR.

FIGURE 1

Differential expression of MCMs in cancer. (A) The expression of MCM2-10 in major cancers affecting women. The red dots represent the TPM value of each MCM in tumor tissues (T), while green dots represents the TPM value of each MCM in normal tissues (N). (B) Expression of MCMs in cervical cancer. The differential expression of MCM2-10 in cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC). The red dots represent the TPM value of each MCM in tumor tissues, while the green dots represent the TPM value of each MCM in normal tissues.

FIGURE 2

Analysis of MCM mutations in cervical cancer (A) The alteration frequencies of MCMs across cervical cancer studies as obtained from cBioPortal. Gene amplification denotes red bar, Mutation is represented as green bars, Structural variant as purple bars, Deep deletion is marked as blue bars, Multiple alteration as grey bars (B) Genetic Alterations: Amplification represented as red, deep deletion represented as blue, No alterations represented as grey.

FIGURE 3

Significant overexpression of MCM10 in cancer. (A) MCM10 expression in different cancers. Box and whisker plot based on GEPIA database, depicts the expression levels of MCM10 in CESC, BRCA, COAD, LUAD, OV, THCA and UCS. T: Tumor (Red), N: Normal (Grey). (B) Gene expression data of 319 samples available from the UCSC Xena database. The Y axis shows the RNAseq- RSEM norm_count Unit: log2 (norm_count+1) gene expression in cervical cancer for MCM2-7, MCM8, MCM9 and MCM10. By comparing the median of normal and tumor, the expression level of MCMs fold change was obtained. Blue box plot represents normal tissue whereas red box plot represents tumor tissues.

FIGURE 4

MCM10 expression in cervical cell lines (HCK1T, C33A, SiHa, and HeLa). (A) Immunofluorescence staining of DAPI (blue), MCM10 (red) and merged image (purple) shows the difference in the intensity of staining (Magnification ×40, Scale bars 50 m). (B) Quantification of immunofluorescence using ImageJ software. Error bar shows the standard deviation. (C) Relative mRNA expression of MCM10 in normal cervical epithelium cell line (HCK1T) and the human cervical cancer cell lines (C33A, SiHa, and HeLa). Error bar shows the standard deviation.