Activins and their related proteins in colon carcinogenesis: insights from early and advanced azoxymethane rat models of colon cancer

Abstract

BackgroundActivin-A may exert pro- or anti-tumorigenic activities depending on cellular context. However, little is known about its role, or the other mature activin proteins, in colorectal carcinoma (CRC). This study measured the expression of activin βA- & βB-subunits, activin type IIA & IIB receptors, smads 2/3/4/6/7 and follistatin in CRC induced by azoxymethane (AOM) in rats. The results were compared with controls and disseminated according to the characteristics of histopathological lesions.MethodsEighty male Wistar rats were allocated into 20 controls and the remaining were equally divided between short ‘S-AOM’ (15 weeks) and long ‘L-AOM’ (35 weeks) groups following injecting AOM for 2 weeks. Subsequent to gross and histopathological examinations and digital image analysis, the expression of all molecules was measured by immunohistochemistry and quantitative RT-PCR. Activin-A, activin-B, activin-AB and follistatin were measured by ELISA in serum and colon tissue homogenates.ResultsColonic pre-neoplastic and cancerous lesions were identified in both AOM groups and their numbers and sizes were significantly (P < 0.05) greater in the L-AOM group. All the molecules were expressed in normal colonic epithelial cells. There was a significantly (P < 0.05) greater expression of βA-subunit, IIB receptor and follistatin in both pre-neoplastic and cancerous tissues. Oppositely, a significant (P < 0.05) decrease in the remaining molecules was detected in both AOM groups. Metastatic lesions were only observed within the L-AOM group and were associated with the most significant alterations of all molecules. Significantly higher concentrations of activin-A and follistatin and lower activin-AB were also detected in both groups of AOM. Tissue and serum concentrations of activin-A and follistatin correlated positively, while tissue activin-AB inversely, and significantly with the numbers and sizes of colonic lesions.ConclusionsNormal rat colon epithelial cells are capable of synthesising, controlling as well as responding to activins in a paracrine/autocrine manner. Colonic activin systems are pathologically altered during tumorigenesis and appear to be time and lesion-dependent. Activins could also be potential sensitive markers and/or molecular targets for the diagnosis and/or treatment of CRC. Further studies are required to illustrate the clinical value of activins and their related proteins in colon cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2914-9) contains supplementary material, which is available to authorized users.

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“…Moreover, the p21, p27, Casp-8 and Casp-3 proteins increased with concomitant declines in CCND1, CCND3, BCL2 and survivin in both cell lines with Act-AB. This study agrees with many prior reports and, altogether, suggest that Act-AB could be a Smad4-independent tumour suppressor protein in CRC [7,[37][38][39]. Our data further advocate that the dysregulation of activins could promote the initiation of CRC independent of anatomical site, whereas loss of Act-AB might contribute to the aggressiveness of right-sided neoplasms during the late cancer stages.…”

Profiling Activins and Follistatin in Colorectal Cancer According to Clinical Stage, Tumour Sidedness and Smad4 Status

“…Concurrently, restoring activin type IIA receptor in mutated malignant enterocytes provoked smad4dependent cell cycle arrest and apoptosis, implying that cancerous cells could bypass the Act-A anti-cancer actions by developing mutations in the Acvr2a or Smad4 genes [14,15]. Moreover, CRC induction in murine elevated Act-A and inhibited Smad4 proteins, whilst hesperidin treatment decreased the tumour numbers and increased the levels of Act-A and Smad4 in malignant tissues [7,33]. By contrast, others have suggested that Act-A is oncogenic since the βAsubunit mRNA and protein alongside Act-A levels increased with CRC progression and linked directly with poor prognosis [17][18][19][20].…”

“…However, more studies involving the different activin type I and II receptors together with Smads 1/5/8, are still needed to validate our hypothesis. FS tightly controls the biological actions of activins by irreversible binding [7,47]. Additionally, FS is pathologically altered in a variety of solid tumours and is thought to counteract the effects of Act-A [47].…”

“…Activins are plethoric proteins that belong to the transforming growth factor (TGF)-β family and normally mediate their cellular actions via Smad4 [ 7 , 8 ]. The hetero- and homodimerization of two β-subunits (βA and βB) produce three mature proteins known as activin-A (βA-βA; Act-A), activin-B (βB-βB; Act-B) and activin-AB (βA-βB; Act-AB) [ 7 , 8 ]. The biological actions of activins are tightly regulated by follistatin (FS), which equally neutralises all activin isoforms [ 9 ].…”

“…The available reports regarding the roles of Act-B, Act-AB, and FS in colon carcinogenesis are scarce [ 7 , 21 ]. Furthermore, none of the previous studies investigated the expression of activins and FS in relation to primary tumour sidedness and Smad4 status.…”