Correction: Inhibiting DNA methylation activates cancer testis antigens and expression of the antigen processing and presentation machinery in colon and ovarian cancer cells.

[This corrects the article DOI: 10.1371/journal.pone.0179501.]

Inhibiting DNA methylation activates cancer testis antigens and expression of the antigen processing and presentation machinery in colon and ovarian cancer cells

<div><p>Innovative therapies for solid tumors are urgently needed. Recently, therapies that harness the host immune system to fight cancer cells have successfully treated a subset of patients with solid tumors. These responses have been strong and durable but observed in subsets of patients. Work from our group and others has shown that epigenetic therapy, specifically inhibiting the silencing DNA methylation mark, activates immune signaling in tumor cells and can sensitize to immune therapy in murine models. Here we show that colon and ovarian cancer cell lines exhibit lower expression of transcripts involved in antigen processing and presentation to immune cells compared to normal tissues. In addition, treatment with clinically relevant low doses of DNMT inhibitors (that remove DNA methylation) increases expression of both antigen processing and presentation and Cancer Testis Antigens in these cell lines. We confirm that treatment with DNMT inhibitors upregulates expression of the antigen processing and presentation molecules B2M, CALR, CD58, PSMB8, PSMB9 at the RNA and protein level in a wider range of colon and ovarian cancer cell lines and treatment time points than had been described previously. In addition, we show that DNMTi treatment upregulates many Cancer Testis Antigens common to both colon and ovarian cancer. This increase of both antigens and antigen presentation by epigenetic therapy may be one mechanism to sensitize patients to immune therapies.</p></div

5-Azacytidine treatment leads to significant re-expression of genes involved in antigen processing and presentation.

<p>Colon cancer cell lines DLD-1, Lovo, HCT-116, Colo320, SW620, Colo201, and HT-29 were treated with 500 nM of 5-AC every 24 hours for 3 consecutive days and harvested at 10 days after the beginning of treatment. RNA was isolated and made into cDNA. qRT-PCR was performed on <i>B2M</i> (Fig 1A), <i>CALR</i> (Fig 1B), <i>CD58</i> (Fig 1C), <i>PSMB8</i> (Fig 1D), <i>PSMB9</i> (Fig 1E), <i>TAP1</i> (Fig 1F), and <i>TAPBP</i> (Fig 1G). Data is presented as log₂ fold change over mock (untreated cells). Significance is indicated on graphs (n.s. = not significant, * = p <0.05, ** = p < 0.005, *** = p < 0.001).</p

Colon cancer lines downregulate antigen processing and presentation molecules relative to normal colon.

<p>RNA was isolated from normal colon and colon cancer cell lines DLD-1, Lovo, HCT-116, Colo320, SW620, Colo201, and HT-29. cDNA was made and qRT-PCR was performed on <i>B2M</i> (Fig 2A), <i>CALR</i> (Fig 2B), <i>CD58</i> (Fig 2C), <i>PSMB8</i> (Fig 2D), <i>PSMB9</i> (Fig 2E), <i>TAP1</i> (Fig 2F), and <i>TAPBP</i> (Fig 2G). Data is presented as log₂ fold change compared to normal colon. Significance is indicated on graphs (n.s. = not significant, * = p <0.05, ** = p < 0.005, *** = p < 0.001).</p

AZA upregulates the MHC I antigen presenting complex on the surface of colon and ovarian cancer cells.

<p>Colon (Fig 4A and 4B) and ovarian (Fig 4C and 4D) cancer cells were treated with 500 nM 5-AC every day for three days and trypsinized 7 days after beginning treatment. Cells were stained with anti-MHC I and 7-AAD; representative plots of MHC I staining are shown for colon (Fig 4A) and ovarian (Fig 4C) cancer cells. Plots of MFI (median fluorescence intensity) for colon (Fig 4B) and ovarian (Fig 4D) cancer cells are shown as an average of three biological replicates. * = p <0.05.</p

Epigenetic silencing of neurofilament genes promotes an aggressive phenotype in breast cancer

Neurofilament heavy polypeptide (NEFH) has recently been identified as a candidate DNA hypermethylated gene within the functional breast cancer hypermethylome. NEFH exists in a complex with neurofilament medium polypeptide (NEFM) and neurofilament light polypeptide (NEFL) to form neurofilaments, which are structural components of the cytoskeleton in mature neurons. Recent studies reported the deregulation of these proteins in several malignancies, suggesting that neurofilaments may have a role in other cell types as well. Using a comprehensive approach, we studied the epigenetic inactivation of neurofilament genes in breast cancer and the functional significance of this event. We report that DNA methylation-associated silencing of NEFH, NEFL, and NEFM in breast cancer is frequent, cancer-specific, and correlates with clinical features of disease progression. DNA methylation-mediated inactivation of these genes occurs also in multiple other cancer histologies including pancreas, gastric, and colon. Restoration of NEFH function, the major subunit of the neurofilament complex, reduces proliferation and growth of breast cancer cells and arrests them in Go/G1 phase of the cell cycle along with a reduction in migration and invasion. These findings suggest that DNA methylation-mediated silencing of the neurofilament genes NEFH, NEFM, and NEFL are frequent events that may contribute to the progression of breast cancer and possibly other malignancies.SCOPUS: ar.jinfo:eu-repo/semantics/publishe