Thymidylate synthase expression and p21(WAF1)/p53 phenotype of colon cancers identify patients who may benefit from 5-fluorouracil based therapy

Integrated analysis reveals a novel 5-fluorouracil resistance-based prognostic signature with promising implications for predicting the efficacy of chemotherapy and immunotherapy in patients with colorectal cancer

BACKGROUND

5-Fluorouracil (5-FU) has been used as a standard first-line treatment for colorectal cancer (CRC) patients. Although 5-FU-based chemotherapy and immune checkpoint blockade (ICB) have achieved success in treating CRC, drug resistance and low response rates remain substantial limitations. Thus, it is necessary to construct a 5-FU resistance-related signature (5-FRSig) to predict patient prognosis and identify ideal patients for chemotherapy and immunotherapy.

METHODS

Using bulk and single-cell RNA sequencing data, we established and validated a novel 5-FRSig model using stepwise regression and multiple CRC cohorts and evaluated its associations with the prognosis, clinical features, immune status, immunotherapy, neoadjuvant therapy, and drug sensitivity of CRC patients through various bioinformatics algorithms. Unsupervised consensus clustering was performed to categorize the 5-FU resistance-related molecular subtypes of CRC. The expression levels of 5-FRSig, immune checkpoints, and immunoregulators were determined using quantitative real-time polymerase chain reaction (RT‒qPCR). Potential small-molecule agents were identified via Connectivity Map (CMap) and molecular docking.

RESULTS

The 5-FRSig and cluster were confirmed as independent prognostic factors in CRC, as patients in the low-risk group and Cluster 1 had a better prognosis. Notably, 5-FRSig was significantly associated with 5-FU sensitivity, chemotherapy response, immune cell infiltration, immunoreactivity phenotype, immunotherapy efficiency, and drug selection. We predicted 10 potential compounds that bind to the core targets of 5-FRSig with the highest affinity.

CONCLUSION

We developed a valid 5-FRSig to predict the prognosis, chemotherapeutic response, and immune status of CRC patients, thus optimizing the therapeutic benefits of chemotherapy combined with immunotherapy, which can facilitate the development of personalized treatments and novel molecular targeted therapies for patients with CRC.

p21 as a Predictor and Prognostic Indicator of Clinical Outcome in Rectal Cancer Patients

The cell cycle plays a key and complex role in the development of human cancers. p21 is a potent cyclin-dependent kinase inhibitor (CDKI) involved in the promotion of cell cycle arrest and the regulation of cellular senescence. Altered p21 expression in rectal cancer cells may affect tumor cells' behavior and resistance to neoadjuvant and adjuvant therapy. Our study aimed to ascertain the relationship between the differential expression of p21 in rectal cancer and patient survival outcomes. Using tissue microarrays, 266 rectal cancer specimens were immunohistochemically stained for p21. The expression patterns were scored separately in cancer cells retrieved from the center and the periphery of the tumor; compared with clinicopathological data, tumor regression grade (TRG), disease-free, and overall survival. Negative p21 expression in tumor periphery cells was significantly associated with longer overall survival upon the univariate (p = 0.001) and multivariable analysis (p = 0.003, HR = 2.068). Negative p21 expression in tumor periphery cells was also associated with longer disease-free survival in the multivariable analysis (p = 0.040, HR = 1.769). Longer overall survival times also correlated with lower tumor grades (p= 0.011), the absence of vascular and perineural invasion (p = 0.001; p < 0.005), the absence of metastases (p < 0.005), and adjuvant treatment (p = 0.009). p21 expression is a potential predictive and prognostic biomarker for clinical outcomes in rectal cancer patients. Negative p21 expression in tumor periphery cells demonstrated significant association with longer overall survival and disease-free survival. Larger prospective studies are warranted to investigate the ability of p21 to identify rectal cancer patients who will benefit from neoadjuvant and adjuvant therapy.

5-Fluorouracil (5-FU) resistance and the new strategy to enhance the sensitivity against cancer: Implication of DNA repair inhibition

5-Fluorouracil (5-FU) has been an important anti-cancer drug to date. With an increase in the knowledge of its mechanism of action, various treatment modalities have been developed over the past few decades to increase its anti-cancer activity. But drug resistance has greatly affected the clinical use of 5-FU. Overcoming this chemoresistance is a challenge due to the presence of cancer stem cells like cells, cancer recurrence, metastasis, and angiogenesis. In this review, we have systematically discussed the mechanism of 5-FU resistance and advent strategies to increase the sensitivity of 5-FU therapy including resistance reversal. Special emphasis has been given to the cancer stem cells (CSCs) mediated 5-FU chemoresistance and its reversal process by different approaches including the DNA repair inhibition process.

