Novartis AG is pushing ahead with one of its most ambitious cancer therapies, a treatment that the Swiss drugmaker says has blockbuster potential as it extends that technology to a wider pool of tumor-ridden patients. Europe’s second-biggest drugmaker is planning to test its CAR-T treatments — which involve extracting immune cells and genetically engineering them to hunt and kill cancer cells before returning them into the patient’s body — on lethal cancers of the brain, pancreas, colon, ovary and lung.