Expression and prognostic impact of alpha thalassemia/mental retardation X-linked and death domain-associated protein in human lung cancer

The Clinical Impact of Death Domain-Associated Protein and Holliday Junction Recognition Protein Expression in Cancer: Unmasking the Driving Forces of Neoplasia

Death domain-associated protein (DAXX) and Holliday junction recognition protein (HJURP) act as chaperones of H3 histone variants H3.3 and centromere protein A (CENPA), respectively, and are implicated in many physiological processes, including aging and epigenetic regulation, by controlling various genes' transcription and subsequently protein expression. Research has highlighted both these biomolecules as participants in key procedures of tumorigenesis, including cell proliferation, chromosome instability, and oncogene expression. As cancer continues to exert a heavy impact on patients' well-being and bears substantial socioeconomic ramifications, the discovery of novel biomarkers for timely disease detection, estimation of prognosis, and therapy monitoring remains of utmost importance. In the present review, we present data reported from studies investigating DAXX and HJURP expression, either on mRNA or protein level, in human tissue samples from various types of neoplasia. Of note, the expression of DAXX and HJURP has been associated with a multitude of clinicopathological parameters, including disease stage, tumor grade, patients' overall and disease-free survival, as well as lymphovascular invasion. The data reveal the tumor-promoting properties of DAXX and HJURP in a number of organs as well as their potential use as diagnostic biomarkers and underline the important association between aberrations in their expression and patients' prognosis, rendering them as possible targets of future, personalized and precise therapeutic interventions.

Regulation and Therapeutic Targeting of MTHFD2 and EZH2 in KRAS-Mutated Human Pulmonary Adenocarcinoma

Activating KRAS mutations occur in about 30% of pulmonary adenocarcinoma (AC) cases and the discovery of specific inhibitors of G12C-mutated KRAS has considerably improved the prognosis for a subgroup of about 14% of non-small cell lung cancer (NSCLC) patients. However, even in patients with a KRAS G12C mutation, the overall response rate only reaches about 40% and mutations other than G12C still cannot be targeted. Despite the fact that one-carbon metabolism (1CM) and epigenetic regulation are known to be dysregulated by aberrant KRAS activity, we still lack evidence that co-treatment with drugs that regulate these factors might ameliorate response rates and patient prognosis. In this study, we show a direct dependency of Methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) and Enhancer of Zeste Homolog 2 (EZH2) expression on mutationally activated KRAS and their prognostic relevance in KRAS-mutated AC. We show that aberrant KRAS activity generates a vulnerability of AC cancer cell lines to both MTHFD2 and EZH2 inhibitors. Importantly, co-inhibition of both factors was synergistically effective and comparable to KRASG12C inhibition alone, paving the way for their use in a therapeutic approach for NSCLC cancer patients.

One carbon metabolism in human lung cancer

Background

Lung cancer remains the major cause of cancer related death worldwide. The discovery of targeted therapies against activating mutations in genes like EGFR considerably improved the prognosis for a subgroup of patients but still leaves a large part without a targeted therapy. One carbon metabolism (1CM) has been investigated in several cancer entities and its increased activity has been linked to higher tumor aggressiveness and reduced prognosis. In spite of 1CM enzymes role and correlation to cancer cells progression, comprehensive analysis for the diagnostic and functional role of the complete 1CM enzymes in lung cancer has not been conducted so far.

Methods

We investigated the prognostic and functional relevance of five major 1CM factors (MTHFD2, PGDH3, SHMT2, MTHFD1 and TYMS) in the three major subclasses of lung cancer [pulmonary adenocarcinoma (AC), squamous cell lung cancer (SQCLC) and small cell lung cancer (SCLC)]. We analyzed 1CM enzymes expression and clinicopathological correlation in patient derived tissue samples of 103 AC, 183 SQCLC and 37 SCLC patients by immunohistochemistry. Furthermore, the effect of 1CM enzymes expression on lung cancer cell proliferation and the response to chemotherapy was investigated in 15 representative AC, SQCLC and SCLC cell lines.

Results

Expression of MTHFD2 and PGDH3 was significantly correlated to a worse overall survival only in AC patients. Cell proliferation assays resolved that all 1CM enzymes have a significant impact on cell growth in AC cell lines and are partially involved in cell proliferation in SQCLC and SCLC cell lines. In addition, expression of MTHFD2 correlated significantly with an increased pemetrexed chemoresistance.

Conclusions

Expression of MTHFD2 significantly reduces the prognosis of AC patients. Furthermore, MTHFD2 expression is crucial for survival of AC cell lines and its expression correlates with resistance against Pemetrexed. As MTHFD2 is almost not expressed in healthy adult tissue, we therefore suggest that the inhibition of MTHFD2 might be a potential therapeutic strategy to surround pemetrexed resistance in AC.

Alpha Thalassemia/Intellectual Disability X-Linked Deficiency Sensitizes Non-Small Cell Lung Cancer to Immune Checkpoint Inhibitors

Background

The immune checkpoint inhibitors (ICIs) have achieved great success in the treatment of non-small cell lung cancer (NSCLC) patients. However, the response rate is low. The molecular mechanism involved in the effectiveness of ICIs remains to be elucidated.

Methods

ATRX mutation incidence among human cancers was analyzed from TCGA database. Atrx-deficient Lewis lung cancer cell line (LLC-sgAtrx) was established via AAV-CRISPR. Subcutaneous and metastasis models were established by subcutaneous and intravenous injection of LLC-sgAtrx and LLC-sgNTC cells into female C57BL/6 mice. The mice were treated with anti-PD1, anti-CLTA4 or Rat IgG2a. Tumor volume was determined by Vernier calipers and the IVIS imaging system. The proportions of CD3+ T cells, CD45+ immune cells, and the expression of pMHC I and PDL1 were determined by flow cytometry. The T cell cytotoxicity was determined by co-culture experiment.

Results

TCGA data showed that Atrx is a tumor suppressor mutated at high frequency among various human cancers. The tumor volume of mice bearing LLC-sgAtrx was significantly shrinked and the median survival of mice was significantly longer after anti-PD1 and anti-CTLA4 treatment. Flowcytometry results showed that Atrx deficiency increase the penetration of CD3+ T cell into the tumor microenvironment and enhanced antigen presentation after IFNγ stimulation. Additionally, the tumor cells with Atrx deficiency were more easily to be damaged by T cells under IFNγ stimulation.

Conclusion

The present study demonstrated that Atrx deficiency sensitize lung cancer cells to ICIs by multiple mechanisms. And ATRX may serve as a promising biomarker for ICIs which helps patient stratification and decision making.