“One concern about the administration of Gln to cancer patients is that it would be employed by rapidly proliferating cells, including malignant cells,51 with the potential enhancement of tumour growth. However, some experimental data appear to indicate that dietary supplements do not increase tumour growth,52 rather, it diminishes growth53,54 by enhancing NK cell activity through the support of host Gln stores and glutathione (GSH) production. Presently, it remains to be clarified as to whether Gln might inhibit tumour metastasis”

“we demonstrated for the first time in this study that Gln [glutamine] inhibited PAF-associated tumour metastasis, in which MAPKs perform a critical role, via the deactivation of ERK, JNK, and p38 MAPKs.”

Glutamine inhibits platelet-activating factor-mediated
pulmonary tumour metastasis
https://sci-hub.ru/10.1016/j.ejca.2011.07.013

…

“We further demonstrated that dietary glutamine supplementation partially increased glutamine levels and restored potent antitumor responses”

Glutamine is essential for overcoming the immunosuppressive microenvironment in malignant salivary gland tumors

https://www.biorxiv.org/content/10.1101/2022.04.29.490103v1

…

“Taken together, our results provide a previously unidentified mechanism by which glutamine supplementation inhibits melanoma tumour growth and suggests a previously unrealized therapeutic avenue using glutamine supplementation in melanoma to cooperate with current therapies and potentially combat resistance mechanisms. Furthermore, our results provide important evidence that glutamine supplementation, rather than the nutrient-limiting approaches, is a simple dietary intervention that has the potential to block melanoma tumour growth and potentiate the effects of anti-melanoma treatments by suppressing epigenetically activated oncogenic pathways.”

Dietary glutamine supplementation suppresses epigenetically-activated oncogenic pathways to inhibit melanoma tumour growth
https://www.nature.com/articles/s41467-020-17181-w