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ARPC2 is a subunit of the Arp2/3 complex, which is essential for lamellipodia, invadopodia and filopodia, and ARPC2 has been identified as a migrastatic target molecule. To identify ARPC2 inhibitors, we generated an ARPC2 knockout DLD-1 human colon cancer cell line using the clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) system and explored gene signature-based strategies, such as a connectivity map (CMap) using the gene expression profiling data of ARPC2 knockout and knockdown cells. From the CMap-based drug discovery strategy, we identified pimozide (a clinically used antipsychotic drug) as a migrastatic drug and ARPC2 inhibitor. Pimozide inhibited the migration and invasion of various cancer cells. Through drug affinity responsive target stability (DARTS) analysis and cellular thermal shift assay (CETSA), it was confirmed that pimozide directly binds to ARPC2. Pimozide increased the lag phase of Arp2/3 complex-dependent actin polymerization and inhibited the vinculin-mediated recruitment of ARPC2 to focal adhesions in cancer cells. To validate the likely binding of pimozide to ARPC2, mutant cells, including ARPC2 F225A , ARPC2 F247A and ARPC2 Y250F cells, were prepared using ARPC2 knockout cells prepared by gene-editing technology. Pimozide strongly inhibited the migration of mutant cells because the mutated ARPC2 likely has a larger binding pocket than the wild-type ARPC2. Therefore, pimozide is a potential ARPC2 inhibitor, and ARPC2 is a new molecular target. Taken together, the results of the present study provide new insights into the molecular mechanism and target that are responsible for the antitumor and antimetastatic activity of pimozide., (© 2019 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.)

Vascular calcification, a pathologic response to defective calcium and phosphate homeostasis, is strongly associated with cardiovascular mortality and morbidity. In this study, we have observed that pyruvate dehydrogenase kinase 4 (PDK4) is upregulated and pyruvate dehydrogenase complex phosphorylation is increased in calcifying vascular smooth muscle cells (VSMCs) and in calcified vessels of patients with atherosclerosis, suggesting that PDK4 plays an important role in vascular calcification. Both genetic and pharmacological inhibition of PDK4 ameliorated the calcification in phosphate-treated VSMCs and aortic rings and in vitamin D3-treated mice. PDK4 augmented the osteogenic differentiation of VSMCs by phosphorylating SMAD1/5/8 via direct interaction, which enhances BMP2 signaling. Furthermore, increased expression of PDK4 in phosphate-treated VSMCs induced mitochondrial dysfunction followed by apoptosis. Taken together, our results show that upregulation of PDK4 promotes vascular calcification by increasing osteogenic markers with no adverse effect on bone formation, demonstrating that PDK4 is a therapeutic target for vascular calcification.

Microphthalmia-associated transcription factor (MITF) is inducible in response to cAMP and has a pivotal role in the melanocyte-specific expression of tyrosinase for skin pigmentation. Here we suggest that the cAMP-binding site of protein kinase A (PKA) is a target in the inhibition of the melanogenic process in melanocytes, as evidenced from the molecular mechanism of small molecules such as bisabolangelone (BISA) and Rp-adenosine 3',5'-cyclic monophosphorothioate (Rp-cAMPS). BISA is a sesquiterpene constituent of Angelica koreana, a plant of the Umbelliferae family, whose roots are used as an alternative medicine. BISA competitively inhibited cAMP binding to the regulatory subunit of PKA and fitted into the cAMP-binding site on the crystal structure of PKA under the most energetically favorable simulation. In α-melanocyte-stimulating hormone (α-MSH)-activated melanocytes, BISA and Rp-cAMPS nullified cAMP-dependent PKA activation, dissociating catalytic subunits from an inactive holoenzyme complex. They resultantly inhibited cellular phosphorylation of the cAMP-responsive element-binding protein (CREB) or another transcription factor SOX9, thus downregulating the expression of MITF or the tyrosinase gene with decreased melanin production. Taken together, this study defined the antimelanogenic mechanism of BISA or Rp-cAMPS with a notable implication of the cAMP-binding site of PKA as a putative target ameliorating melanocyte-specific hyperpigmented disorder.