Amyloid precursor-like protein 2 suppresses irradiation-induced apoptosis in Ewing sarcoma cells and is elevated in immune-evasive Ewing sarcoma cells

Abstract

Despite surgery, chemotherapy, and radiotherapy treatments, the children, adolescents, and young adults who are diagnosed with metastasized Ewing sarcoma face a dismal prognosis. Amyloid precursor-like protein 2 (APLP2) has recently been implicated in the survival of cancer cells and in our current study, APLP2’s contribution to the survival of Ewing sarcoma cells was examined. APLP2 was readily detected in all Ewing sarcoma cell lines analyzed by western blotting, with the TC71 Ewing sarcoma cells expressing the lowest level of APLP2 among the lines. While irradiation induces apoptosis in TC71 Ewing sarcoma cells (as we determined by quantifying the proportion of cells in the sub-G₁ population), transfection of additional APLP2 into TC71 decreased irradiation-induced apoptosis. Consistent with these findings, in parallel studies, we noted that isolates of the TC71 cell line that survived co-culture with lymphokine-activated killer (LAK) cells (which kill by inducing apoptosis in target cells) displayed increased expression of APLP2, in addition to smaller sub-G₁ cell populations after irradiation. Together, these findings suggest that APLP2 lowers the sensitivity of Ewing sarcoma cells to radiotherapy-induced apoptosis and that APLP2 expression is increased in Ewing sarcoma cells able to survive exposure to cytotoxic immune cells.

Keywords: :

• amyloid precursor-like protein 2
• cytotoxic
• Ewing sarcoma
• immune evasion
• immunotherapy
• lymphokine-activated killer cell
• radiation

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

The authors thank Drs Eugenie Kleinerman, Vinod Labhasetwar, and Ted Hansen for providing cell lines for this project. We also gratefully acknowledge Dr Xiaojian Wang and Brittney Smith for technical support, Dr Janina Baranowska-Kortylewicz for assistance in the irradiation experiments, and the assistance of the personnel of the University of Nebraska Medical Center Cell Analysis Facility in the flow cytometry experiments. This work was supported by an Edna Ittner Pediatric Research Support Fund Grant (to SJ), an Eppley Cancer Center Pediatric Research Grant and NIH R03CA176557 (to JCS), NIH COBRE (P20RR018759/P20GM103489) and SPORE (P50CA127297) Developmental Grants (to JCS), Nebraska DHHS-LB506 Grants (to YY and JCS), a Structural Biology and Biophysics Training Program Fellowship from the Department of Education GAANN Program (to HLP), an NIH Training Grant T32CA009476 Fellowship (to HLP) and a UNMC Graduate Studies Office Emley Fellowship/Regents Tuition Fellowship (to HLP).

Notes

†Current affiliation: Department of Experimental Therapeutics; University of Texas MD Anderson Cancer Center; Houston TX USA

‡Current affiliation: Department of Internal Medicine; University of Nebraska Medical Center; Omaha, NE USA

§Current affiliation: Biology Department; University of Nebraska at Omaha; Omaha, NE USA