Regulatory effects of lncRNA ATB targeting miR-200c on proliferation and apoptosis of colorectal cancer cells

This investigation was intended to elucidate whether long noncoding RNA (lncRNA)-activated by transforming growth factor-β (ATB) interacting with miR-200c could mediate colorectal cancer (CRC) progression, offering potential strategies for diagnosing and treating CRC. Here totally 315 patients with CRC were recruited, and their CRC tissues and adjacent normal tissues were gathered. Concurrently, four colon cancer cell lines (ie, SW620, Lovo, HCT116, and SW480) and the human colon mucosal epithelial cell line (NCM460) were also purchased. Moreover, si-ATB, si-NC, miR-200c mimic, miR-200c inhibitor, and miR-NC were prepared for transfection into the CRC cells, and their effects on CRC cell lines were evaluated based on the conduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, colony formation assay, and flow cytometry assay. Eventually, the Luciferase reporter gene assay was carried out to judge if there existed a targeted relationship between ATB and miR-200c. The results of Cox regression analyses suggested that overexpressed lncRNA ATB, underexpressed miR-200c, poor tumor differentiation, lymph-vascular invasion, and perineural invasion were symbolic of shortened survival of the patients with CRC (all P < .05). Besides, transfection of pcDNA3.1-ATB and miR-200c inhibitor could boost the viability and proliferation of Lovo and SW620 cell lines (all P < .05). Meanwhile, the expressions of p53 and p21 were also reduced under treatments of pcDNA3.1-ATB and miR-200c inhibitor (P < .05). In addition, CDK2 seemed to reverse the contribution of miR-200c to intensifying viability and proliferation of Lovo and SW420 cell lines (P < .05). Furthermore, ATB might downregulate miR-200c expression by targeting it (P < .05), and CDK2 was subjected to dual regulation of both ATB and miR-200c (P < .05). In conclusion, the lncRNA ATB/miR-200c/CDK2 signaling was responsible for intensified proliferation and prohibited apoptosis of CRC cells, which might provide effective approaches for diagnosing and treating CRC.

MDMX is a prognostic factor for non-small cell lung cancer and regulates its sensitivity to cisplatin

PURPOSE

Chemoradiotherapy is the standard treatment modality for advanced non-small cell lung cancer (NSCLC). However, drug and radiation resistance remain major factors influencing its clinical outcome. The purpose of this study was to evaluate whether MDMX can affect the chemosensitivity and clinical outcome of NSCLC.

METHODS

Quantitative real-time PCR (qRT-PCR) was performed to assess MDMX mRNA expression levels in 105 primary NSCLC tissues, its corresponding non-cancerous tissues and two NSCLC-derived cell lines (A549 and SK-MES-1). In addition, immunohistochemistry was carried out to detect MDMX protein expression in the primary NSCLC tissues. The MDMX expression levels were correlated with clinicopathological and survival features. The effects of MDMX expression knockdown on NSCLC cell proliferation and chemosensitivity were evaluated using MTT, flow cytometry and soft agar colony assays.

RESULTS

We found that the mRNA expression level of MDMX in NSCLC tissues was significantly higher than that in its corresponding non-tumorous tissues. High MDMX expression was found to be related to poor tumor cell differentiation, advanced TNM stages and the occurrence of lymph node metastases. Patients with a high MDMX expression level exhibited a lower overall survival rate than those with a low expression level. Multivariate analysis showed that a high MDMX protein expression level may serve as an independent prognostic factor for NSCLC patients. In addition, we found that MDMX expression knockdown combined with cisplatin treatment in vitro significantly increased apoptosis and decreased soft agar colony formation in NSCLC-derived cells.

CONCLUSIONS

Our data indicate that MDMX expression may serve as an independent unfavorable prognostic factor for NSCLC patient outcome, which in turn may at least partly be due to the ability of the MDMX protein to regulate the proliferative capacity and chemosensitivity of NSCLC cells.

E2F1/TS Immunophenotype and Survival of Patients with Colorectal Cancer Treated with 5FU-Based Adjuvant Therapy

The predictive value of thymidylate synthase (TS) expression alone for 5FU-based treatment of colorectal cancer (CRC) has not been clinically confirmed. Little is known on the association of expression of E2F1, which controls the transcription of genes encoding proteins engaged in DNA synthesis including TS, and survival of patients with CRC. The purpose of this study is to assess the correlation between expression of both E2F1 and TS in CRCs and survival of patients administered adjuvant 5FU-based chemotherapy, in order to find a better predictor of treatment outcome than expression of TS or E2F1 alone. Nuclear TS and E2F1 were detected by immunohistochemistry in tissue microarrays from 190 CRCs (Astler-Coller stage B2 or C). Multivariate analysis identified significant association of the combined E2F1+TS+ immunophenotype with worse OS (HR = 3,78, P = 0,009) and DFS (HR = 2,30, P = 0,03) of patients with colon cancer. There were significant differences between E2F1+TS+ and E2F1-TS- Kaplan-Meier survival curves in relation to DFS (P = 0.008) and OS (P = 0.01). About 37 and 31 % difference in 3-year DFS and OS respectively were seen between patients with E2F1+TS+ vs. E2F1-TS- colon cancer immunophenotype. The E2F1+TS+ immunophenotype may be a marker of poor prognosis (the worst DFS and OS) of patients with colon cancer treated with 5FU-based adjuvant therapy. A subgroup of patients with this immunophenotype may require different and perhaps more aggressive treatment than 5FU-based chemotherapy. Thus, the combined E2F1/TS immunophenotype could be a potential indicator of colon cancer sensitivity to 5FU.

