Aurora kinase A (AURKA) promotes the progression and imatinib resistance of advanced gastrointestinal stromal tumors

AURKA Activates FOXO3a to Form a Positive Feedback Loop in the Proliferation and Migration of Keloid Fibroblasts

Objective: Keloids are benign fibroproliferative disorders with invasive growth exceeding the wound boundary. Aurora kinase A (AURKA) is a serine/threonine kinase highly expressed in various tumors, facilitating tumor growth and invasion. Currently, the role of AURKA in keloid remains unclear. Approach: Fibroblasts were isolated from keloid and normal skin samples. AURKA was evaluated by qPCR, Western blot, and immunohistochemistry. Transcriptome sequencing and dual-luciferase reporter assays were applied to figure out targets of AURKA. Following expression alteration and MLN8237 (an AURKA kinase inhibitor, AKI) treatment, phenotypical experiments were conducted to clarify biological functions of AURKA along with its target, and to probe into the clinical potential of AURKA inhibition. Results: AURKA was upregulated in keloid tissues and fibroblasts. Forkhead box O 3a (FOXO3a) was verified as a downstream of AURKA. Further experiments demonstrated that AURKA transactivated FOXO3a by binding to FOXO3a, while FOXO3a directly transactivated AURKA. Functionally, AURKA and FOXO3a cooperated in enhancing the proliferation and migration of keloid fibroblasts via protein kinase B (AKT) phosphorylation. Although MLN8237 weakened the proliferation and migration in keloid fibroblasts, the transactivation of AURKA on FOXO3a was independent of kinase activity. Innovation: This study reveals that AURKA and FOXO3a compose a transactivation loop in enhancing the proliferative and migrative properties of keloid fibroblasts, and proposes AURKA as a promising target. Conclusion: AURKA/FOXO3a loop promotes the proliferation and migration of keloid fibroblasts via AKT signaling. Despite the anti-keloid effects of AKIs, AURKA acts as a transcription factor independently of kinase activity, deepening our understanding on AKI insensitivity.

The multifaceted landscape behind imatinib resistance in gastrointestinal stromal tumors (GISTs): A lesson from ripretinib

Gastrointestinal stromal tumors (GISTs) are rare mesenchymal sarcomas and the gold-standard treatment is represented by tyrosine kinase inhibitors (TKIs). Unfortunately, first-line treatment with the TKI imatinib usually promotes partial response or stable disease rather than a complete response, and resistance appears in most patients. Adaptive mechanisms are immediately relevant at the beginning of imatinib therapy, and they may represent the reason behind the low complete response rates observed in GISTs. Concurrently, resistant subclones can silently continue to grow or emerge de novo, becoming the most representative populations. Therefore, a slow evolution of the primary tumor gradually occurs during imatinib treatment, enriching heterogeneous imatinib resistant clonal subpopulations. The identification of secondary KIT/PDGFRA mutations in resistant GISTs prompted the development of novel multi-targeted TKIs, leading to the approval of sunitinib, regorafenib, and ripretinib. Although ripretinib has broad anti-KIT and -PDGFRA activity, it failed to overcome sunitinib as second-line treatment, suggesting that imatinib resistance is more multifaceted than initially thought. The present review summarizes several biological aspects suggesting that heterogeneous adaptive and resistance mechanisms can also be driven by KIT or PDGFRA downstream mediators, alternative kinases, as well as ncRNAs, which are not targeted by any TKI, including ripretinib. This may explain the modest effect observed with ripretinib and all anti-GIST agents in patients.

Advances in the research of the mechanism of secondary resistance to imatinib in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. At present, surgery is the first-line treatment for primary resectable GISTs; however, the recurrence rate is high. Imatinib mesylate (IM) is an effective first-line drug used for the treatment of unresectable or metastatic recurrent GISTs. More than 80% of patients with GISTs show significantly improved 5-year survival after treatment; however, approximately 50% of patients develop drug resistance after 2 years of IM treatment. Therefore, an in-depth research is urgently needed to reveal the mechanisms of secondary resistance to IM in patients with GISTs and to develop new therapeutic targets and regimens to improve their long-term prognoses. In this review, research on the mechanisms of secondary resistance to IM conducted in the last 5 years is discussed and summarized from the aspects of abnormal energy metabolism, gene mutations, non-coding RNA, and key proteins. Studies have shown that different drug-resistance mechanism networks are closely linked and interconnected. However, the influence of these drug-resistance mechanisms has not been compared. The combined inhibition of drug-resistance mechanisms with IM therapy and the combined inhibition of multiple drug-resistance mechanisms are expected to become new therapeutic options in the treatment of GISTs. In addition, implementing individualized therapies based on the identification of resistance mechanisms will provide new adjuvant treatment options for patients with IM-resistant GISTs, thereby delaying the progression of GISTs. Previous studies provide theoretical support for solving the problems of drug-resistance mechanisms. However, most studies on drug-resistance mechanisms are still in the research stage. Further clinical studies are needed to confirm the safety and efficacy of the inhibition of drug-resistance mechanisms as a potential therapeutic target.