Inhibition of Haspin Kinase Promotes Cell-Intrinsic and Extrinsic Antitumor Activity

Abstract

Patients with melanoma resistant to RAF/MEK inhibitors (RMi) are frequently resistant to other therapies, such as immune checkpoint inhibitors (ICI), and individuals succumb to their disease. New drugs that control tumor growth and favorably modulate the immune environment are therefore needed. We report that the small-molecule CX-6258 has potent activity against both RMisensitive (RMS) and-resistant (RMR) melanoma cell lines. Haspin kinase (HASPIN) was identified as a target of CX-6258. HASPIN inhibition resulted in reduced proliferation, frequent formation of micronuclei, recruitment of cGAS, and activation of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway. In murine models, CX-6258 induced a potent cGAS-dependent type-I IFN response in tumor cells, increased IFNg-producing CD8 þ T cells, and reduced Treg frequency in vivo. HASPIN was more strongly expressed in malignant compared with healthy tissue and its inhibition by CX-6258 had minimal toxicity in ex vivo-expanded human tumor-infiltrating lymphocytes (TIL), proliferating TILs, and in vitro differentiated neurons, suggesting a potential therapeutic index for anticancer therapy. Furthermore, the activity of CX-6258 was validated in several Ewing sarcoma and multiple myeloma cell lines. Thus, HASPIN inhibition may overcome drug resistance in melanoma, modulate the immune environment, and target a vulnerability in different cancer lineages. Significance: HASPIN inhibition by CX-6258 is a novel and potent strategy for RAF/MEK inhibitor-resistant melanoma and potentially other tumor types. HASPIN inhibition has direct antitumor activity and induces a favorable immune microenvironment.

Chromatin Bridges, not Micronuclei, Activate cGAS after Drug-induced Mitotic Errors in Human Cells

“…Micronuclei and gross nuclei induced by all drugs tested showed strong cGAS enrichment (Figure 2C). These observations show that cGAS localization to micronuclei is not a reliable proxy for cGAS activation, contrary to assumptions in recent papers (Gratia et al, 2019; Melms et al, 2020).…”

Combination of CHEK1/2 inhibition and ionizing radiation results in abscopal tumor response through increased micronuclei formation

“…In this work, we utilized the Chk1/2i inhibitor, AZD7762 in conjunction with ionizing radiation to provide proof of principle that pharmacologically forcing cell cycle progression following genotoxic stress is able to cause a resultant increase in the formation of micronuclei. This builds upon models shown in prior work indicating that cell cycle progression through mitosis coupled with DNA damage are the necessary factors for micronuclei formation 11 , 16 , and that cell cycle checkpoint kinase inhibition can drive mitotic catastrophe, inflammatory signaling, and cell-intrinsic and extrinsic anti-tumor activity 25 , 31 , 34 . Furthermore, we show that the combination treatment leads to increased expression of IFN-β mRNA and protein in vitro and an effect on an abscopal (unirradiated) tumor in vivo with increased expression of genes involved in immune activation and increased CD8+ T-cell infiltration, consistent with an increased systemic immune response.…”

CRISPR/Cas9 screening identifies a kinetochore‐microtubule dependent mechanism for Aurora‐A inhibitor resistance in breast cancer

“…Further, in agreement with our finding, a very recent study using CRISPR/Cas9 screening also identified a synthetic lethal interaction between Haspin inhibition and the pan-Aurora (A and B) kinase inhibitor VX680 in HCT116 colon carcinoma cells [60]. However, at odds with our finding, the authors found that the pan-Aurora (A and B) inhibitor VX-680 played a synthetic lethal role by targeting Aurora-B, but not Aurora-A.…”