Delivery of a BET protein degrader via a CEACAM6-targeted antibody-drug conjugate inhibits tumour growth in pancreatic cancer models.

Pancreatic ductal adenocarcinoma (PDAC) has the worst prognosis of all cancers. To improve PDAC therapy, we establish screening systems based on organoid and co-culture technologies and find a payload of antibody-drug conjugate (ADC), a bromodomain and extra-terminal (BET) protein degrader named EBET. We select CEACAM6/CD66c as an ADC target and developed an antibody, #84.7, with minimal reactivity to CEACAM6-expressing normal cells. EBET-conjugated #84.7 (84-EBET) has lethal effects on various PDAC organoids and bystander efficacy on CEACAM6-negative PDAC cells and cancer-associated fibroblasts. In mouse studies, a single injection of 84-EBET induces marked tumor regression in various PDAC-patient-derived xenografts, with a decrease in the inflammatory phenotype of stromal cells and without significant body weight loss. Combination with standard chemotherapy or PD-1 antibody induces more profound and sustained regression without toxicity enhancement. Our preclinical evidence demonstrates potential efficacy by delivering BET protein degrader to PDAC and its microenvironment via CEACAM6-targeted ADC.

ER-851, a Novel Selective Inhibitor of AXL, Overcomes Resistance to Antimitotic Drugs.

Innate and adaptive resistance to cancer therapies, such as chemotherapies, molecularly targeted therapies, and immune-modulating therapies, is a major issue in clinical practice. Subpopulations of tumor cells expressing the receptor tyrosine kinase AXL become enriched after treatment with antimitotic drugs, causing tumor relapse. Elevated AXL expression is closely associated with drug resistance in clinical samples, suggesting that AXL plays a pivotal role in drug resistance. Although several molecules with AXL inhibitory activity have been developed, none have sufficient activity and selectivity to be clinically effective when administered in combination with a cancer therapy. Here, we report a novel small molecule, ER-851, which is a potent and highly selective AXL inhibitor. To investigate resistance mechanisms and identify driving molecules, we conducted a comprehensive gene expression analysis of chemoresistant tumor cells in mouse xenograft models of genetically engineered human lung cancer and human triple-negative breast cancer. Consistent with the effect of AXL knockdown, cotreatment of ER-851 and antimitotic drugs produced an antitumor effect and prolonged relapse-free survival in the mouse xenograft model of human triple-negative breast cancer. Importantly, when orally administered to BALB/c mice, this compound did not induce retinal toxicity, a known side effect of chronic MER inhibition. Together, these data strongly suggest that AXL is a therapeutic target for overcoming drug resistance and that ER-851 is a promising candidate therapeutic agent for use against AXL-expressing antimitotic-resistant tumors.

Periostin blockade overcomes chemoresistance via restricting the expansion of mesenchymal tumor subpopulations in breast cancer.

Recent studies suggest a functional involvement of Epithelial-Mesenchymal Transition (EMT) in tumor chemoresistance. Specifically, EMT is associated with chemoresistance and poor prognosis in triple-negative breast cancer. However, no effective therapy targeting EMT has been developed. Here, we report that periostin, an extracellular matrix protein, was induced upon chemotherapy and tightly correlated with the EMT gene signature and poor prognosis in breast cancer. In triple-negative breast cancer xenografts, chemotherapy upregulated periostin expression in tumor cells, triggered expansion of mesenchymal tumor cells and promoted invasion in residual tumors. Knockdown of periostin inhibited outgrowth and invasion of mesenchymal tumor cells upon chemotherapy. Furthermore, chemotherapy upregulated cancer-specific variants of periostin and application of a blocking antibody specifically targeting those variants overcame chemoresistance and halted disease progression without toxicity. Together, these data indicate that periostin plays a key role in EMT-dependent chemoresistance and is a promising target to overcome chemoresistance in triple-negative breast cancer.

Multitargeting strategy using lenvatinib and golvatinib: maximizing anti-angiogenesis activity in a preclinical cancer model.

