MLH1-mediated recruitment of FAN1 to chromatin for the induction of apoptosis triggered by O6-methylguanine

O6 -Methylguanines (O6 -meG), which are produced in DNA by the action of alkylating agents, are mutagenic and cytotoxic, and induce apoptosis in a mismatch repair (MMR) protein-dependent manner. To understand the molecular mechanism of O6 -meG-induced apoptosis, we performed functional analyses of FANCD2 and FANCI-associated nuclease 1 (FAN1), which was identified as an interacting partner of MLH1. Immunoprecipitation analyses showed that FAN1 interacted with both MLH1 and MSH2 after treatment with N-methyl-N-nitrosourea (MNU), indicating the formation of a FAN1-MMR complex. In comparison with control cells, FAN1-knockdown cells were more resistant to MNU, and the appearances of a sub-G1 population and caspase-9 activation were suppressed. FAN1 formed nuclear foci in an MLH1-dependent manner after MNU treatment, and some were colocalized with both MLH1 foci and single-stranded DNA (ssDNA) created at damaged sites. Under the same condition, FANCD2 also formed nuclear foci, although it was dispensable for the formation of FAN1 foci and ssDNA. MNU-induced formation of ssDNA was dramatically suppressed in FAN1-knockdown cells. We therefore propose that FAN1 is loaded on chromatin through the interaction with MLH1 and produces ssDNA by its exonuclease activity, which contributes to the activation of the DNA damage response followed by the induction of apoptosis triggered by O6 -meG.福岡歯科大

Signet Ring Cell Carcinoma of Unknown Primary Complicated with Pulmonary Tumor Thrombotic Microangiopathy and Krukenberg Tumor

Pulmonary tumor thrombotic microangiopathy (PTTM) is a rare disease that shows hypoxia with severe pulmonary hypertension related to malignant tumor. Diagnosis is difficult due to rapid clinical progression and the need to demonstrate pathological findings from lung biopsy. A 64-year-old woman visited our hospital with hypoxia and pulmonary hypertension. Diffuse granular shadows in the centrilobular area and ground-glass shadows in both lungs and left ovarian tumor were found on radiological imaging. PTTM was suspected, but pulmonary artery blood aspiration by right cardiac catheter failed to detect cancer cells. We could not obtain lung or ovary biopsies because of hypoxia or pulmonary hypertension. The patient died due to respiratory failure. Signet ring cell carcinoma of unknown primary, PTTM, and Krukenberg tumor were diagnosed on autopsy. Since early diagnosis facilitates adequate treatment, physicians should not miss the opportunity for biopsy in cases of suspected PTTM

Transforming growth factor-beta and sonic hedgehog signaling in palatal epithelium regulate tenascin-C expression in palatal mesenchyme during soft palate development.

福岡歯科大学2020年

CO2 laser therapy accelerates the healing of ulcers in the oral mucosa by inducing the expressions of heat shock protein-70 and tenascin C

The treatment of ulceration or stomatitis with laser therapy is known to accelerate healing and relieve pain, but the underlying biological mechanism is not fully understood. The present study used a mouse model of ulceration to investigate the molecular mechanisms by which CO2 laser therapy accelerated the wound healing process. An ulcer was experimentally created in the palatal mucosa of the mouse and irradiated with light from a CO2 laser. Compared with controls (no irradiation), laser irradiation induced the proliferation of epithelial cells and faster re-epithelialization of the wound area. Immunohistochemistry experiments showed that heat shock protein-70 (HSP70) was expressed mainly in the epithelium of normal palatal tissue, whereas there was little tenascin C (TnC) expression in the epithelium and mesenchyme under normal conditions. Laser irradiation induced HSP70 mRNA and protein expression in the lamina propria as well as TnC expression in the mesenchyme underlying the renewing epithelium. Epithelial cells and fibroblasts were exposed to heated culture medium or laser irradiation to establish whether hyperthermia mimicked the effect of laser irradiation. Culture of fibroblasts in heated medium increased the expressions of both TnC and TGF-β1, whereas laser irradiation induced only TnC expression. The present study indicates that CO2 laser irradiation exerts a photobiogenic effect to up-regulate TnC expression without inducing TGF-β1 expression. We suggest that CO2 laser therapy has an advantage over thermal stimulation