Hepatocellular carcinoma is one of the leading causes of cancer-related death worldwide and one of the greatest challenges in  oncology. This tumor begins in the cells of the liver and, in most cases, develops in an organ that has already been damaged for years. Cirrhosis, chronic viral hepatitis, advanced fatty liver disease, iron overload, long-term alcohol use, and other liver conditions can create persistent inflammation that favors cancer development.

One reason this cancer is so difficult to treat is that it affects a vital organ. The liver processes nutrients, removes toxins, produces important blood proteins, and helps maintain metabolic balance. Therefore, treating a liver tumor requires precision: the goal is not only to destroy the cancer, but also to preserve as much healthy liver function as possible.

In early stages, some patients may benefit from surgery, liver transplantation, or local ablation. However, when hepatocellular carcinoma is advanced, very large, invades blood vessels, or develops in a liver with poor functional reserve, treatment options become more limited. In those cases, intra-arterial therapies, systemic treatments, and immunotherapy may be used, but achieving a complete and durable response with low toxicity remains difficult.

To address this challenge, physicians and researchers from Williams Cancer Institute, together with academic collaborators, developed an innovative strategy: combining pulsed electric field ablation, known as PEF, with intratumoral immunotherapy. This approach was reported in patients with advanced hepatocellular carcinoma and proposes a powerful idea: treating the tumor from within so the immune system can recognize it more effectively.

The strategy works in two main steps. First, PEF applies electric pulses directly to the tumor. These pulses disrupt cancer cell membranes, cause cellular damage, and promote the release of tumor antigens and neoantigens. Then, immunotherapy is injected directly into the tumor to activate immune cells, remove inhibitory signals, and modify the tumor microenvironment.

In simple terms, the treatment aims to make the tumor stop “hiding” from the immune system. By damaging it locally and releasing its internal signals, the cancer may become more visible to immune cells. Intratumoral immunotherapy then attempts to strengthen this response so the body can recognize and attack the tumor with greater precision.

A cancer that grows in an inflamed organ

To understand why hepatocellular carcinoma is so complex, it is important to consider the environment where it develops. The liver can withstand years of repeated injury. It can regenerate and adapt after long exposure to inflammation, infections, toxins, or metabolic stress. But this capacity has limits.

When injury continues for years, liver tissue can become fibrotic and eventually progress to cirrhosis. In this environment, liver cells repeatedly divide and repair themselves, increasing the chance of accumulating mutations. Some of these mutations affect genes that control cell death, DNA repair, or proliferation. Over time, certain cells may begin to survive when they should die, divide abnormally, and become malignant.

This is why hepatocellular carcinoma often appears in a liver that is already compromised. Treatment must therefore control the tumor while protecting the remaining liver function.

Why hepatocellular carcinoma may respond to immunotherapy

The immune system is designed to recognize threats, including abnormal cells. However, many tumors learn to escape immune detection. Some reduce the signals that make them visible, others activate immune “brakes,” and others create microenvironments that suppress immune activity.

Hepatocellular carcinoma has an important feature: it may have a relatively high tumor mutational burden. This means its cells can accumulate many DNA changes. Some mutations generate abnormal proteins, which can be broken into fragments called neoantigens. These neoantigens may be recognized by the immune system as foreign.

This makes hepatocellular carcinoma an interesting target for immunotherapy. But having neoantigens is not enough. The immune system needs access to them, must process them, present them, and activate an effective response. This is where the combination of PEF and intratumoral immunotherapy becomes especially relevant.

PEF: opening the tumor to reveal its signals

Pulsed electric field ablation is a nonthermal technology. Unlike ablation methods that destroy tissue mainly through heat or cold, PEF uses short, intense electric pulses to alter cell membranes.

The cell membrane controls what enters and leaves the cell. When PEF is applied to the tumor, electric pulses can create pores in this membrane, a process known as electroporation. If the damage is strong enough, the membrane loses stability and the tumor cell may die.

In cancer, this may be useful not only because it damages malignant cells, but also because it can promote the release of tumor antigens, neoantigens, and damage signals. In other words, PEF may help expose biological information that was previously trapped inside tumor cells.

Simply put, PEF does not only aim to destroy tumor cells. It may also help reveal what makes those cells different.