Almost all cancers show intrinsic and/or evasive resistance to vascular endothelial growth factor (VEGF) inhibitors by multiple mechanisms. Serum angiopoietin-2 (Ang2) level has been proposed as a potential biomarker of VEGF inhibitor response in several cancers. From these clinical observations, the Ang2 and Tie2 (its receptor) axis has been focused on as a promising target. Here, we show a novel strategy to circumvent the resistance by combining multi-tyrosine kinase inhibitors lenvatinib (VEGF receptor, fibroblast growth factor receptor, and RET inhibitor) and golvatinib (E7050; c-Met, Tie2, and EphB4 inhibitor). Tie2 identifies a highly pro-angiogenic macrophage subset, Tie2-expressing macrophages (TEM). Angi-Tie2 and EphB4-EphrinB2 signaling plays critical roles in pericyte-mediated vessel stabilization. In vitro analyses suggested that golvatinib combined with lenvatinib inhibited pericyte-mediated vessel stabilization and TEM differentiation. In thyroid and endometrial cancer models, golvatinib and lenvatinib inhibited pericyte network development and TEM infiltration, resulting in severe perfusion disorder and massive apoptosis. Body weight loss was tolerable, and no macroscopic change was observed. These preclinical studies suggest that modulation of the tumor microenvironment by a strategic and well-tolerated combination of multi-targeting tyrosine kinase inhibitors may sensitize cancer to VEGF inhibitors.

Lenvatinib in combination with golvatinib overcomes hepatocyte growth factor pathway-induced resistance to vascular endothelial growth factor receptor inhibitor.

Vascular endothelial growth factor receptor (VEGFR) inhibitors are approved for the treatment of several tumor types; however, some tumors show intrinsic resistance to VEGFR inhibitors, and some patients develop acquired resistance to these inhibitors. Therefore, a strategy to overcome VEGFR inhibitor resistance is urgently required. Recent reports suggest that activation of the hepatocyte growth factor (HGF) pathway through its cognate receptor, Met, contributes to VEGFR inhibitor resistance. Here, we explored the effect of the HGF/Met signaling pathway and its inhibitors on resistance to lenvatinib, a VEGFR inhibitor. In in vitro experiments, addition of VEGF plus HGF enhanced cell growth and tube formation of HUVECs when compared with stimulation by either factor alone. Lenvatinib potently inhibited the growth of HUVECs induced by VEGF alone, but cells induced by VEGF plus HGF showed lenvatinib resistance. This HGF-induced resistance was cancelled when the Met inhibitor, golvatinib, was added with lenvatinib. Conditioned medium from tumor cells producing high amounts of HGF also conferred resistance to inhibition by lenvatinib. In s.c. xenograft models based on various tumor cell lines with high HGF expression, treatment with lenvatinib alone showed weak antitumor effects, but treatment with lenvatinib plus golvatinib showed synergistic antitumor effects, accompanied by decreased tumor vessel density. These results suggest that HGF from tumor cells confers resistance to tumor endothelial cells against VEGFR inhibitors, and that combination therapy using VEGFR inhibitors with Met inhibitors may be effective for overcoming resistance to VEGFR inhibitors. Further evaluation in clinical trials is warranted.

Prevention of hematogenous metastasis by neutralizing mice and its chimeric anti-Aggrus/podoplanin antibodies.

The platelet aggregation-inducing factor, Aggrus (also known as podoplanin), is reported to contribute to cancer metastasis by mediating cancer cell-platelet interaction. Aggrus has been shown to be upregulated in many different types of cancers. Thus, not only the functional inhibition of Aggrus, but also its application as a cancer-specific antigen has therapeutic potential. Among a series of anti-Aggrus mAb established previously, no mouse anti-human Aggrus mAb exists that possesses the ability to neutralize platelet aggregation. For precise preclinical examinations of mouse and monkey models, the establishment of Aggrus-neutralizing mouse mAb and their chimeric Abs is needed. In this study, we established two mouse anti-human Aggrus mAb, P2-0 and HAG-3. A precise analysis of their epitopes revealed that P2-0 recognized the conformation near the bioactive O-glycosylation site at the Thr(52) residue. In contrast, HAG-3 recognized the amino-terminus side at a short distance from the conformation recognized by P2-0. We observed that only P2-0 attenuated Aggrus-induced platelet aggregation and Aggrus binding to its platelet receptor, that is, the C-type lectin-like receptor-2. Consistent with these data, only P2-0 prevented the experimental metastasis of human Aggrus-overexpressing CHO cells. Subsequently, we cloned the complementary determining region of P2-0 and produced the murine/human chimeric P2-0 antibody. This chimeric antibody maintained its inhibitory activity of Aggrus-induced platelet aggregation and experimental metastasis. Thus, P2-0 and its chimeric antibody are expected to aid the development of preclinical and clinical examinations of Aggrus-targeted cancer therapy.

