Non-melanoma skin tumors: Rapid prediction of invasiveness using mechanobiology

Introduction

Skin cancer is the most common human malignancy, more people have had skin cancer than all other cancers combined. The main cause of cancer morbidity, including in skin cancers, is formation of metastases and recurrence; those require cell invasion into surrounding tissue. Invasive subpopulations of cells mechanically interact with their environment, thus we have developed a rapid (2hr) mechanobiology-based assay to quantify their metastatic risk. We have shown that the mechanically invasive subset of cancer cells, seeded on an impenetrable, physiological-stiffness, synthetic gel, will forcefully push into and indent the gel; non-invasive, benign or normal cells do not considerably indent. We have recently shown that larger mechanically invasive subsets agree with increased in vitro metastatic potential and also with grim clinical prognosis, by the histopathology and patient outcomes, e.g. in pancreatic cancer. Here, we demonstrate ability to rapidly identify non-melanoma invasive skin cancer samples.

Materials and Methods

Suspected non-melanoma skin tumor were excised and a small non-edge sample was taken for invasiveness determination. Enzymatic degradation was used to extract cells, which are then seeded on polyacrylamide gels (1-2 kPa stiffness). After 1hr cell-attachment the percentage of indenting cells and their attained depths on the gel were determined by microscopy. The bulk of the tumor-samples were sent for detailed histopathological examination, including tumor-sizing, maximal depth, Clark`s level, presence of desmoplasia/acantholysis, special histopathologic subtypes (basosquamous etc.), and mitotic index. Clinical follow-up of patients over 6 months showed no recurrence.

Results and Discussion

Non-invasive basal and squamous cell carcinomas (i.e. BCC and SCC) exhibit below 18% indenting cells, as compared to >30% invasive SCC and desmoplastic (fibrotic) BCC samples; depths were 2-6mm, control-scar was similar to non-invasive. Our mechanical invasiveness measure directly agrees with the clinical histopathology. Thus, using small amounts of cells (100k/ml), we can separate invasive/non-invasive non-melanoma with high sensitivity.

Conclusions

Mechanical invasiveness can rapidly (~2hr) distinguish BCC and SCC and reveal secondary processes e.g. desmoplasia (neoplasm-associated fibrosis) and risk of local-invasiveness or metastasis. Combined with histopathology it can provide a rapid diagnosis and prediction of clinical metastatic risk.