Modulation of host glutamine anabolism enhances the sensitivity of small cell lung cancer to chemotherapy

Strategies to Target Chemoradiotherapy Resistance in Small Cell Lung Cancer

Background: Small cell lung cancer (SCLC) is a lethal form of lung cancer with few treatment options and a high rate of relapse. While SCLC is initially sensitive to first-line DNA-damaging chemo- and radiotherapy, relapse disease is almost universally therapy-resistant. As a result, there has been interest in understanding the mechanisms of therapeutic resistance in this disease. Conclusions: Progress has been made in elucidating these mechanisms, particularly as they relate to the DNA damage response and SCLC differentiation and transformation, leading to many clinical trials investigating new therapies and combinations. Yet there remain many gaps in our understanding, such as the effect of epigenetics or the tumor microenvironment on treatment response, and no single mechanism has been found to be ubiquitous, suggesting a significant heterogeneity in the mechanisms of acquired resistance. Nevertheless, the advancement of techniques in the laboratory and the clinic will improve our ability to study this disease, especially in patient populations, and identify methods to surmount therapeutic resistance.

HIF-1α-HPRT1 axis promotes tumorigenesis and gefitinib resistance by enhancing purine metabolism in EGFR-mutant lung adenocarcinoma

BACKGROUND

The mutations of oncogenic epidermal growth factor receptor (EGFR) is an important cause of lung adenocarcinoma (LUAD) malignance. It has been knowm that metabolic reprogramming is an important hallmark of malignant tumors, and purine metabolism is a key metabolic pathway for tumor progression and drug resistance, but its relationship with the EGFR-mutant LUAD is unclear.

METHODS

Metabolic reprogramming was studied through capillary electrophoresis-time of flight mass spectrometry (CE-TOF/MS)-based metabolic profiling analysis. Cell proliferation in vitro was evaluated by EdU staining and cell cycle assay. Tumorigenicity in vivo was tested by subcutaneous tumor formation experiment in nude mice. The binding of hypoxia-inducible factor-1 alpha (HIF-1α) and hypoxanthine phosphoribosyltransferase 1 (HPRT1) was detected by DNA pull‑down assay and Chromatin immunoprecipitation (ChIP) assays. HIF-1α, HPRT1, DNA damage and cell apoptosis related genes were examined by western blot. In addition, RNA sequencing, mass spectrometry and bioinformatics analysis were performed.

RESULTS

We found that mutated EGFR (muEGFR) upregulates HPRT1 to promote purine metabolism and tumorigenesis of EGFR-mutant LUAD. Mechanistically, muEGFR increases HIF-1α expression through protein stability. Meanwhile, up-regulated HIF-1α bound to the promoter of HPRT1 and transcriptionally activates HPRT1 expression, enhancing purine metabolism to maintain rapid tumor cell proliferation in EGFR-mutant LUAD. Further, gefitinib inhibited the synthesis of purine nucleotides, and HPRT1 inhibition increased the sensitivity of gefitinib to EGFR-mutant LUAD.

CONCLUSIONS

Our study reveals that muEGFR-HIF-1α-HPRT1 axis plays a key role in EGFR-mutant LUAD and provides a new strategy-inhibiting purine metabolism for treating EGFR-mutant LUAD.

Glutamine Metabolism and Prostate Cancer

Glutamine (Gln) is a non-essential amino acid that is involved in the development and progression of several malignancies, including prostate cancer (PCa). While Gln is non-essential for non-malignant prostate epithelial cells, PCa cells become highly dependent on an exogenous source of Gln. The Gln metabolism in PCa is tightly controlled by well-described oncogenes such as MYC, AR, and mTOR. These oncogenes contribute to therapy resistance and progression to the aggressive castration-resistant PCa. Inhibition of Gln catabolism impedes PCa growth, survival, and tumor-initiating potential while sensitizing the cells to radiotherapy. Therefore, given its significant role in tumor growth, targeting Gln metabolism is a promising approach for developing new therapeutic strategies. Ongoing clinical trials evaluate the safety and efficacy of Gln catabolism inhibitors in combination with conventional and targeted therapies in patients with various solid tumors, including PCa. Further understanding of how PCa cells metabolically interact with their microenvironment will facilitate the clinical translation of Gln inhibitors and help improve therapeutic outcomes. This review focuses on the role of Gln in PCa progression and therapy resistance and provides insights into current clinical trials.

Actionable Driver Events in Small Cell Lung Cancer

Small cell lung cancer (SCLC) stands out as the most aggressive form of lung cancer, characterized by an extremely high proliferation rate and a very poor prognosis, with a 5-year survival rate that falls below 7%. Approximately two-thirds of patients receive their diagnosis when the disease has already reached a metastatic or extensive stage, leaving chemotherapy as the remaining first-line treatment option. Other than the recent advances in immunotherapy, which have shown moderate results, SCLC patients cannot yet benefit from any approved targeted therapy, meaning that this cancer remains treated as a uniform entity, disregarding intra- or inter-tumoral heterogeneity. Continuous efforts and technological improvements have enabled the identification of new potential targets that could be used to implement novel therapeutic strategies. In this review, we provide an overview of the most recent approaches for SCLC treatment, providing an extensive compilation of the targeted therapies that are currently under clinical evaluation and inhibitor molecules with promising results in vitro and in vivo.