You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Protein", "Chemical"].

Please return the output as a JSON object of the format: {"Chemical" : ["Dexamethasone", ...], "Protein" : ["BRCA-1", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Molecular Mechanisms of the antitumor activity of SB225002: A novel microtubule inhibitor.
SB225002 (SB) is an IL-8 receptor B (IL-8RB) antagonist that has previously been shown to inhibit IL-8-based cancer cell invasion, and to possess in vivo anti-inflammatory and anti-nociceptive effects. The present study presented an evidence for the cell cycle-targeting activity of SB in a panel of p53-mutant human cancer cell lines of different origin, and investigated the underlying molecular mechanisms. A combination of cell cycle analysis, immunocytometry, immunoblotting, and RNA interference revealed that SB induced a BubR1-dependent mitotic arrest. Mechanistically, SB was shown to possess a microtubule destabilizing activity evidenced by hyperphosphorylation of Bcl2 and BclxL, suppression of microtubule polymerization and induction of a prometaphase arrest. Molecular docking studies suggested that SB has a good affinity towards vinblastine-binding site on β-tubulin subunit. Of note, SB265610 which is a close structural analogue of SB225002 with a potent IL-8RB antagonistic activity did not exhibit a similar antimitotic activity. Importantly, in P-glycoprotein overexpressing NCI/Adr-Res cells the antitumor activity of SB was unaffected by multidrug resistance. Interestingly, the mechanisms of SB-induced cell death were cell-line dependent, where in invasive hepatocellular carcinoma HLE cells the significant contribution of BAK-dependent mitochondrial apoptosis was demonstrated. Conversely, SB activated p38 MAPK signaling in colorectal adenocarcinoma cells SW480, and pharmacologic inhibition of p38 MAPK activity revealed its key role in mediating SB-induced caspase-independent cell death. In summary, the present study introduced SB as a promising antitumor agent which has the potential to exert its activity through dual mechanisms involving microtubules targeting and interference with IL-8-drivin cancer progression.
{"Chemical": ["vinblastine", "SB265610", "SB225002"], "Protein": ["\u03b2-tubulin", "IL-8 receptor B", "p38", "P-glycoprotein", "IL-8RB", "BAK", "p53", "BubR1", "Bcl2", "IL-8", "BclxL", "caspase", "MAPK"]}