FANCD2 depletion sensitizes cancer cells repopulation ability in vitro

Case report: Highly response to low-dose brachytherapy in recurrent retroperitoneal leiomyosarcoma with FANCD2 frameshift mutation: a unique case study

We report a case of recurrent retroperitoneal leiomyosarcoma in a male who achieved a rapid and robust but transient clinical response to low-dose iodine-125 brachytherapy. A FANCD2 frameshift mutation was detected by gene sequencing in the cancerous tissue.

Fanconi anemia complementation group D2 promotes sensitivity of endometrial cancer cells to chemotherapeutic agents by inhibiting the ferroptosis pathway

BACKGROUND

Resistance can develop during treatment of advanced endometrial cancer (EC), leading to unsatisfactory results. Fanconi anemia complementation group D2 (Fancd2) has been shown to be closely related to drug resistance in cancer cells. Therefore, this study was designed to explore the correlation of Fancd2 with EC resistance and the mechanism of Fancd2.

METHODS

Real-time quantitative PCR (RT-qPCR) was used to detect the expression of Fancd2 in EC tissues and cells. EC cells (Ishikawa) and paclitaxel-resistant EC cells (Ishikawa/TAX) were transfected to knock down Fancd2. In addition, the ferroptosis inhibitor Ferrostatin-1 was adopted to treat Ishikawa/TAX cells. The sensitivity of cancer cells to chemotherapeutic agents was observed via 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, and inhibitory concentration (IC)50 was calculated. Reactive oxygen species (ROS) levels were measured by flow cytometry, the activity of malondialdehyde (MDA) and the levels of glutathione (GSH) and Fe2+ in cells were detected by corresponding kits, and protein expression of solute farrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) was obtained through western blot.

RESULTS

Compared with the normal tissues and endometrial epithelial cells, Fancd2 expression was significantly increased in EC tissues and Ishikawa cells, respectively. After knock-down of Fancd2, Ishikawa cells showed significantly increased sensitivity to chemotherapeutic agents. Besides, compared with Ishikawa cells, the levels of ROS, the activity of MDA, and the levels of GSH and Fe2+ were significantly decreased in Ishikawa/TAX cells, while the expression levels of SLC7A11 and GPX4 were significantly increased. Knock-down of Fancd2 significantly increased the ferroptosis levels in Ishikawa/TAX cells, but this effect could be reversed by Ferrostatin-1.

CONCLUSION

Fancd2 increases drug resistance in EC cells by inhibiting the cellular ferroptosis pathway.

The Molecular Basis of Ubiquitin-Conjugating Enzymes (E2s) as a Potential Target for Cancer Therapy

Ubiquitin-conjugating enzymes (E2s) are one of the three enzymes required by the ubiquitin-proteasome pathway to connect activated ubiquitin to target proteins via ubiquitin ligases. E2s determine the connection type of the ubiquitin chains, and different types of ubiquitin chains regulate the stability and activity of substrate proteins. Thus, E2s participate in the regulation of a variety of biological processes. In recent years, the importance of E2s in human health and diseases has been particularly emphasized. Studies have shown that E2s are dysregulated in variety of cancers, thus it might be a potential therapeutic target. However, the molecular basis of E2s as a therapeutic target has not been described systematically. We reviewed this issue from the perspective of the special position and role of E2s in the ubiquitin-proteasome pathway, the structure of E2s and biological processes they are involved in. In addition, the inhibitors and microRNAs targeting E2s are also summarized. This article not only provides a direction for the development of effective drugs but also lays a foundation for further study on this enzyme in the future.

