Recombinant Human Transmembrane protein 105 (TMEM105)

What is TMEM105 and what are its known biological functions?

TMEM105 is a transmembrane protein that has emerged as a significant factor in cancer biology. Current research indicates TMEM105 functions as a glycolysis-related long non-coding RNA (lncRNA) in multiple cancer types. In thyroid papillary carcinoma, TMEM105 has been characterized as a cell cycle-related lncRNA that predicts progression-free survival . Additionally, in breast cancer, TMEM105 facilitates glycolysis and promotes cancer cell invasion by modulating lactate dehydrogenase A (LDHA) expression .

TMEM105 affects multiple cellular processes, including:

• Regulation of cellular metabolism, particularly glycolysis

• Modulation of cancer cell proliferation and migration

• Influence on cancer metastasis, especially to the liver in breast cancer

• Regulation of disulfidptosis, a form of cell death

Studies across different cancer types consistently demonstrate TMEM105's oncogenic properties, suggesting its fundamental role in cancer cell metabolism and survival.

How does TMEM105 expression vary across normal and cancerous tissues?

TMEM105 expression exhibits significant variation between normal tissues and different cancer types. In breast cancer, expression analysis reveals a progressive increase in TMEM105 levels from adjacent normal tissues to primary breast cancer to breast cancer liver metastasis (BCLM) . This stepwise elevation suggests TMEM105 plays a role in both cancer initiation and progression.

Analysis of The Cancer Genome Atlas (TCGA) dataset indicates TMEM105 is notably overexpressed in several human cancers, including bladder urothelial carcinoma and esophageal carcinoma among others . The universal upregulation of TMEM105 across multiple cancer types points to its potential fundamental role in oncogenesis rather than being specific to any single cancer type.

What cellular pathways and molecular mechanisms involve TMEM105?

TMEM105 participates in several critical cellular pathways:

Glycolysis Regulation: TMEM105 enhances glycolysis in cancer cells. In breast cancer, TMEM105 regulates LDHA expression by sponging miR-1208, thereby promoting glycolysis . This creates a positive feedback loop where glycolytic production of lactate enhances TMEM105 expression through the SHH-MAZ signaling pathway .

Glucose Uptake: In pancreatic cancer, TMEM105 influences cellular glucose uptake. Knockdown of TMEM105 significantly decreases intracellular glucose levels .

Disulfidptosis Regulation: TMEM105 modulates disulfidptosis in pancreatic cancer. When TMEM105 is knocked down, cells exhibit more pronounced F-actin contraction and cell shrinkage in glucose-free environments, indicating increased susceptibility to disulfidptosis .

c-MYC Pathway: Gene Set Enrichment Analysis (GSEA) based on TCGA data reveals TMEM105 is significantly associated with the c-MYC pathway. TMEM105 engages this glycolysis-related transcription factor to induce GLUT1 expression .

What are effective protocols for TMEM105 knockdown in cancer cell lines?

Based on published research, the following protocol has proven effective for TMEM105 knockdown:

siRNA Transfection Protocol:

• Purchase small interfering RNAs (siRNAs) from a reliable source (e.g., Gene Pharma, Shanghai, China)

• Seed cells at appropriate density in a 6-well plate and incubate overnight

• Add 50 pmol siRNA to 200 μl of Opti-MEM medium and incubate for 5 minutes

• Separately add 2.5 μl of transfection reagent (e.g., Dharmacon) to 200 μl of Opti-MEM medium and incubate for 5 minutes

• Mix the two solutions, incubate for 20 minutes, and add to the 6-well plate

• Incubate for 48 to 72 hours before analysis

Validated siRNA Sequences for TMEM105:

• si-TMEM105-1: 5'-CCCAUAGCUGACACUUCUA-3' (sense), 5'-UAGAAGUGUCAGCUAUGGG-3' (antisense)

• si-TMEM105-2: 5'-GGCAAGCUCUGAUCUUACA-3' (sense), 5'-UGUAAGAUCAGAGCUUGCC-3' (antisense)

For stable knockdown, shRNA lentiviruses using the same sequences can be constructed to infect target cells (e.g., Mia PaCa-2 cells for pancreatic cancer studies) .

