## 5 Conclusions  
Non-thermal, low intensity MMW irradiation in the 75-105 GHz range was shown to specifically affect lung cancer cells without adversely affecting immortalized MCF-10A cells. Irradiation of H1299 cells for 10 min resulted in cell death a few days later, while healthy MCF10A cells remained unaffected even after prolonged irradiation for 16 min (Figure S1). The experiments demonstrate that appropriately tuned W-band (75-105 GHz) MMW treatment can selectively cause lung cancer cell death in vitro. Our study is the first to use the sweeping regime in the W-band (75-105 GHz) MMW frequency range for treatment of cancer cells. This technique of irradiation uses a sweeping spectral regime rather than discrete frequencies providing an integrated effect and has never been investigated in previous studies, which used discrete frequency regimes only [41; 42]. Torsional Eigen modes of axially symmetric biomolecules such as carbohydrates, proteins, and DNA are likely the reason for the observed power absorption [22]. Estimates based on direct measurements of torsional mode constants place the Eigen frequency for carbohydrates around 70 GHz within the MMW spectrum [43]. Our hypothesis is that under W-band (75-105 GHz) MMW irradiation with low energy dosage, one part of the H1299 cell populations tried to repair the damage without success activating pro-apoptotic mechanisms, which promoted and resulted in mortality. Some of the cells succeeded to repair the damage and continued dividing and a third group of cells with irreparable damage and incomplete repair promoted a cell senescence mechanism increasing the formation of polyploidy cells. Un-repaired cellular damages, especially in infrequently dividing cells, can accumulate and cause progressive blockage of transcription, loss of gene expression capability and ultimately aging of the cells. Illustratively, changes in DNA conformation or in DNA-protein bonds have been observed corresponding to sharp frequency resonances in the MMW bandwidth [44]. Clinical adaptation of this treatment is limited by the current unavailability of non-invasive devices operating in this bandwidth. Overcoming the low penetration depth of MMW in biological tissue, pulsed irradiation regimes operating within safety limits [45] enables deeper penetration and is a potential approach for further development of devices operating in MMW spectrum. This study demonstrates W-band (75-105 GHz) MMW irradiation delivering an extended energy dosage over 10 min effectively terminates H1299 human lung cancer cell viability. The technique and parameters of using W-band (75-105 GHz) MMW therapy to target H1299 cancer cells specifically without affecting healthy non-tumorigenic MCF-10A epithelial cells encourages clinical adoption of this method as an effective treatment for lung cancer. The following are available online at [[http://www.mdpi.com/2076-3417/10/14/4813/s1](http://www.mdpi.com/2076-3417/10/14/4813/s1)]([http://www.mdpi.com/2076-3417/10/14/4813/s1](http://www.mdpi.com/2076-3417/10/14/4813/s1)), Figure S1: The mortality or senescence effects were not observed on MCF-10A cell lines after irradiation. Conceptualization, K.K., J.L., A.Y., J.L., and S.L.-A. ; software, K.K., K.I., A.B., and S.L.-A. ; validation, K.K., K.I., and S.L.-A. ; formal analysis, K.K., K.I., A.B., and S.L.-A. ; investigation, K.K., K.I., and S.L.-A. ; resources, K.K., J.L., A.Y., and S.L.-A. ; data curation, K.K., A.Y., J.L., and S.L.-A; writing--original draft preparation, K.K., A.B., and S.L.-A. ; writing--review and editing, K.K., A.Y., A.B., and S.L.-A. ; visualization, K.K., K.I., A.B., and S.L.-A. ; supervision, S.L.-A. ; project administration. A.Y. and S.L.-A. ; and funding acquisition, K.K., J.L., A.Y., and S.L.-A. All authors have read and agreed to the published version of the manuscript. This research was funded by the Ariel Applied Cancer Research Grant and the Eva and Henry Frankel Foundation (Denmark).