The novel metastasis promoter Merm1/Wbscr22 enhances tumor cell survival in the vasculature by suppressing Zac1/p53-dependent apoptosis.

Understanding metastasis is integral to curative cancer treatments. Using a mouse genetic screening model, we identified Merm1/Wbscr22 as a novel metastasis promoter that includes a methyltransferase fold in its structure. Merm1 showed high levels of expression in invasive breast cancer. Ectopic expression of Merm1 in nonmetastatic cells enhanced metastasis formation without affecting cell growth and motility. The intact methyltransferase fold of Merm1 was required for metastasis formation. Interestingly, Merm1 expression promoted cell survival after entrapment in the lung microvasculature. Consistent with these results, knockdown of endogenous Merm1 in tumor cells reduced lung retention and metastasis formation. On the basis of comparative transcriptome analysis, Merm1 expression was negatively correlated with the expression of tumor suppressor Zac1. We confirmed that Merm1 suppressed Zac1 expression with histone H3 methylation at Lys(9) in the Zac1 promoter region. Zac1 can induce apoptosis through its ability to transcriptionally coactivate p53, which regulates apoptosis in the vasculature and is often downregulated in metastasis. We found that Zac1 knockdown reduced the p53-dependent apoptosis that was enhanced by Merm1 knockdown, thereby increasing lung retention of metastatic cells. Our findings show that Merm1 enhances cancer cell survival in the vasculature by suppressing Zac1/p53-dependent apoptosis, thereby enhancing metastasis.

Tetraspanin family member CD9 inhibits Aggrus/podoplanin-induced platelet aggregation and suppresses pulmonary metastasis.

CD9 has been reported to play a role in tumor metastasis suppression. However, it is not fully understood how CD9 affects the hematogenous spread of tumor cells. To clarify a new mechanism (or mechanisms), we generated HT1080 cells that had been transfected with a CD9-expressing plasmid. Ectopic expression of CD9 in HT1080 cells actually reduced their metastatic ability. CD9 expression reduced lung retention and platelet aggregation activity of the transfectants. Because HT1080 cells express the metastasis-promoting, platelet aggregation-inducing factor Aggrus/podoplanin on their surface, we examined the relationship between CD9 and Aggrus. We discovered that CD9 formed a complex with Aggrus via transmembrane domains 1 and 2 (TM1 and TM2) of CD9. Investigation of the interaction revealed that each CD9 and Aggrus interacted homophilically, and that they colocalized in low-density membrane fractions. Deleting TM1 and TM2 attenuated the ability of CD9 to interact homophilically or to localize in low-density membrane fractions. The expression of CD9-wild-type (WT), but not CD9 lacking TM1 and TM2, attenuated the platelet aggregation and metastasis induced by forced expression of Aggrus in CHO cells. Therefore, CD9 may act as a metastasis suppressor, at least in part, by neutralizing Aggrus-mediated platelet aggregation.

Podoplanin expression in primary central nervous system germ cell tumors: a useful histological marker for the diagnosis of germinoma.

Podoplanin, a mucin-like transmembrane sialoglycoprotein, promotes platelet aggregation and may be involved in cancer cell migration, invasion, metastasis, and malignant progression. Podoplanin/aggrus is highly expressed in testicular seminoma, suggesting that it may be a sensitive marker for testicular seminomas. Here we investigated the expression of podoplanin in central nervous system (CNS) germ cell tumors (GCTs) by immunohistochemical staining of tumor samples from 62 patients. In 40 of 41 (98%) germinomas (including germinomatous components in mixed GCTs), podoplanin was diffusely expressed on the surface of germinoma cells; lymphocytes, interstitial cells, and syncytiotrophoblastic giant cells were negative for podoplanin. Except for immature teratomas (12/17; 71%), podoplanin expression was absent in non-germinomatous GCTs, including seven teratomas, seven embryonal carcinomas, seven yolk sac tumors, and seven choriocarcinomas. In immature teratomas, focal podoplanin staining was observed in fewer than 10% of immature squamous and columnar epithelial cells. Thus, podoplanin expression may be a sensitive immunohistochemical marker for germinoma in CNS GCTs. As such, it may be useful for diagnosis, for monitoring the efficacy of treatment, and as a potential target for antibody-based therapy.