Optimal cumulative cisplatin dose during concurrent chemoradiotherapy among children and adolescents with locoregionally advanced nasopharyngeal carcinoma: A real-world data study

PURPOSE

To identify an optimal cumulative cisplatin dose along with concurrent chemoradiotherapy (CC-CCD) for children and adolescents with locoregionally advanced nasopharyngeal carcinoma (CALANPC) using real-world data.

MATERIALS AND METHODS

Using an NPC-specific database at our center, 157 patients younger than 19 years old with non-disseminated CALANPC and receiving neoadjuvant chemotherapy (NAC) plus cisplatin-based concurrent chemoradiotherapy (CCRT) were enrolled. Confounding factors were controlled by conducting propensity score matching analysis. Primary endpoints include disease-free survival (DFS) and distant metastasis-free survival (DMFS).

RESULTS

The optimal threshold for CC-CCD with respect to DFS was 160 mg/m² based on recursive partitioning analyses (RPA). Therefore, a uniform threshold of 160 mg/m² (≥160 vs. <160 mg/m²) was selected to classify patients between high and low CC-CCD groups for survival analysis. Patients receiving low CC-CCD showed a significant decrease in 5-year DFS (76.6% vs 91.3%; P = 0.006) and DMFS (81.3% vs 93.5%; P = 0.009) compared to those receiving high CC-CCD. Multivariate analyses indicated that high CC-CCD as an favorable prognostic influence for DFS (P = 0.007) and DMFS (P = 0.008). Further matched analysis identified 65 pairs in both high and low CC-CCD groups. In the matched cohort, high CC-CCD was still identified as a favorable factor for prognosis in DFS (HR, 0.23; 95% CI, 0.08-0.70; P = 0.010) and DMFS (HR, 0.23; 95% CI, 0.06-0.82; P = 0.023).

CONCLUSION

CC-CCD exerts significant treatment effects and 160 mg/m² CC-CCD may be adequate to provide antitumor effects for CALANPC receiving NAC plus CCRT.

Identification of an N6-methyladenosine-mediated positive feedback loop that promotes Epstein-Barr virus infection

N6-methyladenosine (m⁶A) is among the most abundant mRNA modifications, particularly in eukaryotes, and is found in mammals, plants, and even some viruses. Although essential for the regulation of many biological processes, the exact role of m⁶A modification in virus–host interaction remains largely unknown. Here, using m⁶A -immunoprecipitation and sequencing, we find that Epstein–Barr virus (EBV) infection decreases the m⁶A modification of transcriptional factor KLF4 mRNA and subsequently increases its protein level. Mechanistically, EBV immediate-early protein BZLF1 interacts with the promoter of m⁶A methyltransferase METTL3, inhibiting its expression. Subsequently, the decrease of METTL3 reduces the level of KLF4 mRNA m⁶A modification, preventing its decay by the m⁶A reader protein YTHDF2. As a result, KLF4 protein level is upregulated and, in turn, promotes EBV infection of nasopharyngeal epithelial cells. Thus, our results suggest the existence of a positive feedback loop formed between EBV and host molecules via cellular mRNA m⁶A levels, and this feedback loop acts to facilitate viral infection. This mechanism contains multiple potential targets for controlling viral infectious diseases.

N(6)-methyladenosine-binding protein YTHDF1 suppresses EBV replication and promotes EBV RNA decay

N⁶‐methyladenosine (m⁶A) modification of mRNA mediates diverse cellular and viral functions. Infection with Epstein–Barr virus (EBV) is causally associated with nasopharyngeal carcinoma (NPC), 10% of gastric carcinoma, and various B‐cell lymphomas, in which the viral latent and lytic phases both play vital roles. Here, we show that EBV transcripts exhibit differential m⁶A modification in human NPC biopsies, patient‐derived xenograft tissues, and cells at different EBV infection stages. m⁶A‐modified EBV transcripts are recognized and destabilized by the YTHDF1 protein, which leads to the m⁶A‐dependent suppression of EBV infection and replication. Mechanistically, YTHDF1 hastens viral RNA decapping and mediates RNA decay by recruiting RNA degradation complexes, including ZAP, DDX17, and DCP2, thereby post‐transcriptionally downregulating the expression of EBV genes. Taken together, our results reveal the critical roles of m⁶A modifications and their reader YTHDF1 in EBV replication. These findings contribute novel targets for the treatment of EBV‐associated cancers.

Nuclear ING2 expression is reduced in human cutaneous melanomas

Cutaneous malignant melanoma is a severe and sometimes life-threatening cancer. The molecular mechanism of melanomagenesis is incompletely understood. Deregulation of apoptosis is probably one of the key factors contributing to the progression of melanoma. The inhibitor of growth (ING) family proteins are candidate tumour suppressors which play important roles in apoptosis. Downregulated expression of ING proteins have been reported in several tumour types, including the loss of nuclear expression of p33ING1b in melanoma. As ING2 exhibits 58.9% homology with p33ING1b, we hypothesized that the aberrant expression of ING2 may be involved in melanomagenesis. Here, we used tissue microarray technology and immunohistochemistry to examine ING2 expression in human nevi and melanoma biopsies. Our data showed that nuclear ING2 expression was significantly reduced in radial growth phase (RGP), vertical growth phase (VGP), and metastatic melanomas compared with dysplastic nevi (P < 0.05). Our data also revealed that nuclear ING2 expression was not associated with patient's gender, age or tumour thickness, ulceration, American Joint Committee on Cancer (AJCC) stage, tumour subtype, location and 5-year survival (P > 0.05). Taken together, our results suggest that nuclear ING2 expression is significantly reduced in human melanomas and that reduced ING2 may be an important molecular event in the initiation of melanoma development.

Reduced Apaf-1 expression in human cutaneous melanomas

Malignant melanoma is a life-threatening skin cancer due to its highly metastatic character and resistance to radio- and chemotherapy. It is believed that the ability to evade apoptosis is the key mechanism for the rapid growth of cancer cells. However, the exact mechanism for failure in the apoptotic pathway in melanoma cells is unclear. p53, the most frequently mutated tumour suppressor gene in human cancers, is a key apoptosis inducer. However, p53 mutation is only found in 15–20% of melanoma biopsies. Recently, it was found that Apaf-1, a downstream target of p53, is inactivated in metastatic melanoma. Specifically, loss of heterozygosity (LOH) of the Apaf-1 gene was found in 40% of metastatic melanoma. To determine if loss of Apaf-1 expression is indeed involved in melanoma progression, we employed the tissue microarray technology and examined Apaf-1 expression in 70 human primary malignant melanoma biopsies by immunohistochemistry. Our data showed that Apaf-1 expression is significantly reduced in melanoma cells compared with normal nevi (χ²=6.02, P=0.014). Our results also revealed that loss of Apaf-1 was not associated with the tumour thickness, ulceration or subtype, patient's gender, age and 5-year survival. In addition, our in vitro apoptosis assay revealed that overexpression of Apaf-1 can sensitise melanoma cells to anticancer drug treatment. Taken together, our data indicate that Apaf-1 expression is significantly reduced in human melanoma and that Apaf-1 may serve as a therapeutic target in melanoma.