Correlation of laminin subunit alpha 3 expression in pancreatic ductal adenocarcinoma with tumor liver metastasis and survival

Pancreatic ductal adenocarcinoma (PDAC), a disease that is prevalently observed within the digestive system, is distinguished by its severe malignancy and exhibits a disconcerting confluence of incidence and mortality.¹ The 5-year survival rate of patients with PDAC is < 10%, with an extremely poor prognosis. If this trend is sustained, the impending decade may witness pancreatic cancer ascending to the rank as the second most lethal cancer.² Most patients with PDAC remain asymptomatic until the disease reaches advanced stages. Ninety percent of patients with PDAC diagnosed only after metastasis have a poor prognosis, with 50% developing systemic metastasis.^3,4 The potential for enduring survival among patients with PDAC considerably depends on tumor size and disease stage. Therefore, early detection of potentially curable cancers is crucial for reducing mortality rates among patients with PDAC. The elucidation of key molecular mechanisms and prospective intervention targets associated with pancreatic cancer metastasis will aid in deciphering the genetic and molecular underpinnings of this disease, provide biomarkers for preliminary warning and metastasis surveillance, and pave the way for enhancing the survival prospects of patients with pancreatic cancer.

Laminin, a heterotrimeric molecule consisting of α, β, and γ subunits, is the primary constituent of the extracellular matrix while collagen and fibronectin form the basement membrane. Among the three subunits of laminin, the α subunit is involved in tissue-specific distribution and biological activity.⁵ Laminin subunit alpha 3 (LAMA3), which encodes for the laminin α subunit, enables its globular carboxyl-terminal domain to engage with integrins at the plasma membrane, thereby participating in intracellular signal transduction.⁶ Currently, LAMA3 contributes to cell proliferation and apoptosis in diverse malignant tumors and modulates tumor progression through signal transduction pathways, such as focal adhesion plaques.^{7, 8, 9} The aberrant expression of LAMA3 in various tumors is inextricably associated with the clinical stage, tumor size, and pathological manifestations of patients.¹⁰ However, the influence of LAMA3 on liver metastasis in PDAC remains unclear. This study aimed to clarify LAMA3 expression in PDAC and investigate the relationship between LAMA3 expression and liver metastasis in patients with unresectable PDAC.

Pancreatic cancer is a highly aggressive neoplasm of the digestive system and is characterized by a mortality rate equal to its incidence rate. Its strong invasiveness and early metastasis render approximately 80% of patient ineligible for surgical intervention at the time of diagnosis. This results in a 5-year survival rate < 10%. Current treatment approaches for PDAC include surgical resection combined with chemotherapy, radiation therapy, interventional therapy, and immunotherapy. Even in patients with resectable localized tumors, the postoperative 5-year survival rate remains approximately 20%.¹² The major contributor to the high mortality rate of PDAC is its propensity for early metastasis, which poses a significant challenge in clinical management. Consequently, there is an urgent need to identify additional predictive biomarkers to enhance the risk stratification of patients with PDAC.

LAMA3, a member of the laminin family, plays a pivotal role in cellular processes by interacting with integrins on the cell membrane and participating in the intracellular signal transduction pathways. Recent studies have implicated elevated LAMA3 expression in various types of tumors, where it appears to promote cell proliferation, apoptosis, and tumor progression by modulating signal transduction pathways.^{7, 8, 9} Zboralski et al. demonstrated the simultaneous functional inactivation of the tumor suppressor mothers against decapentaplegic homolog 4 (SMAD4) and invasive growth of tumors in rectal and pancreatic cancers. Laminin 332 (LM-332) is the target of SMAD4, a positive transcriptional regulator that promotes the transcription of LAMA3, LAMB3, and LAMC2 genes encoding LM-332. SMAD4 mediates transcriptional activity through distinct molecular mechanisms associated with the LAMA3, LAMB3, and LAMC2 promoters.¹³ Additionally, Huang et al. highlighted the increased expression of LAMA3 protein in PDAC tumor cells relative to that in normal pancreatic cells. They further showed that high LAMA3 expression promoted the proliferation, migration, and invasion of PDAC tumor cells.⁵ However, the effect of LAMA3 on liver metastasis in PDAC has not been fully elucidated. This study aimed to clarify the expression profile of LAMA3 in PDAC and investigate its potential association with liver metastasis in patients diagnosed with unresectable PDAC.

