Detection of predictive and prognostic biomarkers and novel targeting therapies for CRC is important to improve its prognosis .
Proline metabolism and resulting products are important for many biological processes which occur in normal and oncogenic process, that lead to development and progression of broad range of cancers [14-16].
PYCR2 is a prolin family member that was studied and has many roles in progression of cancers of various organs, but its role in CRC oncogenesis and progression was not sufficiently studied.
In the current study we assessed the expression of PYCR2 in malignant tissues and adjacent non-neoplastic colonic mucosa and found that PYCR2 expression was upregulated in malignant more than normal tissues which indicate its role in CRC oncogenesis. Additionally, tissue protein expression of PYCR2 was upregulated in high grade and advanced stage CRC which indicated its role in cancer progression and development of metastases. Furthermore, we showed that increased PYCR2 expression was associated with shortened survival and poor outcome of CRC patients.
Our results were in line with Yin et al., , who represent the first to investigate genetic roles of PYCR2 in CRC oncogenesis, progression and shortened overall survival time.
Additionally, our results are similar to results of Wang et al.,  who assessed genetic and tissue protein expression of PYCR2 in CRC and other tumor types. They have found that levels of PYCR2 are up-regulated in CRC tumor tissues at the mRNA and protein levels.
PYCR2 was found to have many roles in CRC progression mainly through controlling apoptosis in cancer cells and mutations in Wnt/b-catenin and Notch signaling pathway pathways which are incriminated in CRC oncogenesis [T. Nakayama et al., , Wang et al.,  results.
Mutations in Wnt pathway result in CRC stem cell expansion in addition to stimulation of epithelial mesenchymal transition process which are responsible for CRC metastases and progression .
Abnormal PYCR2 expression was associated with abnormalities in Jagged1/Notch signaling pathway in CRC that was correlated with CRC development and progression [19, 20].
PYCR2 was found to be correlated with MYC levels in CRC and MYC knockdown lead to reduction of CRC growth, progression and metastasis [21, 22].
Yin et al.,  study demonstrated the roles of PYCR2 in apoptosis in CRC as its silencing could induce cell apoptosis by increasing levels of proapoptotic factors and decreasing levels of antiapoptotic factors.
PYCR2 has other studied roles in CRC metastases by activation of matrix metalloproteinases (MMPs) which mediate CRC cell invasion and migration through degradation of extracellular matrix (ECM) [13, 23]
All these previous results and results of current study showed that PYCR2 up-regulation could lead to CRC progression and metastases through several mechanisms that need to be clarified.
To clarify role of PYCR2 in CRC, we assessed levels of another biomarker which is ZBTB18 in sections from CRC and adjacent non-neoplastic tissues of colonic mucosa.
To our knowledge, There are few studies assessed its roles in CRC carcinogenesis and the current study represent the first one which assessed both PYCR2 and ZBTB18 tissue protein expression in CRC.
ZBTB18 expression was high in non-neoplastic colon mucosa and its expression is down-regulated in malignant tissues; additionally decreased ZBTB18 expression was associated with increased tumor invasion and metastases. We assessed the association of ZBTB18 with patient survival and we found that intense expression was associated with favorable outcome and longer survival time. Our results highlighted the possible tumor suppressor role of ZBTB18 in CRC patients.
Our results were similar to results of Sarah Bazzocco et al., 2021 who was first to investigate values of tissue protein expression of ZBTB18 in CRC tumorigenesis and declared that some zinc finger proteins participated in CRC tumorigenesis
ZBTB18 was formerly found to play an essential role in supporting normal myogenesis  and normal brain development , but its role in normal intestinal epithelium development and CRC carcinogenesis have not sufficiently clarified.
ZBTB18 expression reduce proliferation of brain tumor cells and promote apoptosis glioblastoma multiforme (GBM) and medulloblastoma (MB) . Additionally, ZBTB18 down regulation was associated with aggressive phenotype, unfavorable survival and poor prognosis of GBM patients . These results are in line with our results in CRC.
Previous reports about roles of ZBTB18 expression in CRC were in line with our results that ZBTB18 down regulation in CRC cells associated with increased growth, proliferation and invasion that consequently associated with poor prognosis.
Our results and results of previous studies collectively showed that ZBTB18 is considered a tumor suppressor gene that could be used in novel targeted therapy against CRC. Therefore, strategies aimed at rescuing ZBTB18 expression or down regulating some of the downstream ZBTB18 targets genes may offer therapeutic potential in colorectal cancer patients [10, 27].
In addition, the present study showed that reduced ZBTB18 expression in the tumors was associated with shorter CRC patient survival which was similar to results of Bazzocco1 et al., , who showed that ZBTB18 expression was reduced in presence of lymph node metastases in comparison to the primary CRC tumors. These findings confirmed the tumor suppressor role of ZBTB18 in CRC tissues that could detect a subset of CRC patients with poor prognosis that will get benefits from aggressive targeted therapy.