Högskolan i Skövde

Background: Colorectal cancer is one of the most frequently diagnosed cancers today. Dlg is a tumor suppressor gene commonly silenced in cancer cells. Many colorectal cancer patients are subject to vitamin D₃ deficiency and/ or an altered microbiome. Treatment using vitamin D₃ or probiotics shown decreased cellular proliferation, invasiveness and induction of apoptosis. This study aimed to knockdown Dlg and map genetic interactions coupled to Dlg downregulation using a Drosophila model. Vitamin D₃ and probiotic treatments were performed to investigate mechanism of action and capacity for Dlg rescue.

Result and discussion: After vitamin D₃ treatment, PGRP-SB1 (p<0.0001) and Drsl2 (p<0.0003) expression was significantly increased. These genes are part of the immune related Toll pathway suggesting its activation. Dlg and Veli (p=0.0042) upregulation could tentatively be through vitamin D receptor regulation of Wnt-signaling pathway, or direct VDR interaction. Traf6 and MPK2 (p38α) (p=0.0049) expression increased after vitamin D₃ treatment suggesting MPK2 activation through Traf6. Pro-apoptotic pathways through Fas or Bax and decreased survival through inhibition of Pi3K/Akt and Ras/Raf pathways are also possible outcomes of MPK2 activation. Probiotic treatment increased PGRP-SB1 (p<0.0001) without enhanced Drsl2 expression, possibly activating the Imd pathway. JNK-induced apoptosis through Erg (p<0.0001) induction was speculated and increased Dlg (p=0.0113) expression was seen after probiotic treatment.

Conclusion: Vitamin D₃ and probiotic treatments increased Dlg expression. Genes linked to polarity, growth and apoptosis were also enhanced suggesting various mechanisms of action. Further studies concerning knockdown and treatments are needed to fully understand the true mechanisms of action and interactions.