Analyst upgrades typically lead to a positive short-term reaction in the stock market as they reflect a change in sentiment and expectations about the company's future performance. The substantial increase in the price target from $2 to $12 by a reputable analyst like Bradley Canino from Stifel is likely to be viewed as a strong endorsement of C4 Therapeutics' potential, thus potentially driving investor interest and a rise in the stock price in the short term.