Antigens, neoantigens, and immune recognition

When a tumor cell is damaged, it can release several types of signals. Some are tumor antigens, molecules associated with the tumor that the immune system can recognize. Others are neoantigens, which arise from cancer-specific mutations and may be more specific to the tumor.

Damaged cells can also release cellular damage signals, which act like an alarm. They tell the immune system that something abnormal is happening in that tissue.

This is where dendritic cells and other antigen-presenting cells become essential. These cells capture tumor fragments, process them, and present them to T cells. If the immune environment is favorable, T cells can become activated, multiply, and recognize tumor cells carrying those same antigens.

For that reason, the release of neoantigens after PEF may be a key step in helping the immune system identify the cancer.

Why inject immunotherapy directly into the tumor?

The second part of the treatment is intratumoral immunotherapy. Instead of delivering drugs only through the bloodstream, the investigators injected them directly into the tumor under imaging guidance. The mixture was combined with contrast for visualization and with gelfoam to help retain the therapy locally.

This approach has a clear logic: if the tumor has created a microenvironment that blocks immune activity, then modifying that microenvironment directly may be useful. Intratumoral immunotherapy aims to concentrate the effect where the problem is: inside and around the tumor.

This may also have safety advantages. Systemic immunotherapies circulate throughout the body and can affect healthy tissues. Intratumoral administration attempts to direct the immune effect toward the tumor site, potentially reducing systemic exposure.

Not one drug, but several immune functions

Intratumoral immunotherapy in this study is better understood as a combination of functions rather than a single medication. The goal was to promote immune-mediated tumor elimination through multiple pathways.

Some agents act as immune alarm activators. For example, CpG activates TLR9, a receptor involved in innate immunity. This can stimulate dendritic cells, natural killer cells, T cells, and B cells, helping alert the immune system to tumor damage.

Other agents target immune checkpoints. Molecules such as PD-1, CTLA-4, LAG3, and B7-H3 can act as brakes on immune responses. Tumors may exploit these pathways to weaken T-cell activity. Blocking these signals aims to restore antitumor immune function.

There are also agents that activate immune costimulation, such as CD40, OX40, and 4-1BB. These pathways help antigen-presenting cells work better and support T-cell survival, expansion, and activity.

Another group aims to remodel the tumor microenvironment. Tumors are surrounded by suppressive immune cells, macrophages, cytokines, altered blood vessels, and protective signals. Some agents attempt to block signals such as CD47, reduce tumor-associated macrophages, limit suppressive immune-cell recruitment, or decrease inflammatory pathways such as IL-1, IL-6, and COX-2.

Finally, some components may cause tumor damage or sensitization, including DNA damage, apoptosis, targeting hypoxic regions, or blocking survival signals. The goal is to weaken the tumor and make it more visible to the immune system.

The tumor microenvironment: cancer’s invisible shield

A tumor is more than a mass of malignant cells. It is an ecosystem made of cancer cells, immune cells, blood vessels, support fibers, inflammatory molecules, and chemical signals. Together, these elements form the tumor microenvironment.

In many cases, this microenvironment protects the tumor. It can reduce T-cell activity, promote protumor macrophages, produce cytokines that support survival and immune escape, and prevent immune cells from entering the tumor properly.

For that reason, modern cancer therapy does not only aim to kill tumor cells directly. It also tries to change the rules of the environment. If the tumor microenvironment becomes less immunosuppressive, immune cells may have a better chance to recognize and attack the cancer.

Figure 1. Proposed mechanism of pulsed electric field ablation combined with intratumoral immunotherapy in hepatocellular carcinoma. PEF disrupts tumor cell membranes, promoting neoantigen release in a high-mutational-burden tumor context. Intratumoral immunotherapy then supports immune activation by enhancing antigen presentation, relieving T-cell inhibition, remodeling the tumor microenvironment, and increasing tumor cell vulnerability through stress and DNA damage.

What the researchers observed

The study describes a small cohort of three patients with advanced hepatocellular carcinoma. Some were not surgical candidates, and one had undergone attempted surgery without tumor resection. The procedures were image-guided and performed percutaneously.

In tumors that responded, imaging showed a reduction in tumor size and a progressive decrease in contrast enhancement. This is important because many active liver tumors enhance with contrast due to their blood supply. When that enhancement decreases, it may suggest less viable tumor tissue.

The researchers also observed changes consistent with cystic necrosis. Some tumors developed imaging features associated with fluid content or cystic change, loss of diffusion restriction, and absent or markedly reduced radiotracer uptake on PET/CT. These findings suggest lower cellularity and reduced metabolic activity.

