Researchers looking for methods to alleviate fatigue in cancer-fighting T-cells have discovered that the Golgi apparatus serves as a straightforward marker; more Golgi correlates with stronger cells.
The Golgi apparatus is responsible for refining, sorting, and packaging proteins to dispatch them to their final locations, whether within the cell or outside it.
While this is a fundamental role, it’s been relatively overlooked in cancer immunology compared to other organelles like mitochondria or the endoplasmic reticulum.
“We wanted to delve deeper into the Golgi apparatus. It’s a crucial organelle. How is it affected or what is its function in T-cells when it comes to combating cancer?” stated Nathaniel Oberholtzer, an M.D./Ph.D. student associated with Shikhar Mehrotra, Ph.D., co-leader of the Cancer Biology & Immunology Research Program at MUSC Hollings Cancer Center and the scientific director of the Center for Cellular Therapy in the MUSC College of Medicine.
Interestingly, the effective operation of the Golgi apparatus is linked to the efficacy of T-cells in destroying cancer cells. Understanding how a signaling pathway alleviates Golgi stress, allowing it to operate efficiently, reveals a potential new therapeutic approach that researchers could explore to enhance T-cells. Oberholtzer’s findings also suggest that the Golgi can serve as a biomarker for selecting the most effective T-cells for immunotherapy.
This research, with Oberholtzer as the primary author and Mehrotra as the senior author, along with a team from Hollings, was published this month in Science Advances.
T-cells, a vital part of the immune system, can eliminate cancer cells. CAR-T cells are specially modified T-cells designed in a laboratory to target specific proteins on the surface of an individual’s cancer cells, customized for each patient.
Both T-cells and CAR-T cells can become “exhausted” due to the challenging conditions in the tumor microenvironment. Mehrotra’s lab is exploring ways to enhance these cells’ longevity and effectiveness against cancer.
“The entire tumor microenvironment favors the tumor itself but creates a hostile climate for the immune cells that are trying to infiltrate it,” Mehrotra explained.
Just like humans, cells are constantly under stress—stress caused by imbalanced biochemical reactions or mechanical stress from movement. Temporary stress can be beneficial; for instance, exercising can enhance muscle strength, and brief cellular stress can prompt a response that ultimately fortifies them.
“However, if this stress becomes chronic, as it does in the tumor microenvironment, the cells experience prolonged stress which can lead to a different phenotype and cell death,” Mehrotra added.
The researchers discovered that applying hydrogen sulfide to the Golgi apparatus enables T-cells to withstand greater stress.
“Hydrogen sulfide is a gaseous signaling molecule found in nearly all mammalian cells. It usually results from various cellular processes but has been shown to play significant signaling roles as well,” Oberholtzer said.
“It modifies proteins through a process known as sulfhydration, where it alters cysteine residues, changing their function.”
In this study, Oberholtzer revealed that the sulfhydration process, which modifies a protein named Prdx4 within the Golgi apparatus, offers protection against oxidative stress.
“The stressors from the tumor microenvironment disrupt the Golgi apparatus, hindering its functionality. Hydrogen sulfide helps safeguard against this disruption,” Oberholtzer noted.
Investigating this protective mechanism led researchers to examine the Golgi apparatus more closely.
“Essentially, using the Golgi apparatus as a simple marker indicates that T-cells with a higher Golgi content are significantly more resilient when it comes to killing tumor cells and managing tumors,” Oberholtzer elaborated.
By utilizing cell sorting technology at the Flow Cytometry & Cell Sorting Shared Resource at Hollings, the researchers categorized T-cells based on their Golgi content. The top 30% were designated as Golgi-high (Golgi-hi), while the bottom 30% were labeled Golgi-low (Golgi-lo).
“Cells exhibiting high Golgi expression display a markedly different phenotype. They are less fatigued and much more effective in tumor control,” Mehrotra stated.
This preclinical investigation indicates that categorizing T-cells into Golgi-hi and Golgi-lo and reinfusing only the Golgi-hi cells in a patient could enhance the likelihood of tumor control.
“Currently, we are conducting validation studies at the Center for Cellular Therapy to potentially initiate a clinical trial, assessing the translational applicability of these findings,” Oberholtzer mentioned.
Further research is also essential to decipher the role of Golgi stress in the context of all organelles within a cell being stressed due to the tumor microenvironment.