Expression and prognostic significance of Fanconi anemia group D2 protein and breast cancer type 1 susceptibility protein in familial and sporadic breast cancer

Fanconi anemia group D2 protein (FANCD2) and breast cancer type 1 susceptibility protein (BRCA1), within the FA/BRCA pathway, are involved in the regulation of DNA damage repair, which is associated with breast cancer (BC) progression. The present study aimed to investigate BRCA1 and FANCD2 expression in breast cancer, and to highlight the association with patient clinical characteristics and prognoses. The BRCA1 and FANCD2 proteins were detected by immunohistochemistry in 335 tissue samples obtained from patients with BC, including 141 patients with familial BC (FBC), 147 patients with sporadic breast cancer (SBC) and 47 patients with benign breast tumors. Western blotting was used to detect the FANCD2 ubiquitination level in 56 frozen specimens that were randomly selected from the SBC group. Protein expression of BRCA1 in the FBC group was positively associated with tumor size, lymphatic invasion, Tumor-Node-Metastasis (TNM) stage, estrogen receptor (ER) status and FANCD2 expression. Protein expression of FANCD2 in the SBC group was positively associated with tumor size, TNM stage, ER status and Ki-67 index. Survival analyses revealed that BRCA1 expression was associated with the decreased disease-free survival (DFS) rate of patients with FBC (versus no BRCA1 expression) and that FANCD2 was associated with decreased DFS of patients with SBC (versus no FANCD expression). Univariable and multivariable analyses demonstrated that BRCA1 expression may be an independent prognostic factor in the FBC group. In the SBC group, FANCD2 high expression and low ubiquitination levels were considered as independent prognostic factors. In conclusion, the present study suggested that BRCA1 and FANCD2 expression, and FANCD2 ubiquitination levels, may be considered of novel potential prognostic value in patients with BC.

Silencing of FANCD2 enhances the radiosensitivity of metastatic cervical lymph node-derived head and neck squamous cell carcinoma HSC-4 cells

Fanconi anemia complementation group D2 (FANCD2) is involved in the key steps of the Fanconi anemia (FA) pathway, which plays a role in the repair of DNA crosslink damage. However, the role of FANCD2 during radiotherapy for head and neck squamous cell carcinoma (HNSCC) is unclear. In this study, the HNSCC cell line HSC-4 was used. Western blotting was used to evaluate the expression of the FANCD2 in HSC-4 cells. We investigated the impact of FANCD2 on the radiosensitivity of HSC-4 cells in vitro and in vivo. TUNEL, western blotting and immunohistochemistry were used to analyze the apoptosis and proteins involved in apoptosis-related pathways after radiotherapy to investigate the relevant mechanism. The present study showed that shRNA interference could effectively and stably silence FANCD2 expression in HSC-4 cells. In vitro, the silencing of FANCD2 inhibited cell proliferation, decreased the survival rate, increased apoptosis and induced S phase arrest in HSC-4 cells after radiotherapy. In vivo, the silencing of FANCD2 could prolong the tumor-forming time and slow tumor growth. In addition, the tumor volume was significantly reduced, the weight was deceased, and the tumor inhibition rate was increased after radiotherapy. TUNEL showed that the silencing of FANCD2 significantly increased apoptosis in HSC-4 cells induced by radiotherapy. Both in vitro and in vivo esperiments revealed that the expression of the Bax and p-p38 proteins in HSC-4 cells, in which FANCD2 had been silenced, was increased after radiotherapy, whereas the expression of the p38 and Bcl2 proteins was decreased. Our results suggested that the silencing of FANCD2 enhanced the radiosensitivity of HSC-4 cells, and its mechanism involves the activation of the p38 MAPK signaling pathway and the regulation of the expression of Bax and Bcl2 proteins. This study provides a novel candidate target for HNSCC therapy.

Targeting cancer cells through antibiotics-induced mitochondrial dysfunction requires autophagy inhibition

A significant part of current research studies utilizes various cellular models which imply specific antibiotics-containing media as well as antibiotics used for clonal selection or promoter de/activation. With the great success of developing such tools, mitochondria, once originated from bacteria, can be effectively targeted by antibiotics. For that reason, some studies propose antibiotics-targeting of mitochondria as part of anticancer therapy. Here, we have focused on the effects of various classes of antibiotics on mitochondria in cancer and non-cancer cells and demonlow mitochondrial membrane potential, reduced ATP production, altered morphology and lowered respiration rate which altogether suggested mitochondrial dysfunction (MDF). This was in parallel with increased level of reactive oxygen species (ROS) and decreased activity of mitochondrial respiration complexes. However, both survival and repopulation capacity of cancer cells was not significantly affected by the antibiotics, perhaps due to a glycolytic shift or activated autophagy. In turn, simultaneous inhibition of autophagy and treatment with antibiotics largely reduced tumorigenic properties of cancer cells suggesting potential strategy for anticancer therapy.