Treatment of LS174T colorectal cancer stem-like cells with n-3 PUFAs induces growth suppression through inhibition of survivin expression and induction of caspase-3 activation

PURPOSE

Colorectal cancer stem cells (CCSCs) are thought to contribute to tumor initiation, progression, metastasis, chemo-resistance and therapy failure. Therefore, assessment of the effectiveness of agents with anti-proliferative activities against CCSCs is warranted. Several studies have shown that different tumorigenic steps, ranging from initiation to metastasis, can be affected by n-3 polyunsaturated fatty acids (PUFAs). Here, we evaluated the effects of the PUFA components docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), alone or in combination, on LS174T cells that serve as a model for colorectal cancer initiating cells with stem cell-like properties.

METHODS

LS174T cells were treated with 50, 100 and 150 μM DHA and EPA, or equal mixtures of DHA/EPA (i.e., 25/25, 50/50 and 75/75 μM), after which cell number, viability, growth inhibition, survivin expression, caspase-3 activation and apoptotic rate were evaluated.

RESULTS

We found that treatment of LS174T cells with increasing PUFA concentrations significantly increased growth inhibition in a dose- and time-dependent manner. After a 72 h treatment with 150 μM DHA and EPA, or their combination (75/75 μM), growth rates were inhibited by 80.3 ± 5.5%, 79.3 ± 5% and 71.1 ± 1%, respectively, compared to untreated cells. We also found that treatment for 48 h with 100 μM DHA and EPA, or their combination (50/50 μM), resulted in 2.9-, 3- and 2.6-fold increases in caspase-3 activation, as well as 54, 62.4 and 100% decreases in survivin mRNA expression levels, respectively, compared to untreated cells. Low survivin mRNA levels combined with high caspase-3 activity levels were found to correlate with a higher growth inhibition in PUFA-treated cells. DHA appears to be a more potent growth inhibitor than EPA and the DHA/EPA combination. An increase in the number of apoptotic cells (early + late), ranging from 12.9 to 44.7%, was observed with increasing DHA doses.

CONCLUSION

From our data we conclude that PUFAs induce growth inhibition via targeting survivin expression in LS174T cells, which serve as a model for CCSCs.

The carboxy-terminal domain of connexin 43 (CT-Cx43) modulates the expression of p53 by altering miR-125b expression in low-grade human breast cancers

PURPOSE

Connexin 43 (Cx43) is a widely expressed gap junction protein. It can also regulate various gap-junction independent processes, including cellular proliferation. The latter regulatory functions have been attributed to its carboxy-terminal domain, CT-Cx43. CT-Cx43 has been found to be expressed independent of full-length Cx43 in various cell types. Its nuclear localization has additionally raised the possibility that it may regulate the expression of particular genes, including miRNAs, known play a role in the regulation of cellular proliferation. Here, we set out to uncover the molecular mechanism(s) underlying CT-Cx43 mediated gene (de-)regulation in human breast cancer.

METHODS

Western blotting and quantitative real time PCR were carried to assess the expression of CT-Cx43 and miR-125b in a panel of 60 primary human breast cancer tissues and its paired normal adjacent tissues. In addition, CT-Cx43 was exogenously expressed in the breast cancer-derived cell line MCF-7 and its effect on the expression of miR-125b and its downstream target p53 were evaluated, as well as its effect on cellular proliferation and death using MTT and LDH assays, respectively.

RESULTS

We found that CT-Cx43, but not full-length Cx43, was down-regulated in low grade human breast cancers. In addition, we found that the tumor suppressor protein p53 exhibited a decreased expression in the CT-Cx43 down-regulated samples. Interestingly, we found that miR-125b, a negative regulator of p53, exhibited an inverse expression relationship with CT-Cx43 in the breast cancer samples tested. This inverse relationship was confirmed by exogenous expression of CT-Cx43 in MCF-7 cells. In addition, we found that CT-Cx43 up-regulation and subsequent miR-125b down-regulation resulted in a decreased proliferation of MCF-7 cells.

CONCLUSIONS

Our data suggest a mechanism by which CT-Cx43 may regulate cell proliferation. Targeting of CT-Cx43 and/or miR-125b may be instrumental for therapeutic intervention in human breast cancer.