In simpler words, some tumors stopped looking like solid, active masses packed with viable cancer cells. Over time, they appeared more cystic, less active, and less metabolically aggressive.

A local treatment with possible systemic impact

One of the most interesting concepts in the study is the possible abscopal effect. This occurs when a treatment applied to one tumor site produces effects in distant lesions or lesions that were not directly treated.

The hypothesis is that PEF releases antigens and neoantigens, intratumoral immunotherapy activates immune cells, and T cells trained against the tumor may circulate and recognize other lesions with similar signals. In this way, the treated tumor could become a local source of immune education.

The article also mentions that PEF may induce tertiary lymphoid structures, organized clusters of immune cells that can act like small immune activation centers within tissue. These structures may help attract tumor-infiltrating lymphocytes specific to hepatocellular carcinoma neoantigens.

Why some tumors respond and others do not

Advanced cancer is often heterogeneous. This means that not all tumor cells are the same. Even within the same patient, one lesion may carry different mutations or immune escape mechanisms than another.

This helps explain why one tumor may respond while another progresses. In the study, one patient with very advanced disease and portal vein tumor thrombus showed favorable changes in the treated mass, but later progressed in untreated sites. The authors suggest this may be related to intertumoral heterogeneity, different neoantigens, and immune evasion mechanisms.

This point is important: the treatment is promising, but it should not be presented as a definitive solution for all patients. Advanced hepatocellular carcinoma remains complex, and each tumor’s biology can strongly influence response.

Why repeated treatment may help

The authors propose that repeated treatments could reinforce previous immune responses. A first exposure to tumor antigens may start the immune response, while later exposures may strengthen, broaden, or refine it.

If another tumor region or lesion is treated, new neoantigens may be released. This could help the immune system recognize more “versions” of the cancer. In heterogeneous tumors, this may be especially important because not all lesions present the same immune targets.

In simple terms, each treatment could act as an immune reminder: it shows the tumor again, stimulates the response again, and may help the immune system learn to recognize more malignant signals.

What is promising and what still needs proof

The results are encouraging: reduced tumor size, decreased enhancement, cystic changes, low metabolic activity in some imaging studies, and no severe toxicities or high-grade adverse events in this small cohort.

However, scientific caution is necessary. The study was retrospective, included only three patients, used heterogeneous protocols, and several agents were used off-label. It was not a randomized clinical trial and did not include a large, uniform patient population.

Therefore, the most accurate message is not that this approach is already an established cure for advanced hepatocellular carcinoma. Rather, it is a promising proof of concept that deserves further investigation through clinical trials with standardized protocols, immune biomarkers, structured follow-up, and clear response criteria.

Conclusion: making visible what the tumor tries to hide

The combination of PEF ablation and intratumoral immunotherapy proposes a different way of thinking about hepatocellular carcinoma treatment. It does not only aim to destroy tumor tissue. It attempts to turn the treated tumor into a site of immune activation.

First, PEF disrupts malignant cell membranes and promotes the release of antigens, neoantigens, and damage signals. Then, intratumoral immunotherapy aims to activate antigen-presenting cells, stimulate T cells, block immune brakes, reduce immunosuppression, and sensitize the tumor.

The central idea is powerful: cancer should not only be attacked; it should also be exposed. Many tumors survive because they hide from or suppress the immune system. This strategy attempts to do the opposite: open the tumor, reveal its internal signals, and modify the environment that protects it.

More research is still needed to confirm its real clinical impact, define which patients may benefit most, and establish safe, reproducible protocols. But the study developed by physicians and researchers from Williams Cancer Institute opens an important question: can we use the tumor itself as a starting point to awaken a broader immune response?

In hepatocellular carcinoma, a complex and aggressive disease deeply linked to liver function, precision matters. The possibility of treating the tumor from within, releasing its signals, and making it more visible to the immune system represents a research direction that deserves close attention.

Main reference:

Soule, E., Vargas, C., Sanchez, R., Cortes, E., Goodyear, N., Barco, R., & Williams, J. (2026). Pulsed electrical field ablation plus intratumoral immunotherapy for hepatocellular carcinoma. Journal of Immunotherapy, 49(5), 214–224. https://doi.org/10.1097/CJI.0000000000000596