How can researchers establish TMEM105 overexpression models?

TMEM105 overexpression can be achieved using the following approach:

• Synthesize an overexpression vector (e.g., Ubi-MCS-SV40-Puromycin) containing the TMEM105 sequence (commercial suppliers like Genechem, Shanghai can provide this service)

• Transfect the vector into target cells following standard transfection protocols

• Select stable cell lines by maintaining transfected cells in complete medium supplemented with puromycin (5μg/mL is an effective concentration)

• Verify overexpression through RT-qPCR and Western blot analysis

For in vivo studies, stable overexpression cell lines (such as Patu8988 for pancreatic cancer) can be established and subcutaneously implanted into animal models (e.g., the posterior axillary line of nude mice) .

What assays are recommended for evaluating TMEM105's impact on cell proliferation and metabolism?

Several complementary assays have been validated for assessing TMEM105's effects:

Cell Proliferation:

• CCK8 assay for cell viability

• Colony formation assay for long-term proliferative potential

• EdU incorporation assay for DNA synthesis and cell proliferation

• Ki-67 immunohistochemical staining for proliferation marker expression in vivo

Cell Migration:

• Transwell assays to assess migration capacity

Cell Death and Metabolism:

• Propidium iodide (PI) staining to detect cell death

• Cytoskeleton staining to visualize F-actin contraction and cell shrinkage

• Intracellular glucose uptake measurement

• NADP+/NADPH ratio detection assays to evaluate redox status

• TUNEL staining to assess apoptosis in vivo

In Vivo Tumor Growth:

• Subcutaneous xenograft models in nude mice

• Patient-derived xenograft (PDX) models for validating clinical relevance

• Measurement of tumor volume and weight

• Immunohistochemical analysis of tumor tissues

How does TMEM105 influence cancer cell proliferation and tumor growth?

TMEM105 functions as an oncogenic factor that promotes cancer cell proliferation and tumor growth through multiple mechanisms:

In Vitro Evidence:
In pancreatic cancer cell lines, knockdown of TMEM105 significantly impairs cell viability and proliferation compared to control groups as demonstrated through CCK8, colony formation, and EdU detection assays . Conversely, TMEM105 overexpression enhances cell proliferation and migration .

In Vivo Evidence:
Subcutaneous implantation of TMEM105-knockdown pancreatic cancer cells in nude mice results in significantly reduced tumor volume and weight compared to control groups . Additionally, Ki-67 staining (a proliferation marker) confirms that TMEM105 knockdown inhibits cancer cell proliferation in vivo . Patient-derived xenograft (PDX) models further validate TMEM105's stimulatory effect on pancreatic cancer progression .

These findings consistently demonstrate that TMEM105 functions as a driver of cancer cell proliferation and tumor growth across different experimental models.

What is TMEM105's relationship with cancer metastasis?

TMEM105 plays a significant role in promoting cancer metastasis, particularly in breast cancer:

Expression in Metastatic Tissues:
Analysis of high-throughput sequencing data reveals TMEM105 expression is higher in breast cancer tissues with liver metastasis compared to primary breast cancers without metastasis . This differential expression pattern was validated through qRT-PCR and in situ hybridization (ISH) analyses of clinical specimens .

Diagnostic Value for Metastasis:
ROC curve analysis of TCGA data demonstrates TMEM105 significantly predicts breast cancer metastasis (AUC = 0.640) . This suggests TMEM105 expression could serve as a biomarker for metastatic potential.

Functional Evidence:
TMEM105 facilitates breast cancer cell invasion, a critical step in the metastatic cascade. Furthermore, TMEM105 is involved in a glycolysis-mediated positive feedback loop that promotes breast cancer liver metastasis .

How does TMEM105 regulate cancer cell metabolism, particularly glycolysis?

TMEM105 functions as a key regulator of cancer cell metabolism through multiple mechanisms:

Glycolysis Promotion:
In breast cancer, TMEM105 facilitates glycolysis by regulating LDHA expression. LDHA is a critical enzyme that converts pyruvate to lactate in the final step of anaerobic glycolysis .

miRNA Sponging Mechanism:
TMEM105 regulates LDHA expression by sponging miR-1208, preventing this microRNA from inhibiting LDHA . This represents a post-transcriptional regulatory mechanism through which TMEM105 enhances glycolysis.

