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Updated: Oct 4, 2025
Evaluation of Tumor-infiltrating Leukocyte Subsets in a Subcutaneous Tumor Model
Published on: April 13, 2015
Tumor-Infiltrating Lymphocyte Function Predicts Response to Neoadjuvant Chemoradiotherapy in Locally Advanced Rectal
Joseph Cherng Huei Kong1, Glen Robert Guerra1, Rosemary Magdalena Millen1
1Joseph Cherng Huei Kong, Glen Robert Guerra, Rosemary Magdalena Millen, Sara Roth, Huiling Xu, Paul Joseph Neeson, Phillip Kevin Darcy, Michael Henry Kershaw, Shienny Sampurno, Jordane Malaterre, David Shi Hao Liu, Toan Duc Pham, Vignesh Narasimhan, Minyu Wang, Yu-Kuan Huang, Jacob McCormick, Andrew Craig Lynch, Satish Warrier, Michael Michael, Jayesh Desai, William Murray, Catherine Mitchell, Samuel Ngan, Wayne Allen Phillips, Alexander Graham Heriot, and Robert George Ramsay, Peter MacCallum Cancer Centre, University of Melbourne, Melbourne; and Kumar Visvanathan and Rosemary Magdalena Millen, St Vincent's Hospital, East Melbourne, Australia.
Purpose:
The presence of tumor-infiltrating lymphocytes (TILs) in tumors is superior to conventional pathologic staging in predicting patient outcome. However, their presence does not define TIL functionality. Here we developed an assay that tests TIL cytotoxicity in patients with locally advanced rectal cancer before definitive treatment, identifying those who will obtain a pathologic complete response (pCR). We also used the assay to demonstrate the rescue of TIL function after checkpoint inhibition blockade (CIB).
Patients And Methods:
Thirty-four consecutive patients were identified initially, with successful completion of the assay before surgery in those 17 patients who underwent full treatment. An in vitro cytotoxic assay of rectal cancer tumoroids cocultured with patient-matched TILs was established and validated. Newly diagnosed patients were recruited with pretreatment biopsy specimens processed within 1 month. Evaluation of TIL-mediated tumoroid lysis was performed by measuring the mean fluorescence intensity of cell death marker, propidium iodide. CIB (anti-programmed cell death protein 1 [anti-PD-1] antibody) response was also assessed in a subset of patient specimens.
Results:
Six of the 17 patients achieved an objective pCR on final evaluation of the resected specimen after neoadjuvant chemoradiotherapy. Cytotoxic killing identified the pCR group with a higher mean fluorescence intensity (27,982 [95% CI, 25,340 to 30,625]) compared with the non-pCR cohort (12,428 [95% CI, 9,434 to 15,423]; p < .001). Assessment of the effectiveness of CIB revealed partial restoration of cytotoxicity in TILs with increased PD-1 expression with anti-PD-1 antibody exposure.
Conclusion:
Evaluating TIL function can be undertaken within weeks of the diagnostic biopsy, affording the potential to alter patient management decisions and refine selection for a watch-and-wait protocol. This cytotoxic assay also has the potential to serve as a platform to assist in the additional development of CIB.
