Long non-coding RNA TILR constitutively represses TP53 and apoptosis in lung cancer.

Non-coding RNAs have an integral regulatory role in numerous functions related to lung cancer development. Here, we report identification of a novel lncRNA, termed TP53-inhibiting lncRNA (TILR), which was found to function as a constitutive negative regulator of p53 expression, including activation of downstream genes such as p21 and MDM2, and induction of apoptosis. A proteomic search for TILR-associated proteins revealed an association with PCBP2, while the mid-portion of TILR was found to be required for both PCBP2 and p53 mRNA binding. In addition, depletion of PCBP2 resulted in phenocopied effects of TILR silencing. TILR was also shown to suppress p53 expression in a post-transcriptional manner, as well as via a positive feedback loop involving p53 and Fanconi anemia pathway genes. Taken together, the present findings clearly demonstrate that TILR constitutively inhibits p53 expression in cooperation with PCBP2, thus maintaining p53 transcriptional activity at a level sufficiently low for avoidance of spurious apoptosis induction.

[A Case of Recurrent Breast Cancer That Was BRCA1 Pathogenic Variant-Positive Successfully Treated with PARP Inhibitor].

The patient was a 51-year-old woman at the time of diagnosis of left breast cancer. She underwent a mastectomy and axillary dissection. Pathological findings were invasive ductal carcinoma of the breast, tumor diameter 25 mm, and metastasis in 2 of 16 removed axillary lymph nodes. The subtype was triple negative. Postoperative chemotherapy was administered, and the patient was followed by follow-up imaging. At the age of 63 years, ultrasonography showed local recurrence, and local mass excision was performed. Genetic abnormalities were suspected since she had a family history of breast cancer, and it was a recurrent case. After genetic counseling, she underwent genetic testing, which revealed a BRCA1 pathogenic variant, so we initiated imaging surveillance. At age 65, a chest CT scan was performed due to respiratory symptoms, and she was diagnosed with multiple lung metastases. Respiratory symptoms improved at the examination 1 month after administration of Poly ADP ribose polymerase(PARP)inhibitor, and the metastatic masses shrank at the CT scan 3 months later. She continues to maintain CR and has no respiratory symptoms at present.

SIRT1 suppresses the senescence-associated secretory phenotype through epigenetic gene regulation.

Senescent cells develop a pro-inflammatory response termed the senescence-associated secretory phenotype (SASP). As many SASP components affect surrounding cells and alter their microenvironment, SASP may be a key phenomenon in linking cellular senesence with individual aging and age-related diseases. We herein demonstrated that the expression of Sirtuin1 (SIRT1) was decreased and the expression of SASP components was reciprocally increased during cellular senescence. The mRNAs and proteins of SASP components, such as IL-6 and IL-8, quickly accumulated in SIRT1-depleted cells, and the levels of these factors were also higher than those in control cells, indicating that SIRT1 negatively regulated the expression of SASP factors at the transcriptional level. SIRT1 bound to the promoter regions of IL-8 and IL-6, but dissociated from them during cellular senescence. The acetylation of Histone H3 (K9) and H4 (K16) of the IL-8 and IL-6 promoter regions gradually increased during cellular senescence. In SIRT1-depleted cells, the acetylation levels of these regions were already higher than those in control cells in the pre-senescent stage. Moreover, these acetylation levels in SIRT1-depleted cells were significantly higher than those in control cells during cellular senescence. These results suggest that SIRT1 repressed the expression of SASP factors through the deacetylation of histones in their promoter regions.