Glucose Uptake:
In pancreatic cancer cells, TMEM105 knockdown significantly decreases intracellular glucose levels, indicating TMEM105's role in glucose uptake regulation .

GLUT1 Regulation via c-MYC:
TMEM105 engages the glycolysis-related transcription factor c-MYC to induce GLUT1 expression . GLUT1 is a major glucose transporter that facilitates glucose uptake into cells, which is essential for glycolysis.

Positive Feedback Loop:
Importantly, glycolytic production of lactate enhances TMEM105 expression in breast cancer cells by activating the SHH-MAZ signaling pathway . This creates a positive feedback loop where TMEM105 promotes glycolysis, which in turn upregulates TMEM105.

What is the significance of TMEM105 in disulfidptosis regulation?

TMEM105 plays a crucial role in modulating disulfidptosis, a form of cell death characterized by the collapse of the cell skeleton:

Correlation with Disulfidptosis Genes:
Analysis using GEPIA website based on TCGA and Genotype Tissue Expression (GTEx) database demonstrates a strong correlation between TMEM105 and disulfidptosis-related genes .

Protective Role Against Disulfidptosis:
In glucose-free environments, knockdown of TMEM105 significantly augments cell death, while TMEM105 overexpression restores survival. Importantly, the application of disulfidptosis inhibitor DTT can inhibit the death caused by glucose deprivation, confirming that TMEM105 mitigates disulfidptosis .

Mechanism of Action:
TMEM105 knockdown cells exhibit more pronounced F-actin contraction and cell shrinkage in glucose-free environments, which are hallmarks of disulfidptosis . Additionally, downregulation of TMEM105 increases the intracellular NADP+/NADPH ratio in glucose-free environments, while TMEM105 overexpression has the opposite effect .

Link to Glucose Metabolism:
Mechanistically, TMEM105 regulates disulfidptosis by modulating glucose uptake, which affects the pentose phosphate pathway (PPP) and the NADP+/NADPH balance. When glucose uptake is reduced (as in TMEM105 knockdown), PPP dysregulation leads to an imbalance of NADP+/NADPH, resulting in cell skeleton collapse and ultimately disulfidptosis .

What is the prognostic value of TMEM105 expression in different cancers?

TMEM105 expression has significant prognostic value across multiple cancer types:

Multivariate Analysis:
Importantly, multivariate analysis confirms TMEM105 expression is an independent predictor for OS in breast cancer (HR = 1.483, p = 0.047), comparable to established prognostic factors such as pathologic stage, lymph node metastasis, and age .

Time-Dependent ROC Analysis:
Time-dependent ROC curve analysis further demonstrates TMEM105's prognostic accuracy over time, with AUC values of 0.711 at 2 years, 0.753 at 3 years, and 0.778 at 5 years .

Other Cancer Types:
TMEM105 is overexpressed in various human cancers, including bladder urothelial carcinoma and esophageal carcinoma, with high expression consistently associated with cancer metastasis and poor prognosis across multiple cancer types .

What is the correlation between TMEM105 expression and clinicopathological characteristics?

TMEM105 expression correlates with numerous clinicopathological factors:

Breast Cancer Characteristics:
In TCGA analysis, TMEM105 expression strongly correlates with:

• Pathological grade

• Distant metastasis

• Histological type

• Estrogen receptor (ER) status

• Progesterone receptor (PR) status

• PAM50 subtype

• Age

• Race

Correlation Table in Breast Cancer:

These correlations suggest TMEM105 could serve as a biomarker for more aggressive disease phenotypes across cancer types, providing valuable prognostic information beyond established clinicopathological factors.

What potential therapeutic approaches might target TMEM105?

Based on mechanistic studies, several therapeutic strategies targeting TMEM105 show promise:

Direct TMEM105 Inhibition:
Given TMEM105's oncogenic role, direct inhibition through RNA interference or other targeted approaches could represent a viable therapeutic strategy. The validated siRNA sequences from experimental studies provide a starting point for developing RNA-based therapeutics .

