Data on the effects of ECM rigidity on actomyosin contractility and invadopodia activity in individual versus pairs of head and neck squamous cell carcinoma cells

Migration through the extracellular matrix (ECM) is essential for cancer cells to escape the primary tumor and invade neighboring tissues with the potential for metastasis [1]. To penetrate tissue barriers, migrating cancer cells degrade the ECM with actin-rich membrane protrusions called invadopodia [2]. We have previously found that invadopodial ECM degradation is regulated by ECM rigidity in a process mediated by contractile forces in individual head and neck squamous cell carcinoma (HNSCC) cells [3], [4]. However, cancer cells often migrate together and interact with each other to alter their actomyosin contractility in response to the biomechanical properties of the ECM [5]. Therefore, we tested whether ECM rigidity promotes biomechanical interactions between cancer cells to enhance proteolytic activity. Using a minimal model of two HNSCC cells in physical contact, we provide data here that actomyosin contractility, invadopodia formation, and ECM degradation increase in response to ECM rigidity when cells are in pairs versus individual cells using traction force and invadopodia assays.


a b s t r a c t
Migration through the extracellular matrix (ECM) is essential for cancer cells to escape the primary tumor and invade neighboring tissues with the potential for metastasis [1] . To penetrate tissue barriers, migrating cancer cells degrade the ECM with actin-rich membrane protrusions called invadopodia [2] . We have previously found that invadopodial ECM degradation is regulated by ECM rigidity in a process mediated by contractile forces in individual head and neck squamous cell carcinoma (HNSCC) cells [3,4] . However, cancer cells often migrate together and interact with each other to alter their actomyosin contractility in response to the biomechanical properties of the ECM [5] . Therefore, we tested whether ECM rigidity promotes biomechanical interactions between cancer cells to enhance proteolytic activity. Using a minimal model of two HNSCC cells in physical contact, we provide data here that actomyosin contractility, invadopodia formation, and ECM degradation increase in response to ECM rigidity when cells are in pairs versus individual cells using traction force and invadopodia assays.

Value of the Data
• The data presented here reveal the impact of ECM rigidity on the contractile and invasive properties of HNSCC cells in contact with each other. • The data may be of interest to researchers studying cancer biology and mechanisms of invasion including the roles of intercellular biophysical interactions between cancer cells migrating in multicellular and collective groups. • The data may provide the basis for future studies to uncover force-dependent mechanisms that augment invadopodia activity in cohesive groups of cancer cells during proteolytic invasion.

Data Description
The analyzed and raw data provided here demonstrate the effects of ECM rigidity on the generation of traction forces and formation of invadopodia and their associated ECM degradation in individual HNSCC cells versus pairs of physically interacting HNSCC cells using the SCC-61 cell line. ECM rigidity was varied from soft ( Fig. 1 ) to hard ( Fig. 2 ) PAAs to mimic normal tissue and tumor-associated mechanical properties, respectively, in vitro [6][7][8] . Physical contact and interactions between HNSCC cells in pairs on the soft ( Fig. 1 A) and hard ( Fig. 2 A) PAAs were confirmed with immunofluorescence. On soft PAAs, traction forces ( Fig. 1 B & D; Table 1 ), ECM degradation, number of actively degrading or mature invadopodia, and number of total invadopodia (i.e., mature and immature or nascent invadopodia) ( Fig. 1 C & E-G; Table 2 ) did not change when com-      Table 3 ), ECM degradation, number of active invadopodia, and number of total invadopodia ( Fig. 2 C & E-G; Table 4 ) increased for HNSCC cells within pairs when compared to individual cells on hard PAAs.

Statistics
As previously described, data were evaluated for normality using the Kolmogorov-Smirnov test, determined to be nonparametric, and compared using a Mann-Whitney test with a p -value < 0.05 considered statistically significant [ 3 , 4 ].

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships which have or could be perceived to have influenced the work reported in this article.