Electrochemotherapy with bleomycin associated with doxorubicin induces tumor regression and decreases the proliferative index in canine cutaneous squamous cell carcinomas

Canine cutaneous squamous cell carcinoma (cSCC) is the most common skin cancer in dogs, and due to its low metastatic rate, local treatments such as electrochemotherapy (ECT) promote disease control or even complete remission and increase the survival time in most cases. This study aimed to evaluate the expression of BAX, Bcl-2, and Ki67 and clinical parameters in dogs with cSCC subjected to ECT. A prospective clinical nonrandomized study was performed in dogs with naturally occurring cSCC treated with ECT. Eighteen lesions (from 11 dogs) were selected, independent of breed, sex and age. The ECT protocol consisted of bleomycin plus doxorubicin followed by electric pulses characterized by 8 biphasic electric pulses lasting 100 ms, 1 Hz and 1000 V/cm. Among the 18 lesions, the lesion volume significantly decreased after treatment (p=0.04). The tumor size at D0 had no impact on survival time or prognosis (P>0.05). A decreased mitotic index was observed at compared with D0 (P=0.019). We also observed more intratumoral necrosis at D21 compared to D0 (P=0.041). The median expression level of Ki67 was 277.96 at D0 and 193.92 at D21. Thus, tumor samples had a lower proliferative index after ECT (D21) (P=0.031). The survival times of subjects with Ki67 values lower and higher than the Ki67 median value were not significantly different (P>0.05). Regarding apoptotic markers, there was no significant difference in BAX or Bcl-2 expression between D0 and D21 (P>0.05) or in overall survival between subjects with different levels of apoptotic markers. Furthermore, a positive correlation was observed between BAX and Bcl-2 before ECT (D0) (P=0.0379, r=0.5067). In conclusion, there was no change in BAX and Bcl-2 protein expression levels in response to ECT at the time points evaluated, and ECT was able to reduce tumor volume and cellular proliferation in cSCC.