# Morphological Changes in H1299 Human Lung Cancer Cells Following W-Band Millimeter-Wave Irradiation
## 5 Conclusions  
The experimental results of this study suggest MMW irradiation in the frequency range of 75-110 GHz (W-band) promotes specific morphological changes following exposure in H1299 human lung cancer cells in an energy (dose)-dependent manner. Changes were observed to be stable with chronic characteristics accumulated and retained even after 10 days of physiological incubation post-irradiation. The effects observed and quantified using physical dimensions/parameters of cell size, circularity, and Feret's diameter demonstrated characteristic features of induced apoptosis and senescence following MMW exposure. The phenomenon of accelerated cellular senescence (ACS) [43], wherein cancer cells undergo terminal growth arrest, is conventionally achieved by using radiotherapy in conjunction with specific chemotherapeutic agents for targeted blockage of cellular pathways. However, radiotherapy results in immun-ocompromise [4] and chemotherapeutics drive drug resistance [23], thereby complicating full recoveries and leading to drug dependence. Although developments of microwave bronchoscopy [47] and cytotoxic effects of MMW exposure have been demonstrated [48], clinical adaptation is restricted due to the presence of thermal ablation used in these methods, which complicates the targeted application at lung tumor sites. This study provides the first threshold energy limits for using MMW irradiation within a non-thermal power density to elicit H1299 cancer cell annihilation, thereby making a clinical adaptation possible. Further, in vivo studies suggest MMWs activate natural killer (NK) cells [49], helping to reduce tumor metastasis. Low-power MMW exposure of mice alleviates the immunosuppressive effects of cancer drugs like Cyclophosphamide (CPA) and enhances the effector functions of CD4 (+) T cells [50]. The present study reports the apoptosis and senescence of cancer cells without the use of chemotherapeutic agents, ionizing radiation, or thermal ablation, thereby overcoming the associated side effects. Prospective clinical application of this method requires further investigations of the penetration depths achievable using endoscopic methods, calibration of dosimetry on clinical samples, and the development of prophylactic detection measures in order to improve the efficacy of treatment. Meta-analysis of NSCLC prognosis shows very high rates of mortality without treatment [51] and more than half the number of patients dying within one year of diagnosis even with treatment due to associated complications. Withrising trends for the development of biomedical devices, the MMW irradiation parameters described in this study hold promising potential for the development of non-invasive procedures to treat human non-small cell lung cancer (NSCLC) in the future. The following are available online at [[http://www.mdpi.com/2076-3417/10/9/3187/s1](http://www.mdpi.com/2076-3417/10/9/3187/s1)]([http://www.mdpi.com/2076-3417/10/9/3187/s1](http://www.mdpi.com/2076-3417/10/9/3187/s1)). Table S1. Fold Changes (the indicated values represent ratios of fold change with reference to control). Conceptualization, K.K., A.Y., J.L. and S.L.-A. ; Methodology, K.K., A.Y., J.L., B.K. ; and S.L.-A. ; Software, K.K., T.B., A.B. and S.L.-A. Validation, K.K., T.B., A.B. and S.L.-A. ; Formal analysis, K.K. ; T.B. and S.L.-A. ; Investigation, K.K., T.B. and S.L.-A. Resources, K.K., A.Y., J.L. and S.L.-A. Data curation, K.K., A.Y. and S.L.-A. Writing--original draft preparation, K.K., A.B. and S.L.-A. Writing--review and editing, K.K., A.B., A.Y. and S.L.-A. Visualization, K.K., T.B., A.B. and S.L.-A. Supervision, S.L.-A. Project administration, S.L.-A. Funding acquisition, K.K., A.Y., J.L. and S.L.-A. All authors have read and agreed to the published version of the manuscript. This research was funded by Ariel University's Internally Supported Grant (Ariel Center for Applied Cancer Research, ACACR) and the Eva and Henry Fraenkel Foundation (Denmark).