If you are enrolled in Part 1, the dose of bosutinib you receive will depend on when you join this study and your treatment history. The first group of participants in each treatment history group will receive the lowest dose level of bosutinib. Each new group will receive a higher dose of bosutinib than the group before it, if no intolerable side effects were seen. This will continue until the highest tolerable dose of bosutinib is found.