By James F. Peltz Los Angeles Times LOS ANGELES — Drugmaker Celgene Corp. agreed to invest an additional $30 million in a cancer-fighting start-up that's majority owned by Los Angeles biotech entrepreneur Dr. Patrick Soon-Shiong, the companies said last week. Celgene's second-round funding would raise its overall investment in NantCell to $105 million, lifting its ownership in the firm to 2.8 percent