Activation of the Fanconi anemia/BRCA pathway at low doses of ionization radiation

Fanconi anemia (FA) is a rare, clinically heterogeneous autosomal recessive or X-linked genetic disease characterized by chromosome fragility, congenital malformations and cancer susceptibility. FA patients are usually radiosensitive when exposed to radiotherapy but the role of the FA in response to ionizing radiation (IR) is controversial. Here we have investigated IR-induced activation of the FA pathway by systematically analyzing monoubiquitination of the central protein FANCD2 and subsequent recruitment to stalled replication forks in primary fibroblasts. We developed an immunolabelling method to simultaneously visualize IR-induced FANCD2 and γH2AX foci in S-phase. We observed FANCD2 foci formation in a subset of IR-induced γH2AX foci in S-phase cells. This was observed at doses of IR ranging from 0.1 to 5.0Gy in a dose dependent non-threshold fashion. Our results indicate that minimum doses of IR can produce replication fork stalling and FA pathway activation during S-phase in primary cells.

Expression of FANCD2 in sporadic breast cancer and clinicopathological analysis

FANCD2 is involved in DNA damage repair and maintenance of chromosome stability. The purpose of this study was to investigate the expression of FANCD2 in sporadic breast cancer tissues and its association with clinicopathological features. A total of 162 Chinese women with invasive breast carcinoma who had no family history in first-degree relatives and 12 normal breast tissues were examined. The expression of FANCD2 was detected by immunohistochemical staining based on a tissue microarray technique. SAS system was used to analyze the data. Twenty-one out of the 162 invasive breast cancers (13%) were negative for FANCD2. The mean percentage of FANCD2 positive cells was significantly lower in breast cancers than in controls (P<0.05). FANCD2 expression was significantly inversely associated with histological grade and TNM stage (P<0.05), but not with axillary lymph node status or other conventional prognostic markers such as ER, PR, Her-2 and PCNA (P>0.05). It was suggested that FANCD2 may play a critical role in breast carcinogenesis. It may become a valuable and independent marker for identifying women with sporadic breast cancer and evaluating the prognosis.

Significance of the Fanconi anemia FANCD2 protein in sporadic and metastatic human breast cancer

FANCD2, a pivotal protein in the Fanconi anemia and BRCA pathway/network, is monoubiquitylated in the nucleus in response to DNA damage. This study examines the subcellular location and relationship with prognostic factors and patient survival of FANCD2 in breast cancer. Antibodies to FANCD2 were used to immunocytochemically stain 16 benign and 20 malignant breast specimens as well as 314 primary breast carcinomas to assess its association with subcellular compartment and prognostic factors using Fisher's Exact test or with patient survival over 20 years using Wilcoxon-Gehan statistics. Immunoreactive FANCD2 was found in the nucleus and cytoplasm of all 16 benign tissues, but nuclear staining was lost from a significant 19/20 malignant carcinomas (P < 0.0001). Antibodies to FANCD2 stained the cytoplasm of 196 primary carcinomas, leaving 118 as negatively stained. Negative cytoplasmic staining was significantly associated with positive staining for the metastasis-inducing proteins S100A4, S100P, osteopontin, and AGR2 (P < or = 0.002). Survival of patients with FANCD2-negative carcinomas was significantly worse (P < 0.0001) than those with positively stained carcinomas, and only 4% were alive at the census date. Multivariate regression analysis identified negative staining for cytoplasmic FANCD2 as the most significant indicator of patient death (P = 0.001). Thus FANCD2's cytoplasmic loss in the primary carcinomas may allow the selection of cells overexpressing proteins that can induce metastases before surgery.