Final answer:
Southam suggested that injections of HeLa cells could stimulate the immune system to fight cancer more effectively and aid in developing cancer vaccines.
Step-by-step explanation:
Based on the second study's results that involved injection of treated cancer cells into patients, Southam likely believed that injections of HeLa cells could potentially enhance the immune response and lead to the development of cancer vaccines.
The HeLa cell research helped understand that the immune system could be harnessed to detect and potentially eliminate cancer cells more effectively than the cancer could proliferate. Therefore, the two things Southam believed the injections of HeLa cells might be able to do are: 1) to enhance the anti-cancer immune response in patients, and 2) to contribute to the development of cancer vaccines which are tailored to boost the immune system's ability to fight off cancer cells within the patient's own body.