Breaking Barriers in Triple Negative Breast Cancer: New Hope with C14 and P8

 

One of the leading causes of death globally, (accounting for around 1 in 9 men, and 1 in 12 women), is Cancer. Cancer is a large group of diseases that can start in almost any organ/tissue of the body when cells grow uncontrollably, go beyond their usual boundaries to invade surrounding tissues, and/or spread to other organs. Among men, the most common types of cancer include lung, prostate, colorectal, stomach, and liver cancer. Among women, breast, colorectal, cervical, and thyroid cancer are commonly observed. In this article, we shall focus on Breast Cancer.

 Breast Cancer involves the abnormal growth of breast cells, leading to tumor formation in many cases. The Breast Cancer cells begin inside the milk ducts and the milk-producing lobules of the breast. We shall focus particularly on the Triple Negative Breast Cancer (TNBC), here. The Triple Negative Breast Cancer is a prime example of Invasive Breast Cancer. Invasive Cancer can spread to nearby lymph nodes or adjacent organs of the body (that is, they can metastasize).

Unlike most Breast Cancer cases, the TNBC cells lack the following:

1. Receptors for Estrogen (ER)

2. Receptors for Progesterone (PR)

3. Epidermal Growth Factor Receptor 2 (HER2)

The absence of the above three receptors gives the cancer its name. TNBC is known for its difficulty in diagnosis and treatment.

 TNBC is most likely to affect:

1. Women and AFAB individuals aged 40 or younger

2. Individuals with BRCA mutations (that is, inherited genetic mutations that increase chances of Breast Cancer)

3. Black or Hispanic Individuals

Some existing treatments for TNBC include:

1. Chemotherapy

2. Immunotherapy

3. Surgery

4. Targeted therapy

5. Radiation therapy

However, the development of resistance to these therapies has been observed in a number of patients. For example, around 60-70% of TNBC patients develop resistance to chemotherapy and radiation therapies. Resistance of this kind can be associated with multiple factors. One such factor is the overactivation of KRAS and its associated signalling pathways. The KRAS gene provides instructions for making a protein called K-Ras that is part of a signaling pathway known as the EGFR/K-RAS/MAPK pathway. The protein relays signals from outside the cell to the cell's nucleus. According to previous reports, patients who express overactive mutant forms of KRAS have been associated with the development of chemoresistance. Additionally, TNBC patients with KRAS mutations also showcase resistance to radiation therapy, which is a prevalent method for breast cancer treatment. This resistance observed in TNBC patients might be due to the highly heterogeneous nature of the tumors, such as high diversity in tumoral cell populations, the presence of cancer stem cells and epithelial-mesenchymal transition characteristics. Overcoming radioresistance in TNBC remains a critical area of research, with ongoing efforts focused on identifying novel therapeutic strategies to enhance the effectiveness of treatments and radiation therapy in this aggressive and challenging breast cancer subtype. 

One such possible novel therapeutic strategy could be the use of KRAS as a therapeutic target. K-Ras4B is the more abundant isoform of the K-Ras protein. Mutant K-Ras4B is associated with around 5%–15% of breast cancers, including TNBC, and plays a role in tumorigenesis by driving key signaling pathways like RAF/MEK/MAPK. In this specific case of breast cancer, up to 23% of premenopausal women with TNBC have been shown to have higher rates of mutations in KRAS gene. 

Targeting mutant forms of K-Ras4B has been a challenge due to its cellular localisation requirements and the number of mutations. Due to this, a new approach involving the usage of a family of small molecules, including C14 and P8 (act as molecular staples), was implemented. C14 is denoted as 2-[(3-chlorophenyl)-methyl-methyl-amino]-N-croman-4-yl-acetamide with a molecular weight of 344.83 g/mol. Five rotatable bonds, a hydrogen bridge donor atom, and three hydrogen bridge acceptor atoms are possessed by the molecule. The functional groups included benzopyrene or chromeno, which is a rigid structure formed by a benzene ring and a six-atom heterocycle with hydrogen at position 1 and a N-methylacetamide group. P8 is designated as 2-[4-(3- chlorophenyl)piperazin-1-yl]-N-[(4R)-chroman-4-yl]acetamide with a molecular weight of 385.9 g/mol and is an analog of the base compound C14. Both compounds are capable of binding to the complex formed by K-Ras4B and the phosphodiesterase subunit delta (PDE6d) to reduce the activity of this GTPase and its associated signaling pathways. 

Cytotoxic effects of both the compounds were studied. The cell lines MDA-MB-231 and MDA- MB-231RR were utilized. These cell lines are particularly relevant because they exhibit TNBC characteristics and express the K- Ras4BG13D mutation. In this case, clear effectiveness was observed by C14 and P8 as antitumoral agents in TNBC cells that express the mutant form of G13D. This was achieved through the stabilization of the molecular complex of K-Ras4BG13D/PDE6d and the reduction of associated signaling pathways. In MDA-MB-231RR cells particularly, both molecules C14 and P8 displayed potent cytotoxic effects, indicating their potential to reduce the viability of radioresistant TNBC cell lines. Moreover, it was observed that C14 and P8 impacted mutant TNBC cells while not causing much harm to the non-tumoral cells. This emphasized the potential advantage of C14 and P8 over traditional treatments and chemotherapy, where the non-tumoral cells get affected as well. 

In conclusion, this study showcased the ways in which C14 and P8 could impact mutant TNBC cells. Both molecules were effective in stabilizing and inhibiting the action of the mutant form of TNBC cells. The antineoplastic evaluation of these compounds demonstrated that both molecules preferentially affected K-Ras4B mutated forms. Furthermore, C14 and P8 influenced critical signaling pathways, related to cell survival and cell cycle regulation thus reducing cell proliferation.

 

REFERENCES:

1. Carrión-Estrada DA, Aguilar-Rojas A, Huerta-Yepez S, Montecillo-Aguado M, Bello M, Rojo-Domínguez A, et al. Antineoplastic effect of compounds C14 and P8 on TNBC and radioresistant TNBC cells by stabilizing the K-Ras4BG13D/PDE6δ complex. Frontiers in Oncology. 2024 Mar 20;14.

‌