Targeting the TMEM105-GLUT1 Axis:
GLUT1 inhibitors such as BAY-876 have demonstrated efficacy in reversing TMEM105-driven tumor growth in vivo. In preclinical models, oral administration of BAY-876 restored the augmentation of tumor weight and volume caused by TMEM105 overexpression . This suggests targeting glucose metabolism downstream of TMEM105 could be therapeutically beneficial.

Disrupting the TMEM105-c-MYC-GLUT1 Pathway:
Since TMEM105 engages the glycolysis-related transcription factor c-MYC to induce GLUT1, targeting this pathway could be effective. Inhibitors of c-MYC could potentially counteract TMEM105's oncogenic effects .

Breaking the Glycolysis Feedback Loop:
Targeting the lactate-responsive SHH-MAZ signaling pathway that enhances TMEM105 expression could break the positive feedback loop between TMEM105 and glycolysis in breast cancer .

TMEM105-miR-1208-LDHA Axis:
Therapeutic approaches aimed at reinforcing miR-1208 function or directly targeting LDHA could counteract TMEM105's effects on glycolysis and cancer metastasis .

What are the critical knowledge gaps in understanding TMEM105 biology?

Despite significant advances, several critical knowledge gaps remain in TMEM105 research:

Structure-Function Relationship:
The three-dimensional structure of TMEM105 protein and how this relates to its function remains unexplored. Structural biology approaches would provide insight into potential drug binding sites.

Tissue-Specific Functions:
While TMEM105's role has been characterized in breast and pancreatic cancers, its function in other cancer types and normal tissues requires further investigation.

Transcriptional Regulation:
Apart from the lactate-responsive SHH-MAZ pathway in breast cancer, the comprehensive transcriptional regulation of TMEM105 across tissues and conditions remains unclear.

Post-Translational Modifications:
Whether TMEM105 undergoes post-translational modifications that affect its function, stability, or localization is unknown.

Interaction Partners:
A systematic identification of TMEM105's protein interaction partners would provide deeper insight into its cellular functions and potential regulatory mechanisms.

How might TMEM105 contribute to therapeutic resistance?

TMEM105's role in metabolic reprogramming suggests potential contributions to therapeutic resistance:

Metabolic Adaptation:
TMEM105's enhancement of glycolysis may provide cancer cells with metabolic flexibility, allowing them to adapt to stress conditions imposed by therapeutics.

Cell Death Evasion:
TMEM105's protection against disulfidptosis indicates its role in cell death evasion mechanisms, which could extend to resistance against apoptosis-inducing therapies .

Connection to Therapy-Relevant Pathways:
TMEM105's engagement with c-MYC, a central oncogenic transcription factor, suggests it may influence resistance to therapies targeting c-MYC-dependent pathways .

Metastatic Phenotype:
Since TMEM105 promotes metastasis, its expression may be associated with more aggressive, therapy-resistant disease phenotypes .

What are promising methodologies for therapeutic targeting of TMEM105?

Emerging methodologies hold promise for therapeutic targeting of TMEM105:

RNA-Based Therapeutics:
Small interfering RNAs (siRNAs) or antisense oligonucleotides specifically designed to silence TMEM105 expression could be developed into therapeutics.

PROTAC Technology:
Proteolysis-targeting chimeras (PROTACs) could be engineered to target TMEM105 protein for degradation, providing an alternative to RNA interference approaches.

Metabolic Inhibitors:
Small molecule inhibitors targeting the metabolic processes influenced by TMEM105, such as GLUT1 inhibitors (e.g., BAY-876), offer a viable indirect approach to counteract TMEM105's effects .

Combination Therapies:
Given TMEM105's involvement in multiple oncogenic processes, combination approaches targeting both TMEM105 and its downstream effectors (e.g., GLUT1, LDHA) could enhance therapeutic efficacy.

Biomarker-Guided Therapy: TMEM105 expression could serve as a biomarker to guide therapeutic decisions, particularly for metabolism-targeting therapies or in patients with metastatic disease.