Assessment of the radiation sensitivity of cervical cancer cell lines

In vitro study of radiosensitivity in colorectal cancer cell lines associated with Lynch syndrome

Introduction

Lynch syndrome patients have an inherited predisposition to cancer due to a deficiency in DNA mismatch repair (MMR) genes which could lead to a higher risk of developing cancer if exposed to ionizing radiation. This pilot study aims to reveal the association between MMR deficiency and radiosensitivity at both a CT relevant low dose (20 mGy) and a therapeutic higher dose (2 Gy).

Methods

Human colorectal cancer cell lines with (dMMR) or without MMR deficiency (pMMR) were analyzed before and after exposure to radiation using cellular and cytogenetic analyses i.e., clonogenic assay to determine cell reproductive death; sister chromatid exchange (SCE) assay to detect the exchange of DNA between sister chromatids; γH2AX assay to analyze DNA damage repair; and apoptosis analysis to compare cell death response. The advantages and limitations of these assays were assessed in vitro, and their applicability and feasibility investigated for their potential to be used for further studies using clinical samples.

Results

Results from the clonogenic assay indicated that the pMMR cell line (HT29) was significantly more radio-resistant than the dMMR cell lines (HCT116, SW48, and LoVo) after 2 Gy X-irradiation. Both cell type and radiation dose had a significant effect on the yield of SCEs/chromosome. When the yield of SCEs/chromosome for the irradiated samples (2 Gy) was normalized against the controls, no significant difference was observed between the cell lines. For the γH2AX assay, 0, 20 mGy and 2 Gy were examined at post-exposure time points of 30 min (min), 4 and 24 h (h). Statistical analysis revealed that HT29 was only significantly more radio-resistant than the MLH1-deficient cells lines, but not the MSH2-deficient cell line. Apoptosis analysis (4 Gy) revealed that HT29 was significantly more radio-resistant than HCT116 albeit with very few apoptotic cells observed.

Discussion

Overall, this study showed radio-resistance of the MMR proficient cell line in some assays, but not in the others. All methods used within this study have been validated; however, due to the limitations associated with cancer cell lines, the next step will be to use these assays in clinical samples in an effort to understand the biological and mechanistic effects of radiation in Lynch patients as well as the health implications.

Regulatory effects of COL1A1 on apoptosis induced by radiation in cervical cancer cells

Background

Cervical cancer is a common cancer of women in developing countries, and radiotherapy still remains its predominant therapeutic treatment. Collagen type I alpha 1 (COL1A1) has been shown to have a radioresistance effect in previous studies. However, such effect of COL1A1 has not yet been revealed in cervical cancer.

Methods

Expression of COL1A1 in cervical cancer tissues and normal tissues was assessed by qRT-PCR and immunohistochemistry. The effect of COL1A1 on radioresistance of human cervical cancer cell lines HeLa and CaSki was assessed using the colony formation assay. Apoptosis alterations were analyzed by flow cytometry. In addition, western blotting was used assessed the alterations of several critical apoptosis and signaling pathway related proteins.

Results

The expression of COL1A1 was significantly increased in cervical cancer tissues compared with normal tissues at the mRNA and protein level. Further, based on COL1A1 knock down and COL1A1 activation cell models, a negative correlation was observed between COL1A1 expression level and radiosensitivity. Moreover, the findings are further supported by apoptosis analysis that COL1A1 activation could inhibit the apoptosis of cervical cancer cells. Subsequently, a significantly decreased expression of p-AKT and Bcl-2, increased expression of Caspase-3 were observed in the LY294002 plus radiation group compared with radiation alone group, while these influences caused by LY294002 or X-ray radiation were reversed after COL1A1 activation.

Conclusions

To our knowledge, this is the only study to profile the mechanisms that COL1A1 plays a crucial role in cervical cells anti-apoptosis induced by radiation. Therefore, our identification of radioresistance-related COL1A1 in cervical cancer could be a starting point to explore the function of collagens, adding a new dimension to our understanding of the cervical cancer, assisting cancer biologists and clinical oncologists in novel therapeutic strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12935-017-0443-5) contains supplementary material, which is available to authorized users.