Identification of Wee1 as a target in combination with avapritinib for gastrointestinal stromal tumor treatment

Mapping the Protein Kinome: Current Strategy and Future Direction

The kinome includes over 500 different protein kinases, which form an integrated kinase network that regulates cellular phosphorylation signals. The kinome plays a central role in almost every cellular process and has strong linkages with many diseases. Thus, the evaluation of the cellular kinome in the physiological environment is essential to understand biological processes, disease development, and to target therapy. Currently, a number of strategies for kinome analysis have been developed, which are based on monitoring the phosphorylation of kinases or substrates. They have enabled researchers to tackle increasingly complex biological problems and pathological processes, and have promoted the development of kinase inhibitors. Additionally, with the increasing interest in how kinases participate in biological processes at spatial scales, it has become urgent to develop tools to estimate spatial kinome activity. With multidisciplinary efforts, a growing number of novel approaches have the potential to be applied to spatial kinome analysis. In this paper, we review the widely used methods used for kinome analysis and the challenges encountered in their applications. Meanwhile, potential approaches that may be of benefit to spatial kinome study are explored.

p53 as a biomarker and potential target in gastrointestinal stromal tumors

KIT and PDGFRA play a major role in the oncogenic process in gastrointestinal stroma tumors (GIST) and small molecules have been employed with great success to target the KIT and PDGFRA pathways in this cancer. However, approximately 10% of patients with GIST are resistant to current targeted drug therapy. There is a need to explore other potential targets. Although p53 alterations frequently occur in most cancers, studies regarding p53 in GIST have been limited. The CDKN2A/MDM2/p53 axis regulates cell cycle progression and DNA damage responses, which in turn control tumor growth. This axis is the major event required for transformation from low- to high-risk GIST. Generally, p53 mutation is infrequent in GIST, but p53 overexpression has been reported to be associated with high-risk GIST and unfavorable prognosis, implying that p53 should play a critical role in GIST. Also, Wee1 regulates the cell cycle and the antitumor activity of Wee1 inhibition was reported to be p53 mutant dependent. In addition, Wee1 was reported to have potential activity in GIST through the regulation of KIT protein and this mechanism may be dependent on p53 status. In this article, we review previous reports regarding the role of p53 in GIST and propose targeting the p53 pathway as a novel additional treatment strategy for GIST.

Comparable long-term survival of patients with colorectal or gastric gastrointestinal stromal tumors treated with endoscopic vs. surgical resection

BACKGROUND AND AIMS

With the development of endoscopic technology, endoscopic treatment has been widely used in Gastrointestinal stromal tumors (GISTs). However, population-based studies comparing the long-term results of patients who received endoscopic treatment vs. Surgery are lacking. We used the Surveillance, Epidemiology, and End Results (SEER) database to analyze the long-term survival of colorectal or gastric GISTs who underwent primary tumor resection (endoscopic therapy or surgery) in the USA.

METHODS

Patients with colorectal or gastric GISTs were selected from the SEER database between 2010 and 2015. Kaplan-Meier analyses and log-rank tests were used to evaluate the difference in the long-term survival between the endoscopic therapy group and the surgery group. We examined the association between different treatments and survival after using the multivariate cox proportional hazards model to adjust the relevant covariates. Besides, we used Propensity score matching (PSM) to overcome the different distributions of covariates between the two groups and then further compare the survival difference.

RESULTS

In total, 2355 patients were enrolled in our study, of which 1999 (84.9%) received surgical treatment and 356 (15.1%) received endoscopic treatment. There was no significant difference in overall survival (OS) between the two groups before PSM. The median OS (73.5 months vs. 72.2 months) and 5-year OS rate (85.7% vs. 81.5%) of endoscopic therapy were similar to surgical patients (P = 0.34). The median Cancer-specific survival (CSS) and 5-year CSS rate in the endoscopic treatment group were higher than the surgical group before PSM, with 81.3 months, 97.1% versus 78.8 months, 92.7% (P = 0.011). After adjusting for other clinical factors and PSM, the long-term OS and CSS did not significantly differ between those treated surgically and treated endoscopically.

CONCLUSION

Based on the American population, we preliminarily found that the long-term OS and CSS did not differ between patients undergoing endoscopic therapy and surgery.

Combined Inhibition of AKT and KIT Restores Expression of Programmed Cell Death 4 (PDCD4) in Gastrointestinal Stromal Tumor

The majority of gastrointestinal stromal tumor (GIST) patients develop resistance to the first-line KIT inhibitor, imatinib mesylate (IM), through acquisition of secondary mutations in KIT or bypass signaling pathway activation. In addition to KIT, AKT is a relevant target for inhibition, since the PI3K/AKT pathway is crucial for IM-resistant GIST survival. We evaluated the activity of a novel pan-AKT inhibitor, MK-4440 (formerly ARQ 751), as monotherapy and in combination with IM in GIST cell lines and preclinical models with varying IM sensitivities. Dual inhibition of KIT and AKT demonstrated synergistic effects in IM-sensitive and -resistant GIST cell lines. Proteomic analyses revealed upregulation of the tumor suppressor, PDCD4, in combination treated cells. Enhanced PDCD4 expression correlated to increased cell death. In vivo studies revealed superior efficacy of MK-4440/IM combination in an IM-sensitive preclinical model of GIST compared with either single agent. The combination demonstrated limited efficacy in two IM-resistant models, including a GIST patient-derived xenograft model possessing an exon 9 KIT mutation. These studies provide strong rationale for further use of AKT inhibition in combination with IM in primary GIST; however, alternative agents will need to be tested in combination with AKT inhibition in the resistant setting.

Antitumor effect of WEE1 blockade as monotherapy or in combination with cisplatin in urothelial cancer

Overcoming cisplatin (CDDP) resistance is a major issue in urothelial cancer (UC), in which CDDP‐based chemotherapy is the first‐line treatment. WEE1, a G₂/M checkpoint kinase, confers chemoresistance in response to genotoxic agents. However, the efficacy of WEE1 blockade in UC has not been reported. MK‐1775, a WEE1 inhibitor also known as AZD‐1775, blocked proliferation of UC cell lines in a dose‐dependent manner irrespective of TP53 status. MK‐1775 synergized with CDDP to block proliferation, inducing apoptosis and mitotic catastrophe in TP53‐mutant UC cells but not in TP53‐WT cells. Knocking down TP53 in TP53‐WT cells induced synergism of MK‐1775 and CDDP. In UMUC3 cell xenografts and two patient‐derived xenograft lines with MDM2 overexpression, in which the p53/cell cycle pathway was inactivated, AZD‐1775 combined with CDDP suppressed tumor growth inducing both M‐phase entry and apoptosis, whereas AZD‐1775 alone was as effective as the combination in RT4 cell xenografts. Drug susceptibility assay using an ex vivo cancer tissue‐originated spheroid system showed correlations with the in vivo efficacy of AZD‐1775 alone or combined with CDDP. We determined the feasibility of the drug susceptibility assay using spheroids established from UC surgical specimens obtained by transurethral resection. In conclusion, WEE1 is a promising therapeutic target in the treatment of UC, and a highly specific small molecule inhibitor is currently in early phase clinical trials for cancer. Differential antitumor efficacy of WEE1 blockade alone or combined with CDDP could exist according to p53/cell cycle pathway activity, which might be predictable using an ex vivo 3D primary culture system.