In this study, we integrated data from the TCGA database with four independent datasets from the GEO database as validation cohorts and found that LAMA3 expression was upregulated in PDAC, validating previous study findings.¹⁴ Furthermore, through the analysis of clinical samples, we observed that LAMA3 was overexpressed in pancreatic carcinoma tissues compared with adjacent noncancerous tissues. When we analyzed clinicopathological data from the UALCAN database, we found that LAMA3 expression levels correlated with the histological grade of tumors in patients with PDAC. However, our analysis of clinical data revealed that high LAMA3 expression was associated with larger tumor size, advanced TNM stage, and liver metastasis. This discrepancy may be due to the inherent bias from our relatively small sample size. Jun et al. demonstrated that overexpression of the α3, β3, and γ2 chains of LM-332 might play a crucial role in the progression and prognosis of PDAC.¹⁵ Based on these findings, we evaluated the prognostic value of LAMA3 expression in patients with PDAC. Using the Kaplan–Meier Plotter dataset, which incorporates data from the GEO, European Genome-phenome Archive, and TCGA databases, we found that high LAMA3 expression was strongly associated with worse OS and RFS in patients with PDAC. Additionally, we followed up 117 patients with PDAC and observed that high LAMA3 expression in PDAC was correlated with poor OS, indicating an overall poor prognosis. Univariate and multivariate Cox regression analyses further demonstrated that LAMA3 was an independent predictive factor for mortality in patients with PDAC. In conclusion, these results strongly support that the expression of LAMA3 can serve as a robust prognostic biomarker of PDAC.

Metastasis, the primary cause of cancer-related mortality, continues to be an area of limited understanding regarding its cellular and molecular mechanisms.¹⁶ Various studies have implicated LAMA3 in different mechanisms of metastasis. Shu et al. demonstrated that the overexpression of LINC00936 hindered ovarian cancer progression by competitively binding to miR-221-3p and modulating LAMA3 expression.⁷ Moreover, Xu et al. reported that LINC00628 could obstruct cell proliferation, invasion, migration, and apoptosis while reducing drug resistance in lung adenocarcinoma cells by downregulating the methylation of the LAMA3 promoter⁸. Kinoshita et al. demonstrated that miRNA-218 modulated the focal adhesion pathway, thereby impeding tumor cell invasion and metastasis.⁹ The liver, which serves as the primary blood-borne drainage site for related organs, such as the portal vein system, colon, and pancreas, is crucial for distant metastasis in patients with PDAC.17 To gain a deeper understanding of the correlation between LAMA3 and liver metastasis in PDAC, we examined independent risk factors associated with liver metastasis. Univariate analysis revealed that histological grade, TNM stage, vascular invasion, and high LAMA3 expression were significantly associated with liver metastasis. Multivariate logistic regression analyses demonstrated that LAMA3 and histological grade were independent predictive factors for liver metastasis in patients with PDAC. These findings indicate that poor differentiation and high LAMA3 expression are correlated with an increased risk of metastasis.

This study has both strengths and limitations, necessitating further investigations to confirm and expand our findings. One of the strengths of this study is the use of data from public databases combined with bioinformatics analysis. This approach allows the utilization of large amounts of data, thus increasing the reliability and statistical power of our findings. We complemented this database analysis with clinical data to verify our results by adding another validation layer. However, this study has some limitations. This study was entirely based on data from public databases; although we used clinical data to confirm our findings, future studies with larger sample sizes and varied population groups are required to further validate our results. We evaluated LAMA3 expression in PDAC tissues using immunohistochemistry, which, although a common and reliable technique, only provides a snapshot of LAMA3 expression and does not provide functional information. Therefore, additional functional experiments are required to better understand the role of LAMA3 in PDAC. Finally, our study did not fully explore the mechanism by which LAMA3 promotes liver metastasis in PDAC. Understanding these mechanisms requires a series of in-depth molecular and cellular biology studies involving in vitro and in vivo models. By identifying and understanding the precise mechanisms involved, new potential therapeutic targets for PDAC can be identified.

This retrospective analysis suggests that LAMA3 may serve as a potential biomarker for predicting the prognosis of patients with PDAC. The increase in LAMA3 expression in PDAC tissues and its association with liver metastasis further underscore its potential role in disease progression. While these findings provide important insights, they also highlight the need for further studies. Understanding the specific mechanisms by which LAMA3 contributes to PDAC progression and liver metastasis may help uncover new therapeutic targets, potentially leading to more personalized treatment strategies.

Increased LAMA3 expression is associated with poor prognosis and liver metastasis in patients with PDAC. Our results indicate that LAMA3 can be a novel predictor of poor prognosis in patients with PDAC and liver metastasis, and LAMA3 may be a promising candidate for targeted therapy for PDAC liver metastasis.